%0 journal article %@ 0268-3768 %A Rodrigues, C.F.,Vilas Boas, M.C.,Blaga, L.,Bartz, O.,Klusemann, B. %D 2024,2024 %J The International Journal of Advanced Manufacturing Technology %N %P 5163-5173 %R doi:10.1007/s00170-024-14054-0 %T Application of Friction Riveting technique for the assembly of electronic components on printed circuit boards (PCB) %U https://doi.org/10.1007/s00170-024-14054-0 %X This study focuses on the effects of reducing the diameter of rivets used in Friction Riveting due to the need for downscaling when joining assemblies on a smaller scale. The Friction Riveting process has shown promising feasibility for a variety of material combinations and applications in the transportation industry. Recent research has explored the potential application of this technique in electronics, specifically for the assembly of printed circuit boards (PCBs), using AA-2024-T351 rivets on thin glass-fiber-reinforced epoxy substrates (FR4). The joint formation of joints produced with PCBs was investigated in terms of process temperature evolution, microstructural changes, and mechanical properties. Joints were obtained at process temperatures ranging from 285 ºC to 368 ºC. The use of 4 mm rivets resulted in extensive delamination, weak joint mechanisms, and cracking, impaired by the different coefficients of thermal expansion of the materials involved. Reducing the rivet diameter to 3 mm significantly improved joint quality. A further reduction to 2.5 mm minimized delamination but led to insufficient anchorage and cracking. Joints produced with a 3 mm rivet diameter achieved the highest ultimate tensile force of 276 N. This study sets the foundation for applying the Friction Riveting process to practical PCB assemblies, demonstrating that optimizing the process parameters to the diameter-to-thickness ratio can balance sufficient rivet anchoring, minimize delamination, and reduce cracking. %0 journal article %@ 2214-8604 %A Huang, C.J.,Chen, T.,Fu, B.L.,Zhang, Z.M.,List, A.,Wiehler, L.,Klusemann, B.,Li, W.Y.,Gärtner, F.,Klassen, T. %D 2024 %J Additive Manufacturing %N %P 104310 %R doi:10.1016/j.addma.2024.104310 %T Ductility and fracture behavior of cold spray additive manufactured zinc %U https://doi.org/10.1016/j.addma.2024.104310 %X Tailoring part strength and ductility in additive manufacturing or repair is vital to successful applications. Therefore, applying cold spray as a deposition technique must be tuned for maximum amounts of well-bonded internal interfaces and sufficient softening of the highly work-hardened deposit. With its low melting temperature, Zinc is an ideal model system for studying phenomena associated with high strain rate deformation and local temperature rise effect, both in single impacts and thick deposits. Despite the low temperatures, Zn single splats already show recrystallization at internal interfaces. The respective amounts scale with increasing process gas temperatures. At higher process temperatures, deposits are almost fully recrystallized. The recrystallization obviously improves bonding at internal and at deposit-substrate interfaces. Under optimum conditions, an ultimate deposit strength of up to 135 MPa and an elongation to failure of 18.4 % are reached, comparable to that of laser-manufactured Zn parts. However, the presence of defects in the form of a high density of high-angle grain boundaries and a certain amount of nonbonded splats interfaces results in a lower ductility than that of bulk Zn. This demonstrates a well-tuned interplay between the minimization of defect densities and softening by recrystallization that would allow for deriving bulk-like properties of cold sprayed material without additional post-treatments. Correlations between simulation and experimental results of microstructures, mechanical properties, and fracture mechanisms supply information about the prerequisites for reaching high ductility. %0 journal article %@ 0257-8972 %A Hoffmann, M.,Roos, A.,Klusemann, B. %D 2024 %J Surface and Coatings Technology %N %P 130610 %R doi:10.1016/j.surfcoat.2024.130610 %T Investigation of microstructural and mechanical properties in AA2024-T351 multi-layer friction surfacing %U https://doi.org/10.1016/j.surfcoat.2024.130610 %X This study on multi-layer friction surfacing (MLFS) as a process for additive manufacturing focuses on the influence of process parameters on the resulting microstructural properties for the precipitation-hardenable Al-Cu-Mg alloy AA2024. The energy input, which is determined by the process parameters, is correlated with the process temperature, which has a direct influence on the microstructure and mechanical properties. At higher process temperatures, e.g. at 450.1∘C, larger average grain sizes, i.e. 2.5 μm, were observed in the deposited material compared to lower temperatures, i.e. 1.2 μm at 380.6∘C. At the same time, hardness (109.2 HV0.1 ↔ 115.7 HV0.1) and ultimate tensile strength (360.8 MPa ↔ 423.3 MPa) were lower at higher temperatures, in particular due to a pronounced overaging. In terms of overall mechanical behavior, the interfaces between the first layer and the substrate are the weak points of MLFS, as they exhibit lower tensile strength compared to the interfaces between the layers. Within the MLFS, the interfaces have a slightly higher hardness, which can be attributed to locally smaller grains. %0 journal article %@ 0045-7825 %A Bock, F.E.,Kallien, Z.,Huber, N.,Klusemann, B. %D 2024 %J Computer Methods in Applied Mechanics and Engineering %N %P 116453 %R doi:10.1016/j.cma.2023.116453 %T Data-driven and physics-based modelling of process behaviour and deposit geometry for friction surfacing %U https://doi.org/10.1016/j.cma.2023.116453 %X In the last decades, there has been an increase in the number of successful machine learning models that have served as a key to identifying and using linkages within the process-structure–property-performance chain for vastly different problems in the domains of materials mechanics. The consideration of physical laws in data-driven modelling has recently been shown to enable enhanced prediction performance and generalization while requiring less data than either physics-based or data-driven modelling approaches independently. In this contribution, we introduce a simulation-assisted machine learning framework applied to the solid-state layer deposition technique friction surfacing, suitable for solid-state additive manufacturing as well as repair or coating applications. The objective of the present study is to use machine learning algorithms to predict and analyse the influence of process parameters and environmental variables, i.e. substrate and backing material properties, on process behaviour and deposit geometry. The effects of maximum process temperatures supplied by a numerical heat transfer model on the predictions of the targets are given special attention. Numerous different machine learning algorithms are implemented, optimized and evaluated to take advantage of their varied capabilities and to choose the optimal one for each target and the provided data. Furthermore, the input feature dependence for each prediction target is evaluated using game-theory related Shapley Additive Explanation values. The experimental data set consists of two separate experimental design spaces, one for varying process parameters and the other for varying substrate and backing material properties, which allowed to keep the experimental effort to a minimum. The aim was to also represent the cross parameter space between the two independent spaces in the predictive model, which was accomplished and resulted in an approximately 44 % reduction in the number of experiments when compared to carrying out an experimental design that included both spaces. %0 journal article %@ 0013-7944 %A Examilioti, T.N.,Karanikolas, D.,Riekehr, S.,Al-Hamdany, N.,Papanikos, P.,Klusemann, B.,Kashaev, N.,Alexopoulos, N.D. %D 2024 %J Engineering Fracture Mechanics %N %P 109811 %R doi:10.1016/j.engfracmech.2023.109811 %T Effect of filler materials on the tensile properties and fracture toughness of laser beam welded AA2198 joints under different ageing conditions %U https://doi.org/10.1016/j.engfracmech.2023.109811 %X The influence of different filler materials on the microstructure, tensile mechanical properties, and fracture toughness of laser beam welded AA2198 alloy as well as the effect of different artificial ageing heat treatments were investigated in this contribution. The welded joints were produced when exploited either, Al-Si (AA4047) or Al-Cu (AA2319) filler wires. It was shown that the Al-Si filler wire gave higher hardness values in the fusion zone when compared to the Al-Cu filler wire. The post heat treatment of the welded specimens increased by approximately +100 % the yield stress and by +20 % the ultimate tensile strength with increasing ageing time, in a similar way to the non-welded material. Elongation at fracture decreased in an inverse proportional manner to yield stress. Artificial ageing before welding gave improved elongation at fracture for the over-aged condition only. The quality index concept showed that the artificial ageing before the welding did not succeed in giving a higher quality of the welded joints, for both filler materials investigated. The opposite was shown on the post heat treatment, where the peak-aged condition increased substantially the ‘quality’ of the welded joints with both filler materials. The critical stress intensity factor was increased by +25 % for the under-aged condition for the post-welded condition and both investigated filler wires as a result of the balance between medium values in strength and ductility, respectively. %0 journal article %@ 2238-7854 %A Pasetti-Rosa, A.,Victoria-Hernandez, J.,da Cunha, P.H.C.P.,de Lima Lessa, C.R.,Bergmann, L.A.,Kurtz, G.,Letzig, D.,Klusemann, B. %D 2024 %J Journal of Materials Research and Technology : JMRT %N %P 4895-4901 %R doi:10.1016/j.jmrt.2024.02.188 %T Behavior of microstructure and mechanical properties in the stir zone of friction stir welded ME21 magnesium alloy %U https://doi.org/10.1016/j.jmrt.2024.02.188 %X In this work, Friction Stir Welding (FSW) of magnesium alloy ME21 in a T-profile is performed with a relatively higher welding speed than usual in this material. The FSW process parameters, i.e., rotational speed and welding speed, are investigated focused within its inherent microstructural and mechanical properties on the stir zones of the welded joints. The concept of a Stribeck Curve in tribological systems, is transferred to FSW to explain the transition between insufficient and full plasticization of the material. The stir zone presented a strong grain refinement due to the activation of dynamic recrystallization along with a completely changed crystallographic texture and orientation due to FSW. The hardness is overall improved, while the ductility and tensile strength were reduced. The microstructure and texture in the stir zone were not strongly influenced by changes in the welding parameters. %0 journal article %@ 0013-7944 %A Becker, N.,dos Santos, J.F.,Klusemann, B. %D 2024 %J Engineering Fracture Mechanics %N %P 109963 %R doi:10.1016/j.engfracmech.2024.109963 %T Experimental investigation of crack propagation mechanism in refill friction stir spot joints of AA6082-T6 %U https://doi.org/10.1016/j.engfracmech.2024.109963 %X Since many aluminum alloys preferred in structural engineering can be welded conventionally only with great effort and energy input interest in alternative joining techniques is growing, such as solid state joining processes. In this work, the effect of refill friction stir spot welding (refill FSSW) on the crack propagation behavior in AA6082-T6 is studied. To be able to identify the individual fracture mechanism, refill FSSW was performed as a blind weld, i.e. only in one sheet designed as C(T)100 specimens. The vertical distance between notch and spot weld was varied and tested in two phases. First, a cyclic pre-crack was induced and then the specimen was caused to fail in quasi-static conditions, resulting in two different fracture modes. The results showed that the cyclic crack is dominated by residual stresses but the microstructure mainly influences the quasi-static crack propagation. It was also found that a stress concentration occurs in the transition area even without a hook. Furthermore, it was found that the crack propagation is not exclusively driven by the local strength but also by the angle at which the crack hits the spot weld. %0 journal article %@ 2045-2322 %A Antunes Duda, E.,Kallien, Z.,da Silva Soares, S.,Hernandez Schneider, T.,Piaggio Cardoso, H.R.,Braga Lemos, G.V.,Falcade, T.,Reguly, A.,Klusemann, B. %D 2024 %J Scientific Reports %N %P 9882 %R doi:10.1038/s41598-024-60431-w %T Corrosion behavior of multi-layer friction surfaced structure from dissimilar aluminum alloys %U https://doi.org/10.1038/s41598-024-60431-w %X Friction surfacing (FS) is a solid-state coating technology for metallic materials, where the deposition of a consumable material on a substrate is enabled via friction and plastic deformation. The deposited layer material commonly presents a significantly refined microstructure, where corrosion could be an issue due to this grain refinement within the layer deposited, possibly creating micro galvanic pairs. The present work investigates the corrosion behavior of the FS deposited material as well as stud base material and substrate using cyclic polarization tests and open circuit potential (OCP) monitoring. Comparing the FS deposited material and the respective consumable stud base material (both AA5083), the grain size is correlated with the results from the corrosion tests, where the deposited material shows more equiaxed and refined grains in comparison to the stud base material. The cyclic potentiostatic polarization tests showed that the stud base material is more resistant to pitting nucleation presenting smaller pits and a lower amount of pits compared to deposited material and substrate. As a complement to OCP test, the stud base material is also more stable on a chloride solution compared to the substrate and the deposited material. %0 journal article %@ 1059-9495 %A Dahmene, F.,Yaacoubi, S.,El Mountassir, M.,Porot, G.,Masmoudi, M.,Nennig, P.,Suhuddin, U.F.H.,Dos Santos, J.F. %D 2024 %J Journal of Materials Engineering and Performance %N %P 1931-1947 %R doi:10.1007/s11665-023-08102-1 %T An Original Machine Learning-Based Approach for the Online Monitoring of Refill Friction Stir Spot Welding: Weld Diagnostic and Tool State Prognostic %U https://doi.org/10.1007/s11665-023-08102-1 %X The process monitoring (PM) of refill friction stir spot welding (Refill FSSW) can play a substantial role in detecting various issues, especially defects in the spot being formed and the tool state degradation, which allows in time intervention to improve the welding process. Since Refill FSSW is somewhat an emergent technology, PM has received scarce attention. In this paper, the performance of PM using acoustic emission (AE) technique is studied for two purposes: detecting defects in weld while being formed and predicting the tool state. To do so, the common defects that can occur during the process were first intentionally created and monitored using AE. The corresponding collected data have served then as an input for two defect detection models. The first one is based on novelty detection and has shown an average classification performance. The second, which shows higher performance, uses multi-class classification algorithms. Concerning the tool state, a novel state index was developed to predict when the process must be stopped in order to clean the tool and avoid hence related weld defects and tool fracture. %0 journal article %@ 2213-9567 %A de Castro, C.C.,Neves, A.M.,Klusemann, B. %D 2024 %J Journal of Magnesium and Alloys %N %P %R doi:10.1016/j.jma.2024.04.002 %T Effect of thermo-mechanical conditions during constrained friction processing on the particle refinement of AM50 Mg-alloy phases %U https://doi.org/10.1016/j.jma.2024.04.002 %X Constrained Friction Processing (CFP) is a novel solid-state processing technique suitable for lightweight materials, such Mg- and Al-alloys. The technique enables grain size refinement to fine or even ultrafine scale. In this study, the effect of CFP on the microstructural refinement of AM50 rods is investigated in terms of particle size and morphology of the eutectic and secondary phases originally present in the base material, in particular the eutectic β-Mg17Al12 and Al-Mn phases. For that purpose, as-cast and solution heat-treated base material and processed samples were analyzed. The Al8Mn5 intermetallic phase was identified as the main secondary phase present in all samples before and after the processing. A notorious refinement of these particles was observed, starting from particles with an average equivalent length of a few micrometers to around 560 nm after the processing. The refinement of the secondary phase refinement is attributed to a mechanism analogous to the attrition comminution, where the combination of temperature increase and shearing of the material enables the continuous breaking of the brittle intermetallic particles into smaller pieces. As for the eutectic phase, the results indicate the presence of the partially divorced β-Mg17Al12 particles exclusively in the as-cast base material, indicating that no further phase transformations regarding the eutectic phase, such as dynamic precipitation, occurred after the CFP. In the case of the processed as-cast material analyzed after the CFP, the thermal energy generated during the processing led to temperature values above the solvus limit of the eutectic phase, which associated with the mechanical breakage of the particles, enabled the complete dissolution of this phase. Therefore, CFP was successfully demonstrated to promote an extensive microstructure refinement in multiple aspects, in terms of grain sizes of the α-Mg phase and presence and morphology of the Al-Mn and eutectic β-Mg17Al12. %0 journal article %@ 0043-2288 %A Quan, W.,Wenya, L.,Xiaogang, D.,Shouwei, R.,Jing, Z.,Klusemann, B. %D 2024 %J Welding in the World %N %P 1783–1790 %R doi:10.1007/s40194-024-01707-7 %T Clarify the forming mechanism and afecting factors of defects in semi-stationary shoulder bobbin tool friction stir welding %U https://doi.org/10.1007/s40194-024-01707-7 %X Different defects of the upper stationary shoulder bobbin tool friction stir welding (SSUBTFSW) were identified in this study, and the Coupled Eulerian–Lagrangian model of SSUBTFSW was used to illustrate the forming mechanism of groove defect. Defects can be classified into groove, crack, and flash, which form simultaneously under excessive heat, while only the groove appears under lower heat during processing. There is a layered asymmetrical material flow from lower to upper surfaces, leading to a groove at the edge of the probe on the advancing side of the joint. Increasing rotation speed and decreasing welding speed reduce the groove defect to the point of elimination. The groove defect size goes through minimum value with the increase of the side tilt angle and the reactive forces of the upper stationary shoulder. %0 journal article %@ 1530-793X %A Malaske, L.,Blaga, L.A.,Bergmann, L.,Ahmad, B.,Zhang, X.,Klusemann, B. %D 2024 %J Journal of Composite Materials %N 17 %P 1987–2003 %R doi:10.1177/00219983241254889 %T Feasibility study of friction stir joining of aluminium with carbon fibre reinforced thermoplastic composite %U https://doi.org/10.1177/00219983241254889 17 %X During the last decades, environmental concerns and limited resources have set focus of research on lightweight, mechanically high-performing structures for the transportation industry, in order to reduce fuel consumptions and CO2 emissions. Friction Stir Joining (FSJ), as a variant of the Friction Stir Welding (FSW), is an innovative friction-based joining technique for metal-composite hybrid structures. Joining in the plasticized state below the melting temperature of the metal leads to a comparatively small heat-affected zone, so that only minor metallurgical changes occur. Additionally, only a short processing time and no additional weight in form of fasteners is needed. The main objective of this study is to evaluate the feasibility of metal-composite structures via FSJ, intending to enable a macro-mechanical interlocking bonding mechanism. Main focus was given to the integration of an aluminium nub inserted in a carbon fiber-reinforced polyphenylene sulfide (CF-PPS) sheet, to ensure sufficient plasticization of the aluminium part and no degradation in the polymer part. Residual stress arising from the friction stir joining process was also characterised using the Contour method. In this study, aluminium alloy 6082-T6 and CF-PPS composite sheets were used to produce long lap joints. Results have shown that the joints were created at almost constant peak temperature slightly above the melting temperature of the PPS but no physical-chemical changes were detected in the PPS. In addition, the influence of a PPS film as interlayer between the sheets was investigated in order to explore a method for preventing galvanic corrosion. Preliminary results indicate that it is not possible to integrate a metal nub to the CF-PPS without interrupting the PPS film. However, it is possible to create a nub within the PPS film. %0 journal article %@ 0364-5916 %A Mathew, E.,Chafle, R.,Klusemann, B. %D 2024 %J Calphad %N %P 102692 %R doi:10.1016/j.calphad.2024.102692 %T CALPHAD-based modeling of pressure-dependent Al, Cu and Li unary systems %U https://doi.org/10.1016/j.calphad.2024.102692 %X The study presents a pressure-dependent CALPHAD-based model for assessment of the Al, Cu and Li unary systems, focusing on phase changes under varying pressures. By incorporating the Murnaghan equation of state and ab initio phonon calculations, the thermal properties for stable and metastable phases are accurately predicted. To ensure a comprehensive representation of the system's response to pressure changes; compressibility, volumetric thermal expansion coefficient as a function of temperature, the derivative of bulk modulus with pressure, and molar volume for the condensed phases are integrated in the framework. The model provides essential insights into pressure-induced transformation, aiding in the understanding of solid-state processing, such as high-pressure torsion and extrusion. The results from this work are in excellent agreement with the experimental literature and can be utilized to enhance phase predictions under non-equilibrium conditions. %0 journal article %@ 1960-6206 %A Diyoke, G.,Rath, L.,Chafle, R.,Ben Khalifa, N.,Klusemann, B. %D 2024 %J International Journal of Material Forming %N %P 26 %R doi:10.1007/s12289-024-01825-z %T Numerical simulation of friction extrusion: process characteristics and material deformation due to friction %U https://doi.org/10.1007/s12289-024-01825-z %X This study employs a finite element thermo-mechanical model, using a Lagrangian incremental setting to investigate friction extrusion (FE) under varying process conditions. The incorporation of rotation in FE generates substantial frictional heat, leading to significantly reduced process forces in comparison to conventional extrusion (CE). The model reveals the interplay between temperature, strain, and strain rate across different microstructural zones of the resulting wire. Specifically, the sticking friction condition in FE enhances initial shear deformation, aligning with a homogeneous spatial strain distribution and predicting complete grain refinement in the extruded wire, as per Zener-Hollomon calculations. On the other hand, under the sliding friction condition in FE, the shear deformation is reduced which results in an inhomogeneous microstructure in the extruded wire. The analysis of material flow in the workpiece reveals distinct transitions from the base material to the thermo-mechanically affected zones. The simulated process force, thermal history, and microstructure during sliding friction conditions align well with the findings from performed friction extrusion experiments. %0 journal article %@ 0264-1275 %A Braun, M.,Chen, T.,Shen, J.,Fassmer, H.,Klusemann, B.,Sheikhi, S.,Ehlers, S.,Müller, E.,Sarmast, A.,Schubnell, J. %D 2024 %J Materials & Design %N %P 113122 %R doi:10.1016/j.matdes.2024.113122 %T Fatigue crack initiation and propagation in plain and notched PBF-LB/M, WAAM, and wrought 316L stainless steel specimens %U https://doi.org/10.1016/j.matdes.2024.113122 %X Additively manufactured (AM) components—either made by laser-powder bed fusion or wire and arc additive manufacturing—typically contain process-related defects on and near surfaces that can be removed by machining. Various studies have shown that post-treatment, such as machining significantly improves the fatigue strength of AM parts. To this day, however, hardly any studies have investigated the fatigue strength of post-treated additively manufactured components with notches. In this study, fatigue tests were performed on plain and notched specimens to determine and compare the crack initiation and crack propagation behavior due to different manufacturing-related effects. Tests were performed on specimens produced by the two aforementioned AM processes and compared to specimens taken from wrought sheets. The fatigue strength of AM materials is influenced by microstructure, defects, residual stress, and notches. PBF-LB/M specimens exhibit the highest fatigue strength in plain, notch-free conditions, attributed to differences in microstructure and static strength affecting fatigue crack initiation. Notched specimens show larger differences among materials, with PBF-LB/M having shorter fatigue crack propagation life related to line-type defect clusters, while the plain PBF-LB/M specimens are less affected as their fatigue strength is primarily determined by fatigue crack initiation. %0 journal article %@ 0921-5093 %A Kallien, Z.,Roos, A.,Knothe-Horstmann, C.,Klusemann, B. %D 2023 %J Materials Science and Engineering: A %N %P 144872 %R doi:10.1016/j.msea.2023.144872 %T Temperature-dependent mechanical behavior of aluminum AM structures generated via multi-layer friction surfacing %U https://doi.org/10.1016/j.msea.2023.144872 %X Multi-layer friction surfacing (MLFS) is a solid state layer deposition technology for metals. In order to make use of the potential of MLFS as technology for additive manufacturing, the material properties of MLFS built structures have to be investigated and understood in detail. This study presents a comprehensive analysis of the mechanical properties of MLFS deposited material from micro-flat tensile testing (MFTT) at elevated temperatures. The specimens obtained from the fine-grained MLFS structures show a slightly higher tensile strength at room temperature but lower tensile strength at testing temperatures of 300 °C and above compared to the stud base material. No significant gradient along the MLFS structure could be observed in terms of mechanical properties. The analyses of fracture surfaces and microstructure of tested MFTT specimens provide insights to deformation mechanism of MLFS deposited and consumable stud material. Especially at high testing temperatures of 500 °C, MLFS deposited structure shows abnormal grain growth which results in the observed tensile behavior. %0 journal article %@ 1044-5803 %A Escobar, J.,Gwalani, B.,Silverstein, J.,Ajantiwalay, T.,Roach, C.,Bergmann, L.,dos Santos, J.F.,Maawad, E.,Klusemann, B.,Devaraj, A. %D 2023 %J Materials Characterization %N %P 112999 %R doi:10.1016/j.matchar.2023.112999 %T Rapid grain refinement and compositional homogenization in a cast binary Cu50Ni alloy achieved by friction stir processing %U https://doi.org/10.1016/j.matchar.2023.112999 %X Friction stir processing (FSP) has been increasingly adopted for joining and processing materials in automotive, aerospace, and industrial construction. During FSP, a dynamic competition between high-speed shear deformation and deformation-induced heating brings about a complex competition between multiple dynamic microstructural evolution mechanisms making it difficult to predict the microstructural evolution pathway. Hence, improved understanding of microstructural evolution mechanisms during FSP can be beneficial for continued growth in the adoption of FSP for demanding applications of future. Towards this goal, this study uses a model binary Cu – 50 at.% Ni alloy to clarify the effect of single and double pass FSP on the microstructural evolution of a coarse grained and compositionally heterogeneous cast microstructure. High energy synchrotron X-ray diffraction, electron backscatter diffraction, and nanoindentation are used to clarify the microstructural evolution due to FSP. The process of compositional homogenization of as-cast segregations is studied by energy dispersive spectroscopy and atom probe tomography. Our results show that a single fast FSP pass at 30 mm.s−1 produces a 100 μm deep layer of submicrometric and hall-petch hardened CuNi grains. The initial cast compositional heterogeneities in a micrometric scale is rapidly transformed to nano-sized domains, mainly confined at grain boundaries. Double pass FSP increases the penetration depth of the processed layer and leads to a 2.9 times grain growth relative to single pass FSP. Grain fragmentation, discontinuous dynamic recrystallization, grain growth, and twinning mechanisms are discussed. These results highlight the value of FSP for ultrafast grain refinement and compositional homogenization of cast alloys. %0 journal article %@ 1359-6454 %A Jin, F.,Fu, B.,Shen, J.,Li, J.,Li, W.,dos Santos, J.F.,Klusemann, B. %D 2023 %J Materials Characterization %N %P 112911 %R doi:10.1016/j.matchar.2023.112911 %T Quasi-in-situ observation of microstructure at the friction interface: shear deformation; dynamic recrystallization and mechanical responses during friction welding process %U https://doi.org/10.1016/j.matchar.2023.112911 %X Friction based joining processes are monitored and controlled according to the collectable and measurable mechanical responses, such as torque or temperature, during the process. These are a result of the underlying physical microstructural mechanism during the process, where joints are formed under shear deformation (SD) and/or dynamic recrystallization (DRX). To ensure a first quality assessment of the joints during processing, it is critical to precisely investigate the relation between (macro)-mechanical and microstructural responses (SD and DRX). In the present study, the transition from SD to DRX in friction welding has been focused and quasi in-situ observed by ‘stop - action’ rotary friction welding (RFW) experiments coupled with electron back-scattered diffraction (EBSD) analysis using pipe structures, which clarifies the characteristics of the mechanical response. Further RFW experiments with different parameters were conducted to obtain a suitable relation that correlate the DRX transition temperatures to the welding parameters. Thereafter, further ‘stop - action’ RFW experiments were performed on rod structures to investigate the spatial - temporal distribution of SD - DRX at the friction interface and accordingly the friction torque characteristics. The results show that the transition from SD to DRX takes place at the peak torque (PT) and the temperature inflection point (TIP). The TIP of pipe-structure specimens is the critical DRX temperature during FW, which is dominated by friction linear speed. The PT is the threshold that distinguishes the dominating mechanism, SD or DRX, at the welding interface when welding rod structures. %0 journal article %@ 0924-0136 %A Li, G.,Chen, T.,Fu, B.,Shen, J.,Bergmann, L.,Zhou, L.,Chen, K.,dos Santos, J.F.,Klusemann, B. %D 2023 %J Journal of Materials Processing Technology %N %P 117984 %R doi:10.1016/j.jmatprotec.2023.117984 %T Semi-stationary shoulder bobbin-tool: A new approach in tailoring macrostructure and mechanical properties of bobbin-tool friction stir welds in magnesium alloy %U https://doi.org/10.1016/j.jmatprotec.2023.117984 %X Bobbin tool friction stir welding has high process flexibility and is particularly suitable for closed structures such as hollow extrusions or pipes. More recently, a bobbin tool concept having one rotating and one stationary shoulder has been proposed. The present investigation developed this novel semi-stationary shoulder concept to bobbin tool friction stir welding of magnesium alloy for the first time. The concept was proved to be feasible by decoupling the upper shoulder from the rotation of the bobbin tool. Holding the upper shoulder stationary during welding led to reduced handling forces as well as torque, enabling higher welding speeds up to 1500 mm/min. This speed is 50% larger than the value achieved by the standard tool concept, which makes the semi-stationary shoulder variant more attractive for industrial applications. Furthermore, holding the upper shoulder stationary modified the original symmetrical refilling of the plasticized metal into an asymmetrical pattern. In case of improper welding parameters being employed, the asymmetrical refilling led to transportation of created volumetric defects close to the upper surface from the mid-thickness and thus facilitated visual inspection of the weld. In the proper sets of welding parameters, the joints produced by the semi-stationary shoulder variant experienced lower level of strain localization during tensile testing than those produced by the standard variant. The weakened strain concentration led to an enhancement of the joint elongation from 82% to 95% of that of the base metal. %0 journal article %@ 2075-4701 %A Bossle, E.P.,Vicharapu, B.,Lemos, G.V.B.,Lessa, C.R.D.L.,Bergmann, L.,dos Santos, J.F.,Clarke, T.G.R.,De, A. %D 2023 %J Metals %N 1 %P 146 %R doi:10.3390/met13010146 %T Friction Stir Lap Welding of Inconel 625 and a High Strength Steel %U https://doi.org/10.3390/met13010146 1 %X The joining of dissimilar hard metals such as high-strength steel and nickel-based alloy is required for shipbuilding and offshore applications to enhance the strength, fracture toughness, and corrosion resistance of the exposed parts. However, the joining of these dissimilar alloys has remained a major challenge due to the limited solubility of Fe and Ni in each other, which commonly results in the formation of brittle intermetallic compounds. We present here a novel investigation on the joining of overlapped nickel-based alloy 625 and marine-grade GL E36 steel plates by friction stir lap welding (FSLW). The interface microstructure and its influence on joint strength are rigorously tested. The main bonding mechanism is found to be the mechanical mixing of Fe and Ni along the interface. The interface thermal cycles are computed by a three-dimensional numerical heat transfer model and their effects on the microstructure are examined. Multiple micro tensile specimens are extracted from the stir zone to examine the through-thickness variation in the stir zone properties. The welded joint is characterized further by evaluating the interface microhardness distribution, lap-shear strength, and surface residual stresses. %0 journal article %@ 2238-7854 %A Rodrigues, C.F.,Blaga, L.,Klusemann, B. %D 2023 %J Journal of Materials Research and Technology : JMRT %N %P 4639-4649 %R doi:10.1016/j.jmrt.2023.04.092 %T Friction Riveting of FR4 substrates for printed circuit boards: Influence of process parameters on process temperature development and joint properties %U https://doi.org/10.1016/j.jmrt.2023.04.092 %X This work investigates the influence of Friction Riveting processing conditions on FR4-PCB substrate/AA2024 rivet joints in terms of process temperature evolution, joint formation, and joint physical-chemical and mechanical properties. The joints were manufactured using 4 mm diameter AA-2024-T3 rivets and FR4 laminates of 1.5 mm thickness with single or double copper-clad layers. The evolution of process temperature evolution was recorded on the FR4 substrate surface and correlated with the resulting joint formation. Most joints obtained with double copper clad layers developed process temperatures above 300 ºC, whereas joints produced with a single copper clad presented slightly lower temperatures, but still above 250 ºC. Rivet anchoring was achieved for both FR4 material combinations in the configuration of a single-base laminate, as well as two and even three overlapped laminates. Thermogravimetric analyses revealed that above 300 ºC intensive thermal degradation occurs on FR4 materials (with 30% mass change), followed by decomposition, resulting in non-uniform heat distribution throughout the thickness. The joint ultimate tensile force was higher for double copper-clad layers and the joints achieved within more than one laminate, showing higher anchoring efficiency. %0 journal article %@ 2238-7854 %A Examilioti, T.N.,Li, W.,Kashaev, N.,Ventzke, V.,Klusemann, B.,Alexopoulos, N.D. %D 2023 %J Journal of Materials Research and Technology : JMRT %N %P 895-908 %R doi:10.1016/j.jmrt.2023.02.206 %T On anisotropic tensile mechanical behavior of Al-Cu-Li AA2198 alloy under different ageing conditions %U https://doi.org/10.1016/j.jmrt.2023.02.206 %X The anisotropic mechanical behavior of Al–Cu–Li (AA2198) alloy under different artificial ageing conditions as well as for different thicknesses of the material was examined in the present investigation. Material characterization was performed for three different sheet directions, namely, longitudinal (0°), diagonal (45°) and transverse (90°) to the rolling direction. The results showed that the grain structure did not have significant changes by applying different artificial ageing times. In T3 heat treatment condition, only δ′ (Al3Li) phase was observed, while with increasing the ageing time, the major precipitates were T1 (Al2CuLi) phases. The latter was found to increase in size with artificial aging time. Almost similar yield strength values were observed for all investigated thicknesses, while the higher thickness specimens showed higher elongation at fracture values. Anisotropy was slightly higher at T3 condition, while the lowest anisotropy degree was noticed at the peak-aged condition. The specimens extracted in the diagonal direction showed high variation in mechanical properties, when compared with the respective results at the other two investigated directions, independently from the thickness of the specimens as well as from heat treatment condition. The smaller thickness specimens presented lower elongation at fracture values and for all investigated sheet directions, since they undergo plane stress conditions. Analysis of work hardening behavior showed that Bauschinger effect, which was not observed in T3 condition, became increasingly more prominent with artificial ageing time in all directions investigated. %0 journal article %@ 0268-3768,1433-3015 %A Rath, Lars,Kallien, Zina,Roos, Arne,Santos, Jorge F. dos,Klusemann, Benjamin %D 2023 %J The International Journal of Advanced Manufacturing Technology %N 5-6 %P 2091-2102 %R doi:10.1007/s00170-022-10685-3 %T Anisotropy and mechanical properties of dissimilar Al additive manufactured structures generated by multi-layer friction surfacing %U https://doi.org/10.1007/s00170-022-10685-3 5-6 %X Friction surfacing (FS) is a solid-state layer deposition process for metallic materials at temperatures below their melting point. While the bonding of the deposited layers to the substrate is proven suitable for coating applications, so far the mechanical properties of additively manufactured stacks have not been systematically investigated. In particular, the effect of successive deposited FS layers, i.e., repetitive thermo-mechanical loading, on the interface properties as well as anisotropy and strength of the deposited stack is unknown. For this purpose, the mechanical properties of FS deposited multi-layer stacks from dissimilar aluminum alloys have been investigated, characterizing layer-to-layer as well as layer-to-substrate bonding interfaces via micro-flat tensile testing. Furthermore, directional dependencies in the stack and failure mechanisms are analyzed. The results show a homogeneous, fine-grained microstructure with average grain sizes between 4.2 and 4.6 μ m within the deposited material. The resulting tensile properties with no significant directional dependency present an ultimate tensile strength between 320 and 326 MPa exceeding the strength of the AA5083 H112 consumable base material. No difference was obtained in terms of layer-to-layer or layer-to-substrate interface strength. Furthermore, homogeneous hardness was observed within the deposited structure, which is in the range of AA5083 base material’s hardness of 91 HV. The results indicate that the FS process in conjunction with the material used is suitable for additively generated structures and highlight the potential of this solid-state layer deposition technology. %0 journal article %@ 0142-1123 %A Bernardi, M.,Suhuddin, U.,Fu, B.,Gerber, J.,Bianchi, M.,Ostrovsky, I.,Sievers, B.,Faes, K.,Maawad, E.,Lazzeri, L.,dos Santos, J.,Klusemann, B. %D 2023 %J International Journal of Fatigue %N %P 107539 %R doi:10.1016/j.ijfatigue.2023.107539 %T Fatigue behaviour of multi-spot joints of 2024-T3 aluminium sheets obtained by refill Friction Stir Spot Welding with polysulfide sealant %U https://doi.org/10.1016/j.ijfatigue.2023.107539 %X The aeronautical industry is looking with interest at friction-based welding for many years due to weight-saving capacities, where fusion-based welding problems can be avoided, allowing also the joining of materials considered complicated to weld with other technologies. Refill Friction Stir Spot Welding (refill FSSW) is a solid-state joining process that shows great potential to be a substitute for single-point joining processes like riveting. The main objective of this study is to investigate the mechanical behaviour of multi-spot joints of AA 2024-T3 obtained by refill FSSW with the addition of a sealant commonly used in riveted joints by the aviation industry. A fatigue test campaign was carried out on the joints with and without sealant to evaluate the possible synergy between the refill FSSW and sealant. The fatigue data obtained are statistically analyzed and compared. According to the comprehensive study including macro- and micro-structure, deformation strain field, residual stress distribution as well as the fatigue crack growth behaviour, the underlying history of multi-spot joints fatigue damage is revealed. The overall results prove that producing lap-joints by refill FSSW with sealant improves considerably the fatigue performance. %0 journal article %@ 2772-3690 %A Kallien, Z.,Knothe-Horstmann, C.,Klusemann, B. %D 2023 %J Additive Manufacturing Letters %N %P 100154 %R doi:10.1016/j.addlet.2023.100154 %T Fatigue crack propagation in AA5083 structures additively manufactured via multi-layer friction surfacing %U https://doi.org/10.1016/j.addlet.2023.100154 %X Multi-layer friction surfacing (MLFS) is a layer deposition technique that allows building structures from metals in solid state. As approach for additive manufacturing, the re-heating during subsequent deposition processes is significantly lower compared to fusion-based techniques. Available research work presents promising properties of MLFS structures from aluminum alloys, reporting no significant directional dependency in terms of tensile strength. The present study focuses on the fatigue crack propagation behavior and the role of layer-to-substrate (LTS) as well as layer-to-layer (LTL) interfaces. Compact tension specimens were extracted in different orientations from the MLFS stacks built from AA5083. The crack propagation parallel and perpendicular to the LTL interfaces as well as from the substrate material across LTS interface into the MLFS deposited material was investigated. The results show that LTL interfaces play no significant role for the crack propagation, i.e. specimens with LTL interfaces perpendicular and parallel to the crack presented no significant differences in terms of their fatigue crack propagation behavior. The specimens where the crack propagated from the substrate material across the LTS interface into the MLFS deposited material showed higher fatigue life than the specimens with crack propagation in the MLFS deposited material only. Crack retardation can be observed as long as the crack propagates within the substrate material, which is associated with compressive residual stresses introduced in the substrate during the layer deposition process. %0 journal article %@ 1438-1656 %A Taghipour, A.,Mazaheri, Y.,McDavid, J.,Sheikhi, S.,Braun, M.,Shen, J.,Klusemann, B.,Ehlers, S. %D 2023 %J Advanced Engineering Materials %N 4 %P 2201230 %R doi:10.1002/adem.202201230 %T Strengthening Mechanisms and Strain Hardening Behavior of 316L Stainless Steel Manufactured by Laser-Based Powder Bed Fusion %U https://doi.org/10.1002/adem.202201230 4 %X The microstructure–properties relations and strengthening mechanisms of additively manufactured 316L stainless steel are comprehensively investigated in this work. The orientation dependency and the strain hardening are studied by tensile testing of as-built specimens fabricated by laser-based powder bed fusion (LPBF) in different directions. The results are compared with those obtained for wrought material. The microstructure of the wrought and the LPBF materials are also comprehensively investigated. Equiaxed grains with random orientation and relatively uniform size (≈30 μm) are observed in the wrought material, where the LPBF samples show columnar grains inside as well as fine equiaxed grains in the bottom of the molten pool. A bimodal grain size distribution, higher values of geometrically necessary dislocations density (≈25–32%), and lower fractions of high-angle grain boundaries (≈24–28%) are observed in LPBF 316L. A significant yield strength and considerable ultimate strength improvement without remarkable elongation decrease are obtained for the LPBF tensile specimens, resulting in a high strength-elongation balance (up to 26 122 MPa%). Two-stage strain hardening is depicted in both wrought and LPBF samples. This is successfully predicted with two-stage Hollomon analysis. However, the LPBF samples illustrate lower strain hardening exponents in comparison with the wrought ones. %0 journal article %@ 0924-0136 %A de Castro, C.C.,Shen, J.,dos Santos, J.F.,Klusemann, B. %D 2023 %J Journal of Materials Processing Technology %N %P 118018 %R doi:10.1016/j.jmatprotec.2023.118018 %T Microstructural development of as-cast AM50 during Constrained Friction Processing: grain refinement and influence of process parameters %U https://doi.org/10.1016/j.jmatprotec.2023.118018 %X Mg and its alloys have a wide range of structural applications despite the limitations regarding the workability and low ductility associated with its hexagonal closed-packed structure. The Constrained Friction Processing (CFP) is a novel processing technique, developed based on the Refill Friction Stir Spot Welding process, that has been proposed as an interesting alternative that can help to overcome challenges associated with the processing of Mg and its alloys. This technique is shown to be able to produce homogenous fine-grained rods. Correlation between processing conditions and the evolved microstructure, i.e. texture and grain size, were established for AM50 rods. In the center, the produced rods present a strong B-fiber texture. As the distance from the center changes along the radial direction, there is a progressive outward tilt of the 〈0001〉 because of specific flow conditions during the processing. CFP is shown to be able to produce fine-grained rods with grain sizes comparable with other severe plastic deformation techniques, with advantages like no requirement of additional preheating and short processing times. %0 journal article %@ 2045-2322 %A Amavisca, C.V.,Bergmann, L.,de L.Lessa, C.R.,Schroeder, J.G.,Ramos, F.D.,Lemos, G.V.B.,Reguly, A.,Klusemann, B. %D 2023 %J Scientific Reports %N %P 10669 %R doi:10.1038/s41598-023-37913-4 %T Feasibility of orbital friction stir welding on clad pipes of API X65 steel and Inconel 625 %U https://doi.org/10.1038/s41598-023-37913-4 %X Orbital friction stir welding (FSW) has been applied to clad pipes, which is certainly of interest to the oil and gas industry. In this context, an FSW system capable of performing sound joints in one pass with full tool penetration was developed. Orbital FSW was executed in 6 mm thick API X65 PSL2 steel clad pipes with 3 mm thick Inconel 625 using a polycrystalline cubic boron nitride (pcBN) tool. The metallurgical and mechanical properties of the joints were investigated. Sound joints with axial forces of 45–50 kN, tool rotational speeds of 400–500 rpm, and a welding speed of 2 mm/s were obtained, illustrating that the developed system can perform FSW joints without volumetric defects. %0 journal article %@ 2772-3690 %A Kallien, Z.,Rath, L.,Roos, A.,Klusemann, B. %D 2023 %J Additive Manufacturing Letters %N %P %R doi:10.1016/j.addlet.2023.100184 %T Application of friction surfacing for solid state additive manufacturing of cylindrical shell structures %U https://doi.org/10.1016/j.addlet.2023.100184 %X Solid-state additive manufacturing (AM) via friction stir based processes experiences increased attention as these techniques are feasible for several similar and dissimilar material combinations and induce significantly lower energy input to the subjacent structure than fusion-based approaches as material melting is avoided. Available research concentrates on linear depositions; however, further development of these techniques towards application necessitate more complex deposition paths, e.g. curves and the crossing of edges or previously deposited layers. In this study the solid-state layer deposition process of friction surfacing (FS) is investigated in terms of process behavior and appearance of the resulting deposit when curved deposition paths are applied. With advancing side on the curve's inner edge, material built-up occurs predominantly on this side of the layer, which results in a deposit of inhomogeneous thickness. This phenomenon is related to the FS process characteristic due to the superposition of rotational and travel movement on a curvature, and is more pronounced for curves with small radii. A further challenge exists for closed structures, where the deposition has to cross previously deposited layers. This can be successfully achieved by reducing the travel speed prior to passing the edge to provide sufficient plasticized material thickness below the stud tip. Overall, the study provides an understanding of the FS process behavior and process parameters for curved paths. Furthermore, recommendations for process control and path planning, e.g. for building closed cylindrical shell structures, are deduced. %0 journal article %@ %A Lehmann, J.,Keller, S.,Esterl, F.,Kashaev, N.,Klusemann, B.,Ben Khalifa, N. %D 2023 %J Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity. ICTP 2023. Lecture Notes in Mechanical Engineering %N %P 352-362 %R doi:10.1007/978-3-031-41341-4_37 %T Deep Rolling for Tailoring Residual Stresses of AA2024 Sheet Metals %U https://doi.org/10.1007/978-3-031-41341-4_37 %X Deep Rolling as a well-known mechanical surface treatment process is investigated with the objective to tailor residual stress profiles over the sheet metal thickness. Experiments are performed in a milling portal on AA2024 aluminum alloy with a hydrostatically mounted deep rolling tool. Residual stress measurements are carried out using the hole drilling method. A numerical simulation using the finite element method (FEM) is set up and experimentally validated. One of the most effective parameters to tailor residual stresses is the deep rolling force, which is directly linked to the hydraulic tool pressure. The residual stress profiles can be described by characteristic values such as the magnitude of the maximum compressive residual stress and its penetration depth. Deep rolling modifies residual stresses not only along the material depth but also along other spatial directions. %0 journal article %@ 0263-8223 %A Sioutis, I.,Tserpes, K.,Tsiangou, E.,Boutin, H.,Allegre, F.,Blaga, L. %D 2023 %J Composite Structures %N %P 116754 %R doi:10.1016/j.compstruct.2023.116754 %T Experimental evaluation of Refill friction Stir spot Welds (RFSSW) as crack arrest features in co-consolidated thermoplastic laminates %U https://doi.org/10.1016/j.compstruct.2023.116754 %X In the present study, an experimental campaign was held in order to evaluate the crack stopping capability of Refill Friction Stir Spot Welds (RFSSW) on co-consolidated thermoplastic composite specimens. The specimens were manufactured in a crack lap shear configuration by using a low melt polyaryletherketone matrix reinforced by T700 carbon fibers. Initially, specimens without the crack arrest features were examined as a baseline, followed by the experimental series containing the features. Both quasi-static and fatigue loading conditions were applied, while the propagation of the interlaminar damage was monitored via C-Scanning and optical measurements. The results reveal the ability of the RFSSW to significantly retard the crack propagation in fatigue, however in quasi-static conditions that was not the case, as the load bearing capability of the joint was only slightly improved. %0 journal article %@ 2213-9567 %A Chen, T.,Fu, B.,Shen, J.,Suhuddin, U.F.H.R.,Wiese, B.,Huang, Y.,Wang, M.,dos Santos, J.F.,Bergmann, J.P.,Klusemann, B. %D 2023 %J Journal of Magnesium and Alloys %N %P %R doi:10.1016/j.jma.2023.10.007 %T Application of novel constrained friction processing method to produce fine grained biomedical Mg-Zn-Ca alloy %U https://doi.org/10.1016/j.jma.2023.10.007 %X In order to obtain Mg alloys with fine microstructures and high mechanical performances, a novel friction-based processing method, name as “constrained friction processing (CFP)”, was investigated. Via CFP, defect-free Mg-Zn-Ca rods with greatly refined grains and high mechanical properties were produced. Compared to the previous as-cast microstructure, the grain size was reduced from more than 1 mm to around 4 µm within 3 s by a single process cycle. The compressive yield strength was increased by 350% while the ultimate compressive strength by 53%. According to the established material flow behaviors by “tracer material”, the plastic material was transported by shear deformation. From the base material to the rod, the material experienced three stages, i.e. deformation by the tool, upward flow with additional tilt, followed by upward transportation. The microstructural evolution was revealed by “stop-action” technique. The microstructural development at regions adjacent to the rod is mainly controlled by twinning, dynamic recrystallization (DRX) as well as particle stimulated nucleation, while that within the rod is related to DRX combined with grain growth. %0 journal article %@ 2238-7854 %A Brandes, A.C.,Roos, A.,Klusemann, B.,Martins, J.P.,dos Santos, J.F.,Carvalho, A.L.M. %D 2023 %J Journal of Materials Research and Technology : JMRT %N %P 7593-7605 %R doi:10.1016/j.jmrt.2023.11.178 %T Process parameter assessment on the dissimilar deposition of AA2024-T351 on AA7475-T761 by Friction Surfacing %U https://doi.org/10.1016/j.jmrt.2023.11.178 %X Friction surfacing as a solid-state deposition process allows the joining of materials with different chemical and physical properties at temperatures below their respective melting points. This experimental work focuses on generating sound, defect-free metallurgical joints between single friction surfacing deposits and substrate surfaces from dissimilar Al alloys of the 2xxx and 7xxx series. In this context, the influence of axial force and deposition speed on surface morphology and deposit geometry of the two heat-treatable Al alloys AA7475 as substrate and AA2024 as deposit are investigated. Process parameter variation shows that an increase in axial force from 8 to 12 kN, in conjunction with a deposition speed of 8 mm/s, leads to smooth surface morphology and consistent deposit width along its length. The AA2024 deposits consist of fine-grained microstructure with higher hardness at the top and lower hardness at the deposit-substrate interface. The joining mechanism is by interdiffusion, with a 7.5 μm thick diffusion zone across the dissimilar interface. Three-point bending tests reveal excellent bonding in the lateral surface of the advancing side due to the absence of delamination for all conditions tested. Minor delamination appears predominantly on the retreating side region for process parameter sets with low axial force. Tensile test results reveal that the AA2024 deposit on the AA7475 substrate presents an ultimate tensile strength equivalent to the AA7475-T651 base material and an increase of 37 % in ductility. %0 journal article %@ 1572-8145 %A Sala, S.T.,Bock, F.E.,Pöltl, D.,Klusemann, B.,Huber, N.,Kashaev, N. %D 2023 %J Journal of Intelligent Manufacturing %N %P %R doi:10.1007/s10845-023-02240-y %T Deformation by design: data-driven approach to predict and modify deformation in thin Ti-6Al-4V sheets using laser peen forming %U https://doi.org/10.1007/s10845-023-02240-y %X The precise bending of sheet metal structures is crucial in various industrial and scientific applications, whether to modify deformation in an existing component or to achieve specific shapes. Laser peen forming (LPF) is proven as an innovative forming process for sheet metal applications. LPF involves inducing mechanical shock waves into a specimen that deforms the affected region to a certain desired curvature. The degree of deformation induced after LPF depends on numerous experimental factors such as laser energy, the number of peening sequences, and the thickness of the specimen. Consequently, comprehending the complex dependencies and selecting the appropriate set of LPF process parameters for application as a forming or correction process is crucial. The main objective of the present work is the development of a data-driven approach to predict the deformation obtained from LPF for various process parameters. Artificial neural network (ANN) was trained, validated, and tested based on experimental data. The deformation obtained from LPF is successfully predicted by the trained ANN. A novel process planning approach is developed to demonstrate the usability of ANN predictions to obtain the desired deformation in a treated region. The successful application of this approach is demonstrated on three benchmark cases for thin Ti-6Al-4V sheets, such as deformation in one direction, bi-directional deformation, and modification of an existing deformation in pre-bent specimens via LPF. %0 journal article %@ 0264-1275 %A Roos, A.,Metternich, F.,Kallien, Z.,Baumann, J.,Ehrich, J.,Kipp, M.,Hanke, S.,Biermann, D.,Klusemann, B. %D 2023 %J Materials & Design %N %P 112390 %R doi:10.1016/j.matdes.2023.112390 %T Friction surfacing of aluminum to steel: influence of different substrate surface topographies %U https://doi.org/10.1016/j.matdes.2023.112390 %X In the present study, AA6082 aluminium is deposited onto AISI 4140 steel substrates via friction surfacing (FS). Aiming to understand the influence of substrate surface for the bonding mechanism during the plasticising as well as the deposition phase, three different surface topographies have been manufactured via grinding and machining. Subsequently, FS process parameter dependencies on the deposits have been investigated. The resulting optical appearance, geometry and microstructure of the deposits have been studied. A deeper surface topography was found to facilitate plasticising and therefore FS layer deposition. Defect-free layer-to-substrate (LTS) joints have been generated for all topographies showing a fine-grained recrystallized microstructure as well as flow lines in the AA6082 deposits following closely the substrate surface topography, whereas no metallurgical changes in the AISI4140 substrates have been detected. At the LTS interfaces, a correlation of flow lines to an increased occurrence of high angle grain boundaries is identified. Appearance, geometries and grain size ratios of the AA6082 deposits show a dependency on substrate surface topography. Although complete bonding was achieved in the LTS joints, no distinct diffusion zone or interfacial mixing was observed. Mechanical interlocking on the micro scale was detected only for the samples with ground substrate surfaces. %0 journal article %@ 1617-7061 %A Safi, A.R.,Chafle, R.,Klusemann, B. %D 2023 %J PAMM: Proceedings in Applied Mathematics and Mechanics %N 1 %P e202200238 %R doi:10.1002/pamm.202200238 %T Analysis of a phase-field finite element implementation for precipitation %U https://doi.org/10.1002/pamm.202200238 1 %X Precipitation hardening is an essential mechanism in materials design of age-hardenable aluminium alloys. The occurrence and distribution of nano-sized particles in such alloys can lead to superior material properties. During thermo-mechanical processing, these particles evolve dynamically as function of temperature and applied load. Therefore, sophisticated modelling frameworks are required to study the underlying phenomena of this microstructural evolution in depth. Phase-field method based on the diffuse interface approach has been successfully employed in literature to study particle nucleation and growth, as well as equilibrium particle shapes. Although phase-field models provide reliable results due to the flexible adaption of the free energy, the method is computationally expensive, requiring efficient solution schemes. The finite-element discretization in deal.II can overcome scalability disadvantages and can outperform standard finite-difference codes. In this work, we used adaptive mesh refinement and adaptive time-stepping and investigate how AMR and the use of the same stiffness matrix for a certain amount of time steps affect the performance of the phase-field model. Particle growth simulations are performed to outline the major benefits of the finite element phase-field model. The numerical strategy is shown to be effective regardless of the initial particle shape by considering different particle morphologies. The results illustrate a significant increase in simulation performance with the applied numerical techniques. %0 journal article %@ 1879-3223 %A Schäfer, H.,Blaga, L.A.,Stöver, E.,Klusemann, B. %D 2023 %J Thin-Walled Structures %N %P 111037 %R doi:10.1016/j.tws.2023.111037 %T Refill friction stir spot welding of thermoplastic composites: Case study on Carbon-fiber-reinforced polyphenylene sulfide %U https://doi.org/10.1016/j.tws.2023.111037 %X Refill Friction Stir Spot Welding (refill FSSW) is an innovative solid-state welding technique that has been successfully applied to various combinations of metallic materials. The objective of the present study is to investigate the feasibility of refill FSSW for polymer–polymer structures, with a specific emphasis on carbon-fiber-reinforced polyphenylene sulfide (CF-PPS). The influence of the key joining parameters, i.e. force, plunge depth, rotational speed, and tool diameter, has been analyzed in terms of the resulting joint microstructure, mechanical strength, and failure mechanisms. The lap shear tests revealed two primary failure modes: interfacial shear failure and nugget pull-out. Fracture surfaces exhibited broken fibers. The depth of the joint was found to play a crucial role in determining the failure mode, with interfacial shear failure resulting in higher lap shear strength. Thermal analyses conducted on the produced joints showed no evidence of thermal degradation, which aligns with the temperature measurements during the process, as they remained below the melting temperature of CF-PPS. %0 journal article %@ 1047-4838 %A Kallien, Z.,Hoffmann, M.,Roos, A.,Klusemann, B. %D 2023 %J JOM: The Journal of the Minerals, Metals and Materials Society %N %P 4212-4222 %R doi:https://doi.org/10.1007/s11837-023-06046-4 %T Correlation of microstructure and local mechanical properties along build direction for multi-layer friction surfacing of aluminum alloys %U https://doi.org/https://doi.org/10.1007/s11837-023-06046-4 %X The process variant of friction surfacing (FS) depositing multiple layers on top of each other is known as multi-layer friction surfacing (MLFS). Due to the solid-state nature of the process, re-heating is significantly reduced compared to common fusion-based AM techniques. The work gives a detailed and fundamental insight into the microstructure along the MLFS build direction for two different aluminum alloys and different process parameters. Focusing on the grain size distribution and recrystallization ratio, the stacks show a higher degree of recrystallization and finer grains at the interfaces. The observed grain sizes at the interfaces were 2.0 µm (AA5083) and 1.1 µm (AA2024), and 5.8 µm (AA5083) and 3.1 µm (AA2024) at the layer center. For the non-precipitation-hardenable alloy (AA5083), the local microstructural trend could be related to the hardness distribution along the stacks, i.e., a slightly higher hardness at the layer interfaces (95 HV) compared to the layer center (90 HV). The relationship is more complex for precipitation-hardenable alloys (AA2024), which show a rise in hardness between 40 HV0.2 and 45 HV0.2 along the stack height. The effect of subsequent layer depositions on the microstructure and hardness is discussed and a distinctive grain size distribution along the build direction was shown to be a fundamental characteristic. %0 journal article %@ 1044-5803 %A Suhuddin, U.F.H.,Rath, L.,Halak, R.M.,Klusemann, B. %D 2023 %J Materials Characterization %N %P 113252 %R doi:10.1016/j.matchar.2023.113252 %T Microstructure evolution and texture development during production of homogeneous fine-grained aluminum wire by friction extrusion %U https://doi.org/10.1016/j.matchar.2023.113252 %X This study aims to understand the microstructure evolution and texture development during friction extrusion of aluminum alloys, focusing on AA7075 as exemplary alloy system. Electron backscatter diffraction technique has been employed to obtain crystallographic data from various regions in front of the die and in the wire. It can be deduced that the combination of continuous dynamic recrystallization and geometric dynamic recrystallization mainly govern the formation of a fine-grained structure, however discontinuous dynamic recrystallization may also play a role at high temperature. The global shear deformation during the process was characterized as a simple shear deformation with dominant B / B̅ simple shear texture components. The material flow is mainly driven by the in-plane shear strain and the extrusion-induced shear strain that are determined by die rotational speed and extrusion force, respectively. The in-plane shear strain strongly affects the formation of a homogeneous fine-grained microstructure in the aluminum wire. In this regard, a novel material flow model for friction extrusion has been proposed. %0 journal article %@ 1059-9495 %A Wang, J.,Fu, B.,Bergmann, L.,Liu, F.,Klusemann, B. %D 2023 %J Journal of Materials Engineering and Performance %N 2 %P 577-586 %R doi:10.1007/s11665-022-07109-4 %T Effect of Welding Speed on Friction Stir Welds of PM2000 Alloy %U https://doi.org/10.1007/s11665-022-07109-4 2 %X Friction stir welding (FSW) was investigated for producing joints of alloy PM2000 with welding speeds from 1 to 3 mm/s. The effect of welding speed on the microstructures and mechanical properties of the joints is analyzed in detail. Lower welding speeds result in fully penetrated PM2000 FSWed joints, while higher welding speeds lead to lack of penetration and small defects at the retreating side. The grain size in the stirring zone is not uniform, and abnormal grain growth in the onion rings structure was detected. The PM2000 FSWed joints showed good mechanical properties, i.e., tensile strength of 97% of the base material with even 6.7% higher elongation was obtained. As typical for FSWed ODS joints, the failure was located in the thermo-mechanical affected zone. In this regard, the stirring zone exhibited an impact toughness of up to 300% compared to the base metal owing to the grain refinement, illustrating the superior performance of joints of PM2000 produced by FSW. %0 journal article %@ 2075-4701 %A Pozdnyakov, V.,Keller, S.,Kashaev, N.,Klusemann, B.,Oberrath, J. %D 2022 %J Metals %N 1 %P 107 %R doi:10.3390/met12010107 %T Coupled Modeling Approach for Laser Shock Peening of AA2198-T3: From Plasma and Shock Wave Simulation to Residual Stress Prediction %U https://doi.org/10.3390/met12010107 1 %X Laser shock peening (LSP) is a surface modification technique to improve the mechanical properties of metals and alloys, where physical phenomena are difficult to investigate, due to short time scales and extreme physical values. In this regard, simulations can significantly contribute to understand the underlying physics. In this paper, a coupled simulation approach for LSP is presented. A global model of laser–matter–plasma interaction is applied to determine the plasma pressure, which is used as surface loading in finite element (FE) simulations in order to predict residual stress (RS) profiles in the target material. The coupled model is applied to the LSP of AA2198-T3 with water confinement, 3×3mm2 square focus and 20 ns laser pulse duration. This investigation considers the variation in laser pulse energy (3 J and 5 J) and different protective coatings (none, aluminum and steel foil). A sensitivity analysis is conducted to evaluate the impact of parameter inaccuracies of the global model on the resulting RS. Adjustment of the global model to different laser pulse energies and coating materials allows us to compute the temporal pressure distributions to predict RS with FE simulations, which are in good agreement with the measurements. %0 journal article %@ 0167-6636 %A Charalampidou, C.,Braga, D.,Bergmann, L.,Kourkoulis, S.,da Silva, L.,Infante, V.,dos Santos, J.,Moreira, P.,Alexopoulos, N. %D 2022 %J Mechanics of Materials %N %P 104122 %R doi:10.1016/j.mechmat.2021.104122 %T The effect of prior adhesive bonding on the corrosion behavior of AA2024 FSWed single lap joints %U https://doi.org/10.1016/j.mechmat.2021.104122 %X Friction stir welding (FSW), when in butt-joint configuration, was found to produce high-mechanically performing joints. However, when in overlap configuration, stress concentration is noticed at the weld edges that significantly reduces the mechanical performance of the joints. Additionally, the welding regions tend to enhance localized corrosion attack due to microstructural changes. In the present work, a new hybrid joint - that is a combination of friction stir welding with a prior step of adhesive bonding of the overlap surface - was investigated. Friction stir welded, adhesive bonded and hybrid single lap joints were exposed to exfoliation corrosion solution - for different exposure times - and mechanically tested to investigate the effect of adhesive bonding on the mechanical behavior of pre-corroded joints. The hybrid joint (adhesive bonding + friction stir welding) showed excellent tensile mechanical performance in terms of deformation, exhibiting approximately 100 % increase when compared against the respective values of adhesive bonded and/or friction stir welded joints. This was attributed to the elimination of the ‘hook defect’ in the friction stir welded area as well as to the out-of-plane displacement restriction of the bonded area. The corrosion-induced degradation mechanisms of the hybrid joint were also investigated and compared against the friction stir welded and the adhesive bonded joints for various exposure times. The hybrid joints outperform the friction stir welded and adhesive bonded joints for all the investigated corrosion exposure times; after very long corrosion exposure times (e.g. 48 h), the hybrid joints maintained their maximum tensile strength by almost 90 %, while the adhesive bonded and the friction stir welded joints retained 85 % and 59 %, respectively. Almost double fracture deformation was noticed for the hybrid joints for all the investigated corrosion exposure times. This superiority was attributed to the dual protection of the intermediate adhesive film; initially the sealing effect protects the lap joint at the primary corrosion stages until debonding takes place and additionally protects the friction stir welded area in-between the lapped sheets from localized corrosion on the interface between the thermo-mechanically affected and heat affected zones. %0 journal article %@ 0924-0136 %A Wang, J.,Fu, B.,Shen, J.,Bergmann, L.,Lu, X.,dos Santos, J.,Klusemann, B. %D 2022 %J Journal of Materials Processing Technology %N %P 117679 %R doi:10.1016/j.jmatprotec.2022.117679 %T A multi-scaled process study of dissimilar friction stir welding of Eurofer RAFM steel to PM2000 ODS alloy %U https://doi.org/10.1016/j.jmatprotec.2022.117679 %X Both the reduced activation ferritic/martensitic (RAFM) steel and oxide dispersion strengthened (ODS) alloys have shown high potential applications in the nuclear industry. In this study, Eurofer RAFM steel and PM2000 ODS alloy in butt joint configuration was welded by friction stir welding (FSW), and a multi-scaled process study including procedure analysis, macro-/micro-structure, mechanical properties as well as deformation behavior was conducted. To obtain defect-free welds with equal strength and toughness matching, an intermediate rotation speed of 300 rpm was applied since it results in sufficient material intermixing both within the stirred zone (SZ) and along the SZ boundary. The SZ is composed of quenching martensite from the Eurofer steel and the recrystallized ferrite from PM2000, which shows significantly increased microhardness and excellent resistance to local deformation. As a result, strain localization occurs within the Eurofer steel during tensile testing. Additionally, a unique phenomenon, abnormal grain growth (AGG), was identified within the SZ of the as-welded joint. The underlying mechanism of AGG is related to the reduction of grain boundary pinning due to the dissolution of nanoparticles. The equiaxed ferrite nucleus with a similar orientation, surrounded by low-angle grain boundaries, gradually merge with each other through grain annexation, resulting in the finally coarsened grains. The reported study offers fundamental knowledge of FSW of RAFM steel to ODS alloy dissimilar combinations, promoting the usage of RAFM/ODS hybrid structures in future applications. %0 journal article %@ 1960-6206 %A Halak, R.,Rath, L.,Suhuddin, U.,dos Santos, J.,Klusemann, B. %D 2022 %J International Journal of Material Forming %N 3 %P 24 %R doi:10.1007/s12289-022-01670-y %T Changes in processing characteristics and microstructural evolution during friction extrusion of aluminum %U https://doi.org/10.1007/s12289-022-01670-y 3 %X This study focuses on characterizing the microstructural evolution of the aluminum alloy 7075 in the friction extrusion process under different extrusion forces and die angles. Depending on these conditions, two fundamentally different extrusion types are found, showing significant differences in the process characteristics and microstructural evolution. One of the two extrusion types is associated with high extrusion force and low die angle, leading to fully recrystallized wires with average grain size around 1.2 μm. The microstructural analysis indicates that the microstructure present in the wires is generated in the charge material by the combination of tool geometry, load induced material flow and friction conditions in the initial stages of the friction extrusion process. The identified processing conditions and influencing factors introduce an alternative route for friction extrusion at low extrusion ratios, capable of producing completely refined wires. %0 journal article %@ 0257-8972 %A Kallien, Z.,Klusemann, B. %D 2022 %J Surface and Coatings Technology %N %P 128350 %R doi:10.1016/j.surfcoat.2022.128350 %T Combined experimental-numerical analysis of the temperature evolution and distribution during friction surfacing %U https://doi.org/10.1016/j.surfcoat.2022.128350 %X Friction surfacing (FS) is a solid state coating technology for similar and dissimilar metallic materials. The coating of the substrate with a consumable material is enabled due to frictional heat and plastic deformation and is performed below the materials' melting temperature. In this work, the spatio-temporal temperature field during FS is investigated within the substrate via a combined experimental-numerical approach. The study presents a robust and efficient thermal process model accounting for the contributions of friction and plasticity as heat input. The geometry of the applied heat source is dependent on the deposit geometry and the evolving flash. Extensive spatial temperature measurements for a dissimilar aluminum alloy combination are used in order to identify the required input parameters and to validate the model. The process temperature profiles for varied process parameters, such as axial force, rotational speed and travel speed as well as substrate thickness and backing plate material are systematically investigated, where experimental and numerical results are in good agreement. Deviations are in particular associated with possible experimental scatter and unknowns regarding the exact position of the measurement as well as modeling assumptions in terms of the heat source geometry. Overall, the detailed comparisons illustrate that the developed numerical model is able to obtain the temperature evolution and distribution during FS deposition with acceptable accuracy for a wide range of process conditions. %0 journal article %@ 0264-1275 %A Huang, C.,List, A.,Shen, J.,Fu, B.,Yin, S.,Chen, T.,Klusemann, B.,Gärtner, F.,Klassen, T. %D 2022 %J Materials & Design %N %P 110494 %R doi:10.1016/j.matdesdx..2022.110494 %T Tailoring powder strengths for enhanced quality of cold sprayed Al6061 deposits %U https://doi.org/10.1016/j.matdesdx..2022.110494 %X As verified by literature, heat-treatments of as-atomized Al-alloy powders before cold spraying, result in microstructural homogenization and deposition efficiency increment. So far, a straightforward correlation between powder strength and consequences for the performance in cold spraying and deposit properties is still missing. This work thus provides reliable analyses of powder strengths in as-atomized and annealed states to the calculation of critical velocities and deposit quality parameter η, as well as the associated influences of powder strength on single-particle adhesion and deposit microstructures and properties. By annealing of as-atomized powder, its strength is reduced by about 60%, which allows decreasing the critical velocity for a successful deposition. Experimental results demonstrate that powder strength-based calculation of quality parameter η allows for a more realistic description of microstructural characteristics and deposits properties. The single-particle impact morphologies as well as the detachment features of adhering splats by cavitation tests visualize the respective deposition characteristics and bonding behaviors. The lower critical velocities by annealing contribute to better single splat adhesion, lower porosity, higher electrical conductivity, as well as improved tensile strength of deposits. The direct correlation of powder pre-annealing and strength in combination with cold spraying parameter variation allows defining effective strategies for improving deposit properties. %0 journal article %@ 2045-2322 %A Lemos, G.V.B.,Farina, A.B.,Piaggio, H.,Bergmann, L.,Ferreira, J.Z.,dos Santos, J.F.,Vander Voort, G.,Reguly, A. %D 2022 %J Scientific Reports %N 1 %P 3482 %R doi:10.1038/s41598-022-07473-0 %T Mitigating the susceptibility to intergranular corrosion of alloy 625 by friction-stir welding %U https://doi.org/10.1038/s41598-022-07473-0 1 %X In this work, friction-stir welding (FSW) was employed to alloy 625 grade I (soft annealed) sheets. Therefore, solid-state based welding was undertaken with a tool rotational speed of 200 rpm and a welding speed of 1 mm/s. Microstructural features were analyzed by light optical and scanning electron microscopy (LOM and SEM). Moreover, microhardness measurements were performed. The susceptibility to intergranular corrosion was verified by the double-loop electrochemical potentiokinetic reactivation (DL-EPR) test. Complementary, intergranular corrosion was also evaluated by the ASTM G28 Method A. FSW promoted grain refinement, increased microhardness, and reduction in the degree of sensitization. Finally, the mean corrosion rate observed in the ASTM G28 Method A test was 0.4406 mm/year, which suggests a good weld quality. %0 journal article %@ 0924-0136 %A Sala, S.,Keller, S.,Chupakhin, S.,Pöltl, D.,Klusemann, B.,Kashaev, N. %D 2022 %J Journal of Materials Processing Technology %N %P 117578 %R doi:10.1016/j.jmatprotec.2022.117578 %T Effect of laser peen forming process parameters on bending and surface quality of Ti-6Al-4V sheets %U https://doi.org/10.1016/j.jmatprotec.2022.117578 %X Laser peen forming (LPF) is a metal forming process that utilizes laser-induced mechanical shock waves to form desired shapes or modify bent structures. The present work focuses on the applicability of LPF to Ti-6Al-4V sheets, to identify an optimal LPF process parameter window and achieve desired bending without compromising the surface quality within the peened region. The effect of LPF process parameters, i.e. laser power density, overlap, type of sacrificial overlay, and the number of peening sequences was investigated for specimens with different thicknesses. The laser power density and number of peening sequences were the most influential parameters that affect the bending of the specimens. Using sacrificial overlay has a significant effect on the bending and surface quality of the specimens. Surface quality after LPF was assessed by measuring the roughness in the peened region. In experiments without a sacrificial overlay, a black titanium oxide residue on the peened region was observed and additionally, small micro-cracks were found in the near surface region. Further characterization of the peened region revealed that the average crack length increased with increase in laser power density. Two possible LPF process parameter combinations were identified to obtain bending in the peened region, where LPF with sacrificial overlay resulted in no surface damage. Furthermore, residual stresses were determined at various LPF process parameters by incremental hole-drilling method in the peened region. %0 journal article %@ 0264-1275 %A Soujon, M.,Kallien, Z.,Roos, A.,Zeller-Plumhoff, B.,Klusemann, B. %D 2022 %J Materials & Design %N %P 110786 %R doi:10.1016/j.matdes.2022.110786 %T Fundamental study of multi-track friction surfacing deposits for dissimilar aluminum alloys with application to additive manufacturing %U https://doi.org/10.1016/j.matdes.2022.110786 %X Friction surfacing is an emerging solid-state coating technology based on frictional heat induced plastic deformation at the tip of a consumable metallic stud that allows to deposit layers with a fine-grained recrystallized microstructure at temperatures below the melting point. The generation of sound, defect-free metallurgical joints between multiple adjacent overlapping friction surfacing deposits, also referred to as multi-track friction surfacing, from dissimilar aluminum alloys is the focus of this experimental work. An extensive volumetric defect analysis is carried out for various overlap configurations, including post-processing strategies in order to assess the inter-track bonding integrity using microscopic characterization techniques and micro-computed tomography. The effect of layer arrangement and overlap distance on the volumetric defect formation in both inter-track and layer-to-substrate interface is quantified and discussed. Post-processing via hybrid friction diffusion bonding process demonstrates a significant reduction in defect volume ratio, proving higher material efficiency. The gained knowledge was used to successfully build a multi-track multi-layer friction surfacing stack, demonstrating the suitability of this process for large-scale additive manufacturing components. The subsequent mechanical analysis reveals excellent homogeneous isotropic tensile properties of the additive structure in the range of the base material tensile strength. %0 journal article %@ 2238-7854 %A Examilioti, T.,Papanikos, P.,Kashaev, N.,Klusemann, B.,Alexopoulos, N. %D 2022 %J Journal of Materials Research and Technology : JMRT %N %P 2431-2446 %R doi:10.1016/j.jmrt.2022.05.197 %T Experimental and numerical investigation of laser beam-welded Al–Cu–Li joints using micro-mechanical characteristics %U https://doi.org/10.1016/j.jmrt.2022.05.197 %X The local tensile mechanical properties of laser beam-welded joints of AA2198 alloy with Al-Si filler wire were experimentally investigated. For this purpose, micro-flat tensile specimens were extracted from the fusion zone and the heat-affected zone. The chemical composition of the filler wire affects the local mechanical properties in the fusion zone, showing an approximately 26 % decrease in yield strength from the radiation exposure side to the weld root side. The effect of post-weld heat treatment on the tensile mechanical behavior was additionally investigated for different heat treatment artificial ageing conditions. The maximum yield strength increase was noticed for 48 h of artificial ageing for the weld root side of the fusion zone. Several approximations were proposed to correlate the hardness measurements with the local tensile mechanical properties of the welded joint that allow for a fast assessment of the tensile mechanical behaviour of the welded joint. To evaluate the effect of (i) artificial ageing and (ii) geometrical imperfections of the weld on the mechanical behavior of the welded joint, finite element analyses were performed, using the local mechanical properties as input to the model. It is shown that the local mechanical properties of the fusion zone play a pivotal role on the strain localization and fracture of the welded joint. %0 journal article %@ 2075-4701 %A André, N.M.,Alessio, R.P.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2022 %J Metals %N 12 %P 2080 %R doi:10.3390/met12122080 %T Microscale Damage Evolution and Failure Behavior of Metal–Composite Friction Spot Joints: Modelling and Experimental Analyses %U https://doi.org/10.3390/met12122080 12 %X This study aimed to understand the damage evolution at the interface of AA2024-T3/CF-PPS friction spot joints. For this purpose, the finite element method was applied and the bonding zones of the joints were discretized based on a traction–separation law. It was observed that the damage had initiated at the AZ (adhesion zone) and then propagated as a symmetric linear front from the edges towards the center of the joined area. Nevertheless, as the damage advanced inside the PDZ (plastically deformed zone), its propagation became an asymmetrical linear front that evolved preferably from the free edge of the composite part due to the higher peeling stresses in this region (asymmetrical secondary bending of the structure). Based on the findings of this study, modifications are proposed to the failure theory previously stated for friction spot joints. %0 journal article %@ 0043-2288 %A Bergmann, L.,Batistão, B.,de Alcantara, N.,Gargarella, P.,Klusemann, B. %D 2022 %J Welding in the World %N 9 %P 1747-1756 %R doi:10.1007/s40194-022-01333-1 %T Effect of rotational speed and double-sided welding in friction stir–welded dissimilar joints of aluminum alloy and steel %U https://doi.org/10.1007/s40194-022-01333-1 9 %X The effect of tool rotational speed and double-sided welding in friction stir welding of aluminum alloy AA5083 and GL A36 steel was investigated. Defect-free joints were obtained in single- and double-sided welding using a rotational speed of 300 rpm. The increase in rotational speed or the application of double-sided welding increased the amount of dispersed steel particles in the aluminum stir zone, which stimulated void formation in the joint. In spite of the grain refinement in the stir zone, hardness is similar for all weld zones of the aluminum alloy, increasing significantly just in the steel near the weld interface due to severe work hardening. Besides this, the studied rotational speeds and double-sided welding did not exert any significant influence on the tensile strength of the joints, despite that a symmetric joint configuration with the welding through the full material thickness is guaranteed in the double-sided welding. The formation of intermetallic compound (IMC) layers is observed due to interdiffusion in the aluminum/steel interface. Investigations via scanning electron microscopy and energy-dispersive X-ray spectroscopy reveal that the IMC layer with 300–400 nm thickness is composed of Fe2Al5 or FeAl3 throughout the entire weld interface. %0 journal article %@ 0268-3768 %A Cruz da Silva, Y.,Caminha Andrade, T.,Vieira de Oliveira Júnior, F.,dos Santos, J.,Marcondes, F.,Miranda, H.,Silva, C. %D 2022 %J The International Journal of Advanced Manufacturing Technology %N 3-4 %P 2721-2733 %R doi:10.1007/s00170-022-09283-0 %T Numerical investigation of dissimilar friction stir welding of AISI 304L and 410S stainless steels %U https://doi.org/10.1007/s00170-022-09283-0 3-4 %X Friction stir welding (FSW) has been successfully used to join dissimilar materials with advantages such as incipient chemical mixing and positive recrystallization of the microstructure. However, to understand how welding parameters affect the thermal cycle and the material flow around the tool is essential to produce joints without defects. In this work, a numerical simulation of dissimilar joints of AISI 304L austenitic stainless steel with AISI 410S ferritic stainless steel using the FSW technique was performed. The equations of the model were discretized by the finite volume method (FVM), and the mixture between the materials was modeled by the volume of fluid method (VOF) using the ANSYS-fluent simulator. The results predicted the temperatures during the welding for different conditions and viscosity changes successfully. Furthermore, they predicted a better combination of welding parameters in relation to flash formation. The VOF method predicted the mixture of the materials. Furthermore, the results indicated the location of each material and thus avoided unnecessary experimental tests. %0 journal article %@ 0925-8388 %A Escobar, J.,Gwalni, B.,Olszta, M.,Silverstein, J.,Ajantiwalay, T.,Overman, N.,Fu, W.,Li, Y.,Bergmann, L.,Maawad, E.,Klusemann, B.,dos Santos, J.,Devaraj, A. %D 2022 %J Journal of Alloys and Compounds %N %P 167007 %R doi:10.1016/j.jallcom.2022.167007 %T Heterogenous activation of dynamic recrystallization and twinning during friction stir processing of a Cu-4Nb alloy %U https://doi.org/10.1016/j.jallcom.2022.167007 %X An interplay between high degree of shear deformation and deformation-induced heating occurs during friction stir processing (FSP) of metals. In medium-to-low stacking fault energy Cu alloys, this can lead to a complex spatially heterogenous activation of dynamic recrystallization (DRX) and twinning mechanisms. Within the Cu-Nb system, the presence of Nb is further expected to influence the DRX mechanism of the Cu matrix. However, the microstructural changes induced by the co-deformation of Nb during FSP are still not well understood. Therefore, this study uses a combination of multimodal microstructural characterization, solution thermodynamics-based predictions, and computational crystal plasticity simulation to reveal the various microstructural evolution mechanisms that can occur during FSP of a Cu-4at%Nb binary model alloy. The formation of softer DRX zones, and harder shear localization regions are revealed using electron backscatter diffraction, transmission electron microscopy, atom probe tomography, and crystal plasticity modeling. %0 journal article %@ 0022-5096 %A Raza, S.,Mittnacht, T.,Diyoke, G.,Schneider, D.,Nestler, B.,Klusemann, B. %D 2022 %J Journal of the Mechanics and Physics of Solids %N %P 105059 %R doi:10.1016/j.jmps.2022.105059 %T Modeling of temperature- and strain-driven intermetallic compound evolution in an Al–Mg system via a multiphase-field approach with application to refill friction stir spot welding %U https://doi.org/10.1016/j.jmps.2022.105059 %X The prospect of joining dissimilar materials via solid-state processes presents an opportunity to obtain multi-material structures having a synergy of desirable properties of the joined materials. However, the issue of the formation of intermetallic compounds at the weld interface of dissimilar materials arises with that, depending upon the temperature and pressure conditions as per phase diagram. As the thickness of the intermetallic compounds may determine the mechanical properties of the joint, understanding the driving mechanisms and evolution of these intermetallic compounds in solid-state joining processes, such as refill friction stir spot welding (refill FSSW), is crucial. In this contribution, we account for the effect of different driving forces in a multiphase-field approach and investigate the evolution of the intermetallic compounds driven by chemical and mechanical forces. A finite-element simulation of the refill FSSW is pursued to obtain the peak temperature and strain at different locations of the weld interface. The microstructure simulations obtained via the multiphase-field model give insight into the morphology and kinetics evolution of the intermetallic compounds for both, the absence of strain (purely chemically-driven model) as well as presence of strain (chemo-mechanically-driven model). The consideration of strain proves to result in thicker intermetallic compound layer. Furthermore, the impact of interface energy and initial grain configuration is found to be significant on the overall intermetallic compounds evolution. %0 journal article %@ 2214-8604 %A Sandmann, P.,Keller, S.,Kashaev, N.,Ghouse, S.,Hooper, P.,Klusemann, B.,Davies, C. %D 2022 %J Additive Manufacturing %N %P 103204 %R doi:10.1016/j.addma.2022.103204 %T Influence of laser shock peening on the residual stresses in additively manufactured 316L by Laser Powder Bed Fusion: A combined experimental–numerical study %U https://doi.org/10.1016/j.addma.2022.103204 %X Detrimental subsurface tensile residual stresses occur in laser powder bed fusion (LPBF) due to significant temperature gradients during the process. Besides heat treatments, laser shock peening (LSP) is a promising technology for tailoring residual stress profiles of additively manufactured components. A multi step process simulation is applied aiming at predicting the residual stress state after applying LSP to a cuboid shaped specimen manufactured by LPBF in two different building directions as well as comparing it with a post-build heat treatment. The validity of the numerical simulation is evaluated based on comparisons of residual stresses determined by incremental hole drilling technique within different stages of the multi step process: in the as-build condition, after subsequent heat treatment as well as after applying LSP to the as-build and heat treated specimens, showing overall a good experimental-numerical agreement throughout each of the process stages. Applying a heat treatment to the as-build LPBF sample at 700 °C for 6 h showed not to be effective in eliminating the surface tensile stress entirely, reducing the tensile residual stresses by 40%. However, the application of LSP on LPBF components showed promising results: LSP was able even to convert the detrimental near surface tensile residual stresses in the LPBF component into compressive residual stresses next to the surface, which is known to be beneficial for the fatigue performance. %0 journal article %@ 1526-6125 %A Ferrari, V.R.,Coury, F.G.,Suhuddin, U.F.H.,Alcântara, N.G.,dos Santos, J.F.,Ohashi, R.,Fujimoto, M.,Koga, G.Y. %D 2022 %J Journal of Manufacturing Processes %N %P 298-315 %R doi:10.1016/j.jmapro.2022.10.001 %T Effects of semi-solid structure on interface formation of dissimilar aluminum to galvanized steel welds produced by load-controlled Refill Friction Stir Spot Welding %U https://doi.org/10.1016/j.jmapro.2022.10.001 %X Refill Friction Stir Spot Welding (Refill FSSW) allows welding dissimilar materials providing excellent bonding between both parts. On this work, a multi-scale analysis of load-controlled Refill FSSW was performed to analyze dissimilar AA6016-T4 and Zn-coated DX56D steel joints. These were produced using optimized process parameters and analyzed in both as-welded and bake-hardened conditions. During the process, fusion and subsequent dispersion of Zn favored the formation of a semi-solid structure characterized by an intense microsegregation. Therefore, incipient melting of Zn-rich phase followed by eutectic reaction was observed. The presence of liquid phases along the grain boundaries led to a complex relationship between mechanical properties, microstructure and processing variables. Joints with enhanced mechanical properties were produced by limiting the growth of intermetallic compounds (IMC) at the interface, which coupled with stir zone (SZ) strengthening due to Zn dispersion, led to less pronounceable secondary bending effects. The bake hardening process was also found to have a substantial influence on diffusion-dependent mechanisms and, consequently, on the final performance of the welded joint. The results highlighted a great potential of load-controlled Refill FSSW for producing high-strength dissimilar joints in short cycles, which is desirable for applications in the automotive industry. %0 journal article %@ 2352-3409 %A Dahmene, F.,Yaacoubi, S.,El Mountassir, M.,Porot, G.,Masmoudi, M.,Nennig, P.,Suhuddin, U.,dos Santos, J. %D 2022 %J Data in Brief %N %P 108750 %R doi:10.1016/j.dib.2022.108750 %T Dataset from healthy and defective spot welds in refill friction stir spot welding using acoustic emission %U https://doi.org/10.1016/j.dib.2022.108750 %X The dataset presented in this paper deals with real-time measurements carried out during the welding of 78 spot welds including heathy and defective states. These measurements are composed of acoustic emission signals and welding parameters. Acoustic emission signals were captured by three different piezoelectric sensors, which are connected to a Vallen AMSY5 system through preamplifiers. Welding parameters where digitized using the M-SCOPE software. Both measurements can be used for the establishment of an automatic criterion able to detect defective spot welds in Refill Friction Stir Spot Welding. %0 journal article %@ 0921-5093 %A Su, Y.,Li, W.,Shen, J.,Bergmann, L.,dos Santos, J.F.,Klusemann, B.,Vairis, A. %D 2022 %J Materials Science and Engineering: A %N %P 144227 %R doi:10.1016/j.msea.2022.144227 %T Comparing the fatigue performance of Ti-4Al-0.005B titanium alloy T-joints, welded via different friction stir welding sequences %U https://doi.org/10.1016/j.msea.2022.144227 %X Ti–4Al-0.005B titanium alloy T-joints were produced with two different friction stir welding (FSW) sequences, and its effect on the low-cycle fatigue performance was investigated. Results show that hysteresis loop became a straight line with no significant fatigue damage occurring at low strain amplitudes (0.2% and 0.4%). As the strain amplitude increased to 0.6%, the area enclosed by the hysteresis loop increased for both T-joints and the base material (BM) due to fatigue damage accumulation. As the stress amplitude decreased gradually with increasing number of cycles, the fatigue life followed this decreasing trend. The fatigue life of single-weld T-joints is close to that of the double-weld T-joints, with a cyclic strain hardening index of the BM being in-between of the two T-joints. However, cyclic strength coefficient of BM is the lowest, and that of the double-weld T-joint is larger than that of the single-weld T-joint. The single-weld T-joint breaks at the heat affected zone (HAZ) on the advancing side, where the double-weld T-joint breaks at the HAZ of the second weld. %0 journal article %@ 2238-7854 %A de Castro, C.,Shen, J.,Plaine, A.,Suhuddin, U.,de Alcantara, N.,dos Santos, J.,Klusemann, B. %D 2022 %J Journal of Materials Research and Technology : JMRT %N %P 857-866 %R doi:10.1016/j.jmrt.2022.07.092 %T Tool wear mechanisms and effects on refill friction stir spot welding of AA2198-T8 sheets %U https://doi.org/10.1016/j.jmrt.2022.07.092 %X Refill Friction Stir Spot Welding (refill FSSW) is a method for joining similar and dissimilar lightweight metallic materials or thermoplastic polymers. The technique produces welds that feature suitable mechanical properties with advantages such as the possibility of industrial scalability and automation. Still, some challenges need to be overcome in order to increase the adoption of this technique in industry. Tool wear is a key issue for friction-based processes, since it impacts the process costs and quality of the welds. In this study, a total of 2350 welds of AA2198-T8 sheets were performed and the effect of wear on probe and shoulder was investigated. While the probe did not suffer any considerable wear after this number of welds, the shoulder underwent wear in different areas, with distinct wear mechanisms. Adhesive wear and plastic deformation were determined as the primary damage mechanisms affecting different areas of the shoulder. Mechanical testing of selected welds has shown a trend towards reduction in the lap shear strength (LSS) as a function of tool wear. Macrostructural analysis of welds' geometrical features shows that profile changes at the shoulder due to wear led to a trend of reduction in stirred zone area and, consequently, joints’ LSS. Modifications in the worn shoulder profile were suggested as possible causes for changes in hook height, which was identified as a further determining factor to the observed reduction in LSS. Still, all tested welds surpassed the minimum lap shear strength standard requirements for aeronautical applications. %0 journal article %@ 1526-6125 %A Bock, F.,Herrnring, J.,Froend, M.,Enz, J.,Kashaev, N.,Klusemann, B. %D 2021 %J Journal of Manufacturing Processes %N %P 982-995 %R doi:10.1016/j.jmapro.2021.02.016 %T Experimental and numerical thermo-mechanical analysis of wire-based laser metal deposition of Al-Mg alloys %U https://doi.org/10.1016/j.jmapro.2021.02.016 %X A finite element model is employed to perform a sequentially coupled thermo-mechanical analysis for enabling rapid process simulations of temperature fields, residual stresses and distortions for the production of additively manufactured parts via laser metal deposition. Experimental identification of characteristic process features such as temperature distribution, melt pool dimensions and bead geometries were used for the initial built-up and calibration of the model. The addition of material during process simulation is realised through reactivating inactive elements during the transient heat transfer analysis and through reactivating a combination of inactive and quiet elements during the mechanical analysis. The travelling heat source is geometrically bounded to precisely control the volume of its energy distribution. The results of the transient heat transfer analysis are sequentially coupled to a mechanical analysis for obtaining information on the resulting residual stresses and deformation. Based on the good agreement between numerical and experimental results of the thermal analysis, conclusions on the corresponding residual stress distributions and deformation are made. It is shown that the model represents an efficient tool for process prediction regarding thermal history, residual stresses and final-part deformations. Finally, the model is utilised to identify parameters and conditions of the process that lead to reduced residual stresses and deformations of the investigated additive part. %0 journal article %@ 0263-8223 %A Lambiase, F.,Balle, F.,Blaga, L.,Liu, F.,Amancio-Filho, S. %D 2021 %J Composite Structures %N %P 113828 %R doi:10.1016/j.compstruct.2021.113828 %T Friction-based processes for hybrid multi-material joining %U https://doi.org/10.1016/j.compstruct.2021.113828 %X The adoption of multi-material lightweight structures has been recognized as one of the most effective and promising solutions to improve fuel efficiency and accelerate the electrification of future transportation systems. A wider application of multi-material lightweight structures has been limited by our capability to fabricate them reliably and cost-effectively at a commercial scale. In the last decade, many friction-based joining processes have been developed and demonstrated their advantages over mechanical fastening and adhesive bonding processes in fabricating future multi-material lightweight structures. This article provides a comprehensive review on the recent advances of five promising friction-based joining processes (friction assisted joining, friction lap welding, friction spot joining, friction riveting, and ultrasonic welding) on the aspects of facilities, joining process, joining mechanism, applicable materials, surface pretreatments, and the influence of process parameters on the performance of the produce joints. This article also provides a summary of the performance of the produced joints under static load, dynamic load, various thermal cycles, or harsh chemical environments. The main similarities and differences among the joining processes are discussed. The paper points out the main knowledge gaps that need to be filled and the research that needs to be conducted to further advance the joining process. This review article will place the friction-based joining process at a new starting point with accelerated developing speed towards higher technical maturity to make the processes available for certifiable industrial applications. %0 journal article %@ 1996-1944 %A Bock, F.,Keller, S.,Huber, N.,Klusemann, B. %D 2021 %J Materials %N 8 %P 1883 %R doi:10.3390/ma14081883 %T Hybrid Modelling by Machine Learning Corrections of Analytical Model Predictions towards High-Fidelity Simulation Solutions %U https://doi.org/10.3390/ma14081883 8 %X Within the fields of materials mechanics, the consideration of physical laws in machine learning predictions besides the use of data can enable low prediction errors and robustness as opposed to predictions only based on data. On the one hand, exclusive utilization of fundamental physical relationships might show significant deviations in their predictions compared to reality, due to simplifications and assumptions. On the other hand, using only data and neglecting well-established physical laws can create the need for unreasonably large data sets that are required to exhibit low bias and are usually expensive to collect. However, fundamental but simplified physics in combination with a corrective model that compensates for possible deviations, e.g., to experimental data, can lead to physics-based predictions with low prediction errors, also despite scarce data. In this article, it is demonstrated that a hybrid model approach consisting of a physics-based model that is corrected via an artificial neural network represents an efficient prediction tool as opposed to a purely data-driven model. In particular, a semi-analytical model serves as an efficient low-fidelity model with noticeable prediction errors outside its calibration domain. An artificial neural network is used to correct the semi-analytical solution towards a desired reference solution provided by high-fidelity finite element simulations, while the efficiency of the semi-analytical model is maintained and the applicability range enhanced. We utilize residual stresses that are induced by laser shock peening as a use-case example. In addition, it is shown that non-unique relationships between model inputs and outputs lead to high prediction errors and the identification of salient input features via dimensionality analysis is highly beneficial to achieve low prediction errors. In a generalization task, predictions are also outside the process parameter space of the training region while remaining in the trained range of corrections. The corrective model predictions show substantially smaller errors than purely data-driven model predictions, which illustrates one of the benefits of the hybrid modelling approach. Ultimately, when the amount of samples in the data set is reduced, the generalization of the physics-related corrective model outperforms the purely data-driven model, which also demonstrates efficient applicability of the proposed hybrid modelling approach to problems where data is scarce. %0 journal article %@ 0939-1533 %A Seiler, M.,Keller, S.,Kashaev, N.,Klusemann, B.,Kästner, M. %D 2021 %J Archive of Applied Mechanics %N 8 %P 3709-3723 %R doi:10.1007/s00419-021-01897-2 %T Phase-field modelling for fatigue crack growth under laser shock peening-induced residual stresses %U https://doi.org/10.1007/s00419-021-01897-2 8 %X For the fatigue life of thin-walled components, not only fatigue crack initiation, but also crack growth is decisive. The phase-field method for fracture is a powerful tool to simulate arbitrary crack phenomena. Recently, it has been applied to fatigue fracture. Those models pose an alternative to classical fracture-mechanical approaches for fatigue life estimation. In the first part of this paper, the parameters of a phase-field fatigue model are calibrated and its predictions are compared to results of fatigue crack growth experiments of aluminium sheet material. In the second part, compressive residual stresses are introduced into the components with the help of laser shock peening. It is shown that those residual stresses influence the crack growth rate by retarding and accelerating the crack. In order to study these fatigue mechanisms numerically, a simple strategy to incorporate residual stresses in the phase-field fatigue model is presented and tested with experiments. The study shows that the approach can reproduce the effects of the residual stresses on the crack growth rate. %0 journal article %@ 0924-0136 %A Schwab, K.,Keller, S.,Kashaev, N.,Klusemann, B. %D 2021 %J Journal of Materials Processing Technology %N %P 117154 %R doi:10.1016/j.jmatprotec.2021.117154 %T Tailoring of residual stresses by specific use of defined prestress during laser shock peening %U https://doi.org/10.1016/j.jmatprotec.2021.117154 %X The aim of the present study is to tailor laser shock peening-induced residual stresses by applying defined prestress. For this purpose, elastic prestress is introduced during laser shock peening application and subsequently released. The influence of prestress on the resulting residual stresses is investigated experimentally by a four-point bending device that allows to prestress the specimen during laser shock peening. Furthermore, a semi-analytical model of laser shock peening, extended by a contribution accounting for the prestress, is used to determine the prestress—residual stress relationship. A linear relation between prestress and compressive residual stress is found when the resulting compressive residual stresses are in the range of 20% to 100% of the yield strength. Generally, tensile prestress leads to a higher magnitude and penetration depth of resulting compressive residual stress after laser shock peening. As a proof of concept, prestress was used to alter a non-equibiaxial residual stress profile into an equibiaxial one, demonstrating the applicability of prestress as effective tool for residual stress design. %0 journal article %@ 2176-1523 %A Vicharapu, B.,Lemos, G.,Bergmann, L.,dos Santos, J.,De, A.,Clarke, T. %D 2021 %J Tecnologia em Metalurgia, Materiais e Mineracao %N %P e2455 %R doi:10.4322/2176-1523.20202455 %T Probing underlying mechanisms for pcBN tool decay during friction stir welding of nickel-based alloys %U https://doi.org/10.4322/2176-1523.20202455 %X Friction stir welding (FSW) of nickel-based alloys can provide joints with improved corrosion resistance and mechanical properties that are deteriorated significantly during fusion welding of these alloys. However, rapid wear and poor longevity of tools are major concerns for FSW of nickel-based alloys. Polycrystalline cubic Boron Nitride (pcBN) has emerged as an alternative tool material due to its enhanced strength and stiffness but its use for FSW of nickel-based alloys is rarely explored. An investigation is therefore undertaken to examine FSW of Inconel 625, which is a commonly used nickel-based alloy, by experimental investigation and computational process modelling. The potential failure mechanisms of pcBN tools during FSW of Inconel 625 are examined. The results showed that the thermal softening of the tungstenrhenium binder phase and dissolution of tungsten into Inconel 625 are potential mechanisms to early wear and failure of the pcBN tools for FSW of Inconel 625. %0 journal article %@ 0924-0136 %A Bouali, A.,André, N.,Silva Campos, M.,Serdechnova, M.,Dos Santos, J.,Amancio-Filho, S.,Zheludkevich, M. %D 2021 %J Journal of Materials Processing Technology %N %P 197-210 %R doi:10.1016/j.jmst.2020.06.038 %T Influence of LDH conversion coatings on the adhesion and corrosion protection of friction spot-joined AA2024-T3/CF-PPS %U https://doi.org/10.1016/j.jmst.2020.06.038 %X Layered double hydroxide (LDH) conversion coatings loaded with corrosion inhibitors were suggested for the surface treatment of the aluminum alloy 2024-T3, prior to friction spot joining with carbon-fiber reinforced polyphenylene sulfide (AA2024-T3/CF-PPS). Vanadate was used as a model corrosion inhibitor. Lap shear testing method revealed an increase of 15% of the joint’s adhesion performance when treated with LDH and before exposure to salt spray. The evaluation of the joints after exposure to salt spray demonstrated a significant difference in the corrosion behavior of the joints when the AA2024-T3 is treated with LDH loaded with nitrate and vanadate species. The LDH intercalated with nitrate revealed a clear improvement in the mechanical and corrosion resistance performance of the joints, even after 6 weeks of salt spray. However, the LDH intercalated with vanadate failed in providing protection against corrosion as well as preserving the mechanical properties of the joints. The effect of the galvanic corrosion was further investigated by zero resistance ammeter measurements as well as localized scanning vibrating electrode technique. %0 journal article %@ 0013-7944 %A Keller, S.,Klusemann, B. %D 2021 %J Engineering Fracture Mechanics %N %P 107415 %R doi:10.1016/j.engfracmech.2020.107415 %T Application of stress intensity factor superposition in residual stress fields considering crack closure %U https://doi.org/10.1016/j.engfracmech.2020.107415 %X The correlation between stress intensity factor (SIF) range and fatigue crack growth is a powerful tool for fail–safe design approaches applied to lightweight structures. The key role is the precise calculation of the SIFs of fatigue load cycles. Advanced material processing can shape residual stresses and make the SIF calculation a challenging task. While the consideration of tensile residual stresses is successfully tackled by the SIF superposition, the treatment of compressive residual stresses needs still clarification. This work demonstrates the application of the SIF superposition principle in regions containing high compressive residual stresses leading to crack closure effects. Crack closure depends on the combined load of residual and applied stresses and is interpreted as a change of crack geometry in this work. Thus the relation between the source, i.e. the applied or residual stress, and its consequence, i.e. the corresponding SIFs, depends on the interaction of the sources, i.e. the combined load. Due to this interaction, residual stress–induced changes of the fatigue behaviour cannot be linked to the residual or applied SIF only. This work proposes two alternative definitions of applied and residual SIF, allowing a clear correlation between either the residual or the applied SIF to fatigue behaviour changes. %0 journal article %@ 0142-1123 %A Sun, R.,Keller, S.,Zhu, Y.,Guo, W.,Kashaev, N.,Klusemann, B. %D 2021 %J International Journal of Fatigue %N %P 106081 %R doi:10.1016/j.ijfatigue.2020.106081 %T Experimental-numerical study of laser-shock-peening-induced retardation of fatigue crack propagation in Ti-17 titanium alloy %U https://doi.org/10.1016/j.ijfatigue.2020.106081 %X Residual stresses induced by laser shock peening in Ti-17 titanium specimens were experimentally and numerically investigated to identify the mechanisms and generation conditions of the retardation of fatigue crack propagation (FCP). The retardation was experimentally observed with fatigue life prolonged by 150%. A multi-step simulation strategy for fatigue life prediction is applied, which successfully predicts the experimentally observed FCP behavior. The fractographic observations and numerical simulation indicate that crack closure, as opposed to other microstructural influences, is the dominant effect on retardation. The studies of multi-FCP aspects show that significant retardation occurs in specimens at high values of residual stresses, small peening gap distances, and lower externally applied loads. %0 journal article %@ 0043-2288 %A Landell, R.,de Lima Lessa, C.,Bergmann, L.,dos Santos, J.,Kwietniewski, C.,Klusemann, B. %D 2021 %J Welding in the World %N %P 393-403 %R doi:10.1007/s40194-020-01007-w %T Investigation of friction stir welding process applied to ASTM 572 steel plate cladded with Inconel®625 %U https://doi.org/10.1007/s40194-020-01007-w %X This study investigates friction stir welding (FSW) in the dissimilar joining process of cladded plates. Samples of 4-mm thick ASTM 572 steel plate cladded with 3-mm thick Inconel®625 represent the base material. In order to limit mixing between the dissimilar materials to keep the corrosion resistance, a two-pass welding procedure was applied. Optimal welding parameters for each pass were identified. The welded specimens were evaluated by light microscopy, SEM equipped with EDS, and mechanical tests such as hardness, bending, and tensile testing. Defect-free joints with excellent surface finish have been obtained with a well-defined interfacial region between both materials. The FSW process changed the microstructure of both metals used in this study to a new refined grain region into the weld with complex microstructure inside the ASTM 572 steel, as well as change from a dendritic to an equiaxial microstructure in the Inconel®625. The breaking and the distribution of the intermetallic and secondary phases of the nickel alloy were promoted by the FSW process, moreover the second welding pass on the Inconel® tempered the steel which had previously been welded in the first FSW weld pass. The mechanical properties within the welding zone increased due to this microstructural rearrangement coupled with the Hall-Petch effect. %0 journal article %@ 2194-1289 %A Wen, Q.,Li, W.,Patel, V.,Bergmann, L.,Klusemann, B.,dos Santos, J. %D 2021 %J Acta Metallurgica Sinica (English Letters) %N %P 125-134 %R doi:10.1007/s40195-020-01101-4 %T Assessing the Bonding Interface Characteristics and Mechanical Properties of Bobbin Tool Friction Stir Welded Dissimilar Aluminum Alloy Joints %U https://doi.org/10.1007/s40195-020-01101-4 %X This study focuses on the bonding interface characteristics and mechanical properties of the bobbin tool friction stir welded dissimilar AA6056 and AA2219 aluminum alloy joints using different welding speeds. Voids arise solely in the stir zone at the AA2219 side. A distinct boundary with limited material mixing develops at the middle section of the bonding interface, while excellent material mixing with an irregularly jagged pattern forms at the top and bottom sections of the bonding interface. Increasing the welding speed, the material mixing is rarely changed at the middle section in comparison with the bottom section. Furthermore, a small difference between Guinier–Preston dissolution and Q phase precipitation leads to rare change of hardness in the heat affected zone (HAZ) at the AA6056 side. The increased hardness of the HAZ at the AA2219 side is attributed to avoidance of the dissolution of θ″ phase precipitates. A maximum tensile strength of 181 MPa is obtained at 300 mm min−1. Fractures occur at the AA6056 side near the top and bottom surfaces and at the bonding interface in the middle section of the joints. The regions close to the top and bottom surfaces of the joints show a better ductility. %0 journal article %@ 0079-6425 %A Meng, X.,Huang, Y.,Cao, J.,Shen, J.,Dos Santos, J. %D 2021 %J Progress in Materials Science %N %P 100706 %R doi:10.1016/j.pmatsci.2020.100706 %T Recent progress on control strategies for inherent issues in friction stir welding %U https://doi.org/10.1016/j.pmatsci.2020.100706 %X Friction stir welding (FSW), a mature solid-state joining method, has become a revolutionary welding technique over the past two decades because of its energy efficiency, environmental friendliness and high-quality joints. FSW is highly efficient in the joining of Al alloys, Mg alloys, Ti alloys, polymers and other dissimilar materials. Recently, FSW has gained considerable scientific and technological attention in several fields, including aerospace, railway, renewable energy and automobile. To broaden the adoption of FSW in manufacturing fields, three inherent issues—back support, weld thinning and keyhole defects—must be addressed to ensure the structural integrity, safety and service life of the manufactured products. This review covers the recent progress on the control strategies for these inherent issues, which are basically divided into self-supported FSW, non-weld-thinning FSW and friction stir-based remanufacturing. Herein, the aim is to focus on the corresponding technical development, process parameters, metallurgical features and mechanical properties. Additionally, the challenges and future outlooks are emphasized systematically. %0 journal article %@ 0263-8223 %A Borba, N.,dos Santos, J.,Amancio-Filho, S. %D 2021 %J Composite Structures %N %P 112871 %R doi:10.1016/j.compstruct.2020.112871 %T Hydrothermal aging of friction riveted thermoplastic composite joints for aircraft applications %U https://doi.org/10.1016/j.compstruct.2020.112871 %X In this paper, the sensitivity of carbon fiber reinforced polyether-ether-ketone friction riveted joints to hydrothermal aging was assessed, addressing the degradation mechanisms and post-aged quasi-static mechanical behavior of the joints. The joints were exposed to 71 °C and 95 % relative humidity for 28 days. Despite the oxidation of the metallic nut and washer as well as cavitation and degradation of the composite, a 23 % increase of joint mechanical performance was observed after 28 days of exposure. It is believed that the temperature and water uptake drove matrix post-crystallization at the surface of the fibers, which led to local strengthening of the composite in the rivet surrounding and, consequently, improved the joint residual strength. %0 journal article %@ 1359-6454 %A Herrnring, J.,Sundman, B.,Staron, P.,Klusemann, B. %D 2021 %J Acta Materialia %N %P 117053 %R doi:10.1016/j.actamat.2021.117053 %T Modeling precipitation kinetics for multi-phase and multi-component systems using particle size distributions via a moving grid technique %U https://doi.org/10.1016/j.actamat.2021.117053 %X The collection and coupling of thermodynamic data following the Calphad framework is important for the computational alloy and process design. The microstructure and the precipitation kinetics have a significant influence on the microstructure and mechanical properties of multi-component alloys in solid state; therefore, it is essential to account for solid state phase transformations via thermo-chemical process simulations. In this work an efficient numerical scheme for a Kampmann-Wagner numerical (KWN) model, which takes into account multi-component nucleation and growth theories via the coupling to the open thermodynamic software-package OpenCalphad, is developed and implemented. By the usage of the Calphad approach, it becomes feasible to describe complex multi-component alloy systems. The developed KWN model can take into account effects resulting from the generation or annihilation of vacancies by an off-equilibrium diffusion constant. For the solution of the particle size distribution an efficient and flexible moving grid algorithm is elaborated, which provides a robust and adaptive solution scheme for the simulation of nucleation, growth, coarsening and reversion. The model is applied to simulate the precipitation kinetics of recently published in-situ anomalous small angle X-ray scattering experiments studying reversion of an AA7xxx alloy and the identified model can reproduce the essential characteristics of these reversion experiments over a wide temperature range. %0 journal article %@ 2075-4701 %A Abbaszadeh, M.,Ventzke, V.,Neto, L.,Riekehr, S.,Martina, F.,Kashaev, N.,Hönnige, J.,Williams, S.,Klusemann, B. %D 2021 %J Metals %N 6 %P 877 %R doi:10.3390/met11060877 %T Compression Behaviour of Wire + Arc Additive Manufactured Structures %U https://doi.org/10.3390/met11060877 6 %X Increasing demand for producing large-scale metal components via additive manufacturing requires relatively high building rate processes, such as wire + arc additive manufacturing (WAAM). For the industrial implementation of this technology, a throughout understanding of material behaviour is needed. In the present work, structures of Ti-6Al-4V, AA2319 and S355JR steel fabricated by means of WAAM were investigated and compared with respect to their mechanical and microstructural properties, in particular under compression loading. The microstructure of WAAM specimens is assessed by scanning electron microscopy, electron back-scatter diffraction, and optical microscopy. In Ti-6Al-4V, the results show that the presence of the basal and prismatic crystal planes in normal direction lead to an anisotropic behaviour under compression. Although AA2319 shows initially an isotropic plastic behaviour, the directional porosity distribution leads to an anisotropic behaviour at final stages of the compression tests before failure. In S355JR steel, isotropic mechanical behaviour is observed due to the presence of a relatively homogeneous microstructure. Microhardness is related to grain morphology variations, where higher hardness near the inter-layer grain boundaries for Ti-6Al-4V and AA2319 as well as within the refined regions in S355JR steel is observed. In summary, this study analyzes and compares the behaviour of three different materials fabricated by WAAM under compression loading, an important loading condition in mechanical post-processing techniques of WAAM structures, such as rolling. In this regard, the data can also be utilized for future modelling activities in this direction. %0 journal article %@ 2227-9717 %A Feier, A.,Becheru, A.,Brîndușoiu, M.,Blaga, L. %D 2021 %J Processes %N 8 %P 1376 %R doi:10.3390/pr9081376 %T Process Transferability of Friction Riveting of AA2024-T351/Polyetherimide (PEI) Joints Using Hand-Driven, Low-Cost Drilling Equipment %U https://doi.org/10.3390/pr9081376 8 %X The present work deals with the transferability of Friction Riveting joining technology from laboratory equipment to adapted in-house, low-cost machinery. A G13 drilling machine was modified for the requirements of the selected joining technique, and joints were performed using polyethermide plates and AA2024 aluminum alloy rivets of 6 mm diameter. This diameter was not previously reported for Friction Riveting. The produced joints were mechanically tested under tensile loading (pullout tests) with ultimate tensile forces of 9500 ± 900 N. All tested specimens failed through full-rivet pullout, which is the weakest reported joint in Friction Riveting. In order to understand this behavior, FE models were created and analyzed. The models produced were in agreement with the experimental results, with failure initiated within the polymer under stress concentrations in the polymeric material above the deformed metallic anchor at an ultimate value of the stress of 878 MPa at the surface of the joint. Stresses decreased to less than half of the maximum value around the anchoring zone while the rivet was removed and towards the surface. The paper thus demonstrates the potential ease of applying and reproducing Friction Riveting with simple machinery, while contributing to an understanding of the mechanical behavior (initialization of failure) of joints. %0 journal article %@ 0921-5093 %A Ehrich, J.,Roos, A.,Klusemann, B.,Hanke, S. %D 2021 %J Materials Science and Engineering: A %N %P 141407 %R doi:10.1016/j.msea.2021.141407 %T Influence of Mg content in Al alloys on processing characteristics and dynamically recrystallized microstructure of friction surfacing deposits %U https://doi.org/10.1016/j.msea.2021.141407 %X Friction Surfacing (FS) coatings are deposited by severe plastic deformation at elevated temperatures (≈0.8*Tliquidus), requiring different process parameters for alloys of even small composition variations. For Al alloys it is known that with increasing Mg content the thermal softening rate decreases, i.e. the material retains higher flow strength under thermomechanical processing. Further, the stacking fault energy (SFE) decreases with increasing Mg content, which influences gliding characteristics of dislocations, and also deformation and recrystallization behavior. To elucidate the influence of such known properties on FS process parameters and resulting coatings, three Al alloys differing only in Mg content (0.27, 2 and 3.5 wt.%) were processed by FS in this study.,Pronounced shear flow localization was observed for increasing Mg content, yielding thin and narrow coatings and requiring a reduction of process speeds. Further, the decrease in SFE with increasing Mg content resulted in lower recrystallized grain size and higher grain orientation differences, due to a lower tendency for dislocation annihilation by recovery. %0 journal article %@ 1359-6462 %A Fu, B.,Shen, J.,Suhuddin, U.,Chen, T.,dos Santos, J.,Klusemann, B.,Rethmeier, M. %D 2021 %J Scripta Materialia %N %P 114113 %R doi:10.1016/j.scriptamat.2021.114113 %T Improved mechanical properties of cast Mg alloy welds via texture weakening by differential rotation refill friction stir spot welding %U https://doi.org/10.1016/j.scriptamat.2021.114113 %X Cast magnesium alloys welds produced by refill friction stir spot welding (refill FSSW) show low lap shear strength (LSS) and constantly fail in stirred zone (SZ) shear mode. The cause is most probably related to the heavily textured microstructure. Here, to re-engineer the resulting microstructure, we propose a novel process variant, the differential rotation refill FSSW (DR-refill FSSW). DR-refill FSSW stimulates discontinuous dynamic recrystallization and produces a bimodal microstructure with weakened texture. Therefore, the deformation incompatibility between SZ and thermal-mechanically affected zone is avoided. The welds have 50% higher LSS than that of standard refill FSSW welds, and fail in a different failure mode, i.e., SZ pull-out mode. DR-refill FSSW provides a new and effective strategy for improving the performance of spot welds based on microstructural engineering. %0 journal article %@ 1617-7061 %A Seiler, M.,Keller, S.,Kashaev, N.,Klusemann, B.,Kästner, M. %D 2021 %J PAMM: Proceedings in Applied Mathematics and Mechanics %N 1 %P e202100210 %R doi:10.1002/pamm.202100210 %T Simulation of fatigue crack growth in residual-stress-afflicted specimen with a phase-field model %U https://doi.org/10.1002/pamm.202100210 1 %X Laser shock peening (LSP) is a promising technique to systematically introduce local compressive residual stresses in metal sheets, inhibiting fatigue cracks in these areas. We model fatigue crack growth in these specimen with the help of a phase-field model for fatigue fracture [1]. First, we parametrise the model using untreated aluminium specimens. In a second step, we use the determined parameters to simulate residual-stress-afflicted specimens, qualitatively reproducing the crack inhibition due to LSP. %0 journal article %@ 0925-8388 %A Escobar, J.,Gwalani, B.,Olszta, M.,Silverstein, J.,Overman, N.,Bergmann, L.,dos Santos, J.F.,Staron, P.,Maawad, E.,Klusemann, B.,Mathaudhu, S.,Devaraj, A. %D 2021 %J Journal of Alloys and Compounds %N %P 161351 %R doi:10.1016/j.jallcom.2021.161351 %T Multimodal analysis of spatially heterogeneous microstructural refinement and softening mechanisms in three-pass friction stir processed Al-4Si alloy %U https://doi.org/10.1016/j.jallcom.2021.161351 %X Solid phase processing methods such as friction stir processing (FSP) offer pathways to refine the microstructure of metallic alloys through the combined action of deformation and deformation-induced heating. However, this thermomechanical coupling during FSP also leads to the occurrence of multiple competing microstructural evolution mechanisms which in turn can lead to locally varying mechanical properties, often distributed heterogeneously in the microstructure. This inherent microstructural and mechanical property heterogeneity in alloys subjected to FSP makes it rather challenging to reveal the microstructure-mechanical property relationships systematically. Therefore in this work, we systematically analyze the relationship between microstructural evolution and local microhardness in a model binary Al-4 at.% Si alloy subjected to three-pass friction stir processing. Spatially resolved high-energy synchrotron X-ray diffraction, electron backscattered diffraction, and scanning transmission electron microscopy were used to understand the heterogeneous microstructural evolution due to the FSP. Our results provide insight into how particle-stimulated grain nucleation, recovery, and recrystallization occur heterogeneously in the Al-Si alloy as a function of the distance from the stir zone, directly influencing the degree of softening. The systematic understanding developed by this work can guide future studies on the influence of FSP process parameters on the microstructural evolution mechanisms and its influence on local mechanical properties %0 journal article %@ 0264-1275 %A Fu, B.,Shen, J.,Suhuddin, U.,Pereira, A.,Maawad, E.,dos Santos, J.,Klusemann, B.,Rethmeier, M. %D 2021 %J Materials & Design %N %P 109997 %R doi:10.1016/j.matdes.2021.109997 %T Revealing joining mechanism in refill friction stir spot welding of AZ31 magnesium alloy to galvanized DP600 steel %U https://doi.org/10.1016/j.matdes.2021.109997 %X The application of magnesium (Mg) inevitably involves dissimilar welding with steel. A novel solid state spot welding method, refill friction stir spot welding (refill FSSW), was utilized to weld AZ31 Mg alloy to galvanized DP600 steel. Although Mg/Fe is an immiscible alloy system, defect-free welds with high strength were successfully obtained in a wide parameter window. The results of microstructure, interfacial reactions, and mechanical properties are reported to reveal the underlying joining mechanism. Due to the melting of Zn coating and subsequent Mg-Zn reactions, Mg-Zn eutectic and intermetallic compounds were detected within welds. Heterogeneous interfacial reactions occur along Mg/steel interface, and the relationship between interfacial structure and fracture behavior was investigated. The joining mechanism is associated with Zn coating and Fe-Al layer: 1) the presence of Zn coating is beneficial for achieving high-quality welding between Mg and steel, it protects the interface from oxidation and contributes to brazing of the weld; 2) the Al present in Mg alloy reacts with Fe, resulting in the growth of Fe-Al layer, which contributes to the diffusion bonding in the interface. The overall results clearly show that refill FSSW is a competitive welding method for joining Mg and galvanized steel. %0 journal article %@ 1996-1944 %A Janga, V.S.R.,Awang, M.,Yamin, M.F.,Suhuddin, U.F.H.,Klusemann, B.,Dos Santos, J.F. %D 2021 %J Materials %N 23 %P 7485 %R doi:10.3390/ma14237485 %T Experimental and Numerical Analysis of Refill Friction Stir Spot Welding of Thin AA7075-T6 Sheets %U https://doi.org/10.3390/ma14237485 23 %X The refill friction stir spot welding (refill FSSW) process is a solid-state joining process to produce welds without a keyhole in spot joint configuration. This study presents a thermo-mechanical model of refill FSSW, validated on experimental thermal cycles for thin aluminium sheets of AA7075-T6. The temperatures in the weld centre and outside the welding zone at selected points were recorded using K-type thermocouples for more accurate validation of the thermo-mechanical model. A thermo-mechanical three-dimensional refill FSSW model was built using DEFORM-3D. The temperature results from the refill FSSW numerical model are in good agreement with the experimental results. Three-dimensional material flow during plunging and refilling stages is analysed in detail and compared to experimental microstructure and hardness results. The simulation results obtained from the refill FSSW model correspond well with the experimental results. The developed 3D numerical model is able to predict the thermal cycles, material flow, strain, and strain rates which are key factors for the identification and characterization of zones as well for determining joint quality. %0 journal article %@ 2238-7854 %A Gera, D.,Fu, B.,Suhuddin, U.,Plaine, A.,Alcantara, N.,dos Santos, J.,Klusemann, B. %D 2021 %J Journal of Materials Research and Technology : JMRT %N %P 2272-2286 %R doi:10.1016/j.jmrt.2021.06.017 %T Microstructure, mechanical and functional properties of refill friction stir spot welds on multilayered aluminum foils for battery application %U https://doi.org/10.1016/j.jmrt.2021.06.017 %X The production of batteries often involves the joining of multilayered foils to a conductive tab. In the present study, a solid state spot welding method, the refill friction stir spot welding (refill FSSW), was employed for welding multilayered commercially pure aluminum (CP–Al) foils to 2024-T3 Al alloy sheets (tab). Defect-free welds with high lap shear strength (LSS) are obtained. In the stirred zone (SZ), 2024 Al alloy is only found within the shoulder refill region, which is greatly refined due to dynamic recrystallization. Unlike overlap joints in thicker sheets, a thermo-mechanically affected zone also forms above the SZ in the probe refill region. “Stop-action” experiments have been conducted to describe joint formation. The presence of the 2024 Al alloy tabs resulted in significant changes to material follow behavior and the formation of microstructural zones not previously observed in conventional refill FSSW overlap welds in thicker sheets. Most welds failed in SZ pull-out mode during LSS test. The cracks initiate at the interface between the upper sheet and the first layer of the multilayered foils and then propagate upward and circumferentially outside the SZ. Welds of multilayered Al foils produced by refill FSSW show low contact resistance. The decomposition of electrochemically active materials in batteries can be avoided by maintaining a minimum distance from the spot-weld. The produced welds with flat appearance, high mechanical properties, and potential to meet industry requirements imply that refill FSSW is a promising welding technique for battery production. %0 journal article %@ 0921-5093 %A Su, Y.,Li, W.,Shen, J.,Fu, B.,dos Santos, J.,Klusemann, B.,Vairis, A. %D 2021 %J Materials Science and Engineering: A %N %P 141698 %R doi:10.1016/j.msea.2021.141698 %T Comparing the local-global deformation mechanism in different friction stir welding sequences of Ti-4Al-0.005B titanium alloy T-joints %U https://doi.org/10.1016/j.msea.2021.141698 %X Titanium alloy T-joints were produced using two different friction stir welding (FSW) sequences, and the local-global deformation mechanisms until fracture were compared. Due to their differing FSW sequence characteristics, the optimal parameter ranges for the two T-joints are different. The stir zone (SZ) of the single-weld T-joint consists of lamellar α grains, while fine equiaxed α grains develop in the double-weld T-joint due to the selection of low heat input. Due to the different local microstructure zones in the joint, deformation inhomogeneity of the T-joint during tensile testing is observed. Independent of the welding sequence and for optimal process conditions, both T-joint configuration show nearly the same maximum tensile strength as the base material (BM), however at a relatively low fracture strain, below 20% of the BM. The local strain hardening rate in different zones of the T-joint was investigated. The strain hardening ability of SZ with fine grains is significantly higher than elsewhere, because the grain size contributes greatly to strain hardening behavior at low strain levels. The single-weld T-joint experienced a symmetric local strain distribution between advancing and retreating side. For the double-weld T-joint, there are significant differences between the first and the second weld area. The fracture morphologies of both T-joints are typical ductile, where the toughness of the single-weld joint is higher than that of the double-weld joint. %0 journal article %@ 2238-7854 %A Chiuzuli, F.,Batistão, B.,Bergmann, L.,Alcantara, N.,dos Santos, J.,Klusemann, B.,Gargarella, P. %D 2021 %J Journal of Materials Research and Technology : JMRT %N %P 5297-5306 %R doi:10.1016/j.jmrt.2021.10.115 %T Effect of the Gap Width in AZ31 Magnesium Alloy Joints Obtained by Friction Stir Welding %U https://doi.org/10.1016/j.jmrt.2021.10.115 %X Thin AZ31 magnesium alloy sheets, i.e., 2 mm thick, are welded by Friction Stir Welding (FSW) in butt joint configuration using gap width up to 1.15 mm. All welds present good surface finishing and no internal defects, except for the weld produced using the maximum gap width. A reduction of the weld thickness within the Stir Zone is seen with the increase in gap width, leading to a maximum thickness reduction of 8.5%. Microstructure and Vickers hardness investigations reveal no influence of the gap width on these properties. Up to a gap width of 0.51 mm, a slight decrease in the Ultimate Tensile Strength (UTS) is observed with increasing gap width. For larger gap widths, the UTS, as well as the fracture strain, are constant. To keep the metallurgical integrity, a maximum gap width of 1 mm seems acceptable for joints of thin AZ31 magnesium alloy sheets produced by FSW. %0 journal article %@ 1044-5803 %A Examilioti, T.,Kashaev, N.,Ventzke, V.,Klusemann, B.,Alexopoulos, N. %D 2021 %J Materials Characterization %N %P 111257 %R doi:10.1016/j.matchar.2021.111257 %T Effect of filler wire and post weld heat treatment on the mechanical properties of laser beam-welded AA2198 %U https://doi.org/10.1016/j.matchar.2021.111257 %X The mechanical behavior of autogenously and non-autogenously laser beam-welded joints of Al-Cu-Li alloy AA2198 and the effect of post weld heat treatment are examined in this contribution. The deformation texture of the base material does not present any significant change in the macrotexture with applying different artificial ageing times. Autogenously and non-autogenously laser beam-welded joints present a decrease in yield stress and ultimate strength in the as-welded condition, approximately 45% and 36–38%, respectively, when compared with AA2198-Τ3 base material. The addition of the AA4047 filler wire increases the Si and Cu content in the grain interior and in the grain boundaries of the fusion zone of the welded joint. Micro-hardness measurements for autogenously laser-welded joints showed a decrease in hardness by 27% for the fusion zone and 42% for the heat-affected zone, when compared with the non-autogenously laser beam-welded joints. Α quality index was exploited to evaluate the tensile mechanical performance of the welded joints. It is observed that the non-autogenously welded joints always show a higher ‘quality’ than the respective autogenously welded joints and the highest quality index in terms of mechanical performance is achieved for the as-welded and the peak-aged conditions, respectively. Regardless of the post weld heat treatment condition, both autogenously and non-autogenously laser-welded specimens fractured in between the equiaxed and fusion zone during tensile loading. %0 journal article %@ 8756-758X %A Kashaev, N.,Ushmaev, D.,Ventzke, V.,Klusemann, B.,Fomin, F. %D 2020 %J Fatigue and Fracture of Engineering Materials and Structures %N 7 %P 1500-1513 %R doi:10.1111/ffe.13226 %T On the application of laser shock peening for retardation of surface fatigue cracks in laser beam‐welded AA6056 %U https://doi.org/10.1111/ffe.13226 7 %X The present study aims to investigate the extent to which the fatigue behaviour of laser beam‐welded AA6056‐T6 butt joints with an already existing crack can be improved through the application of laser shock peening. Ultrasonic testing was utilized for in situ (nondestructive) measurement of fatigue crack growth during the fatigue test. This procedure allowed the preparation of welded specimens with surface fatigue cracks with a depth of approximately 1.2 mm. The precracked specimens showed a 20% reduction in the fatigue limit compared with specimens without cracks in the as‐welded condition. Through the application of laser shock peening on the surfaces of the precracked specimens, it was possible to recover the fatigue life to the level of the specimens tested in the as‐welded condition. The results of this study show that laser shock peening is a very promising technique to recover the fatigue life of welded joints with surface cracks, which can be detected by nondestructive testing. %0 journal article %@ 0927-0256 %A Herrnring, J.,Sundman, B.,Klusemann, B. %D 2020 %J Computational Materials Science %N %P 109236 %R doi:10.1016/j.commatsci.2019.109236 %T Diffusion-driven microstructure evolution in OpenCalphad %U https://doi.org/10.1016/j.commatsci.2019.109236 %X The diffusion process in multicomponent alloys has a significant influence on the evolution of the microstructure. The Calphad approach is a powerful method for describing the equilibrium state as well as the kinetics of non-equilibrium systems via the Gibbs energy. In this work, the principles of multicomponent diffusion theory are considered intensively, and an equation for the fluxes in the case of substitutional-interstitial diffusion is given for implementation. Additionally, the calculation of mobility matrices and thermodynamic factors is addressed. As an application case, substitutional diffusion is implemented in OpenCalphad and is used for calculating the growth rate for spherical precipitates from a supersaturated aluminum matrix. The growth rate has been integrated into the Kampmann–Wagner numerical model, which describes nucleation, growth, and coarsening for spherical precipitates. A AlMgZnCu alloy is considered, which has great significance in the field of materials processing. %0 journal article %@ 0264-1275 %A Borba, N.Z.,Körbelin, J.,Fiedler, B.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2020 %J Materials and Design %N %P 108369 %R doi:10.1016/j.matdes.2019.108369 %T Low-velocity impact response of friction riveted joints for aircraft application %U https://doi.org/10.1016/j.matdes.2019.108369 %X In this paper, the sensitivity of carbon fiber reinforced polyether-ether-ketone (CF-PEEK) friction riveted joints to impact damage was assessed as well as the damage propagation during fatigue and quasi-static mechanical testing. The joints were impacted with energies between 5 J and 30 J at room temperature and the impact damage was evaluated through microscopy and ultrasonic C-scan. Two damage types were identified: barely-visible impact damage with mainly shear-driven damage in the first plies of the composite and visible impact damage with delamination and premature failure of the rivet-composite interface owing to peel stresses upon the impact event. The joint strength and fatigue life were not compromised by the barely-visible impact damage, while a 40% decrease of quasi-static strength and lower fatigue resistance were achieved for visible impact damage. Despite altered fatigue behavior of impacted joints, damage accumulated towards fatigue was not critical to the joint mechanical integrity, confirmed by the residual strength of up to 96% after 1000000 cycles for 20 J impacts. %0 journal article %@ 1475-1305 %A Sandmann, P.,Nielsen, M.,Keller, S.,Maawad, E.,Staron, P.,Klusemann, B. %D 2020 %J Strain : the journal of the British Society for Strain Measurement %N 4 %P e12338 %R doi:10.1111/str.12338 %T Combined experimental–numerical study on residual stresses induced by a single impact as elementary process of mechanical peening %U https://doi.org/10.1111/str.12338 4 %X Peening processes can be used as a fatigue enhancement treatment for metallic structures by locally introducing compressive residual stresses. A combined experimental–numerical study on a single‐impact process with a drop tower on the aluminium alloy AA5754, representing the elementary process of mechanical peening, has been performed to investigate different impact parameters on the residual stress profile. Residual stresses have been measured using high‐energy X‐Ray diffraction. A three‐dimensional finite element model is used to predict the residual stresses numerically. The elastic strain components from the numerical results are used to calculate residual stresses by assuming either a plane stress or a plane strain state for different specimen thickness to assess the validity of respective assumption. The validity of the numerical simulation is evaluated based on comparisons of the elastic strain profiles and the percentage loss in kinetic energy of the steel ball due to the impact for four different energies, showing overall a good agreement in the experimental–numerical comparisons. %0 journal article %@ 0013-7944 %A Scheider, I.,Barbini, A.,dos Santos, J. %D 2020 %J Engineering Fracture Mechanics %N %P 107010 %R doi:10.1016/j.engfracmech.2020.107010 %T Numerical residual strength prediction of stationary shoulder friction stir welding structures %U https://doi.org/10.1016/j.engfracmech.2020.107010 %X The residual strength of a structure made of dissimilar Aluminium panels joined by a stationary shoulder friction stir welding (SSFSW) process is predicted by numerical simulation using finite elements including cohesive elements for crack propagation. The yield strength and strain hardening parameters within the stirred zone and adjacent thermo-mechanically affected and heat affected zones are derived from a tensile specimen cut out from the panel perpendicular to the weld seam. The identification is conducted by a hybrid numerical/experimental procedure with an inverse search by help of digital image correlation in order to obtain the strain field at the welded surface and to compare them to the numerical calculation. The crack propagation parameters are retrieved from specimens with crack in the stir zone and heat affected zone on either side. After this identification procedure, the fracture behaviour of a coupon specimen with a crack crossing the weld is predicted. %0 journal article %@ 2075-4701 %A Sikhamov, R.,Fomin, F.,Klusemann, B.,Kashaev, N. %D 2020 %J Metals %N 4 %P 495 %R doi:10.3390/met10040495 %T The Influence of Laser Shock Peening on Fatigue Properties of AA2024-T3 Alloy with a Fastener Hole %U https://doi.org/10.3390/met10040495 4 %X The objective of the present study was to estimate the influence of laser shock peening on the fatigue properties of AA2024-T3 specimens with a fastener hole and to investigate the possibility to heal the initial cracks in such specimens. Fatigue cracks of different lengths were introduced in the specimens with a fastener hole before applying laser shock peening. Deep compressive residual stresses, characterized by the hole drilling method, were generated into the specimens by applying laser shock peening on both sides. Subsequently, the specimens were subjected to fatigue tests. The results show that laser shock peening has a positive effect regarding the fatigue life improvement in the specimens with a fastener hole. In addition, laser shock peening leads to a healing effect on fatigue cracks. The efficiency of this effect depends on the initial crack length. The effect of laser shock peening on the fatigue life periods was determined by using resonant frequency graphs. %0 journal article %@ 0268-3768 %A Ferreira, A.,Campanelli, L.,Suhuddin, U.,Alcantara, N.,dos Santos, J. %D 2020 %J The International Journal of Advanced Manufacturing Technology %N %P 3523-3531 %R doi:10.1007/s00170-019-04819-3 %T Investigation of internal defects and premature fracture of dissimilar refill friction stir spot welds of AA5754 and AA6061 %U https://doi.org/10.1007/s00170-019-04819-3 %X The occurrence of internal defects in welded samples of AA5754-AA6061 produced by refill friction stir spot welding was investigated. A design of experiments using Box-Behnken method followed by a statistical examination using analysis of variance (ANOVA) and response surface modeling were utilized as analysis tools, which proved to be a reliable optimization methodology. This optimization successfully produced sound joints with high lap-shear strength. The statistical analysis showed a large influence of linear plunge depth, quadratic rotational speed, and two-way interaction of feeding rate and rotational speed on lap-shear strength of the welds. A quadratic hypersurface model for predicting weld performance was successfully generated. The subsequent investigation was performed by changing welding parameters, one factor at a time (OFAT), which confirmed the high dependence of lap-shear strength on rotational speed by producing an undesirable outlier. Metallographical analysis on the outlier sample pointed out the occurrence of voids and refilling defects, associated in large scale to low friction heat input. The outlier sample also produced a wing-shaped structure that possibly obstructed the flow of softened material toward void closure. The existence of those defects shows evidence of premature crack in the outlier sample. A subtle adjustment in rotational speed to1000 rpm proved to be sufficient to eliminate the defects and produce stronger welds. Although the problem of refilling defects could be solved, the mechanical properties in the weld were worsened compared to that of base material. %0 journal article %@ 1996-1944 %A Goushegir, S.,Scharnagl, N.,dos Santos, J.,Amancio-Filho, S. %D 2020 %J Materials %N 5 %P 1144 %R doi:10.3390/ma13051144 %T Durability of Metal-Composite Friction Spot Joints under Environmental Conditions %U https://doi.org/10.3390/ma13051144 5 %X The current paper investigates the durability of the single-lap shear aluminum-composite friction spot joints and their behavior under harsh accelerated aging as well as natural weathering conditions. Four aluminum surface pre-treatments were selected to be performed on the joints based on previous investigations; these were sandblasting (SB), conversion coating (CC), phosphoric acid anodizing (PAA), and PAA with a subsequent application of primer (PAA-P). Most of the pre-treated specimens retained approximately 90% of their initial as-joined strength after accelerated aging experiments. In the case of the PAA pre-treatment, the joint showed a lower retained strength of about 60%. This was explained based on the penetration of humidity into the fine pores of the PAA pre-treated aluminum, reducing the adhesion between the aluminum and composite. Moreover, friction spot joints produced with three selected surface pre-treatments were held under outside natural weathering conditions for one year. PAA-P surface pre-treated specimens demonstrated the best performance with a retained strength of more than 80% after one year. It is believed that tight adhesion and chemical bonding reduced the penetration of humidity at the interface between the joining parts. View Full-Text %0 journal article %@ 0921-5093 %A Froend, M.,Ventzke, V.,Dorn, F.,Kashaev, N.,Klusemann, B.,Enz, J. %D 2020 %J Materials Science and Engineering A %N %P 138635 %R doi:10.1016/j.msea.2019.138635 %T Microstructure by design: An approach of grain refinement and isotropy improvement in multi-layer wire-based laser metal deposition %U https://doi.org/10.1016/j.msea.2019.138635 %X The additive production of metallic components with high-throughput is usually associated with high process temperatures and slow cooling rates. This typically results in strongly oriented columnar grain growth along the building direction of the structure having exceedingly large grain sizes. As a result, such structures show typically low strength and anisotropic mechanical behaviour in as-deposited condition. Consequently, post-processing is commonly performed to homogenize and eventually increase the mechanical properties of the deposited structures. In this regard, precise control of the applied process energy allows a modification of the local temperature distribution and cooling conditions during the additive manufacturing process, which strongly influence the resulting solidification microstructure. The aim of the present study is the development of an approach that allows to influence the solidification conditions in wire-based laser metal deposition of an Al-Mg alloy through specific adjustments of the laser irradiation. It was found that significantly different solidification microstructures in as-deposited condition can be achieved by adjusting the laser beam irradiance within a range resulting in conduction mode welding conditions while keeping the heat input constant. The application of high laser beam irradiances, close to the transition to keyhole mode welding, results in structures with a homogeneous large-grained solidification microstructure exhibiting a degree of anisotropy of around 12% between building direction and the direction of deposition. In contrast, the use of low laser beam irradiance close to the lower limit of stable melting, results in structures with a significantly refined microstructure. Consequently, an increase of yield strength of up to around 20% and microhardness of up to 13%, as compared to structures processed with high laser beam irradiance, could be obtained. Moreover, the anisotropy of the as-deposited structure was reduced to a degree lower than 2%. %0 journal article %@ 0263-8223 %A Borba, N.,Kötter, B.,Fiedler, B.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2020 %J Composite Structures %N %P 111542 %R doi:10.1016/j.compstruct.2019.111542 %T Mechanical integrity of friction-riveted joints for aircraft applications %U https://doi.org/10.1016/j.compstruct.2019.111542 %X The predictability of damage evolution is a challenge for mechanical joints of composite structures due to the highly nonlinear material behavior. In this study, friction riveting was investigated as an alternative joining technology for composite laminates by analyzing experimentally the joint mechanical behavior under different loading scenarios. The failure and fracture micro-mechanisms of composite laminate single lap joints were studied under quasi-static and cyclic loading. The joints failed mainly by rivet detachment from the composite hole, followed by adhesive/cohesive failure of the squeezed material, and rivet pull-through failure. Despite lower quasi-static strength of friction-riveted joints (6.2 ± 0.3 kN) compared to reference bolted joints (8.7 ± 0.2 kN), their fatigue life was higher by 88%. The main improving contributions were: the squeezed material, working as an adhesive between the composite parts and an additional fracture micro-mechanism, and the absence of clearance at the rivet-composite interface, which promoted an improved load transfer between the joined parts. %0 journal article %@ 0257-8972 %A Kallien, Z.,Rath, L.,Roos, A.,Klusemann, B. %D 2020 %J Surface and Coatings Technology %N %P 126040 %R doi:10.1016/j.surfcoat.2020.126040 %T Experimentally established correlation of friction surfacing process temperature and deposit geometry %U https://doi.org/10.1016/j.surfcoat.2020.126040 %X Friction surfacing (FS), a solid-state joining process, is a coating technology for metallic materials. Friction and plastic deformation enable the deposition of a consumable material on a substrate below the melting temperature. Process temperatures are an important factor determining the quality and geometry of the deposit. A detailed experimental study of the process temperatures during FS of dissimilar aluminum alloys is performed. The process temperature profiles for varied process parameters, i.e. axial force, rotational speed and travel speed as well as process environment, are investigated. The results show that axial process force and rotational speed are the dominant process parameters affecting the temperatures during the FS process. Additionally, backing material and substrate thickness have significant impact on the process temperatures. The correlation of deposit geometry with process temperature shows thinner and slightly wider deposits for increasing process temperatures. This finding pronounces the importance of the temperature for the friction surfacing process with regard to geometry of the resulting deposit. %0 journal article %@ 0268-3768 %A Examilioti, T.,Kashaev, N.,Enz, J.,Klusemann, B.,Alexopoulos, N. %D 2020 %J The International Journal of Advanced Manufacturing Technology %N %P 2079-2092 %R doi:10.1007/s00170-020-05893-8 %T On the influence of laser beam welding parameters for autogenous AA2198 welded joints %U https://doi.org/10.1007/s00170-020-05893-8 %X The effects of different autogenous laser beam welding process parameters on the fusion zone (FZ) geometry, microstructure, and tensile mechanical properties were investigated for 5-mm-thick AA2198 alloy sheets. Porosity formation and hot cracking are observed for low laser powers and welding velocities, while the porosity level is essentially reduced with increasing laser power. The characteristic cross-sectional geometry of the welded joints changes with increasing laser power, taking shapes from narrow V shape to rectangular I shape, and the results are discussed based on the “closed” and “open” keyhole formation during laser beam welding. A methodology is exploited in terms of quantifying the geometrical dimensions of the cross-section of the FZ in order to promote the welded joints with a narrow width as well as with a rectangular shape. The optimal process parameters, leading to FZ close to the desirable rectangular I shape and with a low number of defects, are identified. Microstructural analyses reveal a pronounced transition zone in between the FZ and the heat-affected zone, which is subdivided into two narrow zones, the partially melted zone (PMZ) and the equiaxed zone. The narrow width of the FZ and PMZ, as well as the rectangular shape of the FZ, enables the autogenous welded joint to reach good tensile deformation properties. %0 journal article %@ 0965-0393 %A Raza, S.,Klusemann, B. %D 2020 %J Modelling and Simulation in Materials Science Engineering %N 8 %P 085003 %R doi:10.1088/1361-651X/aba1df %T Multiphase-field modeling of temperature-driven intermetallic compound evolution in an Al–Mg system for application to solid-state joining processes %U https://doi.org/10.1088/1361-651X/aba1df 8 %X Solid-state joining of dissimilar materials results typically in the formation of intermetallic compounds at the weld interface, which strongly determines the resulting mechanical properties. To tailor the joint strength, understanding of the formation of the intermetallic compound and their driving mechanisms is crucial. In this study, the evolution of temperature-driven Al3Mg2 and Al12Mg17 intermetallic compounds in an Al-Mg system for application to solid-state joining processes via a multiphase-field approach is numerically investigated. To this end, the CALPHAD approach to obtain the thermodynamic parameters of the relevant phases is used in conjunction with the multiphase-field model. The simulation results are qualitatively compared with experimental results in the literature in terms of thickness and morphology of intermetallic grains, exhibiting a reasonable agreement. The influence of grain boundary diffusion and interface energy on the morphology and kinetics of the intermetallic compound grains is investigated in detail with the established multiphase-field model. %0 journal article %@ 2352-4928 %A Alessio, R.,Andre, N.,Goushegir, S.,dos Santos, J.,Mazzaferro, J.,Amancio-Filho, S.T. %D 2020 %J Materials Today Communications %N %P 101205 %R doi:10.1016/j.mtcomm.2020.101205 %T Prediction of the mechanical and failure behavior of metal-composite hybrid joints using cohesive surfaces %U https://doi.org/10.1016/j.mtcomm.2020.101205 %X Friction Spot Joining (FSpJ) is an alternative technique developed to manufacture hybrid lightweight structures by joining metal to composites. This work has developed a finite element model to evaluate the failure behavior of aluminum alloy 2024-T3 and carbon-fiber-reinforced polyphenylene sulfide single spot joints produced by FSpJ. Cohesive surface behavior was applied to model the interface between aluminum and composite in the joint. The different bonding zones of the FSpJ joint were discretized in the model with a specific traction-separation law. The numerical and experimental force versus displacement curves have presented deviations of 8% for the ultimate lap shear force (ULSF) and 1.6% for displacement at failure. The evolution of the damage in the joint occurred preferably from the free edge of the composite due to the differential stiffness between aluminum and the composite. The influence of the edge distance on the mechanical behavior of the joints was also investigated using FEM. It has been observed that longer overlap lengths redistribute the stress in the bonding area more uniformly, thereby delaying the damage evolution in the bonding zones. %0 journal article %@ 1996-1944 %A Abibe, A.,Sônego, M.,Canto, L.,dos Santos, J.,Amancio-Filho, S. %D 2020 %J Materials %N 5 %P 1027 %R doi:10.3390/ma13051027 %T Process-Related Changes in Polyetherimide Joined by Friction-Based Injection Clinching Joining (F-ICJ) %U https://doi.org/10.3390/ma13051027 5 %X This work presents a comprehensive study on the effects of the Friction-based Injection Clinching Joining (F-ICJ) process on the microstructure and local properties of the stake head. The manuscript evaluates the consequences on the quasi-static mechanical performance of hybrid joints of amorphous polyetherimide (PEI) with aluminium AA6082. Through an overlay of microhardness map on a cross-polarized transmitted-light optical microscopy (CP-TLOM) image, two lower-strength microstructural zones in the PEI stake head were observed: a plastically-deformed zone (PDZ) and a thermo-mechanically-affected zone (PTMAZ). When compared to the base material, PDZ and PTMAZ have a reduction of 12%–16% and 8%–12%, respectively, in local mechanical properties. The reduced local strength was associated with distinct volumes of loosely packed PEI chains with unsteady chain conformation and thus larger free volume in the affected regions. The mechanical strength reduction is reversible through physical aging by thermal annealing the joints, which additionally shows that process-induced thermomechanical degradation of PEI by chain scission, as evidenced by size exclusion chromatography (SEC) analysis, does not appear to affect local mechanical strength. An evaluation of typical loading regimes of staked joints in lap shear (average ultimate force of 1419 ± 43 N) and cross tensile (average ultimate force of 430 ± 44 N) testing indicates that the process-induced changes of PEI do not compromise the global mechanical performance of such a structure. These findings provide a better understanding of the relationships between processing, microstructure, and properties for further F-ICJ process optimization. %0 journal article %@ 0043-2288 %A da Silva, Y.,Oliveira Júnior, F.,dos Santos, J.,Marcondes, F.,Silva, C. %D 2020 %J Welding in the World %N 4 %P 2019-2032 %R doi:10.1007/s40194-020-00980-6 %T Numerical investigation of the influence of FSW parameters on the heat and mass transfer of austenitic stainless steels %U https://doi.org/10.1007/s40194-020-00980-6 4 %X The friction stir weld (FSW) method was developed in 1991 by The Welding Institute (TWI) and is very useful for manufacturing components with low fusion weldability. The success of this relatively new technique is due, in part, to an appropriate combination of some parameters. In order to understand the influence of the parameters such as rotation speed, axial force, and welding velocity, simulations were carried out using the AISI 304L stainless steel. In this work, the process was considered to be a 3D non-Newtonian fluid and the heat input was calculated from the friction between the tool and the plate and from the plastic deformation. The thermal results were compared with the experimental results from the thermocouple measurements. Furthermore, the material flow was related to the formation of defects observed in the experimental welds. The results of the simulation were able to determine the temperature distribution and heat flow, as well as to predict defects in the welding. The simulated viscosity values enabled the prediction of the parameters most likely to cause the formation of flashes. In addition, the injection of inert particles into the model made it possible to predict the formation of wormholes. %0 journal article %@ 0013-4686 %A Silva, D.,Campanelli, L.,Bergmann, L.,dos santos, J.,Hammer, P.,Della Rovere, C.,Aquino, J. %D 2020 %J Electrochimica Acta %N %P 136900 %R doi:10.1016/j.electacta.2020.136900 %T On the stability of the passive Ti-6Al-4V film of friction stir welds with stainless steel: Effect of not native metal species %U https://doi.org/10.1016/j.electacta.2020.136900 %X Mechanical and microstructural characteristics of Ti-6Al-4V/stainless steel (SS) dissimilar friction stir welds have been well described in the literature; however, little is known about the electrochemical properties of such welds in terms of the passive film stability of TiO2 grown in oxidizing media. To clarify this issue, potentiodynamic polarization, cyclic voltammetry, and electrochemical impedance measurements were carried out in the Ti-6Al-4V alloy to analyze the effects of Fe and Cr contamination from the underlying SS on the passive film stability of TiO2 in concentrated (6.0 and 11.5 mol L–1) HNO3 solutions. Lower transpassive potentials were observed for samples in the stirred zone (SZ) than those of the base metal (BM) due to Fe and Cr contamination. Anodic charges obtained during cyclic voltammetry using 6.0 mol L–1 HNO3 showed that the grown passive film was completely dissolved and regrown after consecutive scans, except for the BM sample. According to the results of X-ray photoelectron spectroscopy (XPS) analyses an Al depleted layer was obtained for the latter condition, which confirms the stability of TiO2 film. The increasing values of charge transfer resistance obtained through electrochemical impedance measurements at distinct potentials in the passive region also supported the stability of the TiO2 film grown in 6.0 mol L–1 HNO3 solution. The formation of a medium frequency inductive loop and low frequency constant phase element are related to the dissolution of the oxide film and adsorption of NO3 species into the formed passive film, respectively, as evidenced by XPS analyses. %0 journal article %@ 1516-1439 %A Santini, F.,Plaine, A.,Afonso, C.,Bergmann, L.,Alcantara, N.,dos Santos, J.,Miyazaki, M. %D 2020 %J Materials Research %N 6 %P e20200309 %R doi:10.1590/1980-5373-MR-2020-0309 %T Microstructure Features and Mechanical Properties of Double-Sided Friction Stir Welded Joints of AA2050-T84 Thick Plates %U https://doi.org/10.1590/1980-5373-MR-2020-0309 6 %X As part of an ongoing process to fully assess the potential for friction stir welding (FSW) to be used in the aerospace industry, an attempt was made to produce double sided FSW joints at traverse speeds equal or higher than 5 mm/s of AA2050-T84 12.7 mm thick plates for high-volume production applications. With an emphasis on weld quality, the local and global mechanical properties were evaluated and correlated with microstructure of the welding area. Sound welds with no volumetric defects were obtained for tool traverse speeds up to 12 mm/s, resulting in yield and ultimate tensile strengths corresponding to 65% and 77% of base material, respectively. The metallurgical and mechanical characterization demonstrate that density of Cu-rich precipitates has a first order effect on micro-hardness variation. In the stir zone the dissolution temperature of this precipitate is achieved and its volume fraction is greatly reduced. The remaining precipitates seems to be partially dissolved and undergone a significant thickening at the welding zones in which the process temperature has not reached the dissolution temperature. Weld fractures after tensile tests were observed to start in the region of hardness minima. %0 journal article %@ 0043-2288 %A Pina Cipriano, G.,Ahiya, A.,dos Santos, J.,Vilaça, P.,Amancio-Filho, S. %D 2020 %J Welding in the World %N %P 47-58 %R doi:10.1007/s40194-019-00803-3 %T Single-phase friction riveting: metallic rivet deformation, temperature evolution, and joint mechanical performance %U https://doi.org/10.1007/s40194-019-00803-3 %X The present work explores the feasibility of single-phase friction riveting on unreinforced thermoplastics. In single phase, the load is kept constant throughout the process, avoiding the forging phase with higher axial force, used in the conventional process. This process variant can constitute an answer when payload restrictions exist. The results demonstrate the feasibility of single-phase friction riveting on unreinforced polyetherimide plates joined by AA2024 rivets with 5 mm of diameter. A Box-Behnken design of experiments and analysis of variance were used to set parameter matrix and understand the correlations between parameters and joint properties. A large variation of the mechanical energy input was observed (151–529 J). Over-deformation and material rupture were observed in higher energy conditions. Lower energy input yielded a bell-shaped rivet plastic deformation, corresponding to the best performance. The maximum process temperatures varied between 461 and 509 °C. This friction riveting process variant allowed a considerable high mechanical strength to be achieved, with ultimate tensile force of 7486 N, comparable with the two-phase friction riveting process, albeit applying lower axial forces, such as 2400 N. Within the investigated conditions, this study proves the feasibility of the single-phase process, achieving good global mechanical performance and energetically efficient conditions, without forging phase. %0 journal article %@ 0043-2288 %A Feistauer, E.,dos Santos, J.,Amanci-Filho, S. %D 2020 %J Welding in the World %N %P 1481-1495 %R doi:10.1007/s40194-020-00927-x %T An investigation of the ultrasonic joining process parameters effect on the mechanical properties of metal-composite hybrid joints %U https://doi.org/10.1007/s40194-020-00927-x %X The ultrasonic joining process was recently introduced as an alternative concept to join through-the-thickness reinforced metal-composite hybrid structures. In this work, the investigation of joining process parameters effect on the joint mechanical performance of Ti-6Al-4V-glass-fiber-reinforced polyetherimide overlap joints was carried out by Box-Behnken design of experiments. The individual and combined effects of joining energy, sonotrode oscillation amplitude, and joining pressure on the ultimate lap shear force were elucidated by response surfaces method and analysis of variance. As a result of this study, a set of optimized joining parameters were obtained to produce joints with high ultimate lap shear force. The obtained reliable reduced model (R2 = 82%) displays a major influence of joining energy (25.3%) and sonotrode oscillation amplitude (21.2%) on the joint mechanical performance. Two-way interaction response surfaces were used to support strategies to optimize the maximum ultimate lap shear force. By comparing the optimized joint condition produced in this work with previously published results an improvement of 79% in ultimate lap shear force was attained, thereby, proving the potential of the proposed process optimization procedure. %0 journal article %@ 0263-8223 %A André, N.,dos Santos, J.,Amancio-Filho, S. %D 2020 %J Composite Structures %N %P 111754 %R doi:10.1016/j.compstruct.2019.111754 %T Impact resistance of metal-composite hybrid joints produced by frictional heat %U https://doi.org/10.1016/j.compstruct.2019.111754 %X The impact resistance of aluminum alloy 2024-T3 and carbon-fiber-reinforced polyphenylene sulfide joints was investigated using drop weight test. The joints were aluminum-side and composite-side impacted to provide a preliminary design guideline for hybrid joints. Four energy levels were investigated for each side: 2 J, 4 J, 6 J and 8 J. The joints presented rebounding behavior for all the energy levels. It implies that in all the cases, the impact energy was not totally absorbed by the joints, although the joints failed at 8 J of impact energy. The interface of the joint presented its threshold for absorption of impact energy around 6.5 J, which was reached when the joint was impacted with 8 J of potential energy, independently of the surface under impact. Thus, this study showed that a single friction spot joint could absorb up to 103 kJ.m−2 of joined area. The joints impacted from the aluminum side presented residual strengths of 84% (2 J), 30% (4 J), and 25% (6 J). For composite-side impacted joints, the residual strengths were 80% (2 J), 54% (4 J), and 45% (6 J). Generally, the aluminum-side impacted joints showed lower residual strength than the composite-side impacted joints. The impact energy introduced from the aluminum side was mostly absorbed in the plastic deformation of the aluminum part, bending the aluminum and promoting the detachment of the interface. Otherwise, the impact energy introduced from the composite side was mostly absorbed by the creation/extension of internal damage through the plies of the composite. Thus, it is expected that the impact energy was only partially transferred to the interface of the joint in the case of composite-side impact. Consequently, these joints presented higher residual strength after impact than the aluminum-side impacted joints. %0 journal article %@ 0921-5093 %A Hessel Silva, B.,Zepon, G.,Bolfarini, C.,dos Santos, J. %D 2020 %J Materials Science and Engineering: A %N %P 138724 %R doi:10.1016/j.msea.2019.138724 %T Refill friction stir spot welding of AA6082-T6 alloy: Hook defect formation and its influence on the mechanical properties and fracture behavior %U https://doi.org/10.1016/j.msea.2019.138724 %X Process parameters optimization was carried out to evaluate the individual effect of rotational speed, feeding rate and plunge depth on the weld strength of an AA6082-T6 aluminum alloy produced by Refill Friction Stir Spot Welding. Statistical analysis allowed to maximize the weld peel and shear strength and a strong correlation between plunge depth and weld resistance was found. It was shown that plunge depth has a strong effect on the formation and shape of the hook defect. Moreover, the fracture behavior of the welds is strongly dependent on the hook defect configuration. By applying the so-called one-factor at a time (OFAT) method combined with macro and microstructure characterization it was possible to identify three possible hook defect configurations. A comprehensive description of the different hook configuration formation is presented by analyzing the microstructure of samples from interrupted welding tests. The configuration of the hook defect depends on the position and direction of the material flow around the sleeve and the drop region. Macro and microstructure analysis of interrupted mechanical test specimens allowed the characterization of the crack initiation site and crack propagation path according to qualitative observations of hook configuration, bonding ligament and the interface region between the heat affected zone and the thermal mechanically affected zone. It was found that the fracture mode is also strongly related to the configuration of the hook defect. The optimized welding condition was reached using intermediate values of plunge depth, which produces a hook pointing down configuration. %0 journal article %@ 2238-7854 %A Batistao, B.,Bergmann, L.,Gargarela, P.,Alcantara, N.,dos Santos, J.,Klusemann, B. %D 2020 %J Journal of Materials Research and Technology %N 6 %P 15132-15142 %R doi:10.1016/j.jmrt.2020.10.078 %T Characterization of dissimilar friction stir welded lap joints of AA5083 and GL D36 steel %U https://doi.org/10.1016/j.jmrt.2020.10.078 6 %X Dissimilar AA5083 to GL D36 steel welds produced by Friction Stir Welding in lap joint configuration, with the aluminum plate placed on the advancing side, are studied regarding their mechanical, microstructural and interfacial properties for varying process parameters, i.e. welding and tool rotational speed. An increase of welding speed or decrease of the rotational speed causes the formation of tunnel defects, a decrease of the steel hook height and reduction of grain size in the aluminum stir zone. The maximum hardness is observed at the weld interface, due to the presence of intermetallic compound layers, identified as the Fe-rich phases as FeAl and Fe3Al. As the rotational speed increases, an increase of the IMCs thickness in the weld interface is found, which contributes to the degradation of the lap shear strength, due to the brittleness and high hardness of these phases. Overall, the maximum lap shear strength is obtained for welds showing macro (steel hook) and micro interlocks, as well as the formation of thin IMC layers at the weld interface. %0 journal article %@ 0933-5137 %A Yamin, M.,Awang, M.,Suhuddin, U.,Sallih, N.,Klusemann, B.,Dos Santos, J. %D 2020 %J Materials Science and Engineering Technology - Materialwissenschaft und Werkstofftechnik %N 6 %P 830-835 %R doi:10.1002/mawe.201900253 %T Mechanical performance optimization of similar thin AA 7075‐T6 sheets produced by refill friction stir spot welding : Optimierung der mechanischen Leistungfähigkeit für artgleich produzierte AA 7075-T6-Bleche durch Rühr-Reib-Punkt-Schweißen %U https://doi.org/10.1002/mawe.201900253 6 %X Refill friction stir spot welding was applied to weld similar thin AA 7075‐T6 aluminum alloy sheets in a spot‐like joint configuration without a keyhole. The welds were produced using a small tool consisting of sleeve and probe with diameters of 6 mm and 4 mm, respectively. Design of experiment was employed to optimize the welding parameters in terms of the cross tensile strength by using Box Behnken Design. Based on analysis of variance, it can be concluded that plunge depth strongly affects the mechanical performance of the weld. Optimal welding parameters in terms of rotational speed, plunge depth and speed are identified to reach a cross tensile strength of up to 660 N. %0 journal article %@ 0032-3888 %A Feistauer, E.,dos Santos, J.,Amancio-Filho, S. %D 2019 %J Polymer Engineering & Science %N 4 %P 661-674 %R doi:10.1002/pen.25022 %T A review on direct assembly of through‐the‐thickness reinforced metal–polymer composite hybrid structures %U https://doi.org/10.1002/pen.25022 4 %X Constant efforts to reduce the structural weight of transportation systems as a solution to control emission levels are currently shaping the way modern cars and airplanes are designed and manufactured. Increased attention has been given to innovative metal–composites multi‐material concepts for the production of lightweight structures. However, the nature of these very dissimilar materials makes their joining a rather complicated task. Recently several technologies have been proposed to overcome process limitation and increase the load transfer between metal and composite in hybrid structures. One of the promising solutions is a new concept known as direct assembling with through‐the‐thickness reinforcements. In this concept, the composite material of a hybrid joint is directly assembled upon a surface‐structured metallic part. Features structured on the metallic part, by a manufacturing phase, act as a through‐the‐thickness reinforcement improving the out‐of‐plane strength and load transfer capabilities of such joints. The current status and state‐of‐art direct assembling technologies are reviewed in this article. Examples of reviewed metal structuring techniques include micromachining, stamping, Surfi‐Sculpt, additive manufacturing, cold metal transfer, and metal injection molding structuring. Direct assembling techniques addressed in this article are vacuum‐assisted resin infusion, resin transfer molding, prepreg/autoclave assembly, and ultrasonic joining. POLYM. ENG. SCI., 59:661–674, 2019. © 2018 The Authors. Polymer Engineering & Science published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers. %0 journal article %@ 2238-7854 %A Lemos, G.V.B.,Farina, A.B.,Menezes Nunes, R.,Pereira da Cunha, P.H.C.,Bergmann, L.,dos Santos, J.F.,Reguly, A. %D 2019 %J Journal of Materials Research and Technology : JMRT %N 3 %P 2528-2537 %R doi:10.1016/j.jmrt.2019.02.011 %T Residual stress characterization in friction stir welds of alloy 625 %U https://doi.org/10.1016/j.jmrt.2019.02.011 3 %X Alloy 625 (UNS N06625) welded sheets were evaluated in the present study. Friction stir welding (FSW) was performed in a range of tool rotational speed from 1200 to 200 rpm, welding speed from 1.0 to 1.5 mm/s and constant axial force. Residual stress states were investigated by X-ray diffraction (XRD). Besides, microstructural features were analyzed by optical microscopy (OM), and scanning electron microscopy (SEM). The FSW application was effective in the Ni-based alloy, promoting different levels of grain refinement, microstructural characteristics, and enhanced microhardness. Results also showed that distinct process parameters led to changes in the joints and distinguishable residual stress distributions. In general, as the tool rotational speed decreased, the grain refinement increased, more homogeneous microstructures and microhardness profiles, and lower residual stresses were achieved within the stirred zones. %0 journal article %@ 1996-1944 %A Zocoller Borba, N.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2019 %J Materials %N 5 %P 745 %R doi:10.3390/ma12050745 %T The Influence of Clamping Pressure on Joint Formation and Mechanical Performance of Ti6Al4V/CF-PEEK Friction-Riveted Joints %U https://doi.org/10.3390/ma12050745 5 %X This work aims at investigating the influence of pre-set clamping pressure on the joint formation and mechanical strength of overlapping direct-friction-riveted joints. A pneumatic fixture device was developed for this work, with clamping pressure varying from 0.2 MPa to 0.6 MPa. A case study on overlapping joints using Ti6Al4V rivets and woven carbon fiber-reinforced polyether-ether-ketone (CF-PEEK) parts were produced. Digital image correlation and microscopy revealed the expected compressive behavior of the clamping system and the continuous pressure release upon the joining process owing to the rivet plastic deformation and the polymer squeezing flow. Two preferential paths of material flow were identified through the alternate replacement of the upper and lower composite parts by a poly-methyl-methacrylate (PMMA) plate—the composite upward and squeezing flow between the parts which induced their separation. The ultimate lap shear forces up to 6580 ± 383 N were achieved for the direct-friction-riveted CF-PEEK overlap joints. The formation of a gap to accommodate squeezed polymer between the composite parts during the process had no influence on the joint mechanical performance. The increase in the clamping pressure for joints produced with a low friction force did not affect the joint-anchoring efficiency and consequently the joint strength. On the other hand, the combined effect of a high-friction force and clamping pressure induced the inverted bell shape of the plastically deformed rivet tip, a lower anchoring efficiency, and the delamination of the composite, all of which decrease the mechanical strength by 31%. Therefore, the higher the friction force and clamping pressure, the more defects would be generated in the composite parts and the more changes in the shape of the plastically deformed rivet tip, leading to a lower level of quasi-static mechanical performance. All the joints failed by initial bearing of the composite and final rivet pull-out. The findings of this work can contribute to further improvement of the clamping design for industrial application. %0 journal article %@ 1996-1944 %A Manente Andre, N.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2019 %J Materials %N 6 %P 891 %R doi:10.3390/ma12060891 %T Evaluation of Joint Formation and Mechanical Performance of the AA7075-T6/CFRP Spot Joints Produced by Frictional Heat %U https://doi.org/10.3390/ma12060891 6 %X The development of lightweight hybrid metal–polymer structures has recently attracted interest from the transportation industry. Nevertheless, the possibility of joining metals and polymers or composites is still a great challenge. Friction Spot Joining (FSpJ) is a prize-winning friction-based joining technique for metal–polymer hybrid structures. The technology is environment-friendly and comprises very short joining cycles (2 to 8 s). In the current work, aluminum alloy 7075-T6 and carbon-fiber-reinforced polyphenylene sulfide (CF-PPS) friction spot joints were produced and evaluated for the first time in the literature. The spot joints were investigated in terms of microstructure, mechanical performance under quasi-static loading and failure mechanisms. Macro- and micro-mechanical interlocking were identified as the main bonding mechanism, along with adhesion forces as a result of the reconsolidated polymer layer. Moreover, the influence of the joining force on the mechanical performance of the joints was addressed. Ultimate lap shear forces up to 4068 ± 184 N were achieved in this study. A mixture of adhesive–cohesive failure mode was identified, while cohesive failure was dominant. Finally, a qualitative comparison with other state-of-the-art joining technologies for hybrid structures demonstrated that the friction spot joints eventually exhibit superior/similar strength than/to concurrent technologies and shorter joining times. %0 journal article %@ 2238-7854 %A Entringer, J.,Reimann, M.,Norman, A.,dos Santos, J.F. %D 2019 %J Journal of Materials Research and Technology : JMRT %N 2 %P 2031-2040 %R doi:10.1016/j.jmrt.2019.01.014 %T Influence of Cu/Li ratio on the microstructure evolution of bobbin-tool friction stir welded Al–Cu–Li alloys %U https://doi.org/10.1016/j.jmrt.2019.01.014 2 %X Two modern aluminum lithium alloys were welded by semi-stationary bobbin tool friction stir welding. The influence of the Cu/Li ratio on precipitation phenomena under process heat impact was investigated by comparing the response of low Cu/Li alloy 2196-T8 and high Cu/Li alloy 2060-T8. Identical process parameters with a weld pitch of one rotation per mm were used to conduct flawless weldments. The thermal history and microstructural features were studied and correlated to the resulting mechanical properties of the welds. Analysis of microstructure using differential scanning calorimetry and high energy X-ray diffraction technique showed significant differences in the precipitation sequence of the base metal and in the welded samples of the two alloys of interest. A low Cu/Li ratio led to a higher softening resulting in a reduction of 43% of base metal yield strength while the high Cu/Li ratio alloy AA 2060 could demonstrate more thermal stability (38% reduction). Severe dissolution of the T1 precipitate and presence of equilibrium phases were confirmed for the stirred zone of both alloys. The heat affected zone suffered dissolution and overaging reactions leading to a mechanically unfavorable microstructure. The low Cu/Li alloy 2196 developed a higher process temperatures and exhibited a more evolved precipitation sequence. %0 journal article %@ 2590-1508 %A Entringer, J.,Meisnar, M.,Reimann, M.,Blawert, C.,Zheludkevich, M.,dos Santos, J.F. %D 2019 %J Materials Letters: X %N %P 100014 %R doi:10.1016/j.mlblux.2019.100014 %T The effect of grain boundary precipitates on stress corrosion cracking in a bobbin tool friction stir welded Al-Cu-Li alloy %U https://doi.org/10.1016/j.mlblux.2019.100014 %X Evidence of stress corrosion cracking has been observed in exposed semi-stationary bobbin tool friction stir welded aluminum-copper-lithium alloy 2060-T8. Microstructural analysis confirmed the heterogeneous microstructure transformation caused by the thermomechanical impact of the welding process. Grain boundary phase accumulation initiated anodic dissolution in NaCl solution under stress. In the center and the heat affected zone of the weld, the microstructure was found to form overaged and high copper containing equilibrium phases promoting intergranular stress corrosion. %0 journal article %@ 8756-758X %A Braga, D.F.O.,Maciel, R.,Bergmann, L.,da Silva, L.F.M.,Infante, V.,dos Santos, J.F.,Moreira, P.M.G.P. %D 2019 %J Fatigue and Fracture of Engineering Materials and Structures %N 6 %P 1262-1270 %R doi:10.1111/ffe.12933 %T Fatigue performance of hybrid overlap friction stir welding and adhesive bonding of an Al‐Mg‐Cu alloy %U https://doi.org/10.1111/ffe.12933 6 %X The need for weight reduction and leaner manufacturing and assembly processes in aircraft construction has led to the pursuit of welding technologies. One such technology that has been considered for this application is friction stir welding (FSW). Since it is a solid‐state joining method, it creates high performing joints in a wide range of materials while avoiding overlap lengths and added weight from fasteners, crack stoppers, doublers, etc. However, the adoption of this technology to the assembly of large fuselage shell components is challenging, due to geometric tolerance management requirements. In this paper, a hybrid joining method is proposed for such application, involving FSW and adhesive bonding. Fatigue performance of single lap joints of AA2024‐T3 Al‐Mg‐Cu alloy was assessed and benchmarked against FSW overlap and adhesive bonded joints. Significant strength and ductility increase was achieved through the hybridization of the overlap FSW joints. Fatigue strength of the hybrid joints was also higher than FSW overlap joints, although not as high as adhesive bonded joints. %0 journal article %@ 2296-8016 %A Bock, F.E.,Aydin, R.C.,Cyron, C.J.,Huber, N.,Kalidindi, S.R.,Klusemann, B. %D 2019 %J Frontiers in Materials %N %P 110 %R doi:10.3389/fmats.2019.00110 %T A Review of the Application of Machine Learning and Data Mining Approaches in Continuum Materials Mechanics %U https://doi.org/10.3389/fmats.2019.00110 %X Machine learning tools represent key enablers for empowering material scientists and engineers to accelerate the development of novel materials, processes and techniques. One of the aims of using such approaches in the field of materials science is to achieve high-throughput identification and quantification of essential features along the process-structure-property-performance chain. In this contribution, machine learning and statistical learning approaches are reviewed in terms of their successful application to specific problems in the field of continuum materials mechanics. They are categorized with respect to their type of task designated to be either descriptive, predictive or prescriptive; thus to ultimately achieve identification, prediction or even optimization of essential characteristics. The respective choice of the most appropriate machine learning approach highly depends on the specific use-case, type of material, kind of data involved, spatial and temporal scales, formats, and desired knowledge gain as well as affordable computational costs. Different examples are reviewed involving case-by-case dependent application of different types of artificial neural networks and other data-driven approaches such as support vector machines, decision trees and random forests as well as Bayesian learning, and model order reduction procedures such as principal component analysis, among others. These techniques are applied to accelerate the identification of material parameters or salient features for materials characterization, to support rapid design and optimization of novel materials or manufacturing methods, to improve and correct complex measurement devices, or to better understand and predict fatigue behavior, among other examples. Besides experimentally obtained datasets, numerous studies draw required information from simulation-based data mining. Altogether, it is shown that experiment- and simulation-based data mining in combination with machine leaning tools provide exceptional opportunities to enable highly reliant identification of fundamental interrelations within materials for characterization and optimization in a scale-bridging manner. Potentials of further utilizing applied machine learning in materials science and empowering significant acceleration of knowledge output are pointed out. %0 journal article %@ 2075-4701 %A Kallien, Z.,Keller, S.,Ventzke, V.,Kashaev, N.,Klusemann, B. %D 2019 %J Metals %N 6 %P 655 %R doi:10.3390/met9060655 %T Effect of Laser Peening Process Parameters and Sequences on Residual Stress Profiles %U https://doi.org/10.3390/met9060655 6 %X Laser Peening (LP) is a surface modification technology that can induce high residual stresses in a metallic material. The relation between LP process parameters, in particular laser sequences, as well as pulse parameters and the resulting residual stress state was investigated in this study. The residual stress measurements, performed with the hole drilling technique, showed a non-equibiaxial stress profile in laser peened AA2024-T3 samples with a clad layer for certain parameter combinations. Shot overlap and applied energy density were found to be crucial parameters for the characteristic of the observed non-equibiaxial residual stress profile. Furthermore, the investigation showed the importance of the advancing direction, as the advancing direction influences the direction of the higher compressive residual stress component. The direction of higher residual stresses was parallel or orthogonal to the rolling direction of the material. The effect was correlated to the microstructural observation obtained via electron backscattered diffraction. Additionally, for peening with two sequences of different advancing directions, the study showed that the order of applied advancing directions was important for the non-equibiaxiality of the resulting residual stress profile. %0 journal article %@ 1617-7061 %A Pozdnyakov, V.,Keller, S.,Kashaev, N.,Klusemann, B.,Oberrath, J. %D 2019 %J PAMM: Proceedings in Applied Mathematics and Mechanics %N 1 %P e201900497 %R doi:10.1002/pamm.201900497 %T Two-step simulation approach for laser shock peening %U https://doi.org/10.1002/pamm.201900497 1 %X Laser shock peening (LSP) is a surface modification technique to introduce compressive residual stresses (RS) with a high magnitude in the near surface region of the material. Due to non‐linear interactions (e.g. laser absorption by plasma, shock wave propagation, etc.) and a high number of parameters, it is difficult to study and optimize the process based on experiments alone. Therefore, a two‐step simulation approach is proposed in this paper, where two models are combined, because one model of the complete process is difficult to derive, due to the different characteristics of the plasma formation and the shock wave propagation in the material. On one hand, a global model including plasma and shock wave descriptions is applied for the LSP of an aluminium sample with water confinement. The numerical solution of this model, applied for a 3×3 mm2 focus size, 5 J and 20 ns (full width at half maximum (FWHM)) laser pulse, allows to determine the temporal plasma pressure evolution on the material surface. On the other hand, a finite element simulation is used to calculate the RS distribution within the target material, where the plasma pressure is applied as a surface loading for the aluminium alloy AA2198‐T3. The simulated residual stresses are fitted to measurements via parameter variation of the global model. The identified values and the two‐step simulation approach can be used in future work to predict stress states of materials after LSP for various process parameters variations. %0 journal article %@ 1059-9495 %A Abbaszadeh, M.,Hönnige, J.R.,Martina, F.,Neto, L.,Kashaev, N.,Colegrove, P.,Williams, S.,Klusemann, B. %D 2019 %J Journal of Materials Engineering and Performance %N 8 %P 4931-4942 %R doi:10.1007/s11665-019-04249-y %T Numerical Investigation of the Effect of Rolling on the Localized Stress and Strain Induction for Wire + Arc Additive Manufactured Structures %U https://doi.org/10.1007/s11665-019-04249-y 8 %X Cold rolling can be used in-process or post-process to improve microstructure, mechanical properties and residual stress in directed-energy-deposition techniques, such as the high deposition rate wire + arc additive manufacturing (WAAM) process. Finite element simulations of the rolling process are employed to investigate the effect of rolling parameters, in particular rolling load and roller profile radius on the residual stress field as well as plastic strain distribution for the profiled roller. The results show the response to rolling of commonly used structural metals in WAAM, i.e., AA2319, S335JR steel and Ti-6Al-4V, taking into account the presence of residual stresses. The rolling load leads to changes in the location and the maximum value of the compressive residual stresses, as well as the depth of the compressive residual stresses. However, the roller profile radius only changes the maximum value of these compressive residual stresses. Changing the rolling load influences the equivalent plastic strain close to the top surface of the wall as well as in deeper areas, whereas the influence of the roller profile radius is negligible. The plastic strain distribution is virtually unaffected by the initial residual stresses prior to rolling. Finally, design curves were generated from the simulations for different materials, suggesting ideal rolling load and roller profile combinations for microstructural improvement requiring certain plastic strains at a specific depth of the additive structure. %0 journal article %@ 0268-3768 %A Lage, S.,Campanelli, L.,Guerra, A.,Shen, J.,dos Santos, J.,da Silva, P.,Bolfarini, C. %D 2019 %J The International Journal of Advanced Manufacturing Technology %N %P 101-110 %R doi:10.1007/s00170-018-2696-0 %T A study of the parameters influencing mechanical properties and the fatigue performance of refill friction stir spot welded AlMgSc alloy %U https://doi.org/10.1007/s00170-018-2696-0 %X Friction spot welds of 1.6-mm-thick AlMgSc alloy were investigated in this work. A design of experiment method was used to evaluate the effect of process parameters on the shear static strength. The optimized condition of parameters was employed in the assessment of the fatigue behavior. The typical hook feature was minimized by restricting the tool penetration into only the upper sheet. As a consequence, shear strength was sensitive to the extension of the welded region rather than the hook morphology. The fatigue performance was affected by the multiple crack initiation sites that resulted from a complex stress state during the axial loading. Striations were observed in practically the entire crack propagation region, suggesting that unstable fatigue crack growth did not take place in this specific weld configuration. %0 journal article %@ 1047-4838 %A Vale, N.,Fitseva, V.,Urtiga Filho, S.,dos santos, J.,Hanke, S. %D 2019 %J JOM: The Journal of the Minerals, Metals and Materials Society %N %P 4339-4348 %R doi:10.1007/s11837-019-03677-4 %T Comparison of Friction Surfacing Process and Coating Characteristics of Ti-6Al-4V and Ti Grade 1 %U https://doi.org/10.1007/s11837-019-03677-4 %X Friction surfacing is a coating process for extending the service life of components by repairing surface damaged, reducing wear, and improving anticorrosion properties. Ti-6Al-4V and titanium grade 1 have been deposited onto Ti-6Al-4V substrate to investigate the differences in material and processing behavior and analyze the coatings’ geometry and hardness. The deposition speed and consumption rate were kept constant at 16 mm/s and 1.8 mm/s, respectively, while the rotational speed was varied to 2000 rpm, 3000 rpm, or 4000 rpm. The force increased with the rotational speed, being about 10 times higher for Ti-6Al-4V compared with titanium grade 1. The peak temperatures were higher for titanium grade 1, and the β-transus temperature was exceeded in all experiments. The hardness of the coatings was about 16% higher compared with that of the Ti-6Al-4V substrate, due to formation of martensitic structure. The hardness did not vary significantly across the width of the coatings. %0 journal article %@ 1996-1944 %A Cipriano, G.P.,Blaga, L.A.,dos Santos, J.F.,Vilaca, P.,Amancio-Filho, S.T. %D 2019 %J Materials %N 12 %P 2489 %R doi:10.3390/ma11122489 %T Fundamentals of Force-Controlled Friction Riveting: Part II - Joint Global Mechanical Performance and Energy Efficiency %U https://doi.org/10.3390/ma11122489 12 %X The present work investigates the correlation between energy efficiency and global mechanical performance of hybrid aluminum alloy AA2024 (polyetherimide joints), produced by force-controlled friction riveting. The combinations of parameters followed a central composite design of experiments. Joint formation was correlated with mechanical performance via a volumetric ratio (0.28–0.66 a.u.), with a proposed improvement yielding higher accuracy. Global mechanical performance and ultimate tensile force varied considerably across the range of parameters (1096–9668 N). An energy efficiency threshold was established at 90 J, until which, energy input displayed good linear correlations with volumetric ratio and mechanical performance (R-sq of 0.87 and 0.86, respectively). Additional energy did not significantly contribute toward increasing mechanical performance. Friction parameters (i.e., force and time) displayed the most significant contributions to mechanical performance (32.0% and 21.4%, respectively), given their effects on heat development. For the investigated ranges, forging parameters did not have a significant contribution. A correlation between friction parameters was established to maximize mechanical response while minimizing energy usage. The knowledge from Parts I and II of this investigation allows the production of friction riveted connections in an energy efficient manner and control optimization approach, introduced for the first time in friction riveting. %0 journal article %@ 2214-8604 %A Froend, M.,Ventzke, V.,Kashaev, N.,Klusemann, B.,Enz, J. %D 2019 %J Additive Manufacturing %N %P 100800 %R doi:10.1016/j.addma.2019.100800 %T Thermal analysis of wire-based direct energy deposition of Al-Mg using different laser irradiances %U https://doi.org/10.1016/j.addma.2019.100800 %X The wire-based direct energy deposition of metallic lightweight materials such as titanium or aluminium alloys has recently received increasing attention in industry and academia. However, high-throughput deposition is mostly associated with process-limiting phenomena such as the development of high temperatures resulting in poor surface quality as well as coarse and unidirectional solidification microstructures. In this regard, laser systems, which are already widely used in industrial processes, allow for a great variety in the controllability of energy inputs, thereby enabling the control of process temperatures and resulting microstructures. The subject of the current study is the detailed elucidation and evaluation of important features such as the development of temperature gradients, resulting cooling rates and thermal cycles for different laser beam irradiances. Significant heat accumulation and process instabilities as well as inhomogeneous thermal profiles along the length and height of the parts were observed at a high laser beam irradiance. In contrast, lower laser beam irradiance resulted in a more stable process with increased cooling rates, which favourably influenced the refinement of the solidification microstructure. %0 journal article %@ 1516-1439 %A do Vale, N.,Fitseva, V.,Hanke, S.,Filho, S.,dos Santos, J. %D 2019 %J Materials Research : Revista Brasileira de Materiais %N %P e20180888 %R doi:10.1590/1980-5373-MR-2018-0888 %T Effects of Friction Surfacing on the Characteristics of Consumable Rods of Ti-6Al-4V %U https://doi.org/10.1590/1980-5373-MR-2018-0888 %X Friction surfacing (FS) is a coating technique applied mainly in corrosion protection and repair of components. The study addresses the effects of deposition and rotational speeds on the rods characteristics and process efficiency for the deposition of Ti-6Al-4V on self-mating substrates by FS. The consumption rate was 1.8 mm/s, deposition speeds of 8, 16 and 24 mm/s and rotational speeds of 2000, 3000 and 4000 rpm. It was shown that the flash forms primarily at the rod, ascending around the tip and leaving the coating without flash. The higher deposition speeds led to a decrease in rod thickness and diameter. For higher rotational speeds, an increase in diameter and decrease in thickness is observed for the flash on the rod. Experiments have shown that the rotational and deposition speeds have a decisive influence on the flash formation. Its microstructure changes due to the welding process and a change in hardness can be observed. %0 journal article %@ 2238-7854 %A Alba, D.,Roos, A.,Wimmer, G.,Gonzalez, A.,Hanke, S.,Dos Santos, J. %D 2019 %J Journal of Materials Research and Technology : JMRT %N 2 %P 1701-1711 %R doi:10.1016/j.jmrt.2018.11.012 %T Application of response surface methodology for optimization of hybrid friction diffusion bonding of tube-to-tube-sheet connections in coil-wound heat exchangers %U https://doi.org/10.1016/j.jmrt.2018.11.012 2 %X This study evaluates the application of a new solid state joining process referred to as hybrid friction diffusion bonding. Based on heat processing and pressure, accelerated diffusion joins the materials. In the present study, two aluminum alloys were welded and characterized using leak tightness tests, tensile pull out tests, and metallographic analysis. Response surface methodology was used to optimize the tensile strength of single-hole tube-sheet samples. A Box–Behnken design was selected to evaluate the relations between the important process parameters and the ultimate tensile strength response to obtain optimal welding parameters. The data were analyzed with analysis of variance and were fitted to a second-order polynomial equation. The three-dimensional response surfaces derived from the mathematical models were applied to determine several optimum input parameters conditions. Under these conditions, the experimental ultimate tensile strength value was 202 MPa, which represents 95% of the base material strength. The experimental results obtained under optimum operating conditions were in agreement with the predicted values. Axial force was found to be the most significant factor affecting the joint strength followed by rotational speed. This can be attributed to their influence on the amount of mechanical energy introduced during the process, which is the parameter that primarily determines the joint strength. %0 journal article %@ 0930-777X %A Sonego, M.,Abibe, A.,Canevarolo, S.,Bettini, S.,dos Santos, J.,Canto, L.,Amancio-Filho, S. %D 2019 %J International Polymer Processing %N 1 %P 100-110 %R doi:10.3139/217.3679 %T Thermomechanical Degradation of Polyetherimide (PEI) by Friction-Based Joining and the Effects on Quasi-Static Mechanical Strength of Hybrid Joints %U https://doi.org/10.3139/217.3679 1 %X This study investigated quantitatively the thermomechanical degradation of polyetherimide (PEI) due to Friction-based Injection Clinching Joining (F-ICJ) and the effects on the mechanical strength of hybrid joints with aluminum. PEI samples extracted from process-affected regions of the joints were characterized in terms of their molecular weight distribution (MWD) and glass transition temperature (Tg), while mechanical strength of the joints was evaluated by cross tensile testing. PEI samples produced by the most severe joining condition showed decrease of 37 % of number-average molecular weight (Mn) and 17 % of weight-average molecular weight (Mw), while polydispersity index (Mw/Mn) increased 33 % as compared with as-received polymer. The chain scission distribution function (CSDF) indicated non-random multiple scissions as the main degradation mechanism of PEI due to F-ICJ. From the dependence of Tg with Mn the parameters of the Fox-Flory equation for PEI were obtained. A fractional factorial design of experiments was adopted to analyze the influence of the process parameters on the polymer degradation, based on Tg values. High level of PEI degradation and microstructural defects caused by high energy inputs have combined negative effect on the ultimate cross tensile force and displacement of joints. In general, these results can contribute to the knowledge of thermomechanical degradation of PEI and help with the optimization of F-ICJ. %0 journal article %@ 0268-3768 %A Chupakhin, S.,Klusemann, B.,Huber, N.,Kashaev, N. %D 2019 %J The International Journal of Advanced Manufacturing Technology %N 5 - 8 %P 1567-1581 %R doi:10.1007/s00170-018-3034-2 %T Application of design of experiments for laser shock peening process optimization %U https://doi.org/10.1007/s00170-018-3034-2 5 - 8 %X Laser shock peening—a very promising life enhancement technique—has demonstrated great success regarding the improvement of fatigue behavior via deep compressive residual stresses. However, the prediction and adaption of residual stress fields on basis of the laser peening parameters are still not comprehensively established. The aim of the current work is to investigate the effects of the laser pulse energy, the number of treatment overlaps as well as the laser spot size on the resulting residual stress distribution, characterized by following quantities: the residual stress close to the surface, the maximum compressive residual stress, and the integral compressive stress area over the specimen depth. For a systematic investigation of all main and interaction-based process parameter effects, and a subsequent parameter optimization, the general full factorial design is employed. The results show that laser shock peening with different process parameter combinations, inducing residual stresses with comparable integral stress area, can lead to a minimum fatigue life extension of approx. 100,000 cycles, representing a minimum fatigue life of 250% of the base material. The experimental scatter in the number of cycles to failure follows the Weibull distribution which qualitatively correlates with the standard deviation of the integral stress area. %0 journal article %@ 1996-1944 %A Falck, R.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2019 %J Materials %N 6 %P 864 %R doi:10.3390/ma12060864 %T Microstructure and Mechanical Performance of Additively Manufactured Aluminum 2024-T3/Acrylonitrile Butadiene Styrene Hybrid Joints Using an AddJoining Technique %U https://doi.org/10.3390/ma12060864 6 %X AddJoining is an emerging technique that combines the principles of the joining method and additive manufacturing. This technology is an alternative method to produce metal–polymer (composite) structures. Its viability was demonstrated for the material combination composed of aluminum 2024-T3 and acrylonitrile butadiene styrene to form hybrid joints. The influence of the isolated process parameters was performed using the one-factor-at-a-time approach, and analyses of variance were used for statistical analysis. The mechanical performance of single-lap joints varied from 910 ± 59 N to 1686 ± 39 N. The mechanical performance thus obtained with the optimized joining parameters was 1686 ± 39 N, which failed by the net-tension failure mode with a failure pattern along the 45° bonding line. The microstructure of the joints and the fracture morphology of the specimens were studied using optical microscopy and scanning electron microscopy. From the microstructure point of view, proper mechanical interlocking was achieved between the coated metal substrate and 3D-printed polymer. This investigation can be used as a base for further improvements on the mechanical performance of AddJoining hybrid-layered applications. %0 journal article %@ 1005-0302 %A Queiroz Caetano, G.de,Carvalho Silva, C.,Motta, M.F.,Miranda, H.C.,Farias, J.P.,Bergmann, L.A.,dos Santos, J.F. %D 2019 %J Journal of Materials Science and Technology %N 2 %P 1878-1887 %R doi:10.1016/j.jmrt.2019.01.004 %T Intergranular corrosion evaluation of friction stir welded AISI 410S ferritic stainless steel %U https://doi.org/10.1016/j.jmrt.2019.01.004 2 %X This study aimed to investigate the susceptibility of AISI 410S ferritic stainless steel to intergranular corrosion when friction stir welded (FSW) using the double-loop electrochemical potentiokinetic reactivation (DL-EPR) test. The highest values obtained for the ratio between the reactivation current (Ir) and the activation current (Ia) were found at the top of the advancing side for the two conditions tested. The steel for Condition 1, which was welded with a rotational speed of 800 rpm and high heat input, gave Ir/Ia peaks 60% greater than Condition 2, which was welded with a rotational speed of 450 rpm and a lower heat input. These peaks were attributed to the presence of precipitates with high chromium content of about 21%. In these FSW welds the sensitization of the AISI 410S steel was detected by the electrochemical test according to the intensity of the undesirable phases formed. The DL-EPR test was clearly able to quantify the different levels of sensitization in the FSW welds according to the energy used by the process parameters. %0 journal article %@ 0045-7825 %A Raza, S.H.,Soyarslan, C.,Bargmann, S.,Klusemann, B. %D 2019 %J Computer Methods in Applied Mechanics and Engineering %N %P 887-909 %R doi:10.1016/j.cma.2018.10.007 %T Computational modeling of amorphous polymers: A Lagrangian logarithmic strain space formulation of a glass–rubber constitutive model %U https://doi.org/10.1016/j.cma.2018.10.007 %X We present a reformulation of the finite strain, rate dependent inelastic glass-rubber material model suggested by Buckley and Jones (1995) and extended by Adams et al. (2000) for modeling the deformation of amorphous polymers in the Lagrangian logarithmic strain space. This not only warrants a hyperelastic characterization in the bonding part which remedies problems associated with hypoelastic approaches devising objective stress rates selected on ad hoc basis, see, e.g., Dooling et al. (2001) and Li and Buckley (2009), but also allows a transparent and naturally objective implementation analogous to the geometrically linear theory. A numerical implementation into Abaqus is pursued where algorithms for stress update and tangent moduli computations are reported. It is shown that significant reduction in nonlinear equation system size is possible in the computation of both bonding and conformational part. The characterization tests include constant-width tension, equi-biaxial tension, and simple shear. To demonstrate the robustness of the developed framework, two hypothetical problems of extreme deformation under tensile and combined tensile and torsion loading are considered. Finally, simulation of an injection stretch-blow molding process is presented as an application problem. %0 journal article %@ 0043-2288 %A Cardillo, M.E.B.,Shen, J.,de Alcantara, N.G.,Afonso, C.R.M.,dos Santos, J.F. %D 2019 %J Welding in the World %N 1 %P 33-41 %R doi:10.1007/s40194-018-0632-4 %T Effect of friction spot welding parameters on the joint formation and mechanical properties of Al to Cu %U https://doi.org/10.1007/s40194-018-0632-4 1 %X Friction spot welding is an appealing technique for joining dissimilar materials, such as aluminum and copper that have significant differences in physical and mechanical properties. To optimize the welding process, a full-factorial design was employed. It is found that in addition to the plunge depth, the interaction between the rotational speed and the plunge depth significantly influences the lap-shear strength of the Al/Cu dissimilar joints. Further investigations on macro- and microstructures show that increasing the plunge depth could deform the Cu sheet into a concave shape to form a mechanical interlocking, and thus increase the joint lap-shear strength; increasing the tool rotational speed, however, may compromise this effect because of the formed tunnel defects on the interface due to high thermal exposure. %0 journal article %@ 0029-5981 %A Talebi, H.,Silani, M.,Klusemann, B. %D 2019 %J International Journal for Numerical Methods in Engineering %N 1 %P 1-17 %R doi:10.1002/nme.6002 %T The scaled boundary finite element method for computational homogenization of heterogeneous media %U https://doi.org/10.1002/nme.6002 1 %X Materials exhibit macroscopic properties that are dependent on the underlying components at lower scales. Computational homogenization using the Finite Element Method (FEM) is often used to determine the effective mechanical properties based on the microstructure. However use of FEM might suffer from several difficulties such as mesh generation, application of periodic boundary conditions or computations in presence of material interfaces and further discontinuities. In this paper we present an alternative approach for computational homogenization of heterogeneous structures based on the Scaled Boundary Finite Element Method (SBFEM). Based on quadtrees, we are applying a simple meshing strategy to create polygonal elements for arbitrary complex microstructures by using a relatively small number of elements. We show on selected numerical examples that the proposed computational homogenization technique represents a suitable alternative to classical FEM approaches capable of avoiding some of the mentioned difficulties while accurately and effectively calculating the macroscopic mechanical properties. An example of a two‐scale semi‐concurrent coupling between FEM and SBFEM is presented, illustrating the complementarity of both approaches. %0 journal article %@ 2238-7854 %A Costa Pereira da Cunha, P.H.,Braga, Lemos, G,V.,Bergmann, L.,Reguly, A.,dos Santos, J.F.,Marinho, R.R.,Piza Paes, M.T. %D 2019 %J Journal of Materials Research and Technology : JMRT %N 1 %P 1041-1051 %R doi:10.1016/j.jmrt.2018.07.014 %T Effect of welding speed on friction stir welds of GL E36 shipbuilding steel %U https://doi.org/10.1016/j.jmrt.2018.07.014 1 %X The aim of this study was to characterize mechanical and microstructural characteristics of friction-stir-welded GL E36 shipbuilding steel. The tool rotational speed was kept constant at 500 rpm and different welding speeds were used (1, 2 and 3 mm/s) to achieve different heat inputs. Thermal cycles were monitored by thermocouples placed near the weld face. The welded joints showed a very good esthetics and homogeneous surface quality that indicate a stability of the considered process parameters. The welded joints properties were analyzed by metallography and mechanical tests such as microhardness, tensile and bending. Macrostructural observations were done at the beginning, middle and ending of the welded length. In addition, radiographic inspection was carried out. The pcBN tool exhibited good wear behavior even after welding around 8.5 m where no apparent loss in dimensions and geometrical features of the probe and shoulder were found. The macrographs displayed different microstructural features and material flow pattern among the heat inputs achieved. A large microstructure gradient was observed, especially within the stirred zone. All the tensile samples broke at the base material showing that the joints achieved higher strength. Microhardness peaks of about 400 HV were also encountered in all the joints. Finally, for welding speeds of 2–3 mm/s the thermocouples presented the most uniform thermal profiles. %0 journal article %@ 0142-1123 %A Keller, S.,Horstmann, M.,Kashaev, N.,Klusemann, B. %D 2019 %J International Journal of Fatigue %N %P 265-276 %R doi:0.1016/j.ijfatigue.2018.12.014 %T Experimentally validated multi-step simulation strategy to predict the fatigue crack propagation rate in residual stress fields after laser shock peening %U https://doi.org/0.1016/j.ijfatigue.2018.12.014 %X Laser shock peening (LSP) is a promising technology to retard the fatigue crack propagation (FCP) in metallic lightweight structures. A multi-step simulation strategy to predict FCP in LSP-induced residual stress fields is proposed and applied. The simulation strategy involves an LSP process simulation, a transfer approach to include the plastic strains in a C(T) specimen model to calculate the residual stresses and a FCP simulation to determine the stress intensity factors. The FCP rate is finally determined via FCP equations. The validity of the simulation strategy including the crack driving quantities prediction is experimentally demonstrated by a novel ‘simulation’ approach. %0 journal article %@ 0924-0136 %A Keller, S.,Chupakhin, S.,Staron, P.,Maawad, E.,Kashaev, N.,Klusemann, B. %D 2018 %J Journal of Materials Processing Technology %N %P 294-307 %R doi:10.1016/j.jmatprotec.2017.11.023 %T Experimental and numerical investigation of residual stresses in laser shock peened AA2198 %U https://doi.org/10.1016/j.jmatprotec.2017.11.023 %X Laser shock peening (LSP) is a surface treatment which improves the fatigue performance of metallic structures by introducing compressive residual stresses. The aim of this paper is the investigation of LSP of the aluminium alloy AA2198. This investigation includes the variation of the laser power density (2.78 GW/cm2 to 25 GW/cm2) and the squared laser focus (1 mm × 1 mm and 3 mm × 3 mm). Additionally, two different temper stages (T3 and T8) and thicknesses (3.2 mm and 4.8 mm) of AA2198 are considered. The study of the LSP process is split into two parts; at first, LSP experiments are performed to clarify the influence of the temper stage, the focus size, the laser power density and the thickness of the specimen on the residual stress field. Secondly, a process model based on the finite element method is employed which requires in particular the adjustment of a suitable laser induced pressure pulse. Due to the different yield strength and strain hardening behaviour of the different temper conditions, AA2198-T8 shows a lower penetration depth of compressive residual stresses compared to AA2198-T3. A smaller focus size leads to higher compressive residual stresses near the surface but a lower penetration depth. To investigate possible shock wave reflections, different base layers in the LSP process are investigated considering a free, a clamped and a glued back-side of the specimen. No differences in terms of resulting residual stresses were observed. The experimental study provides some preliminary assumptions which are used to simplify the simulation set-up. Residual stresses are measured by the incremental hole drilling method using electronic speckle pattern interferometry (ESPI) as well as synchrotron X-ray diffraction. The calculated residual stresses in the simulation are averaged layer-wise over a sample area for comparison with the measured residual stresses. The model is used to simulate the LSP process for the considered temper stages and focus sizes to predict the resulting residual stresses. Simulated and measured residual stress profiles show for the different cases very good agreement. %0 journal article %@ 0021-8464 %A Manente Andre, N.,Goushegir, S.M.,Scharnagl, N.,dos Santos, J.F.,Canto, L.B.,Amancio-Filho, S.T. %D 2018 %J The Journal of Adhesion %N 9 %P 723-742 %R doi:10.1080/00218464.2017.1378101 %T Composite surface pre-treatments: improvement on adhesion mechanisms and mechanical performance of metal-composite friction spot joints with additional film interlayer %U https://doi.org/10.1080/00218464.2017.1378101 9 %X Friction spot joints of aluminum alloy 2024-T3 and carbon-fiber-reinforced polyphenylene sulfide (CF-PPS) were produced with PPS film interlayer. Mechanical grinding, sandblasting and sandblasting combined with plasma activation were performed on the composite part to enhance the interface adhesion. The surface features – roughness, wettability and chemical activation – were correlated with the ultimate lap shear force of the joints. The composite surface with the highest surface roughness (sandblasting: 5.3 ± 0.6 µm) led to joints approximately 95% stronger (3068 ± 192 N) than the joints with the lowest surface roughness (mechanical grinding: 0.6 ± 0.1 µm, 1573 ± 84 N). The increase in surface roughness enlarged the effective contact surface area, leading to a better micro-mechanical interlocking between PPS film and composite. Although functional groups were identified in the plasma-treated specimens using X-ray photoelectron spectroscopy, no contribution to the mechanical strength of the joints were observed. The fracture surface analysis supported the conclusion that sandblasting was the most effective treatment, maximizing the mechanical performance of the joints. Impressions containing pieces of carbon fibers were identified on the interlayer surface. It indicates effective micro-mechanical interlocking at the interface of interlayer-composite achieved with the sandblasted specimens. %0 journal article %@ 0167-577X %A Borba, N.Z.,Blaga, L.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2018 %J Materials Letters %N %P 31-34 %R doi:10.1016/j.matlet.2017.12.033 %T Direct-Friction Riveting of polymer composite laminates for aircraft applications %U https://doi.org/10.1016/j.matlet.2017.12.033 %X Friction Riveting is an alternative joining technology to the conventional mechanical fastening suitable for woven-reinforced polymer composites. In this paper, the feasibility of Direct-Friction Riveting is demonstrated for Ti6Al4V rivet and carbon-fiber reinforced polyether-ether-ketone laminate single lap joints. Due to high shear rates, elevated process temperatures (500-900°C) and fast cooling rates (38 ± 2°C/s) experienced by the rivet tip, α’-martensitic structures were identified in the rivet anchoring zone along with fiber and polymer entrapment at the rivet-composite interface. An average ultimate lap shear force of 7.4 ± 0.6 kN similar to conventional lock-bolted single lap joints was achieved. These results indicate that Direct-Friction Riveting is a competitive method with potential for improvement and further application in aircraft structures. %0 journal article %@ 1806-0374 %A Martinazzi, D.,Lemos, G.V.B.,Cardoso, H.R.P.,dos Santos, R.E.,Ferreira, J.Z.,Bergmann, L.,dos Santos, J.F.,Reguly, A. %D 2018 %J Periodico Tche Quimica %N 29 %P 53-60 %T Estudo da Sensitizacao em Juntas Soldadas de Inconel® 625 Produzidas Atraves da Soldagem por Friccao e Mistura Mecanica - Sensitization Study in Friction Stir Welds of Inconel®625 %U 29 %X Resumo: Os novos desafios da indútria do óleo e gás requerem a utilização de materiais com maior de estabilidade química e propriedades mecânicas superiores. A liga 625, popularmente conhecida como Inconel® 625, é comumente utilizada como revestimento de pipelines e outros componentes. Portanto, o estudo de métodos de união que produzem juntas soldadas com excelente qualidade é essencial. Neste estudo, chapas soldadas de Inconel 625 foram produzidas através da Soldagem por Fricção e Mistura Mecânica (Friction Stir Welding) e estas foram submetidas a um tratamento térmico para avaliação da susceptibilidade à corrosão intergranular com a técnica de Reativação Potenciocinética de Ciclo Duplo (Double Loop Electrochemical Potentiokinetic Reactivation Test, DL-EPR). A influência do tratamento térmico na sensitização das juntas soldadas também foi avaliada através de microscopia ótica e microdureza. Os resultados indicam a formação de carbonetos devido ao aumento de dureza após o tratamento térmico e, assim, diferentes graus de sensitização.,Abstract:The new challenges of the oil and gas industry require noble materials with chemical stability and,greater mechanical properties. Alloy 625, popularly known as Inconel® 625, is used as a cladding material for pipelines and other components. Therefore, the study of joining methods that produce excellent welded joints is essential. Thus, in this study, welded sheets of Inconel 625 were produced by Friction Stir Welding(FSW) and afterwards they were subjected to a heat treatment to evaluate the susceptibility to sensitization by the Double Loop Electrochemical Potentiokinetic Reactivation (DL-EPR)technique. In addition, microhardnessprofiles were performed before and after the isothermal treatment. The microhardness results indicated that the increased hardness is due to the carbides formation after heat treatment. On the other hand, electrochemical tests showed that FSW process can significantly affect the degree of sensitization. %0 journal article %@ 1073-5623 %A Shen, J.,Lage, S.B.M.,Suhuddin, U.F.H.,Bolfarini, C.,dos Santos, J.F. %D 2018 %J Metallurgical and Materials Transactions A %N 1 %P 241-254 %R doi:10.1007/s11661-017-4381-6 %T Texture Development and Material Flow Behavior During Refill Friction Stir Spot Welding of AlMgSc %U https://doi.org/10.1007/s11661-017-4381-6 1 %X The microstructural evolution during refill friction stir spot welding of an AlMgSc alloy was studied. The primary texture that developed in all regions, with the exception of the weld center, was determined to be 〈110〉 fibers and interpreted as a simple shear texture with the 〈110〉 direction aligned with the shear direction. The material flow is mainly driven by two components: the simple shear acting on the horizontal plane causing an inward-directed spiral flow and the extrusion acting on the vertical plane causing an upward-directed or downward-directed flow. Under such a complex material flow, the weld center, which is subjected to minimal local strain, is the least recrystallized. In addition to the geometric effects of strain and grain subdivision, thermally activated high-angle grain boundary migration, particularly continuous dynamic recrystallization, drives the formation of refined grains in the stirred zone. %0 journal article %@ 1059-9495 %A Goebel, J.,Reimann, M.,dos Santos, J.F. %D 2018 %J Journal of Materials Engineering and Performance %N 10 %P 5212-5219 %R doi:10.1007/s11665-018-3551-z %T Influence of Cu/Li Ratio on the Welding Forces and Mechanical Properties of Two Bobbin Tool Friction Stir Welded Al-Cu-Li Alloys %U https://doi.org/10.1007/s11665-018-3551-z 10 %X Increasing space activities produce a high number of space objects and lead to increasing collision risks which urges leading industries to look for future removal strategies. Material substitution in order to raise demisability during atmospheric reentry is a possible solution. Modern aluminum lithium alloys are under consideration to replace high-temperature melting materials like titanium. Further, friction stir welding was proposed as suitable joining technology in order to avoid high heat inputs during manufacturing. In this work, two modern Al-Li-Cu alloys, AA 2060 and AA 2196, in peak-aged temper were welded using the stationary shoulder variant of bobbin tool friction stir welding. Identical process parameters led to defect-free welds in both alloys. The macrostructural and microstructural features are shown and analyzed. The welds were mechanically tested to an efficiency of 78 and 70% of the base metal ultimate tensile strength for AA 2060 T8 and AA 2196 T8, respectively. The process forces as well as the thermal cycle experienced by the workpiece material were used to explain the mechanical performance. The difference in composition regarding the Cu/Li ratio of the alloys was taken into account when the mechanical properties were correlated with the thermally affected microstructure of the weldments. %0 journal article %@ 0267-0836 %A Lemos, G.V.B.,Cunha, P.H.C.P.,Nunes, R.M.,Bergmann, L.,dos Santos, J.F.,Clarke, T. %D 2018 %J Materials Science and Technology %N 1 %P 95-103 %R doi:10.1080/02670836.2017.1361148 %T Residual stress and microstructural features of friction-stir-welded GL E36 shipbuilding steel %U https://doi.org/10.1080/02670836.2017.1361148 1 %X The purpose of the present study was to fulfil the knowledge gap concerning residual stresses evaluation of friction stir welded GL E36 shipbuilding steel. Plates of 6 mm thickness were welded using two different welding speeds (1 and 3 mm s−1) at a constant rotational speed of 500 rev min−1. This led to different thermal cycles and the objective is to analyse the resulting microstructures and residual stress states. Therefore, in this work, residual stresses were evaluated by X-ray diffraction; metallography and microhardness testing were performed to support these measurements. Results showed that welds produced with different heat inputs have distinguishable residual stress distributions. Increases in the welding speed led to higher residual stress and microhardness in the stir zone. %0 journal article %@ 0167-577X %A Falck, R.,Goushegir, S.M.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2018 %J Materials Letters %N %P 211-214 %R doi:10.1016/j.matlet.2018.01.021 %T AddJoining: a novel additive manufacturing approach for layered metal-polymer hybrid structures %U https://doi.org/10.1016/j.matlet.2018.01.021 %X A novel assembling technique based on additive manufacturing and materials joining principles has been introduced for layered metal-polymer hybrid structures. The AddJoining technique produces layered hybrid structures, using polymer 3D printing methods. The feasibility of the technique was demonstrated using fused deposition modeling for single-lap joint configuration. Microstructure and mechanical strength of the joints were studied using two combinations of materials; aluminum 2024-T3 with acrylonitrile butadiene styrene and aluminum 2024-T3 with alternate layers of polyamide-6 and carbon-fiber-reinforced polyamide-6. The latter reached an average ultimate lap-shear strength of 21.9 ± 1.1 MPa. This exploratory investigation showed the potential of AddJoining to produce metal-polymer layered structures. %0 journal article %@ 2075-4701 %A Barbini, A.,Carstensen, J.,dos Santos, J.F. %D 2018 %J Metals %N 4 %P 202 %R doi:10.3390/met8040202 %T Influence of Alloys Position, Rolling and Welding Directions on Properties of AA2024/AA7050 Dissimilar Butt Weld Obtained by Friction Stir Welding %U https://doi.org/10.3390/met8040202 4 %X Friction stir welding (FSW) was carried out for the butt joining of dissimilar AA2024-T3 and AA7050-T7651 aluminium alloys with 2-mm thicknesses. A comparison between the position and orientation of different materials was performed by varying the welding speed while keeping the rotational speed constant. Through an analysis of the force and torque produced during welding and a simple analytical model, the results indicate that the heat input was reduced when the AA7050 alloy was located in the advancing side (AS) of the joint. The different material positions influenced the material transportation and the interface in the centre of the stir zone (SZ). The microhardness of both materials was lower when they were in the AS of the joint. The differences in the hardness values were reduced at higher welding speeds when the heat input was decreased. The mechanical performance increased when the lower strength alloy was located in the AS. The material orientation exhibited a small influence when the AA7050 alloy was in the AS and in general on the resulting microhardness for all the cases analysed. The tensile strength values were very similar for both orientations, but an increase in the yield strength could be measured when the materials were oriented in the transverse direction. %0 journal article %@ 0079-6425 %A Bargmann, S.,Klusemann, B.,Markmann, J.,Schnabel, J.E.,Schneider, K.,Soyarslan, C.,Wilmers, J. %D 2018 %J Progress in Materials Science %N %P 322-384 %R doi:10.1016/j.pmatsci.2018.02.003 %T Generation of 3D representative volume elements for heterogeneous materials: A review %U https://doi.org/10.1016/j.pmatsci.2018.02.003 %X This work reviews state of the art representative volume element (RVE) generation techniques for heterogeneous materials. To this end, we present a systematic classification considering a wide range of heterogeneous materials of engineering interest. Here, we divide heterogeneous solids into porous and non-porous media, with 0 < void volume fraction < 1 and void volume fraction = 0, respectively. Further subdivisions are realized based on various morphological features. The corresponding generation methods are classified into three categories: (i) experimental methods targeting reconstruction through experimental characterization of the microstructure, (ii) physics based methods targeting simulation of the physical process(es) responsible for the microstructure formation and evolution, and (iii) geometrical methods concentrating solely on mimicking the morphology (ignoring the physical basis of the microstructure formation process). These comprise of various mathematical tools such as digital image correlation, tessellation, random field generation, and differential equation solvers. For completeness, relevant up-to-date software tools, used at various stages of RVE generation – either commercial or open-source – are summarized. Considered methods are reviewed based on their efficiency and predictive performance with respect to geometrical and topological properties of the microstructures. %0 journal article %@ 0921-5093 %A Feistauer, E.E.,Bergmann, L.A.,dos Santos, J.F. %D 2018 %J Materials Science and Engineering A %N %P 454-464 %R doi:10.1016/j.msea.2018.06.056 %T Effect of reverse material flow on the microstructure and performance of friction stir welded T-joints of an Al-Mg alloy %U https://doi.org/10.1016/j.msea.2018.06.056 %X Friction stir welding (FSW) has been developed and commercially applied with success to connect large and complex structures. However, process optimization is still required to improve the mechanical performance of the T assemblies. Therefore, a second welding pass was applied in this work and was performed backwards, while maintaining the same tool rotation direction. Thus, due to the creation of a reverse material flow, a second advance side over the previously retreating side of the joint was formed, which significantly reduced the defects typically found in FSWed T-joints. The joints were manufactured with dissimilar Al–Mg alloys (AA5083), which is of particular interest to the shipbuilding sector. The microstructural analysis revealed that the second pass significantly reduced the kissing bonding defect on the joints retreating side. As a result, the mechanical properties were improved under quasi-static loading, reaching performance levels comparable to those of the base material. A digital image correlation system (DIC) linked to a tensile test system was used to investigate the local strain fields of the T-joints under two different loading conditions. The fatigue strength was also evaluated and the FSWed T-joints reached the fatigue keen with a nominal load range of 88.4 MPa under skin loading. %0 journal article %@ 1526-6125 %A Froend, M.,Riekehr, S.,Kashaev, N.,Klusemann, B.,Enz, J. %D 2018 %J Journal of Manufacturing Processes %N %P 721-732 %R doi:10.1016/j.jmapro.2018.06.033 %T Process development for wire-based laser metal deposition of 5087 aluminium alloy by using fibre laser %U https://doi.org/10.1016/j.jmapro.2018.06.033 %X In recent decades, laser metal deposition, as a part of additive manufacturing, developed into a promising methodology in industrial fields. In recent years, there has been an increased interest in the processability of lightweight high-strength structural materials, such as aluminium alloys. However, in terms of wire-based laser metal deposition, there is still a lack of knowledge with regard to the processability of aluminium alloys. In this research, the process development for wire-based laser metal deposition of a 5087 aluminium alloy (AlMg4.5 MnZr) has been conducted. It is observed that pre-heating is beneficial in terms of porosity and distortion reduction. Within optimized parameter ranges, it is possible to control the geometric shape, dilution, and aspect ratios of the deposited layers in a systematic way. Accordingly, defect-free layers with tailored geometrical features can be processed and adapted to specific process requirements. %0 journal article %@ 1059-9495 %A Reimann, M.,Goebel, J.,dos Santos, J.F. %D 2018 %J Journal of Materials Engineering and Performance %N 10 %P 5220-5226 %R doi:10.1007/s11665-018-3519-z %T Microstructure Evolution and Mechanical Properties of Keyhole Repair Welds in AA 2219-T851 using Refill Friction Stir Spot Welding %U https://doi.org/10.1007/s11665-018-3519-z 10 %X The search for a suitable friction-based keyhole repair technique that fulfills the requirements for high-quality repair welds has become an important research topic, especially for aerospace applications. In order to provide and analyze an universal keyhole repair method for lightweight metals, refill friction stir spot welding is applied to through-hole repairs in 3- and 6-mm-thick sheets of precipitate hardening AA 2219-T851. Keyholes with a diameter of 7.5 mm were repair welded achieving a defect-free microstructure. The correlation between the microstructural evolution imposed by the repair process and the resulting mechanical properties is shown. A comprehensive analysis of the precipitate evolution in peak-aged AA 2219 during RFSSW is presented. Thermal cycle measurements revealed high heating rates and peak temperatures of up to 520 °C in the weld center. The thermal cycle caused mainly dissolution and minor equilibrium phase formation in the stirred zone. In the HAZ, overaging of the strengthening precipitates dominates with minor dissolution and equilibrium phase formation only in the direct proximity of the SZ. Microstructural analysis revealed typical weld zone formation with inhomogeneous grain size distribution in the SZ. The resulting mechanical properties are dominated by an inhomogeneous hardness distribution with lowest hardness in the TMAZ at 5 mm from the center of the weld. During tensile loading main yielding and the final fracture occur in the area of lowest strength. Tensile testing showed yield strength of 40 to 46% and UTS of 28 to 25% below BM values in 3- and 6-mm-thick sheets, respectively. The sheet thickness and post-weld natural aging were found to influence the mechanical properties of the weld significantly. %0 journal article %@ 1005-0302 %A Wang, F.F.,Li, W.Y.,Shen, J.,Wen, Q.,dos Santos, J.F. %D 2018 %J Journal of Materials Science and Technology %N 1 %P 135-139 %R doi:10.1016/j.jmst.2017.11.001 %T Improving weld formability by a novel dual-rotation bobbin tool friction stir welding %U https://doi.org/10.1016/j.jmst.2017.11.001 1 %X A novel dual-rotation bobbin tool friction stir welding (DBT-FSW) was developed, in which the upper shoulder (US) and lower shoulder (LS) have different rotational speeds. This process was tried to weld 3.2 mm thick aluminum-lithium alloy sheets. The metallographic analysis and torque measurement were carried out to characterize the weld formability. Experimental results show that compared to conventional bobbin tool friction stir welding, the DBT-FSW has an excellent process stability, and can produce the defect-free joints in a wider range of welding parameters. These can be attributed to the significant improvement of material flow caused by the formation of a staggered layer structure and the unbalanced force between the US and LS during the DBT-FSW process. %0 journal article %@ 0924-0136 %A de Queiroz Caetano, G.,Silva, C.C.,Motta, M.F.,Miranda, H.C.,Farias, J.P.,Bergmann, L.A.,dos Santos, J.F. %D 2018 %J Journal of Materials Processing Technology %N %P 430-436 %R doi:10.1016/j.jmatprotec.2018.07.018 %T Influence of rotation speed and axial force on the friction stir welding of AISI 410S ferritic stainless steel %U https://doi.org/10.1016/j.jmatprotec.2018.07.018 %X The Friction Stir Welding process parameters were varied to provide a combination of an acceptable surface finish, absence of cracks, and full tool penetration. Two levels of rotation speed and axial forces from 10 to 30 kN were applied, whilst keeping the welding speed constant at 1 mm/s. One of the defects analyzed was the production of flashes. This can occur due to an increase in axial force and because of the instability in its applications, which implies directly on the formation of volumetric defects along the stir zone. FSW joints without root flaws can be achieved through a correct balance between the axial force and rotation speed, which also allows a greater immersion of the tool probe in the joint. Both rotation speeds using an axial force of around 20 kN proved to be good welding parameters for the FSW process. The welding of the AISI 410S steel (under these conditions) resulted in joints without internal defects and with a good surface finish. %0 journal article %@ 2589-1529 %A Herrnring, J.,Staron, P.,Kashaev, N.,Klusemann, B. %D 2018 %J Materialia %N %P 243-255 %R doi:10.1016/j.mtla.2018.08.010 %T Multiscale process simulation of residual stress fields of laser beam welded precipitation hardened AA6082 %U https://doi.org/10.1016/j.mtla.2018.08.010 %X In this study, a multiscale modelling approach for the determination of residual stresses for the laser beam welded, precipitation hardened aluminium alloy AA6082-T6 is presented and applied. The material behaviour is described by an elasto-visco-plastic material model, specially suited for fusion welding processes. The microstructure evolution during the welding process has a direct influence on the macroscopic mechanical properties. The modelling approach accounts for the change in the microstructure via a Kampmann-Wagner Numerical model which takes into account the kinetics of the precipitates. The macroscopic mechanical properties are determined via classic dislocation theory, which accounts for the interaction between dislocations and precipitates. The temperature field of the welding process is described by a highly efficient semi-analytical approach. The solution of the temperature field in connection with a three dimensional moving heat source is achieved by using the method of Green’s functions. By employing the method of Green’s functions, it is possible to reduce the numerical effort significantly. The results of this modelling approach are compared to temperature, hardness as well as residual stress measurements, obtained from synchrotron X-ray diffraction, for welded sheets to clarify the accuracy of the applied model. %0 journal article %@ 2452-3216 %A Fomin, F.,Klusemann, B.,Kashaev, N. %D 2018 %J Procedia Structural Integrity %N %P 273-278 %R doi:10.1016/j.prostr.2018.12.046 %T Surface modification methods for fatigue properties improvement of laser welded Ti64 butt joints %U https://doi.org/10.1016/j.prostr.2018.12.046 %X Surface and internal defects formed upon laser beam welding (LBW) have been recognized as a serious problem because they cause stress concentration leading to premature failure of a welded component. This paper seeks to remedy these weld imperfections by applying various post-weld treatments and analyzing their effect on the high cycle fatigue (HCF) performance of welded joints. High efficiency of laser-based post-processing techniques after welding such as laser surface remelting (LSR) and laser shock peening (LSP) was demonstrated and compared with conventional approaches. The study reveals that welding porosity determines the internal crack initiation of the surface-treated weldments. Influence of process parameters on porosity level and the HCF properties is presented in detail. Based on an extensive experimental study, practical guidelines needed to mitigate the notch effect from defects and to maximize the fatigue performance of the laser-welded Ti-6Al-4V butt joints are given. %0 journal article %@ 0255-5476 %A Herrnring, J.,Kashaev, N.,Klusemann, B. %D 2018 %J Materials Science Forum, THERMEC 2018 %N %P 1411-1417 %R doi:10.4028/www.scientific.net/MSF.941.1411 %T Precipitation Kinetics of AA6082: An Experimental and Numerical Investigation %U https://doi.org/10.4028/www.scientific.net/MSF.941.1411 %X The development of simulation tools for bridging different scales are essential for understanding complex joining processes. For precipitation hardening, the Kampmann-Wagner numerical model (KWN) is an important method to account for non-isothermal second phase precipitation. This model allows to describe nucleation, growth and coarsening of precipitation hardened aluminum alloys based on a size distribution for every phase which produces precipitations. In particular, this work investigates the performance of a KWN model by [1-3] for Al-Mg-Si-alloys. The model is compared against experimental data from isothermal heat treatments taken partially from [2]. Additionally, the model is used for investigation of the precipitation kinetics for a laser beam welding process, illustrating the time-dependent development of the different parameters related to the precipitation kinetics and the resulting yield strength. %0 journal article %@ 1359-6454 %A dos Santos, J.F.,Staron, P.,Fischer, T.,Robson, J.D.,Kostka, A.,Colegrove, P.,Wang, H.,Hilgert, J.,Bergmann, L.,Huetsch, L.L.,Huber, N.,Schreyer, A. %D 2018 %J Acta Materialia %N %P 163-172 %R doi:10.1016/j.actamat.2018.01.020 %T Understanding precipitate evolution during friction stir welding of Al-Zn-Mg-Cu alloy through in-situ measurement coupled with simulation %U https://doi.org/10.1016/j.actamat.2018.01.020 %X Friction Stir Welding (FSW) imparts both heat and deformation to the metal being joined, producing profound microstructural changes that determine the weld properties. In the case of welding of aerospace aluminium alloys, the most important change is the modification of the size, nature, and fraction of strengthening precipitates. To understand these changes requires the ability to measure the microstructural evolution during the welding process. This paper describes a new tool, the FlexiStir system, a portable friction stir unit designed for use in a high-energy synchrotron beamline that enables in-situ studies of microstructural evolution during FSW. FlexiStir has been used to measure precipitate evolution during FSW of aluminium alloy 7449-TAF and provide time-resolved measurement of precipitate size and volume fraction via small angle X-ray scattering (SAXS). These measurements have been interpreted with the aid of a previously developed microstructural model. The model predictions and SAXS measurements are in good qualitative agreement and demonstrate the complex precipitate transformation, dissolution, and reprecipitation events that occur during welding. %0 journal article %@ 1044-5803 %A Froend, M.,Ventzke, V.,Riekehr, S.,Kashaev, N.,Klusemann, B.,Enz, J. %D 2018 %J Materials Characterization %N %P 59-67 %R doi:10.1016/j.matchar.2018.05.022 %T Microstructure and microhardness of wire-based laser metal deposited AA5087 using an Ytterbium fibre laser %U https://doi.org/10.1016/j.matchar.2018.05.022 %X Wire-based additive manufacturing has been increasingly investigated in recent years. Although it is possible nowadays to manufacture structures that are free from inner defects such as porosity and cracks using wire and arc additive manufacturing, there is still a lack of knowledge regarding wire-based laser metal deposition of aluminium and its alloys. In order to be able to produce locally tailored part properties, it is necessary to understand the process parameter to material property relationships. Using laser energy sources, it becomes possible to analyse in detail the heat input and to observe occurring microstructural evolutions. This work includes a microstructural and mechanical characterization of an AA5087 wall structure. Detailed analyses of the chemical composition, texture, and microhardness of the structure have been performed. The microstructure contains different grain orientations as well as grain shapes and sizes along the structure, resulting in locally different material properties. The results have been analysed and discussed in reference to fundamental theories such as the Hall–Petch and Orowan mechanisms. %0 journal article %@ 1996-1944 %A Cipriano, G.P.,Blaga, L.A.,dos Santos, J.F.,Vilaca, P.,Amancio-Filho, S.T. %D 2018 %J Materials %N 11 %P 2294 %R doi:10.3390/ma11112294 %T Fundamentals of Force-Controlled Friction Riveting: Part I - Joint Formation and Heat Development %U https://doi.org/10.3390/ma11112294 11 %X This work presents a systematic study on the correlations between process parameters and rivet plastic deformation, produced by force-controlled friction riveting. The 5 mm diameter AA2024 rivets were joined to 13 mm, nominal thickness, polyetherimide plates. A wide range of joint formations was obtained, reflecting the variation in total energy input (24–208 J) and process temperature (319–501 °C). The influence of the process parameters on joint formation was determined, using a central composite design and response surface methodology. Friction time displayed the highest contribution on both rivet penetration (61.9%) and anchoring depth (34.7%), and friction force on the maximum width of the deformed rivet tip (46.5%). Quadratic effects and two-way interactions were significant on rivet anchoring depth (29.8 and 20.8%, respectively). Bell-shaped rivet plastic deformation—high mechanical interlocking—results from moderate energy inputs (~100 J). These geometries are characterized by: rivet penetration depth of 7 to 9 mm; maximum width of the deformed rivet tip of 9 to 12 mm; and anchoring depth higher than 6 mm. This knowledge allows the production of optimized friction-riveted connections and a deeper understanding of the joining mechanisms, further discussed in Part II of this work. %0 journal article %@ 2212-8271 %A Froend, M.,Ventzke, V.,Riekehr, S.,Kashaev, N.,Klusemann, B.,Enz, J. %D 2018 %J Procedia CIRP %N %P 131-135 %R doi:10.1016/j.procir.2018.08.062 %T Microstructure and hardness evolution of laser metal deposited AA5087 wall-structures %U https://doi.org/10.1016/j.procir.2018.08.062 %X Wire-based laser metal deposition enables to manufacture structures with very high deposition rates in comparison to powder-based laser additive manufacturing. However, this advantage is generally accompanied with a high energy input. Thus, an accumulation of heat within the structure can result. In addition, the heat conduction conditions can also change with increasing structure height, leading to inhomogeneous microstructural formation along the part. The present study deals with the evolution of the microstructure and hardness in laser metal deposited AA5087 wall structures. In this regard, two samples processed at adapted parameters for different deposition rates are investigated. %0 journal article %@ 1005-0302 %A Barbini, A.,Carstensen, J.,dos Santos, J.F. %D 2018 %J Journal of Materials Science and Technology %N 1 %P 119-127 %R doi:10.1016/j.jmst.2017.10.017 %T Influence of a non-rotating shoulder on heat generation, microstructure and mechanical properties of dissimilar AA2024/AA7050 FSW joints %U https://doi.org/10.1016/j.jmst.2017.10.017 1 %X Friction stir welding (FSW) and stationary shoulder friction stir welding (SSFSW) were carried out for the butt joining of dissimilar AA2024-T3 and AA7050-T7651 aluminium alloys with thicknesses of 2 mm. A comparison between the two processes was performed by varying the welding speed while keeping the rotational speed constant. Through the analysis of the force and torque produced during welding and a simple analytical model, it was possible to show that in SSFSW there is more effective coupling with the tool and the heat produced is more efficiently distributed. This process decreases both the welding area and the diffusion at the interface of the two alloys compared with FSW. The minimum microhardness occurred at the advancing side (AS) at the interface between the thermo-mechanically affected zone (TMAZ) and the stir zone (SZ) in both processes, although the decrease was more gradual in SSFSW. This interface is also where all specimens failed for both welding technologies. An increase in tensile strength was measured in SSFSW compared with standard FSW. Furthermore, it was possible to establish the mechanical performance of the material in the fracture zone using digital image correlation. %0 journal article %@ 0255-5476 %A Froend, M.,Bock, F.,Ventzke, V.,Riekehr, S.,Kashaev, N.,Klusemann, B.,Enz, J. %D 2018 %J Materials Science Forum, THERMEC 2018 %N %P 988-994 %R doi:10.4028/www.scientific.net/MSF.941.988 %T Experimental Investigation of Temperature Distribution during Wire-Based Laser Metal Deposition of the Al-Mg Alloy 5087 %U https://doi.org/10.4028/www.scientific.net/MSF.941.988 %X Wire-based laser metal deposition enables to manufacture large-scale components with deposition rates significant higher compared to powder-based laser additive manufacturing techniques, which are currently working with deposition rates of only a few hundred gram per hour. However, the wire-based approach requires a significant amount of laser power in the range of several kilowatts instead of only a few hundred watts for powder-based processes. This excessive heat input during laser metal deposition can lead to process instabilities such as a non-uniform material deposition and to a limited processability, respectively. Although, numerous possibilities to monitor temperature evolution during processing exist, there is still a lack of knowledge regarding the relationship between temperature and geometric shape of the deposited structure. Due to changing cooling conditions with increasing distance to the substrate material, producing a wall-like structure results in varying heights of the individual tracks. This presents challenges for the deposition of high wall-like structures and limits the use of constant process parameters. In the present study, the temperature evolution during laser metal deposition of AA5087 using constant process parameters is investigated and a scheme for process parameter adaptions in order to reduce residual stress induced componential distortions is suggested. %0 journal article %@ 0924-0136 %A Goebel, J.,Reimann, M.,Norman, A.,dos Santos, J.F. %D 2017 %J Journal of Materials Processing Technology %N %P 37-45 %R doi:10.1016/j.jmatprotec.2017.02.011 %T Semi-stationary shoulder bobbin tool friction stir welding of AA2198-T851 %U https://doi.org/10.1016/j.jmatprotec.2017.02.011 %X The aluminum lithium alloy AA2198-T851 has been bobbin tool friction stir welded using a tool concept with one stationary and one rotating shoulder. Defect free welds in 3 mm thick sheet have been produced featuring a high quality surface finish on the stationary side. The macrostructure forms an asymmetrical shape with microstructural characteristics known from standard friction stir welding. Because of only one rotating side a material flow direction towards the stationary shoulder has been observed. A parameter survey shows that a weld pitch of one mm per rotation combined with high pressure between the shoulders lead to good results. Mechanical performance of 82% of base metal ultimate tensile strength and 77% of base metal hardness have been achieved. The fracture analysis indicates two competing fracture modes, one being in the heat affected zone and the other at the borderline of the stirred zone on the advancing side. The first mode forms due to thermal cycle influence, whereas the second location suffers from weak bonding as a result of the thermal cycle and experienced deformation. %0 journal article %@ 0268-3768 %A Bachmann, M.,Carstensen, J.,Bergmann, L.,dos Santos, J.F.,Wu, C.S.,Rethmeier, M. %D 2017 %J The International Journal of Advanced Manufacturing Technology %N 1-4 %P 1443-1452 %R doi:10.1007/s00170-016-9793-8 %T Numerical simulation of thermally induced residual stresses in friction stir welding of aluminum alloy 2024-T3 at different welding speeds %U https://doi.org/10.1007/s00170-016-9793-8 1-4 %X The paper deals with a numerical finite element simulation of the residual stress evolution in friction stir welding of 6 mm thick aluminum alloy AA2024-T3. The transient thermal field during the welding process was calculated with the commercial code COMSOL Multiphysics 5.0. Therefore, a thermal-pseudo-mechanical (TPM) heat source was implemented. A subsequent mechanical simulation was performed with varying hardening models for different welding speeds of 60 and 300 mm/min. The influence of softening of the material, which was due to hardening precipitation dissolution associated to the heating, was also investigated. Experiments in terms of thermocouple measurements as well as Vickers hardness and X-ray measurements of the residual stresses were conducted and compared to numerically obtained results. A qualitatively as well as quantitatively good agreement was found for different applied welding speeds. %0 journal article %@ 1042-6914 %A Fitseva, V.,Hanke, S.,dos Santos, J.F. %D 2017 %J Materials and Manufacturing Processes %N 5 %P 557-563 %R doi:10.1080/10426914.2016.1257799 %T Influence of rotational speed on process characteristics in friction surfacing of Ti-6Al-4V %U https://doi.org/10.1080/10426914.2016.1257799 5 %X Friction surfacing process is employed to deposit metallic coatings, whereby similar and dissimilar material combinations can be realized. The process can be applied as a local repair technology, or the coating material can locally modify the surfaces. One advantage of this process is that the coatings are deposited in solid state without reaching the melting range of materials, thereby avoiding dilution with the substrate. The involved severe plastic deformation under high temperatures alters the microstructure of the coating material, leaving it fully dynamically recrystallized. The current work focuses on deposition of Ti-6Al-4V coatings. For that material, the process parameter rotational speed plays a major role in the material’s response during processing. Two different regimes with a threshold at 2000 min−1 exist, upon which the flow behavior of Ti-6Al-4V significantly differs, affecting among others the coating dimensions. Microstructural analysis reveals that the material is deformed in a high temperature β phase, and the high cooling rates (46.4 Ks−1) lead to martensitic transformation. The β grain size differs in the low and high rotational speed regimes. This study shows that metallurgical processes play an important role in friction surfacing, since they influence all relevant process characteristics, including microstructure, material efficiency and process forces. %0 journal article %@ 1362-1718 %A Suhuddin, U.F.H.,Fischer, V.,Kostka, A.,dos Santos, J.F. %D 2017 %J Science and Technology of Welding and Joining %N 8 %P 658-665 %R doi:10.1080/13621718.2017.1300744 %T Microstructure evolution in refill friction stir spot weld of a dissimilar Al–Mg alloy to Zn-coated steel %U https://doi.org/10.1080/13621718.2017.1300744 8 %X In the present study, dissimilar welds of an Al–Mg–Mn alloy and a Zn-coated high-strength low-alloy steel were welded by refill friction stir spot welding. The maximum shear load recorded was approximately 7.8 kN, obtained from the weld produced with a 1600 rev min−1 tool rotational speed. Microstructural analyses showed the formation of a solid–liquid structure of an Al solid solution in Mg–Al-rich Zn liquid, which gives rise to the formation of Zn-rich Al region and microfissuring in some regions during welding. Exposure of steel surface to Mg–Al-rich Zn liquid led to the formation of Fe2Al5 and Fe4Al13 intermetallics. The presence of defective Zn-rich Al regions and Fe–Al intermetallics at the faying surface affects the weld strength. %0 journal article %@ 1362-1718 %A Lemos, G.V.B.,Hanke, S.,dos Santos, J.F.,Bergmann, L.,Reguly, A.,Strohaecker, T.R. %D 2017 %J Science and Technology of Welding and Joining %N 8 %P 643-657 %R doi:10.1080/13621718.2017.1288953 %T Progress in friction stir welding of Ni alloys %U https://doi.org/10.1080/13621718.2017.1288953 8 %X In recent years, interest has been increasing in application of Nickel alloys in the oil industry. For subsea engineering, the possibility to weld high-strength materials in an effective manner is essential. Friction Stir Welding (FSW) is alternative to join several materials retaining their properties or even improving them. This fact is relevant for Corrosion-Resistant Alloys (CRA) used in deep-water exploitation of hydrocarbons. Publications up to now have focused on FSW of Inconel® series as alloy 600, 625, and 718. To provide a solid basis for development, this review discusses the crucial points for FSW. The tool materials are described, as well as the joint microstructure and properties achieved. Furthermore, the basics of the corrosion resistance and the early corrosion studies of FSW joints are presented. It is concluded that FSW is a promising process for Ni alloys, but depends on upcoming research regarding tool technology and corrosion investigations. %0 journal article %@ 0043-1648 %A Hanke, S.,Lemos, G.V.B.,Bergmann, L.,Martinazzi, D.,dos Santos, J.F.,Strohaecker, T.R. %D 2017 %J Wear %N %P 403-408 %R doi:10.1016/j.wear.2017.01.070 %T Degradation mechanisms of pcBN tool material during Friction Stir Welding of Ni-base alloy 625 %U https://doi.org/10.1016/j.wear.2017.01.070 %X In Friction Stir Welding (FSW), interactions between the plasticized stirred material and the tool significantly affect resulting weld properties. When welding metals with high strength and melting point, the tribological load on the tool is severe, and poses the main limiting factor for the technology's industrial exploitation. Since tool materials are loaded to their limits, it is essential to understand the interactions of specific tool material and welded metal combinations.,In the present study 3.2 mm alloy 625 sheets were joined using a pcBN tool with W-Re binder phase. Wear lead to a change in tool geometry followed by tool fracture. In SEM investigations the welds revealed typical banded structures, composed of small grains and non-metallic phases containing W from the tool material. The tool surface is extensively covered by adhering sheet metal. Further, BN grain pull-outs and appearances of diffusive wear are visible on the worn tool surface.,Tool wear is mainly caused by detachment of BN grains due to thermal softening of the metallic binder phase and dissolution of BN in the hot material in the stirred zone. Using low rotational speeds resulting in lower process temperatures reduces tool wear and results in a homogeneous stirred zone. %0 journal article %@ 1559-3959 %A Schneider, K.,Klusemann, B.,Bargmann, S. %D 2017 %J Journal of Mechanics of Materials and Structures %N 4 %P 471-484 %R doi:10.2140/jomms.2017.12.471 %T Fully periodic RVEs for technological relevant composites: not worth the effort! %U https://doi.org/10.2140/jomms.2017.12.471 4 %X The setup of a finite element model for homogenization featuring a fully periodic geometry and a fully periodic mesh topology in combination with a high quality discretization is a cumbersome task and might significantly reduce the overall efficiency in multiscale finite element simulations.,In this work, we examine multiple methodologies of setting up finite element models for homogenization purposes that extenuate these difficulties. Approaches resulting in periodic and nonperiodic representative volume element topologies in the microstructural generation process are introduced. Furthermore, we review and analyze various types of boundary conditions that either enforce periodicity or do not require periodicity of the underlying discretization. Approximate periodic boundary conditions are discussed in detail.,The benchmark study proves that a fully periodic topology and mesh discretization with periodic boundary conditions is not necessary in order to identify effective macroscopic material parameters for technologically relevant composites. %0 journal article %@ 1996-1944 %A Zocoller Borba, N.,Afonso, C.R.M.,Blaga, L.,dos Santos, J.F.,Canto, L.B.,Amancio-Filho, S.T. %D 2017 %J Materials %N 2 %P 184 %R doi:10.3390/ma10020184 %T On the Process-Related Rivet Microstructural Evolution, Material Flow and Mechanical Properties of Ti-6Al-4V/GFRP Friction-Riveted Joints %U https://doi.org/10.3390/ma10020184 2 %X In the current work, process-related thermo-mechanical changes in the rivet microstructure, joint local and global mechanical properties, and their correlation with the rivet plastic deformation regime were investigated for Ti-6Al-4V (rivet) and glass-fiber-reinforced polyester (GF-P) friction-riveted joints of a single polymeric base plate. Joints displaying similar quasi-static mechanical performance to conventional bolted joints were selected for detailed characterization. The mechanical performance was assessed on lap shear specimens, whereby the friction-riveted joints were connected with AA2198 gussets. Two levels of energy input were used, resulting in process temperatures varying from 460 ± 130 °C to 758 ± 56 °C and fast cooling rates (178 ± 15 °C/s, 59 ± 15 °C/s). A complex final microstructure was identified in the rivet. Whereas equiaxial α-grains with β-phase precipitated in their grain boundaries were identified in the rivet heat-affected zone, refined α′ martensite, Widmanstätten structures and β-fleck domains were present in the plastically deformed rivet volume. The transition from equiaxed to acicular structures resulted in an increase of up to 24% in microhardness in comparison to the base material. A study on the rivet material flow through microtexture of the α-Ti phase and β-fleck orientation revealed a strong effect of shear stress and forging which induced simple shear deformation. By combining advanced microstructural analysis techniques with local mechanical testing and temperature measurement, the nature of the complex rivet plastic deformational regime could be determined. %0 journal article %@ 0268-3768 %A Santana, L.M.,Suhuddin, U.F.H.,Oelscher, M.H.,Strohaecker, T.R.,dos Santos, J.F. %D 2017 %J The International Journal of Advanced Manufacturing Technology %N 9-12 %P 4213-4220 %R doi:10.1007/s00170-017-0432-9 %T Process Optimization and Microstructure Analysis in Refill Friction Stir Spot Welding of 3-mm-thick Al-Mg-Si Aluminum Alloy %U https://doi.org/10.1007/s00170-017-0432-9 9-12 %X Novel ultra-high-strength aluminum alloys provide enormous lightweighting potential for modern car body design. However, joining such alloys can be challenging. Refill friction stir spot welding is a solid state joining process that provides fundamental advantages compared to conventional joining technologies when welding aluminum alloys. This work presents refill friction stirspot welding for joining3-mm-thick Al-Mg-Si alloys. The welded joints have been optimized for shear load condition by the design of experiment and analysis of variance. The results show that it is possible to obtain welds of relatively thick Al-Mg-Si alloys with good mechanical properties. Microstructure analyses show that rotational speed and plunge depth play important rolesin the bonded width and hook height, which affect the mechanical performance of the joint. %0 journal article %@ 0924-0136 %A Hanke, S.,dos Santos, J.F. %D 2017 %J Journal of Materials Processing Technology %N %P 257-267 %R doi:10.1016/j.jmatprotec.2017.04.021 %T Comparative study of severe plastic deformation at elevated temperatures of two aluminium alloys during friction surfacing %U https://doi.org/10.1016/j.jmatprotec.2017.04.021 %X Aluminium alloys 5083 and 6082 were deposited by Friction Surfacing (FS) under the same process conditions. Process characteristics including torque and forces, temperatures and the deposit microstructure were compared. The observed differences are discussed with regard to material strength, thermal softening rate and recrystallization mechanisms.,AA 6082 plasticises faster, reaching ≈30 K higher temperatures, thicker and wider coatings and a higher material efficiency. The specific energy required for plastification is in the same order of magnitude as the activation energy for self-diffusion, emphasising the influence of dynamic recrystallization (DRX) mechanisms. A tendency for lower grain size and larger variations in grain boundary misorientation observed for AA 5083 points towards a shift in the steady-state DRX balance towards dislocation generation, due to the higher Mg content of this alloy. This corresponds to the lower process speeds required for AA 5083. AA 6082 may undergo more localized shear because of its high thermal softening rate and additional loss of strength through dissolution of Mg2Si with increasing temperature. This may contribute to a higher energy and material efficiency for plastification and deposition of AA 6082 by FS. %0 journal article %@ 0924-0136 %A Reimann, M.,Goebel, J.,Gartner, T.M.,dos Santos, J.F. %D 2017 %J Journal of Materials Processing Technology %N %P 157-166 %R doi:10.1016/j.jmatprotec.2017.02.025 %T Refilling termination hole in AA 2198–T851 by refill friction stir spot welding %U https://doi.org/10.1016/j.jmatprotec.2017.02.025 %X Friction stir welding features a joining technology with only few drawbacks. The exit hole inevitably left by the tool is a major disadvantage. In order to eliminate volume defects such as termination holes or voids in friction stir welds, refill friction stir spot welding was used for keyhole repair. The keyhole closure process was employed to 3 mm thick sheets of aluminum-lithium alloy AA 2198-T851. Exit holes with a diameter of 7.5 mm in semi–stationary shoulder bobbin tool friction stir welds were refilled successfully.,To characterize the refilling process characteristic process parameters such as position, force and torque of the tool parts have been monitored. The welds have been analyzed with regards to microstructural features, the local and global mechanical performance as well as the thermal cycle. The properties of the repair welds have been compared to friction stir welded butt joints and keyhole closure welds in bare sheet.,A systematic investigation comparing and combining the two friction based processes has shown that refill friction stir spot welding is able to be applied as keyhole closure technique in sheet material and in semi–stationary shoulder bobbin tool friction stir welds. Defect free welds with known microstructural features were achieved. The mechanical performance of keyhole closure welds using refill friction stir spot welding in semi–stationary shoulder bobbin tool friction stir welds is comparable to the performance of keyhole closure welds in bare sheets. High-strength keyhole closure welds with efficiencies of 78 % in terms of ultimate tensile strength were achieved. %0 journal article %@ 0030-3992 %A Froend, M.,Fomin, F.,Riekehr, S.,Alvarez, P.,Zubiri, F.,Bauer, S.,Klusemann, B.,Kashaev, N. %D 2017 %J Optics and Laser Technology %N %P 123-131 %R doi:10.1016/j.optlastec.2017.05.017 %T Fiber laser welding of dissimilar titanium (Ti-6Al-4V/cp-Ti) T-joints and their laser forming process for aircraft application %U https://doi.org/10.1016/j.optlastec.2017.05.017 %X The weldability of dissimilar T-joints between commercially pure titanium (cp-Ti) Grade 2 skin and Ti-6Al-4V Grade 5 stringer using a continuous wave 8 kW ytterbium fiber laser as well as the possibility of subsequent laser straightening process of these joints were investigated. Based on the industrial standards ISO 4578:2011 and AWS D17.1:200, process development to compensate inherent angular distortion after welding by laser heating with the same equipment as for welding was carried out. The obtained results were effectively transferred to a 6-stringer-demonstrator with a length up to 500 mm. To investigate the shape and morphology of the welding seam as well as to verify its freedom from defects using the defined process parameters, metallographic transverse cross-sections and X-ray analyses were realized. In addition, the behavior of the welding seam geometry and the bending behavior of the specimens for varied process parameters were elucidated. For the welding process special attention to the shielding conditions and to the local and angular laser beam positioning was payed. To straighten the welded joints, laser straightening parameters inducing no microstructural changes were identified. %0 journal article %@ 0104-9224 %A Lemos, G.V.B.,Nunes, R.M.,Doll, P.,Bergmann, L.,Strohaecker, T.R.,dos Santos, J.F. %D 2017 %J Soldagem & Inspecao %N 1 %P 35-45 %R doi:10.1590/0104-9224/si2201.05 %T Residual Stress Evaluation in Friction Stir Welds of Inconel 625 - Avaliacao das Tensoes Residuais em Juntas Soldadas de Inconel 625 Obtidas Atraves da Soldagem por Friccao e Mistura Mecanica %U https://doi.org/10.1590/0104-9224/si2201.05 1 %X The use of noble materials is a basic requirement in applications where an aggressive environment such as offshore industry and nuclear energy. In this scenario, the Inconel 625 is often used as clad material in rigid pipes. Thus, nickel superalloys play a fundamental role in the deepwater exploration fields and, therefore, understanding of modern welding methods applied to these alloys and their consequences in the residual stress states is very important. Hence, this work evaluates the residual stress distributions after Friction Stir Welding (FSW) applied on Inconel 625 sheets. FSW was performed with tool rotational speed in the range of 200 to 1200 rpm and welding speed constant. Measurements of superficial residual stresses were investigated by X-ray Diffraction. In addition, macrostructures and heat input were evaluated. Although there are only few reports related to FSW applied on Inconel alloys, probably due to this welding process difficulty, it has been regarded that there is cumulative application of a solid state welding as an excellent alternative for nickel superalloys. The results showed that different welding parameters produced distinctly welded joints and consequently changes in the residual stress distributions. Finally, an increase in the tool rotation speed increased the residual stress in the stir zone.,A utilização de materiais nobres é requisito básico em aplicações onde existe um ambiente agressivo como na indústria do petróleo e nuclear. Neste panorama, a liga Inconel 625 é frequentemente utilizada como material de cladeamento no revestimento interno de dutos rígidos. Assim, as superligas de níquel exercem papel fundamental nos campos de exploração de águas profundas e, por isso, o conhecimento de métodos modernos de soldagem aplicados a estas ligas e suas consequências nos estados de tensões residuais é importante. Portanto, o presente trabalho faz uma avaliação das tensões residuais após a Soldagem por Fricção e Mistura Mecânica (SFMM) em chapas soldadas de Inconel 625. A união das chapas foi realizada com rotação da ferramenta 200 e 1200 rpm e velocidade de soldagem constante (1mm/s). As medições de tensões residuais na superfície das juntas soldadas foram investigadas através da técnica de difração de raios-X. Além disso, foram avaliadas as macroestruturas e o aporte térmico de acordo com os parâmetros de soldagem empregados. Embora não existam muitos trabalhos relacionados ao processo SFMM para ligas de Inconel, provavelmente devido à sua dificuldade de soldagem, tem sido percebido um aumento na aplicação da soldagem no estado sólido como excelente alternativa para as superligas à base de níquel. Os resultados mostraram que diferentes parâmetros de processo produziram juntas soldadas distintas e, consequentemente, variações na distribuição de tensões residuais. Por fim, um aumento na velocidade de rotação da ferramenta ocasionou um aumento nas tensões residuais na zona de mistura. %0 journal article %@ 0043-2288 %A Goushegir, S.M.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2017 %J Welding in the world %N 6 %P 1099-1115 %R doi:10.1007/s40194-017-0509-y %T Influence of aluminum surface pre-treatments on the bonding mechanisms and mechanical performance of metal-composite single-lap joints %U https://doi.org/10.1007/s40194-017-0509-y 6 %X The use of frictional heat for joining thermoplastic-based materials to metals has grown in importance in recent years. Friction spot joining is a relatively new joining technology suitable to join metal-polymer and composite overlap structures. In this work, the influence of various aluminum surface pre-treatments on the bonding mechanisms and mechanical performance of single-lap shear and cross-tensile joints was studied. Mechanical, chemical, and electrochemical pre-treatments were applied to the aluminum surface prior to the joining process. All surface pre-treatments increased the joint strength to some extent, compared with specimens without surface pre-treatments. Some of the treatments (chemical and electrochemical) led to the formation of strong chemical bonding between the aluminum and composite. Phosphoric acid anodizing with additional primer layer showed the best performance in increasing the joint’s strength. The reason was the strong bond formation between the primer layer and the matrix of the composite during the joining cycle. Moreover, the morphology and chemical composition of the aluminum after surface pre-treatments were analyzed in detail to study the correlation between bonding mechanisms and the mechanical performance of the joints. Finally, fracture surface of the joints was analyzed optically and by SEM, demonstrating parts of the composite remained attached to the aluminum after failure. %0 journal article %@ 0167-577X %A Huang, Y.,Lv, Z.,Wan, L.,Shen, J.,dos Santos, J.F. %D 2017 %J Materials Letters %N %P 172-175 %R doi:10.1016/j.matlet.2017.07.081 %T A new method of hybrid friction stir welding assisted by friction surfacing for joining dissimilar Ti/Al alloy %U https://doi.org/10.1016/j.matlet.2017.07.081 %X A new method of friction surfacing assisted hybrid friction stir welding (FS-HFSW) technique was developed to improve the joint efficiency and avoid the pin abrasion for joining of dissimilar Ti/Al joints. The FSW tool with enlarged head and concave end-face was designed to broaden the lap width and promote material flow. The maximum tensile load reached 12.2 kN, representing 85.3% of the parent Al alloy, with a ductile fracture locating at the heat affected zone of base Al. The excellent bonding of Ti and Al was based on the combined effects of nanoscale TiAl3 IMCs layer and complex mechanical inter-locking. %0 journal article %@ 0950-7116 %A Proenca, B.C.,Blaga, L.,dos Santos, J.F.,Canto, L.B.,Amancio Filho, S.T. %D 2017 %J Welding International %N 7 %P 509-518 %R doi:10.1080/09507116.2016.1218627 %T Friction riveting (‘FricRiveting’) of 6056 T6 aluminium alloy and polyamide 6: influence of rotational speed on the formation of the anchoring zone and on mechanical performance %U https://doi.org/10.1080/09507116.2016.1218627 7 %X Metal-polymer hybrid structures can be used as an alternative solution for reducing weight and fuel consumption in the transport industry, which aims to minimise the emission of harmful gases that have a greenhouse effect. Friction riveting is a relatively new technique for joining metal-polymer hybrid structures. The process is based on the generation of frictional heat between the components, resulting in the plastic deformation of the end of the metal rivet, which is anchored inside the polymer component. This study assessed the technical feasibility of joining AA 6056 T6 and PA6, focusing on the influence of the rotational speed of the rivet on the mechanical performance of the joints. The maximum temperature reached during the process increased with the rotational speed, from 291 ± 6 °C with 10,000 rev/min to 375 ± 5 °C with 15,000 rev/min. The use of higher rotational speeds led to the tip of the rivet undergoing plastic deformation during the friction phase. This produced mechanically stronger joints, because the metal rivet was anchored more securely in the polymer block. The AA 6056 T6-PA6 joints perform well in terms of tensile strength, reaching 85% of the tensile strength of the metal rivet. We therefore confirmed that it is possible to join AA 6056 T6 and PA6 using the technique of friction riveting, and that rotational speed directly affects the tensile strength of the joints. %0 journal article %@ 1516-1439 %A Lopes do Vale, N.,Fitseva, V.,Hanke, S.,Urtiga Filho, S.L.,dos Santos, J.F. %D 2017 %J Materials Research : Revista Brasileira de Materiais %N 2 %P 830-835 %R doi:10.1590/1980-5373-mr-2016-1011 %T Influence of Rotational Speed in the Friction Surfacing of Titanium Grade 1 on Ti-6Al-4V %U https://doi.org/10.1590/1980-5373-mr-2016-1011 2 %X Titanium Grade 1 was deposited on Ti-6Al-4V, 2 mm thickness, by Friction Surfacing. The process parameters were rotational speed, deposition speed and consumption rate. Only the rotational speed was varied in order to evaluate the influence of this parameter on the coatings generated. The applicability of the process has been described for a large number of materials, although the depositions of titanium alloys are still not widely studied. The objective is to investigate the effects of the rotational speed on the coatings' geometry and microstructural evolution. This investigation has shown that Titanium Grade 1 coatings can be deposited onto a Ti-6Al-4V by Friction Surfacing depending on the rotational speed. The coatings' surface homogeneity was influenced by the rotational speed, being inhomogeneous for the lowest speed. The coatings' thickness and width increased with enhancing this speed. The heat affected zone in the substrate corresponded to the complete thickness under the depositions. %0 journal article %@ 0268-3768 %A Tier, M.D.,Rosendo, T.S.,Mazzaferro, J.A.,Mazzaferro, C.P.,dos Santos, J.F.,Strohaecker, T.R. %D 2017 %J The International Journal of Advanced Manufacturing Technology %N 1-4 %P 267-276 %R doi:10.1007/s00170-016-9370-1 %T The weld interface for friction spot welded 5052 aluminium alloy %U https://doi.org/10.1007/s00170-016-9370-1 1-4 %X Friction Spot Welding (FSpW) is considered to be a competitive technique for producing high quality welds, especially in lightweight alloys. The geometric defects and features originating at the interface between the two welded sheets have an important influence on the mechanical performance of the joint. This work investigates the weld microstructure for FSpW in AA 5052 sheets produced using tool rotational speeds of 900, 1400 or 1900 rpm. OM and SEM were used to analyse the microstructural features of the weld. The mechanical performance was investigated using shear tensile testing, and the fracture mechanisms were assessed by SEM. Three distinct weld interfaces were observed and named as follows: primary bonding, partial bonding and secondary bonding. For welds processed at a lower tool rotational speed (900 rpm), the equivalent bonding ligament is increased, resulting in better joint mechanical performance. %0 journal article %@ 0309-3247 %A Chupakhin, S.,Kashaev, N.,Klusemann, B.,Huber, N. %D 2017 %J The Journal of Strain Analysis for Engineering Design %N 3 %P 137-151 %R doi:10.1177/0309324717696400 %T Artificial neural network for correction of effects of plasticity in equibiaxial residual stress profiles measured by hole drilling %U https://doi.org/10.1177/0309324717696400 3 %X The hole drilling method is a widely known technique for the determination of non-uniform residual stresses in metallic structures by measuring strain relaxations at the material surface caused through the stress redistribution during drilling of the hole. The integral method is a popular procedure for solving the inverse problem of determining the residual stresses from the measured surface strain. It assumes that the residual stress can be approximated by step-wise constant values, and the material behaves elastically so that the superposition principle can be applied. Required calibration data are obtained from finite element simulations, assuming linear elastic material behavior. That limits the method to the measurement of residual stresses well below the yield strength. There is a lack of research regarding effects caused by residual stresses approaching the yield strength and high through-thickness stress gradients as well as the correction of the resulting errors. However, such high residual stresses are often introduced in various materials by processes such as laser shock peening, for example, to obtain life extension of safety relevant components. The aim of this work is to investigate the limitations of the hole drilling method related to the effects of plasticity and to develop an applicable and efficient method for stress correction, capable of covering a wide range of stress levels. For this reason, an axisymmetric model was used for simulating the hole drilling process in ABAQUS involving plasticity. Afterward, the integral method was applied to the relaxation strain data for determining the equibiaxial stress field. An artificial neural network has been used for solving the inverse problem of stress profile correction. Finally, AA2024-T3 specimens were laser peened and the measured stress fields were corrected by means of the trained network. To quantify the stress overestimation in the hole drilling measurement, an error evaluation has been conducted. %0 journal article %@ 0268-3768 %A Plaine, A.H.,Suhuddin, U.F.H.,Alcantara, N.G.,dos Santos, J.F. %D 2017 %J The International Journal of Advanced Manufacturing Technology %N 9-12 %P 3703-3714 %R doi:10.1007/s00170-017-0439-2 %T Microstructure and mechanical behavior of friction spot welded AA6181-T4/Ti6Al4V dissimilar joints %U https://doi.org/10.1007/s00170-017-0439-2 9-12 %X Friction spot welding has become an excellent alternative to produce dissimilar joints in a fast and reliable way. This paper investigates the microstructure and the mechanical behavior of friction spot welded AA6181-T4/Ti6Al4V dissimilar joints produced by two different tool rotational speeds, 2500 and 3000 rpm, previously demonstrated to be the welding parameter with the most influence on the mechanical performance of these joints. Temperature profiles indicated that tool rotational speed directly affects the process temperature and, consequently, the metallurgical reaction taking place at the joint interface. Higher temperatures (3000 rpm condition) resulted in a complex and cracked Ti/Al interface because of the local melting of the aluminum plate. In contrast, by decreasing the process temperature (2500 rpm condition), a continuous thin TiAl3 layer was observed, increasing the lap shear resistance of the joints. Moreover, the local Von Mises strain distribution of a sound joint under lap shear was successfully associated with the different stages of a typical force–displacement curve and used to elucidate the fracture evolution. Lastly, the fatigue behavior of the joints indicated that FSpW dissimilar welds exhibited a better performance than FSpW aluminum similar joints. %0 journal article %@ 0261-3069 %A Reimann, M.,Goebel, J.,dos Santos, J.F. %D 2017 %J Materials and Design %N %P 283-294 %R doi:10.1016/j.matdes.2017.07.013 %T Microstructure and mechanical properties of keyhole repair welds in AA 7075-T651 using refill friction stir spot welding %U https://doi.org/10.1016/j.matdes.2017.07.013 %X To develop a suitable keyhole closure process in high-strength AlZnMg(Cu) alloys, refill friction stir spot welding was used to perform repair welds of through holes of 7.5 mm diameter in AA 7075-T651 plates with 6 mm thickness. The thermal cycle and the evolution of microstructural features were investigated in detail. The mechanical performance of the welds was studied based on the changes in microstructure and temperature exposure caused by the welding process.,Thermal cycle measurements revealed high heating rates and peak temperatures of up to 540 °C in the weld center. Leftover grains from the base metal that did not recrystallize were determined in the stirred zone of the weld center. The welds showed a W-shaped hardness distribution with a lowest hardness of 70% of base metal values in the heat affected zone. Under quasi-static loading, two failure modes were determined, with mode 1 failure occurring in the heat affected zone and mode 2 failure occurring in the outer regions of the stirred zone with crack initiation in the lower portions of the weld. Post-weld natural aging was proven to be highly significant for the mechanical properties of the welds and is effective for up to 4 weeks after welding. %0 journal article %@ 0921-5093 %A Pohl Meinhardt, C.,Scheid, A.,dos Santos, J.F.,Bergmann, L.A.,Borges, Favaro, M.,Fortis Kwietniewski, C.E. %D 2017 %J Materials Science and Engineering A %N %P 48-56 %R doi:10.1016/j.msea.2017.08.117 %T Hydrogen embrittlement under cathodic protection of friction stir welded UNS S32760 super duplex stainless steel %U https://doi.org/10.1016/j.msea.2017.08.117 %X Hydrogen Induced Stress Cracking (HISC) resistance of super duplex stainless steels is basically controlled by the material's microstructure. Friction stir welding is a low heat input joining process that has the potential to maintain the base metal original resistance to HISC since it does not significantly alter the proportion of ferrite and austenite. This work evaluated the susceptibility to HISC under cathodic protection of friction stir welded super duplex stainless steel UNS S32760. Microstructure evaluation revealed a recommended proportion of ferrite and austenite phases as well a refinement of the overall stir zone microstructure. Fracture toughness tests in synthetic sea water under cathodic protection of − 895 mVsce indicated that the microstructure of the stir zone is actually less sensitive to HISC than the microstructure of the base metal. %0 journal article %@ 0261-3069 %A Plaine, A.H.,Suhuddin, U.F.H.,Afonso, C.R.M.,Alcantara, N.G.,dos Santos, J.F. %D 2016 %J Materials and Design %N %P 224-231 %R doi:10.1016/j.matdes.2015.12.170 %T Interface formation and properties of friction spot welded joints of AA5754 and Ti6Al4V alloys %U https://doi.org/10.1016/j.matdes.2015.12.170 %X This study aims to understand the influence of dwell time on the microstructure of the interface and lap shear strength of friction spot welded joints of AA5754 and Ti6Al4V alloys. The interface reaction layer consists mainly of TiAl3 intermetallic compound. It was noticed that dwell time significantly influences the diffusion process during the friction spot welding, thereby modifying the thickness of the interface and thus affecting the mechanical performance of the joints. Minimizing or optimizing the brittle TiAl3 phase was demonstrated to be the key issue to achieve high strength Ti/Al dissimilar joints. The intermetallic compound growth kinetics was also examined showing that an incubation time of approximately 2.7 s is necessary before it nucleates at the Ti/Al interface and grows laterally to form a continuous layer. Afterwards, the TiAl3 layer grows toward the Al during thickening with a corresponding growth rate of k = 2.92 × 10− 7 m/s. These results are critical to understand the microstructure–properties relationship and contribute with additional improvements on the joint performance. %0 journal article %@ 0965-9978 %A Schneider, K.,Klusemann, B.,Bargmann, S. %D 2016 %J Advances in Engineering Software %N %P 177-188 %R doi:10.1016/j.advengsoft.2016.06.001 %T Automatic three-dimensional geometry and mesh generation of periodic representative volume elements for matrix-inclusion composites %U https://doi.org/10.1016/j.advengsoft.2016.06.001 %X This paper introduces an efficient method to automatically generate and mesh a periodic three-dimensional microstructure for matrix-inclusion composites. Such models are of major importance in the field of computational micromechanics for homogenization purposes utilizing unit cell models. The main focus of this contribution is on the creation of cubic representative volume elements (RVEs) featuring a periodic geometry and a periodic mesh topology suitable for the application of periodic boundary conditions in the framework of finite element simulations. Our method systematically combines various meshing tools in an extremely efficient and robust algorithm. The RVE generation itself follows a straightforward random sequential absorption approach resulting in a randomized periodic microstructure. Special emphasis is placed on the discretization procedure to maintain a high quality mesh with as few elements as possible, thus, manageable for computer simulations applicable to high volume concentrations, high number of inclusions and complex inclusion geometries. Examples elucidate the ability of the proposed approach to efficiently generate large RVEs with a high number of anisotropic inclusions incorporating extreme aspect ratios but still maintaining a high quality mesh and a low number of elements. %0 journal article %@ 1747-1567 %A Richter-Trummer, V.,Zhang, X.,Irving, P.E.,Pacchione, M.,Beltrao, M.,dos Santos, J.F. %D 2016 %J Experimental Techniques %N 3 %P 921-935 %R doi:10.1111/ext.12116 %T Fatigue Crack Growth Behaviour in Friction Stir Welded Aluminium–Lithium Alloy Subjected to Biaxial Loads %U https://doi.org/10.1111/ext.12116 3 %X In this article, biaxial load fatigue crack growth tests are reported. Specimens were made of an advanced aluminium–lithium alloy AA2198-T8 joined by the friction stir welding process, capable of producing advanced integral metallic structures that can offer significant cost and weight savings over the current joining methods. Two material rolling directions are considered in relation to the welding and crack growth direction. Welding-induced initial distortion was measured before the experiment for better result interpretation. Test specimens are representative of two different weld orientations, that is longitudinal weld parallel to the material rolling direction and circumferential weld perpendicular to the material rolling direction for investigating the inherent material anisotropy of aluminium–lithium alloys. In all tests, the fatigue crack was initiated in the thermo-mechanical process zone of the weld and propagated parallel to the weld joint line. It is shown that the rolling direction of the selected aluminium alloy strongly affects the crack growth path. The specimens welded orthogonally to the rolling direction exhibit a shorter fatigue crack growth life than the specimens welded parallel to the rolling direction. %0 journal article %@ 1359-835X %A Goushegir, S.M.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2016 %J Composites / A %N %P 121-128 %R doi:10.1016/j.compositesa.2015.11.001 %T Failure and fracture micro-mechanisms in metal-composite single lap joints produced by welding-based joining techniques %U https://doi.org/10.1016/j.compositesa.2015.11.001 %X Welding-based joining technologies have been recently developed for metal-composite lightweight structures. In this work, the welding-based joining technology, friction spot joining, was selected to study the failure and fracture micro-mechanisms of an aluminum-composite single lap joint. Failure analysis suggested that the radial cracks nucleate at the periphery of the bonding area and propagate rapidly until failure of the so-called adhesion zone. Upon further loading the cracks propagate into the transition and plastically deformed zones leading to a reduction of the stiffness of the joint. The findings of the fractography demonstrated a mixed brittle-ductile fracture. Three zones were identified on the fracture surfaces: a smooth and featureless area demonstrating brittle fracture, a quasi-smooth area representing a mixture of ductile and brittle fractures and finally a zone with a highly rough surface implying ductile fracture of the composite part. Further, fiber pull-out and breakage were identified as additional fracture micro-mechanisms. %0 journal article %@ 0268-3768 %A Plaine, A.H.,Gonzalez, A.R.,Suhuddin, U.F.H.,dos Santos, J.F.,Alcantara, N.G. %D 2016 %J The International Journal of Advanced Manufacturing Technology %N 5 %P 1575-1583 %R doi:10.1007/s00170-015-8055-5 %T Process parameter optimization in friction spot welding of AA5754 and Ti6Al4V dissimilar joints using response surface methodology %U https://doi.org/10.1007/s00170-015-8055-5 5 %X This study shows experimental and numerical results of friction spot welding of AA5754 and Ti6Al4V alloys. The determination of proper welding parameters plays an important role for the weld strength. Experimental tests, conducted according to combinations of process parameters such as tool rotational speed (RS) and dwell time (DT), were investigated with response surface methodology using a 3k factorial design of experiments. Sound joints with elevated shear strength were achieved and the influence of the main process parameters on joint strength evaluated. DT was the parameter with the largest influence on the joint shear resistance (58.9 %), followed by its interaction with RS (38.1 %). Higher strength was correlated to the thickness and morphology of the joint interface. A numerical model for predicting lap shear strength was successfully developed and used to optimize welding parameters in order to produce high-performance joints with less energy consumption and high efficiency. %0 journal article %@ 0142-1123 %A Effertz, P.S.,Infante, V.,Quintino, L.,Suhuddin, U.,Hanke, S.,dos Santos, J.F. %D 2016 %J International Journal of Fatigue %N %P 381-390 %R doi:10.1016/j.ijfatigue.2016.02.030 %T Fatigue life assessment of friction spot welded 7050-T76 aluminium alloy using Weibull distribution %U https://doi.org/10.1016/j.ijfatigue.2016.02.030 %X Friction spot welding is a solid state welding process suitable to obtain spot like-joints in overlap configuration. The process is particularly useful to weld lightweight materials in similar and dissimilar combinations, and therefore an interesting alternative to other joining techniques (rivets, resistance welding, etc.). Optimum process parameters have been defined using the Taguchi method by maximizing the response variable (the lap shear strength). A study of the fatigue life was carried out on specimens welded with the above mentioned optimized process parameters. Fatigue tests were performed using a stress ratio of R = 0.10. Two-parameter Weibull distribution was used to analyze statistically the fatigue life for the joined overlapped sheets. Subsequently, the Weibull plots were drawn, as well as S–N curves considering different reliability levels. The results show that for a relatively low load, corresponding to 10% of the maximum supported by the joint, the number of cycles surpasses 1 × 106, hence infinite life of the service component can be attributed. Fatigue fracture surfaces were investigated for the highest and lowest loads tested using scanning electron microscope (SEM). %0 journal article %@ 0142-2421 %A Goushegir, S.M.,Scharnagl, N.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2016 %J Surface and Interface Analysis :SIA %N 8 %P 706-711 %R doi:10.1002/sia.5816 %T XPS analysis of the interface between AA2024-T3 / CF-PPS friction spot joints %U https://doi.org/10.1002/sia.5816 8 %X Friction spot joining (FSpJ) is an advanced, alternative technology suitable for joining metal-composite overlap structures. In this paper, the principles of the FSpJ technique are briefly described. Furthermore, the influence of aluminum surface pretreatments (conversion coating and phosphoric acid anodizing) on the adhesion between aluminum alloy AA2024-T3 and carbon-fiber-reinforced poly(phenylene sulfide) (CF-PPS) friction spot joints was examined. X-ray photoelectron spectroscopy (XPS) was used to investigate the changes in the chemical composition of the aluminum after surface pretreatments, as well as chemical bond formation at the interface between the aluminum and composite. The joints were mechanically loaded until failure, and the fracture surface of the joints were analyzed on the aluminum side. XPS results showed evidence of Al–C and Zr–C bond formation at the interface for the selected surface pretreatments in the course of the joining cycle. Chemical bond formation was confirmed through the analysis of C1s and Al2p regions in which the appearance of new peaks with different binding energies compared with the aluminum and composite were identified. %0 journal article %@ 1359-8368 %A Andre, N.M.,Goushegir, S.M.,dos Santos, J.F.,Canto, L.B.,Amancio-Filho, S.T. %D 2016 %J Composites / B %N %P 197-208 %R doi:10.1016/j.compositesb.2016.03.011 %T Friction Spot Joining of aluminum alloy 2024-T3 and carbon-fiber-reinforced poly(phenylene sulfide) laminate with additional PPS film interlayer: Microstructure, mechanical strength and failure mechanisms %U https://doi.org/10.1016/j.compositesb.2016.03.011 %X Friction Spot Joining is an innovative friction-based joining technique for metal–polymer hybrid structures. In this work, aluminum alloy 2024-T3 and CF-PPS friction-spot joints were produced with additional PPS film interlayer. The joints were investigated in terms of the microstructure, mechanical performance under quasi-static loading and failure mechanisms. Macro- and micro-mechanical interlocking as well as adhesion forces were identified to dictate bonding mechanisms in the FSp joint with film interlayer. The ultimate lap shear force of the joints (2700 ± 115 N up to 3070 ± 165 N) were 20%–55% higher than the corresponding joints without interlayer, due to the larger bonding area, better load distribution and improved micro-mechanical interlocking. The failure analysis of the joints revealed a mixture of adhesive-cohesive failure, whereas cohesive failure was dominant. %0 journal article %@ 0167-577X %A Feistauer, E.E.,Guimaraes, R.P.M.,Ebel, T.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2016 %J Materials Letters %N %P 1-4 %R doi:10.1016/j.matlet.2016.01.137 %T Ultrasonic joining: A novel direct-assembly technique for metal-composite hybrid structures %U https://doi.org/10.1016/j.matlet.2016.01.137 %X Ultrasonic joining (U-Joining) is a new direct assembly technique developed by Helmholtz-Zentrum Geesthacht that uses ultrasonic energy to join fiber-reinforced thermoplastics to surface-structured metallic parts produced by metal injection molding. Ultrasonic vibration and pressure create frictional heat at the materials interface, which softens the composite matrix and allows the reinforcement (structured on the surface of the metallic part) to penetrate the composite. As a result, a metal-composite hybrid joint with improved out-of-plane strength is achieved. In this work, the features of U-Joining are briefly introduced, and the feasibility of the technique is demonstrated with Ti-6Al-4V/glass-fiber-reinforced polyetherimide joints. Optical microscopy reveals that a close contact between metal and composite was achieved after U-joining. Lap shear testing of six-pin joints showed an improvement in strength of up to 5.5 times (2011±530 N) that of pin-less reference joints (368±29 N). %0 journal article %@ 0104-9224 %A Andre, N.M.,Goushegir, S.M.,dos Santos, J.F.,Canto, L.B.,Amancio Filho, S.T. %D 2016 %J Soldagem & Inspecao %N 1 %P 2-15 %R doi:10.1590/0104-9224/SI2101.02 %T Influence of the Interlayer Film Thickness on the Mechanical Performance of AA2024-T3/CF-PPS Hybrid Joints Produced by Friction Spot Joining - Influencia da Espessura do Filme Polimerico Intermediario na Resistencia Mecanica de Juntas Hibridas de Alumínio 2024-T3 e CF-PPS Produzidas por Uniao Pontual por Friccao %U https://doi.org/10.1590/0104-9224/SI2101.02 1 %X Friction Spot Joining (FSpJ) is an innovative friction-based joining technique for metal-polymer hybrid structures. Friction spot joints of aluminum alloy 2024-T3 and carbon-fiber reinforced poly(phenylene sulfide) composite laminate (CF-PPS) were produced with an additional PPS film interlayer. Two different film thicknesses were investigated in this study: 100 and 500 µm. Lap shear testing demonstrated that the joints produced with 100 µm film (2093 ± 180 N) were stronger than the joints with 500 µm (708 ± 69 N). Additionally, the fracture surface analysis revealed a larger bonding area for the joints with 100 µm film (53 ± 2 mm2) as compared to the joints with 500 µm film (40 ± 1 mm2). Considering the low thermal conductivity of PPS, the thinnest film is more likely to soften by the frictional heat during the joining process. Hence, the low viscosity of the molten PPS favors the wettability of the parts’ surface. Microstructural analyses proved that the metallic nub formation and the interdiffusion of PPS chains between film and composite matrix are also favored for thinner film use. Thus, superior adhesion between the partners is achieved. Therefore, it was concluded that the addition of the thinnest film interlayer leads to stronger joints.,Resumo,A União Pontual por Fricção (FSpJ) é uma técnica inovadora para união de estruturas híbridas metal-polímero e baseia-se na geração de calor por fricção. Juntas de alumínio 2024-T3 e compósito laminado de poli(sulfeto de fenileno) com fibra de carbono (CF-PPS) foram produzidas com filme intermediário de PPS. Duas espessuras de filme foram investigadas: 100 e 500 µm. Ensaios de cisalhamento sob tração demonstraram que as juntas com filmes de 100 µm são mais resistentes (2093 ± 180 N) em relação às juntas com filme de 500 µm (708 ± 69 N). Adicionalmente, as superfícies de fratura das juntas revelaram áreas de união maiores para as juntas com filmes de 100 µm (53 ± 2 contra 40 ± 1 mm2). Para o filme mais fino, a extensão do amolecimento devido ao calor friccional é maior. Consequentemente, a baixa viscosidade atingida com a fusão do polímero favorece a molhabilidade das superfícies dos componentes da junta pelo PPS amolecido, resultando em melhor adesão entre as partes. Ademais, análises microestruturais demonstraram que a formação do cerne metálico e a interdifusão das moléculas de PPS entre compósito e filme também são favorecidas. Portanto, concluiu-se que a adição do filme mais fino produziu juntas mais resistentes. %0 journal article %@ 0924-0136 %A Reimann, M.,Gartner, T.,Suhuddin, U.,Goebel, J.,dos Santos, J.F. %D 2016 %J Journal of Materials Processing Technology %N %P 12-18 %R doi:10.1016/j.jmatprotec.2016.05.013 %T Keyhole closure using friction spot welding in aluminum alloy 6061–T6 %U https://doi.org/10.1016/j.jmatprotec.2016.05.013 %X A new approach to refill keyholes using the friction spot welding (FSpW) technology was developed. Keyholes with a diameter of 7.5 mm in aluminum alloy 6061–T6 rolled sheets were filled with a cylindrical plug of the same material. Afterwards, the FSpW process joins the plug to the surrounding workpiece resulting in a sealed keyhole.,Microstructural analysis and mechanical testing of keyhole closures have been performed. The mechanical properties have been determined in terms of microhardness, tensile strength, yield strength and elongation at fracture. Design of experiments and analysis of variance techniques were employed to evaluate the influence of the gas shielding, post-weld heat treatments and the plug itself on the properties of the welds.,The experimental results demonstrate that the proposed method is suitable to refill keyholes in AA 6061–T6 and produce flawless joints with a superior surface appearance. The welds show high strength and hardness, especially when heat treatments are applied. The high strength of the welds were achieved at the expense of elongation at fracture, which is caused by a strengthened zone in the center of the welds. %0 journal article %@ 0142-1123 %A Plaine, A.H.,Suhuddin, U.F.H.,Alcantara, N.G.,dos Santos, J.F. %D 2016 %J International Journal of Fatigue %N %P 149-157 %R doi:10.1016/j.ijfatigue.2016.06.005 %T Fatigue behavior of friction spot welds in lap shear specimens of AA5754 and Ti6Al4V alloys %U https://doi.org/10.1016/j.ijfatigue.2016.06.005 %X The fatigue behavior of single friction spot welded AA5754 and Ti6Al4V dissimilar joints was investigated based on experimental observations. Fatigue tests were performed in a constant amplitude load control servo-hydraulic machine with a load ratio of R = 0.1 at room temperature. Two-parameter Weibull distribution was used to analyze statistically the fatigue data for the joined overlapped sheets. Weibull graphics were plotted for each stress amplitude value. Subsequently, S–N curves were drawn for different reliability levels (10%, 50%, 90% and 99%) for the benefit of designers. A fatigue limit of 25 MPa was determined for the AA5754/Ti6Al4V joints (at survival level of 50%), corresponding to 15% of the maximum average static fracture load. Two different types of fatigue failure modes were observed for the specimens. Under high cyclic loads, the failure occurred in the upper Al sheet because of the higher stress concentration at the notch tip leading to crack initiation followed by its propagation through the thickness toward the joint surface and, subsequently, along the specimen width direction. Under low cyclic loads, “through weld” failure was observed as the crack rapidly propagated along the interfacial surface until a critical point at which the remaining cross section could no longer sustain the shear overload and failed. A fatigue crack growth mechanism based on the paths of the dominant fatigue cracks was then proposed and used to explain the fatigue fracture evolution under different loading conditions. %0 journal article %@ 0104-9224 %A Zocoller Borba, N.,Blaga, L.,dos Santos, J.F.,Canto, L.B.,Amancio-Filho, S.T. %D 2016 %J Soldagem & Inspecao %N 1 %P 30-43 %R doi:10.1590/0104-9224/SI2101.04 %T Influence of Rotational Speed on the Microstructure and Mechanical Performance of Friction-Riveted Thermosetting Composite Joints - Influencia da Velocidade de Rotacao do Rebite na Microestrutura e no Desempenho Mecanico de Juntas de Composito Termofixo Rebitadas por Friccao %U https://doi.org/10.1590/0104-9224/SI2101.04 1 %X Facing the actual demand for efficient joining technologies for multi-materials structures, Friction Riveting was shown to be an alternative joining technology for thermoset composite profiles in civil infrastructure. This process is based on plasticizing and deforming the tip of a rotating metallic rivet within a polymeric component through frictional heating. The feasibility of friction-riveted hybrid joints of Ti-6Al-4V/glass-fiber reinforced thermoset polyester was already demonstrated in a separate work. This paper complements this study by analyzing the rivet rotational speed effect on the process temperature, joint microstructure and the local and global mechanical properties of the joint. Joints were produced using two different levels of rotational speed: 9000 rpm and 10000 rpm (the other parameters were kept constant). The results showed process temperatures (655-765 °C) up to 96% higher than the onset decomposition temperature of the polyester matrix (370 °C); this led to severe degradation of the composite in the joint area. The increase in rotational speed, and therefore in heat generation, led to a statistically insignificant increase of the rivet penetration depth and the rivet diameter widening. However, the extension of the degraded composite area increased 47% which was responsible to deteriorate in 50% the joint tensile strength (from 4.0 ± 1.2 kN to 2.0 ± 0.7 kN). Moreover, the microhardness map of the joined rivet evidenced possible phase transformations in the alloy, favoring the material hardening by increasing in rotational speed. However, no correlations could be established between the changes in hardness and the joint tensile strength since the joints majority failure by full rivet pull-out. Thereby, for the improvement of friction-riveted Ti-6Al-4V/ glass-fiber reinforced thermoset polyester joints, the optimization of rotational speed is essential. This can guarantee the formation of efficient anchored joints and wider rivet tip deformation, concomitantly with the minimizing of the extension of the matrix degradation and finally leading to better tensile strength of the joints.,A Rebitagem por Fricção tem se demonstrado como alternativa para união de perfis de compósito termofixo aplicados na construção civil, frente às necessidades atuais por tecnologias eficientes de união de estruturas multimateriais. Nesse processo, a extremidade de um rebite metálico é plastificada e forjada dentro de um componente polimérico, via calor friccional. Sua viabilidade técnica já foi demonstrada para juntas de Ti-6Al-4V/poliéster termofixo reforçado com fibra de vidro. Este artigo tem como objetivo complementar esse estudo através da análise do efeito da velocidade de rotação do rebite na temperatura do processo, microestrutura e propriedades mecânicas locais e globais das juntas. Foram fabricadas juntas com dois níveis de velocidade de rotação: 9000 rpm e 10000 rpm (os demais parâmetros foram mantidos constantes). Temperaturas do processo (655-765 °C) superiores em 96% da temperatura de início de decomposição da matriz de poliéster (370 °C) foram atingidas, desencadeando degradação polimérica acentuada na região de união. O aumento da velocidade de rotação e, portanto, do aporte térmico, não contribuiu estatisticamente para o aumento na profundidade de penetração e na largura da extremidade deformada do rebite. Porém, a extensão da área polimérica degradada aumentou em 47%, a qual resultou em redução proporcional de 50% da resistência à tração das juntas (de 4,0 ± 1,2 kN para 2,0 ± 0,7 kN). Adicionalmente, mapas de microdureza no rebite evidenciaram possíveis transformações de fase da liga que favoreceram seu endurecimento, com o aumento da velocidade de rotação. Contudo, nenhuma correlação pôde ser evidenciada entre a dureza e o desempenho mecânico das juntas sob tração, já que as amostras falharam majoritariamente por arrancamento completo do rebite da placa de compósito. Portanto, no desenvolvimento de juntas rebitadas por fricção de Ti-6Al-4V/ poliéster termofixo reforçado com fibra de vidro, a otimização da velocidade de rotação é essencial para se obter suficiente deformação plástica do rebite e minimizar a extensão da degradação da matriz de poliéster, garantindo um satisfatório desempenho mecânico sob tração das juntas. %0 journal article %@ 0261-3069 %A Fitseva, V.,Hanke, S.,dos Santos, J.F.,Stemmer, P.,Gleising, B. %D 2016 %J Materials and Design %N %P 112-123 %R doi:10.1016/j.matdes.2016.07.132 %T The role of process temperature and rotational speed in the microstructure evolution of Ti-6Al-4V friction surfacing coatings %U https://doi.org/10.1016/j.matdes.2016.07.132 %X Friction surfacing is a solid state technique for depositing metallic coatings. Coating materials are thermo-mechanically processed at high temperatures during deposition. The high degree of deformation involved leads to a dynamically recrystallised fine grained microstructure. For Ti-6Al-4V, the microstructure and mechanical properties of coatings generated by friction surfacing have not been studied yet. The current work focuses on investigating effects of rotational speed on microstructure, grain size evolution and mechanical properties of the coating material.,Various rotational speeds in a wide range, exceeding the range of deformation used in many other severe plastic deformation processes, were used to generate Ti-6Al-4V coatings by friction surfacing. Their influence on the thermal cycle and consequently on microstructure formation was revealed. The β grain size is related to the rotational speed and thermal cycle. Grain refinement at low rotational speed was observed, while higher rotational speeds and corresponding increase in maximum temperature led to grain coarsening. Although the peak temperature dominates the grain size evolution, dynamic recrystallisation during friction surfacing counteracts this effect, reducing the grain size by one order of magnitude. The coatings exhibit a hardness ascent about 15% due to martensite formation, high dislocation density and oxide precipitations. %0 journal article %@ 0104-9224 %A Azevedo, J.,Quintino, L.,Infante, V.,Miranda, R.M.,dos Santos, J.F. %D 2016 %J Soldagem & Inspecao %N 1 %P 16-29 %R doi:10.1590/0104-9224/SI2101.03 %T Friction Stir Welding of Shipbuilding Steel with Primer %U https://doi.org/10.1590/0104-9224/SI2101.03 1 %X Friction Stir Welding has proven its merits for welding of aluminium alloys and is focused in expanding its material database to steel and titanium and also to assess new joint configurations. The use of welded structures in shipbuilding industry has a long tradition and continuously seeks for innovation in terms of materials and processes maintaining, or even, reducing costs. Several studies have been performed in the past years on FSW of steel. However, just recently were reported defect-free welds, free of martensite with stable parameters in steel without Primer. FSW of steel with primer has not been addressed. This work aims to fulfil a knowledge gap related to the use of friction stir for welding shipbuilding steel by analysing the effect of welding parameters on the metallurgical characteristics and mechanical properties of welds obtained with an innovative FSW tool in joining steel plates with a primer. Welds were performed in 4mm thick GL-A36 steel plates painted with a zinc based primer followed by a detailed microscopic, chemical and mechanical analysis. The results that matching fatigue properties are obtained using this technique, in FSW of shipbuilding steel with Primer. %0 journal article %@ 0261-3069 %A Abibe, A.B.,Sonego, M.,dos Santos, J.F.,Canto, L.B.,Amancio-Filho, S.T. %D 2016 %J Materials and Design %N %P 632-642 %R doi:10.1016/j.matdes.2015.12.087 %T On the feasibility of a friction-based staking joining method for polymer–metal hybrid structures %U https://doi.org/10.1016/j.matdes.2015.12.087 %X The increased use of hybrid structures to reduce weight currently faces the limitations of traditional joining methods. Consequently there is a niche for development of new joining techniques, which can reduce or overcome some of the existing limitations. This paper presents for the first time the new Friction-based Injection Clinching Joining technique (F-ICJ), describing the microstructure and changes in local properties of joints between polyetherimide (PEI) and aluminum alloy 6082-T6. A shear layer around the rotating tool composes a polymer thermomechanically affected zone (PTMAZ), which presents pores as a result of evolution of gaseous products. The PTMAZ shows decreases of 8% to 12% in local strength compared to the base material, as measured by microhardness. Ultimate forces of 1419 ± 43 N in lap shear and 430 ± 44 N in cross tensile were achieved for F-ICJ joints. These levels are similar to ultrasonic staking joints of the same material combination, but the hollow design of F-ICJ stakes accounts for improved strength-to-weight ratio (18% in lap shear, 21% in cross tensile). Although the F-ICJ process currently requires longer cycles (7.5 s) than state-of-the-art ultrasonic staking (2.8–2.9 s), generated results indicate that the F-ICJ process is a competitive staking joining method with potential for improvement. %0 journal article %@ 0020-7403 %A Soyarslan, C.,Klusemann, B.,Bargmann, S. %D 2016 %J International Journal of Mechanical Sciences %N %P 53-66 %R doi:10.1016/j.ijmecsci.2016.07.028 %T The effect of yield surface curvature change by cross hardening on forming limit diagrams of sheets %U https://doi.org/10.1016/j.ijmecsci.2016.07.028 %X The paper aims at clarification of the role of reduction in yield locus curvature on forming limit diagrams. To this end, a cross-hardening model showing a reduction of yield surface curvature is used which accounts for dynamic and latent hardening effects associated with dislocation motion during loading. The model's three-dimensional tensorial as well as reduced plane-stress vector formulations are given. The first quadrants of forming limit diagrams are numerically produced using finite element models of the Marciniak-Kuczyński test with spatially correlated random defect distribution as localization triggering mechanism. The effect of cross hardening is investigated in detail. It is demonstrated that for plane strain loading path there occurs no difference in localization predictions of the models with and without cross hardening whereas for biaxial strain paths a delayed localization is observed in the cross hardening model as compared to the one without cross hardening effects. This is in accordance with the relative bluntness of the yield surface at the points of load path change towards localization. These results are complemented by Nakazima test simulations where similar observations are made. %0 journal article %@ 0965-0393 %A Klusemann, B.,Bargmann, S.,Estrin, Y. %D 2016 %J Modelling and Simulation in Materials Science Engineering %N 8 %P 085016 %R doi:10.1088/0965-0393/24/8/085016 %T Fourth-order strain-gradient phase mixture model for nanocrystalline fcc materials %U https://doi.org/10.1088/0965-0393/24/8/085016 8 %X The proposed modeling approach for nanocrystalline materials is an extension of the local phase mixture model introduced by Kim et al (2000 Acta Mater. 48 493–504). Local models cannot account for any non-uniformities or strain patterns, i.e. such models describe the behavior correctly only as long as it is homogeneous. In order to capture heterogeneities, the phase mixture model is augmented with gradient terms of higher order, namely second and fourth order. Different deformation mechanisms are assumed to operate in grain interior and grain boundaries concurrently. The deformation mechanism in grain boundaries is associated with diffusional mass transport along the boundaries, while in the grain interior dislocation glide as well as diffusion controlled mechanisms are considered. In particular, the mechanical response of nanostructured polycrystals is investigated. The model is capable of correctly predicting the transition of flow stress from Hall–Petch behavior in conventional grain size range to an inverse Hall–Petch relation in the nanocrystalline grain size range. The consideration of second- and fourth-order strain gradients allows non-uniformities within the strain field to represent strain patterns in combination with a regularization effect. Details of the numerical implementation are provided. %0 journal article %@ 1013-9826 %A Feistauer, E.,Bergmann, L.,dos Santos, J.F. %D 2016 %J Key Engineering Materials, Aluminium Constructions: Sustainability, Durability and Structural Advantages %N %P 91-96 %R doi:10.4028/www.scientific.net/KEM.710.91 %T Performance of friction stir welded tailor welded blanks in AA5059 and AA6082 alloys for marine applications %U https://doi.org/10.4028/www.scientific.net/KEM.710.91 %X Tailor welded blank (TWB) concepts in aluminum alloys, welded by friction stir welding (FSW), are an attractive solution to reduce structural weight of structures applied on the transportation sector. In the present work the mechanical performance and microstructural features of dissimilar friction stir welded TWBs were assessed. Welds were produced with alloys of particular interest to the shipbuilding sector (AA6082 and AA5083, with a thickness combination of 6 and 8 mm respectively) and the effect of rotational speed on the weld properties was investigated. A digital image correlation system (DIC) was used to characterize the local strain fields during the quasi-static tensile tests. Microstructure analysis revealed the presence of a remnant oxide line (ROL) at the stir zone. Moreover, the rotational speed directly affected the ROL distribution and consequently the mechanical properties of the welds. The TWB produced with low rotation speed and high force (600 rpm and 20kN) has shown the highest mechanical performance and failed at the thermo-mechanical affected zone of the AA6082 plate. The micromechanisms of fracture were assessed by SEM and revealed a ductile fracture with large amounts of dimples spread out on the fracture surface. %0 journal article %@ 1362-1718 %A Wang, F.F.,Li, W.Y.,Shen, J.,Zhang, Z.H.,Li, J.L.,dos Santos, J.F. %D 2016 %J Science and Technology of Welding and Joining %N 6 %P 479-483 %R doi:10.1080/13621718.2015.1132128 %T Global and local mechanical properties and microstructure of Bobbin tool friction-stir-welded Al–Li alloy %U https://doi.org/10.1080/13621718.2015.1132128 6 %X AA2198–T851 sheets were welded by bobbin tool friction stir welding using a rotational speed of 800 rpm and welding speed of 42 mm min−1. The microstructure and precipitates within the joint were characterised by transmission electron microscopy. The global and local mechanical behaviour was determined using a digital image correlation system. Specific attention was given to the relationship between the local microstructure and properties across the joint, which govern the global strength and ductility of the welds. A lower global elongation of the joint is caused by the premature strain localisation in the softened zone. %0 journal article %@ 1617-7061 %A Klusemann, B. %D 2016 %J PAMM: Proceedings in Applied Mathematics and Mechanics %N 1 %P 361-362 %R doi:10.1002/pamm.201610169 %T Modeling of microstructural pattern formation in crystal plasticity %U https://doi.org/10.1002/pamm.201610169 1 %X The mechanical behavior of most materials is dictated by a present or emergent underlying microstructure which is a direct result of different, even competing physical mechanisms occurring at lower length scales. In this work, energetic microstructure interaction via different non-convex contributions to the free energy in metals is modeled. For this purpose rate dependent gradient extended crystal plasticity models at the glide-system level are formulated. The non-convex energy serves as the driving force for the emergent microstructure. The competition between the kinetics and the relaxation of the free energy is an essential feature of the model. Non-convexity naturally arises in finite-deformation single-slip crystal plasticity and the results of the gradient model for this case are compared with an effective laminate model based on energy relaxation. Similarities as well as essential differences are observed and explained. %0 journal article %@ 0268-3768 %A Huang, Y.,Wang, Y.,Wan, L.,Liu, H.,Shen, J.,dos Santos, J.F.,Zhou, L.,Feng, J. %D 2016 %J The International Journal of Advanced Manufacturing Technology %N 1 %P 1115-1123 %R doi:10.1007/s00170-016-8603-7 %T Material-flow behavior during friction-stir welding of 6082-T6 aluminum alloy %U https://doi.org/10.1007/s00170-016-8603-7 1 %X Material-flow behavior during friction-stir welding of 6082-T6 aluminum alloy has been visualized by marker insert technique. Four stacked layers were evolved in welding nugget zone (WNZ) in the transverse section. The material-flow behavior in vertical direction was detected by observing the distribution of Cu foil fragments and Al-Cu intermetallic compounds. The downward and upward flows encounter each other at the advancing side in the material depositing process, changing the morphology of WNZ. A conceptual balanced-flow model and a plastic material-flow model were used to describe the material-flow behavior, and the origin of the downward material flow in the advancing side was discussed. The excess-material flow derived by the welding tool due to the existence of the tilt angle is crucial to the weld formation. %0 journal article %@ 0950-7116 %A Goncalves, J.,dos Santos, J.F.,Canto, L.B.,Amancio Filho, S.T. %D 2016 %J Welding International %N 4 %P 247-254 %R doi:10.1080/09507116.2015.1096466 %T Improvement of friction spot welding (FSpW) to join polyamide 6 and polyamide 66/carbon fibre laminate %U https://doi.org/10.1080/09507116.2015.1096466 4 %X Friction spot welding is an innovative technique developed and patented in 2005 by the research centre Helmholtz Zentrum Geesthacht. Advantages of the process include fast joining cycles, low operational costs and good mechanical performance. It was originally developed to weld lightweight metals and has been continuously improved to weld polymers. There are only a few studies on friction spot welding of thermoplastics, and the welding of polymeric composites by Friction spot welding (FSpW) is still unpublished. This study demonstrated the technical feasibility of welding a polyamide 6 (PA6) plate over a carbon fibre polyamide 66 laminate (CF-PA66) by FSpW. The thermal history, the surface finish, the microstructure of the weld region and the mechanical shear strength of PA6/CF-PA66 lap joints were investigated. The increase in the diameter of the clamping ring – originally designed for welding lightweight metals – led to the selection of welding parameters that result in high heat input, resulting in an increased welded area and lower notch left by the tool in the sample that improved the surface finish of the weld. This optimisation resulted in a PA6/CF-PA66 joint with lap shear strength of 35 MPa (2196 N), with fracture occurring mainly in the top plate of PA6. %0 journal article %@ 1022-6680 %A Suhuddin, U.,Piccolo, D.,Fischer, V.,dos Santos, J.F. %D 2015 %J Advanced Materials Research, Advanced Materials Research and Production %N %P 485-488 %R doi:10.4028/www.scientific.net/AMR.1112.485 %T Friction Spot Welding of Similar AA5754 to AA5754 Aluminum Alloys and Dissimilar AA5754 Aluminum to AZ31 Magnesium Alloys %U https://doi.org/10.4028/www.scientific.net/AMR.1112.485 %X Friction spot welding is a solid-state spot welding process developed and patented by Helmholtz-Zentrum Geesthacht, Germany. A non-consumable rotating tool consisting of two rotating parts, a pin and a sleeve, and one stationary clamping ring is used to join two or more similar/dissimilar sheets of materials in lap configuration. The result is a spot welded lap connection with minimal material loss and a flat surface without keyhole. The present work presents a summary of results from studies in similar AA5754 to AA5754 Al alloys and dissimilar AA5754 Al to AZ31 Mg alloys. %0 journal article %@ 1073-5623 %A Shen, J.,Wang, F.,Suhuddin, U.F.H.,Hu, S.,Li, W.,dos Santos, J.F. %D 2015 %J Metallurgical and Materials Transactions A %N 7 %P 2809-2813 %R doi:10.1007/s11661-015-2948-7 %T Crystallographic Texture in Bobbin Tool Friction-Stir-Welded Aluminum %U https://doi.org/10.1007/s11661-015-2948-7 7 %X Bobbin tool friction-stir welding was used to join 3.2-mm-thick AA2198. The textural results show that four sub zones are formed vertically in the stirred zone. The materials in upper and lower two zones underwent negative and positive shears, respectively; they are uniformly recognized as dominate C and minor A simple shear components. %0 journal article %@ 1996-1944 %A Gerstein, G.,Klusemann, B.,Bargmann, S.,Schaper, M. %D 2015 %J Materials %N 1 %P 285-301 %R doi:10.3390/ma8010285 %T Characterization of the Microstructure Evolution in IF-Steel and AA6016 during Plane-Strain Tension and Simple Shear %U https://doi.org/10.3390/ma8010285 1 %X In the current work, the evolutions of grain and dislocation microstructures are investigated on the basis of plane strain tension and simple shear tests for an interstitial free steel (DC06) and a 6000 series aluminum alloy (AA6016-T4). Both materials are commonly-used materials in the automobile industry. The focus of this contribution is on the characterization and comparison of the microstructure formation in DC06 and AA6016-T4. Our observations shed light on the active mechanisms at the micro scale governing the macroscopic response. This knowledge is of great importance to understand the physical deformation mechanisms, allowing the control and design of new, tailor-made materials with the desired material behavior. %0 journal article %@ 0261-3069 %A Goushegir, S.M.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2015 %J Materials and Design %N %P 431-442 %R doi:10.1016/j.matdes.2015.06.044 %T Influence of process parameters on mechanical performance and bonding area of AA2024/carbon-fiber-reinforced poly(phenylene sulfide) friction spot single lap joints %U https://doi.org/10.1016/j.matdes.2015.06.044 %X The effects of friction spot joining process parameters on the bonding area and mechanical performance,of single lap joints were investigated using full-factorial design of experiments and analysis of variance.,On one hand, the main process parameters with significant influence on the bonding area were joining,pressure, tool rotational speed and joining time. On the other hand, tool rotational speed and joining,pressure displayed the highest influence on the lap shear strength of the joints followed by tool plunge,depth, whereas the joining time was not statistically significant. The interaction between the rotational,speed and joining time was the only interaction with a significant effect on the mechanical performance.,Joints with ultimate lap shear forces varying between 1698 ± 92 N and 2310 ± 155 N were obtained. It,was observed that generally a larger bonding area as a result of higher heat input leads to an increased,mechanical performance of the joints. The generated regression model by the analysis of variance was,used to identify an optimized set of parameters for increasing the lap shear strength of the joints to,2280 ± 88 N. Furthermore, the process temperature was monitored, which varied in the range of,370–474 C. %0 journal article %@ 2213-8463 %A Krohn, H.,Hanke, S.,Beyer, M.,dos Santos, J.F. %D 2015 %J Manufacturing Letters %N %P 17-20 %R doi:10.1016/j.mfglet.2015.04.004 %T Influence of external cooling configuration on friction surfacing of AA6082 T6 over AA2024 T351 %U https://doi.org/10.1016/j.mfglet.2015.04.004 %X Friction surfacing is a solid-state surface engineering technology. Previous studies have shown that underwater friction surfacing has some advantages in efficiency and homogeneity of the deposited material. To use these advantages a water spray cooling system was implemented to achieve a more flexible process. This concept has been investigated by depositing Al alloy AA6082 T6 on AA2024 T351 substrate. The efficiency of the process was increased from 19% to 31% without influencing the properties of the deposited material. Temperature measurements revealed that the intensity and chosen location of cooling also affect the process characteristics and allow modifying the coating geometry. %0 journal article %@ 0003-6951 %A Thamburaja, P.,Klusemann, B.,Adibi, S.,Bargmann, S. %D 2015 %J Applied Physics Letters %N 5 %P 051903 %R doi:10.1063/1.4907398 %T The plastic yield and flow behavior in metallic glasses %U https://doi.org/10.1063/1.4907398 5 %X Metallic glasses have vast potential applications as components in microelectronics- and nanoelectronics-type devices. The design of such components through computer simulations requires the input of a faithful set of continuum-based constitutive equations. However, one long-standing controversial issue in modeling the plastic behavior of metallic glasses at the continuum level is the use of the most appropriate plastic yield criterion and flow rule. Guided by a series of molecular dynamics simulations conducted at low-homologous temperatures under homogeneous deformations, we quantitatively prove that the continuum plastic behavior in metallic glasses is most accurately described by a von Mises-type plastic yield criterion and flow rule. %0 journal article %@ 1359-8368 %A Altmeyer, J.,Suhuddin, U.F.H.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2015 %J Composites / B %N %P 130-140 %R doi:10.1016/j.compositesb.2015.06.015 %T Microstructure and mechanical performance of metal-composite hybrid joints produced by FricRiveting %U https://doi.org/10.1016/j.compositesb.2015.06.015 %X The mechanical performance and microstructure of friction riveted metallic-insert joints made of polyether ether ketone composite reinforced with 30% short carbon fibers and titanium grade 3 was studied. The metallic-insert joints reached a maximal pull-out tensile force of 10.6 kN, which corresponds to 100% of the titanium base material strength. It was shown the pull-out force increased as the rivet tip widened. Frictional heat during the process was mainly generated by the friction between the tip of the rivet and the composite substrate in the friction zone. Microstructural analyses of the metallic part of the joint revealed the presence of different microstructural zones: a friction zone, and two thermomechanically affected zones 1 and 2. Based on the composite morphology, the composite part of the joint was categorized into three different zones: the stir zone, a thermomechanically affected zone and a heat-affected zone. A study of the material flow showed that the flow of the composite was strongly affected by the rotation and axial movement of the rivet. %0 journal article %@ 0261-3069 %A Wang, F.F.,Li, W.Y.,Shen, J.J.,Hu, S.Y.,Li, J.L.,dos Santos, J.F.,Huber, N. %D 2015 %J Materials and Design %N %P 933-940 %R doi:10.1016/j.matdes.2015.07.096 %T Effect of tool rotational speed on the microstructure and mechanical properties of bobbin tool friction stir welding of Al-Li alloy %U https://doi.org/10.1016/j.matdes.2015.07.096 %X A third-generation Al-Li alloy AA2198 has been successfully welded by bobbin tool friction stir welding. The stirred zone, displaying an hourglass shape, consists of recrystallized Al grains and precipitates remaining in solution. Joint line remnants have been found in all etched welds. Symmetrical hardness profiles have been obtained in the thickness direction, which indicates that the joints have homogenous through-thickness mechanical properties. As the rotational speed increases, the grain size of the stirred zone increases, whereas the density of strengthening particles decreases; the joint line remnants become compressed remarkably in the shoulder-dominated zone while less changes occur in the probe-dominated zone; the softest region shrinks and shifts outward, the average hardness of the stirred zone increases and the hardness profile along the cross section of the joint changes from the U-shaped to W-shaped. The tensile strength of the joint initially increases with rotational speed and then decreases with the maximal strength efficiency reaching 80%; three fracture modes have been observed and cracking initiates at the joint line remnant propagating towards the heat-affected zone, and finally to the border between the thermal-mechanically affected zone and stirred zone. %0 journal article %@ 0261-3069 %A Esteves, J.V.,Goushegir, S.M.,dos Santos, J.F.,Canto, L.B.,Hage, E.Jr.,Amancio-Filho, S.T. %D 2015 %J Materials and Design %N %P 437-445 %R doi:10.1016/j.matdes.2014.06.070 %T Friction spot joining of aluminum AA6181-T4 and carbon fiber-reinforced poly(phenylene sulfide): Effects of process parameters on the microstructure and mechanical strength %U https://doi.org/10.1016/j.matdes.2014.06.070 %X Friction spot joining is an alternative technique to produce metal-composite overlap joints. The main process parameters are tool rotational speed, plunge depth, joining time and joining force. In this study, the individual effect of the process parameters on the microstructure and mechanical strength of hybrid AA6181-T4/CF-PPS double lap joints was investigated using Taguchi method and analysis of variance (ANOVA). Produced joints presented mechanical performance from 2107 N to 3523 N. Joints failed by brittle fracture at the interface between aluminum alloy and composite, with displacement-at-peak load values from 0.7 mm to 0.9 mm. Tool rotational speed was the parameter with the largest influence on the joint shear resistance, followed by the joining time, plunge depth and joining force. Higher strength was correlated to the extension of the bonding area and macro-mechanical interlocking related to the formation of a metallic indentation (metallic nub) slightly inserted into the composite. Larger bonding areas were shown to be related to higher heat input (as a result of longer joining times and intermediate rotational speeds) leading to larger consolidated polymeric layers at the metal-composite interface. Higher macro-mechanical interlocking was obtained at larger plunge depths. Joining force was shown to be related to crevice and pore filling of the metal surface by supporting spreading of the molten polymer. Higher joining forces led to better wetting of the interface, increasing adhesive forces and joint mechanical performance. Nevertheless excessive joining forces caused squeezing flow of the molten layer reducing joint strength, since a large adhesive area was lost. %0 journal article %@ 0257-8972 %A Fitseva, V.,Krohn, H.,Hanke, S.,dos Santos, J.F. %D 2015 %J Surface and Coatings Technology %N %P 56-63 %R doi:10.1016/j.surfcoat.2015.07.039 %T Friction surfacing of Ti–6Al–4V: Process characteristics and deposition behaviour at various rotational speeds %U https://doi.org/10.1016/j.surfcoat.2015.07.039 %X By the process of friction surfacing, coatings are generated from metallic materials at temperatures below their melting range. The high degree of deformation while depositing leads to grain refinement in the microstructure, which has a positive effect on the mechanical properties of the layer. The applicability of the process has been described for a large number of materials. The deposition of Ti–6Al–4V has been reported in one publication but was not systematically studied. Therefore, the main aims of the present work are to define the process parameter fields for the deposition of Ti–6Al–4V leading to flash and defect free coatings and associate them with geometric features of the deposited layer.,This investigation has shown that Ti–6Al–4V coatings can be effectively deposited onto a Ti–6Al–4V substrate by friction surfacing. A wide range of process parameters was established in which coatings of high quality have been obtained. The consumption rate control has been implemented as an efficient mode for the deposition of Ti–6Al–4V coatings. Temperature measurements at the coating interface have been accomplished showing that the coating material has been deformed in the β-phase. Furthermore, the homogeneity of the coating surface has been established to be a function of the rotational speed. The coatings exhibited a defect-free bond at the interface with the substrate. Two process parameter ranges with respect to the flash formation have been established. One of them enables flash-free coatings and the other generates coatings with flash formation on the retreating side, which can be controlled by the rotational and deposition speeds. Moreover, an increase in the rotational speed has been shown to lead to an increase in the coating thickness and width as well as an increase in the deposition efficiency up to 39 %. %0 journal article %@ 0104-9224 %A Andrade, T.C.,Silva, C.C.,Miranda, H.C.de,Motta, M.F.,Farias, J.P.,Bergman, L.A.,dos Santos, J.F. %D 2015 %J Soldagem & Inspecao %N 4 %P 467-478 %R doi:10.1590/0104-9224/SI2004.13 %T Microstructure of AISI 410S Ferritic Stainless Steel and AISI 304L Austenitic Stainless Steel Dissimilar Weld Joined by FSW Process - Microestrutura de uma Solda Dissimilar entre o Aço Inoxidável Ferrítico AISI 410S e o Aço Inoxidável Austenítico AISI 304L Soldado pelo Processo FSW %U https://doi.org/10.1590/0104-9224/SI2004.13 4 %X This study aims to investigate the microstructure formed in dissimilar welding between AISI 410S ferritic stainless steel and AISI 304L austenitic stainless steels plates by friction stir welding process. The welding was performed setting the following parameters: rotation 450 rpm; welding speed of 1.0 mm/s; and axial force 40 kN. The AISI 410S was positioned on the advancing side while the AISI 304L steel was positioned in the retracting side. The analysis consisted of metallographic preparation and microstructural characterization by optical microscopy and scanning electron microscopy. For AISI 410S ferritic stainless steel was found martensite formation in association with ferrite in the stir zone (SZ), thermomechanically affected zone (TMAZ) and heat-affected zone (HAZ). The characteristics of the FSW welding process for the ferritic stainless steel resulted in grain refining, whether in the SZ, TMAZ and HAZ. In the austenitic stainless steel side, the same behavior was not found.,O presente trabalho visa investigar a microestrutura formada na soldagem dissimilar entre chapas de aços inoxidáveis ferríticos AISI 410S e aços inoxidáveis austeníticos AISI 304L pelo processo friction stir welding. A soldagem foi realizada com o ajuste dos seguintes parâmetros: rotação 450 rpm; velocidade de soldagem de 1,0 mm/s; e força axial 40 kN. O aço AISI 410S foi posicionado no lado de avanço enquanto que o aço AISI 304L foi posicionado no lado de retrocesso. A análise consistiu de preparação metalográfica e caracterização microestrutural por microscopia ótica e microscopia eletrônica de varredura. Para o aço AISI 410S foi observada a formação de martensita associada com ferrita na zona de mistura (ZM), zona termomecanicamente afetada (ZTMA) e na zona afetada pelo calor (ZAC). As características do processo de soldagem FSW resultaram num refino de grão para o aço inoxidável ferrítico, posicionado no lado de avanço, tanto na ZM quanto nas ZTMA e ZAC. O mesmo comportamento não foi observado para o lado austenítico. %0 journal article %@ 0043-1648 %A Hanke, S.,Fischer, A.,dos Santos, J.F. %D 2015 %J Wear %N %P 332-338 %R doi:10.1016/j.wear.2015.07.010 %T Sliding wear behaviour of a Cr-base alloy after microstructure alterations induced by friction surfacing %U https://doi.org/10.1016/j.wear.2015.07.010 %X Friction surfacing is a method suitable to generate a wide variety of metallic coatings by means of frictional heating and severe shear deformation. It is a solid-state joining method, and therefore may be applied to non-fusion weldable as well as non-deformable brittle materials, as Cr-based alloys are. In the present study coatings of Cr60Ni40 alloy are generated onto Nimonic 80A substrates. Microstructural investigations of the coating material are carried out and compared to the usual cast state. The wear behaviour of the coatings as well as the cast material is examined under reciprocating sliding against 52100 ball bearing steel by means of a ball-on-flat test rig, lubricated with silicone oil to prevent oxidation. In this tribological system, wear takes place by abrasion with microploughing being the predominant submechanism, surface fatigue as well as adhesion by materials transfer of Cr60Ni40 from the flats to the steel balls. White etching layers form on Cr60Ni40 underneath the worn surfaces, which show cracks and delaminations. The amount of wear of all coatings is within the same magnitude compared to the cast state but slightly smaller. This can be explained by the distinctly finer microstructure (grain boundary strengthening) and a high degree of supersaturation of the solid solutions (solid solution strengthening) within the coatings. The results of this study show that it is possible to generate coatings of brittle alloys like Cr60Ni40 by friction surfacing, which show a slightly better wear behaviour under reciprocating sliding. Thus, in combination with a ductile substrate, these coatings are likely to extend the range of applicability of such high-temperature wear and corrosion resistant alloys. %0 journal article %@ 0167-577X %A Goncalves, J.,dos Santos, J.F.,Canto, L.B.,Amancio-Filho, S.T. %D 2015 %J Materials Letters %N %P 509-509 %R doi:10.1016/j.matlet.2015.08.036 %T Friction spot welding of carbon fiber-reinforced polyamide 66 laminate %U https://doi.org/10.1016/j.matlet.2015.08.036 %X Friction spot welding (FSpW) is an innovative technique developed by the Helmholtz Zentrum Geesthacht (WO/2001/036144). FSpW uses the friction between a rotating tool and workpieces to generate enough heat to cause macromolecular interdiffusion across the interface of the joining partners to create the weld. In this work, the feasibility of FSpW on carbon fiber-reinforced polyamide 66 laminate (CF-PA66) was evaluated through lap shear testing and optical microscopy. CF-PA66 welds with good surface finishing, an absence of degradation flaws and an average lap-shear strength of 26.8±0.8 MPa were achieved. These welds have comparable mechanical performance to state-of-the-art ultrasonic welds, which indicates the potential of the FSpW process for fiber-reinforced polymer composites. %0 journal article %@ 0167-6636 %A Soyarslan, C.,Klusemann, B.,Bargmann, S. %D 2015 %J Mechanics of Materials %N %P 21-30 %R doi:10.1016/j.mechmat.2015.03.003 %T A directional modification of the Levkovitch–Svendsen cross-hardening model based on the stress deviator %U https://doi.org/10.1016/j.mechmat.2015.03.003 %X In the original Levkovitch–Svendsen cross-hardening model parallel and orthogonal projections required for the yield surface evolution with respective dynamic and latent hardening effects are associated with the unit plastic flow direction View the MathML sourcenp=Ėp/|Ėp|. This work gives a detailed investigation regarding the consequences and proposes the use of the so–called radial direction ns=[S-X]/|S-X|ns=[S-X]/|S-X| instead where S=dev(σ)S=dev(σ). It is shown that for an initially plastically anisotropic material under load paths with proportional stresses the original model brings a continuous directional change in the plastic strains. Eventually, even if the dynamic hardening component is bypassed, the material model predicts additional strengthening in loading direction due to latent hardening. In this undesired response, the broken coaxiality of the stress deviator and plastic strain rate tensor with initial anisotropy is the cause. This entanglement of isotropic/kinematic hardening and latent hardening creates difficulties – especially in the parameter identification even for the simplest uniaxial loading. The introduced modification to the model remedies this undesired feature and, hence, makes it possible to isolate the hardening sources during parameter identification stage. The discussions are supported by analytically and numerically derived yield loci for various scenarios. Our analytical studies allow definition of critical material parameter limits for the latent hardening parameter slsl in terms of the initial anisotropy and the constant stress deviator ratio. %0 journal article %@ 0261-3069 %A Plaine, A.H.,Gonzalez, A.R.,Suhuddin, U.F.H.,dos Santos, J.F.,Alcantara, N.G. %D 2015 %J Materials and Design %N %P 36-41 %R doi:10.1016/j.matdes.2015.05.082 %T The optimization of friction spot welding process parameters in AA6181-T4 and Ti6Al4V dissimilar joints %U https://doi.org/10.1016/j.matdes.2015.05.082 %X Friction spot welding is a relatively new solid-state joining process able to produce overlap joints between similar and dissimilar materials. In this study, the effect of the process parameters on the lap shear strength of AA6181-T4/Ti6Al4V single joints was investigated using full-factorial design of experiment and analyses of variance. Sound joints with lap shear strength from 4769 N to 6449 N were achieved and the influence of the main process parameters on joint performance was evaluated. Tool rotational speed was the parameter with the largest influence on the joint shear resistance, followed by its interaction with dwell time. Based on the experimental results following response surface methodology, a mathematical model to predict lap shear strength was developed using a second order polynomial function. The initial prediction results indicated that the established model could adequately estimate joint strength within the range of welding parameters being used. The model was then used to optimize welding parameters in order satisfy engineering demands. %0 journal article %@ 0104-9224 %A Proenca, B.C.,Blaga, L.,dos Santos, J.F.,Canto, L.B.,Amancio Filho, S.T. %D 2015 %J Soldagem & Inspecao %N 4 %P 489-500 %R doi:10.1590/0104-9224/SI2004.15 %T Friction Riveting of Aluminum Alloy 6056 T6 and Polyamide 6: Role of the Rotation Speed on the Formation of the Anchoring Zone and Mechanical Performance - Rebitagem por Friccao (“FricRiveting”) de Liga de Alumínio 6056 T6 e Poliamida 6: Influencia da Velocidade de Rotacao na Formacao da Zona de Ancoragem e no Desempenho Mecanico %U https://doi.org/10.1590/0104-9224/SI2004.15 4 %X Hybrid metal-polymer structures are an alternative solution to reduce weight and fuel consumption in the transportation industry in order to minimize the emission of noxious gases in regard to the greenhouse effect. Friction Riveting is a relatively new technique for joining metal-polymer hybrid structures. The process relies on the generation of frictional heat between the components causing the plastic deformation of the metallic rivet and its anchoring in the polymer component. This study evaluated the technical feasibility of friction-riveted AA 6056 T6 and PA6 joints, and the influence of the rotational speed (RS) on the maximum process temperature and on the mechanical performance of the joints. The maximum temperature reached increased with the rotational speed, from 291 ± 6 °C at 10000 rev/min to 375 ± 5 °C at 15000 rev/min. The use of greater rotational speeds induced the plastic deformation of the tip of the metallic rivet during the frictional phase. This led to mechanically stronger joints due to the larger anchoring of the metallic rivet within the polymeric plate. The AA 6056 T6-PA6 joints had good tensile strength, achieving 85% of the metallic rivet’s tensile strength. Therefore, the feasibility of friction-riveted AA 6056 T6-PA6 joints was proven. Furthermore, it was shown that the rotational speed influences directly the rivet anchoring and thus the tensile strength of the joints. %0 journal article %@ 0261-3069 %A Huetsch, L.L.,Huetsch, J.,Herzberg, K.,dos Santos, J.F.,Huber, N. %D 2014 %J Materials and Design %N %P 980-988 %R doi:10.1016/j.matdes.2013.08.108 %T Increased Room Temperature Formability of Mg AZ31 by High Speed Friction Stir Processing %U https://doi.org/10.1016/j.matdes.2013.08.108 %X The aim of this work is to investigate the formability at room temperature of the Mg alloy AZ31 by friction stir processing. Defect-free process zones were created using process speeds of up to 10 m/min, the resulting microstructure and grain size were analyzed. Microstructural zones with varying texture were identified by electron backscatter diffraction. Tensile tests supported by digital image correlation analysis revealed different deformation behavior and enhanced ductility in the thermo mechanically affected zone which was associated with the variation in grain size and texture. Finally, the sheet forming behavior of the processed material was investigated, using the Nakajima test method with Hasek specimen geometries. Forming limit diagrams for several process conditions reveal a continuous increase in formability with increasing processing speed. Additionally, the local anisotropy was analyzed by comparison of the R values at the point of highest strain, to quantify the impact of processing on formability. %0 journal article %@ 0921-5093 %A Suhuddin, U.,Fischer, V.,Kroeff, F.,dos Santos, J.F. %D 2014 %J Materials Science and Engineering A %N %P 384-389 %R doi:10.1016/j.msea.2013.10.057 %T Microstructure and mechanical properties of friction spot welds of dissimilar AA5754 Al and AZ31 Mg alloys %U https://doi.org/10.1016/j.msea.2013.10.057 %X In the present study, friction spot welding or refill friction stir spot welding was performed to consolidate dissimilar AA5754 Al and AZ31 Mg alloys. The intermetallic compounds of Al12Mg17 and Al3Mg2 were primarily found in the weld, distributed at the interface between the base materials and in the Al top sheet. The distribution of the intermetallic compounds and the interfacial area between the base materials affect the lap shear strength of the weld. It is concluded that the material flow induced by tool movement plays an important role in both the distribution of the intermetallic compounds and the interfacial area between the base materials. %0 journal article %@ 1478-6435 %A Bargmann, S.,Xiao, T.,Klusemann, B. %D 2014 %J Philosophical Magazine %N 1 %P 1-19 %R doi:10.1080/14786435.2013.838326 %T Computational modelling of submicron-sized metallic glasses %U https://doi.org/10.1080/14786435.2013.838326 1 %X The present contribution is concerned with the modelling and computation of stable shear localization process in submicron-sized metallic glasses. To this end, a non-local thermodynamically consistent, continuum mechanical, constitutive model is developed. In our previous work, we formulated the model in the small strain framework. In current work, this model is extended to finite strains. The numerical implementation is carried out with the help of the finite element method. Numerical examples are presented – illustrating the general model behaviour which is correlated to experimental observations. It is shown that the proposed finite deformation model is well suitable to predict the stable shear localization process in submicron-sized metallic glasses and its size effect. The model confirms that with decreasing sample size the shear localization process starts at a later deformation state. Additionally, the finite deformation model is able to predict the failure process in submicron-sized metallic glasses as well as the delay of it with decreasing sample size qualitatively correct. %0 journal article %@ 0924-0136 %A Gandra, J.,Krohn, H.,Miranda, R.M.,Vilaca, P.,Quintino, L.,dos Santos, J.F. %D 2014 %J Journal of Materials Processing Technology %N 5 %P 1062-1093 %R doi:10.1016/j.jmatprotec.2013.12.008 %T Friction surfacing - A review %U https://doi.org/10.1016/j.jmatprotec.2013.12.008 5 %X Friction surfacing (FS) is a solid state technology with increasing applications in the context of localized surface engineering. FS has been investigated mainly for producing fine grained coatings, which exhibit superior wear and corrosion properties. Since no bulk melting takes place, this process allows dissimilar joining of materials that would be otherwise incompatible or difficult to deposit by fusion based methods. Several studies also emphasize its energy efficiency and low environmental impact as key advantages when compared with other alternative technologies. Main applications include repair of worn or damaged surfaces through building up or crack sealing. It has also been applied to enhance surface properties at specific areas in the manufacturing of parts and tools. A wide range of material combinations have been deposited by FS, mainly alloy and stainless steels. Aluminium, magnesium and titanium alloys have also been investigated, including the production of metal matrix composites.,Starting with a brief introduction, this review presents a detailed description of the thermo-mechanical and microstructural transformations as well as process modelling approaches. The material combinations investigated so far and the effect of process parameters are also addressed. An overview of the main technologic and equipment advances is presented, including: computational optimization models, surface preparation, gas protection, post-processing methods, pre-heating and cooling. An assessment of the material deposition rate and the specific energy consumption is also provided, comparing friction surfacing to mainstream electric arc, laser and thermal spraying based processes. Based on current process advantages and disadvantages, an outlook on future research and development is provided.,Friction surfacing has a significant potential for further industrial applications and is being developed as a practicable alternative to mainstream coating processes. The present review paper provides a broad overview throughout the fundamentals of FS and the most relevant technology developments, establishing both a theoretical and technical basis for new researchers and industrial practitioners searching for new coating alternatives. %0 journal article %@ 0261-3069 %A Altmeyer, J.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2014 %J Materials and Design %N %P 164-176 %R doi:10.1016/j.matdes.2014.03.042 %T Effect of the friction riveting process parameters on the joint formation and performance of Ti alloy/short-fibre reinforced polyether ether ketone joints %U https://doi.org/10.1016/j.matdes.2014.03.042 %X The feasibility of friction riveting on short carbon fibre-reinforced thermoplastic polymers was investigated in this work. A design of experiments (DoE) was used to investigate the impact of rotational speed, friction time, friction pressure and forging pressure on joint formation and performance. The joint formation was studied using the mushrooming efficiency, the rivet penetration depth and the mechanical energy input. The tensile pull-out force was used to describe the mechanical performance of the investigated metallic-insert joints made of grade 3 titanium and short carbon fibre-reinforced polyether ether ketone (PEEK). All samples were scanned with X-rays before any mechanical testing to acquire the dimensions of the anchored rivet inside the reinforced polymer, elucidating their correlations with the mechanical performance. The DoE model can be used to tailor joint formation and performance. A parameter-set that improves the pull-out performance was determined using an analysis of variance. The analysis revealed that high rotational speed, friction time and forging pressure caused high pull-out forces. The metallic-insert joints reached high pull-out tensile strength between 6.3 kN and 10.7 kN. The dimensions of the deformed metallic rivet were correlated with the mechanical performance of the joint: the larger the widening of the rivet tip, the higher the pull out force was. Furthermore, widening of the rivet tip by 70% led to the maximal tensile pull-out force (10.7 kN), corresponding to the base material strength of the titanium rivet (10.7 kN). At this threshold value (70%), the failure mode also changed from failure mode III (pull-out of rivet) to failure mode I (rivet failure). %0 journal article %@ 0261-3069 %A Feistauer, E.E.,Bergmann, L.A.,Barreto, L.S.,dos Santos, J.F. %D 2014 %J Materials and Design %N %P 323-332 %R doi:10.1016/j.matdes.2014.02.042 %T Mechanical behaviour of dissimilar friction stir welded tailor welded blanks in Al–Mg alloys for Marine applications %U https://doi.org/10.1016/j.matdes.2014.02.042 %X Tailor welded blanks (TWB) in Al alloys are an attractive structural solution for application in the shipbuilding sector, mainly due to reductions in weight and lower production costs. In the present study, the global and local mechanical properties of dissimilar friction stir welded TWB were assessed. The joints were manufactured with dissimilar Al–Mg alloys and thicknesses (6 and 8 mm) of particular interest to the shipbuilding sector (AA5083 and AA5059). A digital image correlation system (DIC) linked to a tensile test system was used to characterise the local strain fields, and true stress–strain curves were generated for several TWB sub-zones. Microhardness and DIC analyses showed that the stir zone of the TWB presented overmatching in relation to the weakest base material, and that the joints displayed excellent overall mechanical performance that was comparable to the AA5059 base material in terms of strength and ductility. The fatigue strength was evaluated by means of tension–tension fatigue tests, and the TWB joints reached the fatigue keen with a stress range of 70 MPa. %0 journal article %@ 0003-6951 %A Shen, J.,Suhuddin, U.F.H.,Barbosa, M.E.B.,dos Santos, J.F. %D 2014 %J Applied Physics Letters %N 19 %P 191901 %R doi:10.1063/1.4876238 %T Eutectic structures in friction spot welding joint of aluminum alloy to copper %U https://doi.org/10.1063/1.4876238 19 %X A dissimilar joint of AA5083 Al alloy and copper was produced by friction spot welding. The Al-MgCuAl2 eutectic in both coupled and divorced manners were found in the weld. At a relatively high temperature, mass transport of Cu due to plastic deformation, material flow, and atomic diffusion, combined with the alloy system of AA5083 are responsible for the ternary eutectic melting. %0 journal article %@ 1359-6454 %A Sarac, B.,Klusemann, B.,Xiao, T.,Bargmann, S. %D 2014 %J Acta Materialia %N %P 411-422 %R doi:10.1016/j.actamat.2014.05.053 %T Materials by design: An experimental and computational investigation on the microanatomy arrangement of porous metallic glasses %U https://doi.org/10.1016/j.actamat.2014.05.053 %X The correlation of a material’s structure with its properties is one of the important unresolved issues in materials science research. This paper discusses a novel experimental and computational approach by which the influence of the pores on the mechanical properties of bulk metallic glasses (BMGs) can be systematically and quantitatively analyzed. The experimental stage involves the fabrication of a template whose pore configurations are pre-determined by computer-aided design tools, and replication of the designed patterns with BMGs. Quasi-static mechanical characterization of these complex microstructures is conducted under uniaxial tension and in-plane compression. For the numerical simulations, a non-local gradient-enhanced continuum mechanical model is established, using thermodynamic principles and periodic boundary conditions. The combination of the experimental and numerical results has identified the importance of the pore configuration, overall porosity and diameter to the spacing ratio of the pores to attain optimized material properties. %0 journal article %@ 0924-0136 %A Rodrigues, C.F.,Blaga, L.A.,dos Santos, J.F.,Canto, L.B.,Hage, E. Jr.,Amancio-Filho, S.T. %D 2014 %J Journal of Materials Processing Technology %N 10 %P 2029-2039 %R doi:10.1016/j.jmatprotec.2013.12.018 %T FricRiveting of aluminum 2024-T351 and polycarbonate: Temperature evolution, microstructure and mechanical performance %U https://doi.org/10.1016/j.jmatprotec.2013.12.018 10 %X Friction Riveting (FricRiveting) is an innovative, fast and energy-efficient spot joining process used to join lightweight hybrid metal–polymer and metal–composite structures. In this process, a cylindrical metallic rivet is used to join one or more thermoplastic components by means of plasticizing and deforming the tip of a metallic rivet through frictional heating and pressure inside the polymeric parts. This work studies the feasibility of the FricRiveting technique for polycarbonate/aluminum 2024-T351 alloy spot joints by investigating the temperature development (measured by infrared thermography), microstructure (evaluated by optical microscopy) and mechanical properties (investigated by tensile testing) of the joints. The thermographic temperature investigation indicated that the average peak process temperatures were from 280 to 360 °C, from 56% to 72% of the AA 2024 eutectic point and below the temperature range of extensive thermal degradation of polycarbonate (480–550 °C). Furthermore, the typical deformed tip of the rivet – the anchoring zone – was attained for all joints investigated in this study, as induced by thermo-mechanical processing. The anchoring efficiency represented by the aspect ratio of the deformed rivet was evaluated by optical microscopy. Aspect ratio values were compared with the process temperatures and the tensile strengths of the joints. Increases in process heat input resulted in larger aspect ratios. High average values of ultimate tensile forces varying from 6659 ± 62 N to 8540 ± 182 N (68.4–87.8% of the ultimate tensile strength of the metallic rivet) were achieved, with final ductile fracture occurring in the metallic rivet for joints with aspect ratios of 0.88 ± 0.02 and in the polymeric base plate for joints with aspect ratios of 0.61 ± 0.03 and 0.68 ± 0.04. The volumetric ratio – a recent, more complex three dimensional approach for evaluating the mechanical performance of the joints – was also investigated, revealing similar interactions with process temperatures and tensile strengths as the aspect ratio. The results of this work proved that FricRiveting is a feasible method for use on the PC-AA 2024-T351 material combination, as it yields strong joints. %0 journal article %@ 0261-3069 %A Dethlefs, A.,Roos, A.,dos Santos, J.F.,Wimmer, G. %D 2014 %J Materials and Design %N %P 7-12 %R doi:10.1016/j.matdes.2014.03.049 %T Hybrid Friction Diffusion Bonding of Aluminium Tube-to-Tube-Sheet Connections in Coil-Wound Heat Exchangers %U https://doi.org/10.1016/j.matdes.2014.03.049 %X The present study presents and evaluates an application of a new solid-state bonding process, hybrid friction diffusion bonding (HFDB). HFDB is used to fabricate tube-to-tube-sheet connections for aluminium coil-wound heat exchangers. An industry-applicable process variant is developed, and its feasibility is demonstrated by gas leak tightness tests and tensile pull-out tests. The joints meet the requirements of industrial applications. Furthermore, the process is characterised by the thermal field development in the weld area and the applied process forces. The microstructure of the joint is investigated, and dynamic recrystallization is assumed to be the primary grain refinement mechanism in the thermo-mechanically affected zone. %0 journal article %@ 0261-3069 %A Li, W.Y.,Fu, T.,Huetsch, L.,Hilgert, J.,Wang, F.F.,dos Santos, J.F.,Huber, N. %D 2014 %J Materials and Design %N %P 714-720 %R doi:10.1016/j.matdes.2014.07.023 %T Effects of tool rotational and welding speed on microstructure and mechanical properties of bobbin-tool friction-stir welded Mg AZ31 %U https://doi.org/10.1016/j.matdes.2014.07.023 %X The effects of rotational and welding speeds on the microstructure and mechanical properties of bobbin-tool friction stir welded (BT-FSW) Mg AZ31 were investigated. The results indicated that the thermo-mechanically affected zone (TMAZ) consisted of equiaxed grains, which were inconsistent with the deformed, rotated and elongated grains found in the TMAZs of bobbin-tool friction stir welded Al alloys and friction stir welded Al and Mg alloys. The average grain size increased as the ratio of the rotational speed to welding speed increased. Excellent welds with no degradation in hardness were produced using a low heat input. Mechanical tests revealed that the ultimate tensile strengths gradually increased with increasing welding speed while keeping the rotational speed constant. The rotational and welding speeds had only slight influences on the yield stress and fracture elongation. %0 journal article %@ 1617-7061 %A Klusemann, B.,Xiao, T.,Bargmann, S. %D 2014 %J PAMM: Proceedings in Applied Mathematics and Mechanics %N 1 %P 529-530 %R doi:10.1002/pamm.201410252 %T Non-local modeling of size effects in amorphous metals %U https://doi.org/10.1002/pamm.201410252 1 %X The present contribution is concerned with the modeling of lengthscale-dependent behavior of submicron sized amorphous metal. As these samples reach the size of a few hundred nanometers, the main deformation mechanism changes from catastrophic to a stable shear localization. For the underlying model description, we resort to a thermodynamically consistent approach. Klusemann & Bargmann [1] presented results for a small strain formulation which was extended recently to finite strains by Bargmann et al. [2]. The non-local material model is formulated with a dual mixed finite element approach. It is shown that the proposed finite deformation model is well suited to predict the stable shear localization process in submicron-sized metallic glasses and its size effect. The model confirms the experimental observation that with decreasing sample size the shear localization process becomes stable and delayed. The finite deformation model is able to predict the failure process in submicron-sized metallic glasses as well as the delay of it with decreasing sample size. %0 journal article %@ 0032-3861 %A Junior, W.S.,Emmler, T.,Abetz, C.,Handge, U.A.,dos Santos, J.F.,Amancio-Filho, S.T.,Abetz, V. %D 2014 %J Polymer %N 20 %P 5146-5159 %R doi:10.1016/j.polymer.2014.08.022 %T Friction spot welding of PMMA with PMMA/silica and PMMA/silica-g-PMMA nanocomposites functionalized via ATRP %U https://doi.org/10.1016/j.polymer.2014.08.022 20 %X In the present study, the feasibility of Friction Spot Welding (FSpW) of a commercial-grade poly(methyl methacrylate) (PMMA) (PMMA GS) and PMMA 6N/functionalized silica (SiO2) nanocomposites was investigated. The silica nanoparticles were functionalized via atom transfer radical polymerization (ATRP) with PMMA chains to achieve a uniform dispersion in the polymer matrix. The successful functionalization of silica nanoparticles with PMMA chains via ATRP was evaluated by ATR-FT-IR and TGA measurements. Rheological investigations of the silica nanocomposites showed a plateau of the storage modulus G′ at low frequencies (0.01–0.03 rad/s) as a result of elastic particle–particle interactions. Overlap friction spot welds consisting of PMMA GS and a 2 wt% SiO2-g-PMMA nanocomposite were successfully prepared and compared to spot joints of PMMA GS welded with PMMA 6N and PMMA 6N/silica nanocomposite with 2 wt% unfunctionalized silica nanoparticles. Raman mappings of selected areas of cross-sectional plastographic specimens revealed an increased mixing behavior between the two polymer plates in the case of PMMA GS/2 wt% SiO2-g-PMMA joints. Although the joints welded with PMMA 6N/silica nanocomposites showed a reduction of 22% in lap shear strength and 21% displacement at peak load compared with the neat PMMA spot welds, they can compete with other state-of-the-art PMMA welding techniques such as thermal bonding and ultrasonic welding, which indicates the potential of friction spot welding as an alternative fabrication technology for joining future nanocomposite engineering parts. %0 journal article %@ 0261-3069 %A Campo, K.N.,Campanelli, L.C.,Bergmann, L.,dos Santos, J.F.,Bolfarini, C. %D 2014 %J Materials and Design %N %P 139-145 %R doi:10.1016/j.matdes.2013.11.002 %T Microstructure and interface characterization of dissimilar friction stir welded lap joints between Ti–6Al–4V and AISI 304 %U https://doi.org/10.1016/j.matdes.2013.11.002 %X The feasibility of dissimilar friction stir welding (FSW) in overlap configuration between Ti–6Al–4V alloy (Ti64) and AISI 304 austenitic stainless steels (304SS) was investigated. Sound joints were achieved when placing titanium as the upper workpiece. Joints were successfully produced by employing a welding speed of 1 mm/s and rotational speeds of 300 and 500 rpm. A lamellar microstructure was formed in the stir zone of Ti64, where grain size was found to increase with increasing rotational speed, and austenitic equiaxed grains were obtained near the interface of 304SS coupon. Energy dispersive X-ray spectroscopy (SEM-EDS) of the interface revealed a thin intermixed region and suggested intermetallic compound formation. Microhardness data in the titanium weld zone for both rotational speeds exhibited slightly lower values than the base material, with the lowest values in the heat affected zone, whereas the microhardness values in the stainless steel side around the weld center were found to be higher than those obtained for the base material. %0 journal article %@ 0261-3069 %A Goushegir, S.M.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2014 %J Materials and Design %N %P 196-206 %R doi:10.1016/j.matdes.2013.08.034 %T Friction Spot Joining of aluminum AA2024/carbon-fiber reinforced poly(phenylene sulfide) composite single lap joints: Microstructure and mechanical performance %U https://doi.org/10.1016/j.matdes.2013.08.034 %X Friction Spot Joining is a promising alternative joining technology for polymer–metal hybrid structures. In this work, the feasibility of Friction Spot Joining of aluminum AA2024-T3 (bare and alclad)/carbon-fiber reinforced poly(phenylene sulfide) is reported. The process temperature and the microstructure of the joints were investigated. Lap shear tensile strength as high as 27 MPa was achieved by using aluminum bare specimens. Sand blasting was also performed as an effective mechanical surface pre-treatment on aluminum surfaces, which resulted in higher surface roughness and accordingly improved mechanical performance for the selected conditions. In addition, the alclad specimens exhibited promising mechanical performance (lap shear strength of up to 43 MPa) that justifies further investigations. Finally, the bonding and failure mechanisms of the joints are briefly discussed. %0 journal article %@ 0020-7683 %A Bargmann, S.,Reddy, B.D.,Klusemann, B. %D 2014 %J International Journal of Solids and Structures %N 15-16 %P 2754-2764 %R doi:10.1016/j.ijsolstr.2014.03.010 %T A computational study of a model of single-crystal strain-gradient viscoplasticity with an interactive hardening relation %U https://doi.org/10.1016/j.ijsolstr.2014.03.010 15-16 %X The behavior of a model of single-crystal strain-gradient viscoplasticity is investigated. The model is an extension of a rate-independent version, and includes a new hardening relation that has recently been proposed in the small-deformation context (Gurtin and Reddy, 2014), and which accounts for slip-system interactions due to self and latent hardening. Energetic and dissipative effects, each with its corresponding length scale, are included. Numerical results are presented for a single crystal with single and multiple slip systems, as well as an ensemble of grains. These results provide a clear illustration of the effects of accounting for slip-system interactions. %0 journal article %@ 0020-7403 %A Behrouzi, A.,Soyarslan, C.,Klusemann, B.,Bargmann, S. %D 2014 %J International Journal of Mechanical Sciences %N %P 101-111 %R doi:10.1016/j.ijmecsci.2014.08.025 %T Inherent and induced anisotropic finite visco-plasticity with applications to the forming of DC06 sheets %U https://doi.org/10.1016/j.ijmecsci.2014.08.025 %X In the current work we present a finite visco-plasticity model accounting for inherent and induced plastic anisotropy as well as Bauschinger effect for the interstitial free (IF) steels and its application to a forming process simulation of DC06 sheets. The inherent plastic anisotropy uses a Hill-48 type structural tensor whereas the induced anisotropy is modeled via its evolution accounting for dynamic (active) and latent (inactive) parts. The latter appears to be an eminent requirement for predicting the qualitative effect of the evolving dislocation microstructures under orthogonal loading path changes, i.e., the cross hardening. A nonlinear isotropic and Armstrong–Frederick type kinematic hardening is also involved. Finally, the rate dependence of the plastic response is incorporated using Johnson–Cook type formulation. The model is implemented as VUMAT user defined material subroutine for ABAQUS and used in a set of sensitivity analyses to present mentioned model features. The model parameters are identified based on a set of experiments involving monotonic shear, uniaxial tension, forward to reverse shear and plane strain tension followed by shear tests. Finally, the channel forming process of a DC06 sheet is simulated. A good agreement with the experimental findings is observed, in both the tool response history curves and the extent of spring-back which is conclusive on the final product geometry. %0 journal article %@ 0104-9224 %A Goncalves, J.,dos Santos, J.F.,Canto, L.B.,Amancio Filho, S.T. %D 2014 %J Soldagem & Inspecao %N 1 %P 19-27 %R doi:10.1590/S0104-92242014000100004 %T Improvement of the Friction Spot Welding (FSpW) to join Polyamide 6 and Polyamide 66/Carbon Fiber Laminate - Aperfeicoamento da Tecnica de Soldagem Pontual por Friccao (FSpW) para Uniao de Poliamida 6 e Laminado de Poliamida 66 com Fibra de Carbono %U https://doi.org/10.1590/S0104-92242014000100004 1 %X Friction Spot Welding is an innovative technique developed and patented in 2005 by the research center Helmholtz Zentrum,Geesthacht (HZG). Advantages of the process include fast joining cycles, low operational costs and good mechanical performance.,It was originally developed to weld lightweight metals and has been continuously improved to weld polymers. There are only few,studies on friction spot welding of thermoplastics and the welding of polymeric composites by FSpW is still unpublished. This study,demonstrated the technical feasibility of welding a polyamide 6 (PA6) plate over a carbon fiber polyamide 66 laminate (CF-PA66) by,FSpW. The thermal history, the surface finish, the microstructure of the weld region and the mechanical shear strength of PA6/CF-PA66,lap joints were investigated. The increase of the diameter of the clamping ring - originally designed for welding lightweight metals - led,to the selection of welding parameters that result in high heat input, resulting in an increased welded area, and lower notch left by the,tool in the sample that improved the surface finish of the weld. This optimization resulted in a PA6/CF-PA66 joint with lap shear strength,of 35 MPa (2196 N), with fracture occurring mainly in the top plate of PA6.,A Soldagem Pontual por Fricção (‘Friction Spot Welding – FSpW’) é uma técnica inovadora que foi desenvolvida e patenteada em 2005,pelo centro de pesquisa alemão Helmholtz Zentrum Geesthacht (HZG). A técnica apresenta ciclos rápidos, baixo custo operacional,e gera soldas com alto desempenho mecânico. Foi inicialmente projetada para a soldagem de ligas metálicas leves. A soldagem de,polímeros é alvo de pesquisas recentes e a soldagem de compósitos poliméricos por FSpW ainda é inédita. Este estudo demonstrou,a viabilidade técnica da soldagem de chapa de poliamida 6 (PA6) e laminado de poliamida 66 e fibra de carbono (CF-PA66) por,FSpW. O histórico térmico, o acabamento superficial, a microestrutura da região da solda e a resistência mecânica ao cisalhamento,de juntas sobrepostas PA6/CF-PA66 foram investigados. O aumento do tamanho do anel de fixação da ferramenta original, projetada,para a soldagem de metais, possibilitou a seleção de parâmetros de soldagem que resultaram em grande aporte térmico, resultando no,aumento da área soldada, num menor entalhe (inscrição) deixado pela ferramenta na amostra, produzindo melhoria no acabamento,superficial da solda. Essa otimização resultou em uma junta PA6/CF-PA66 com resistência ao cisalhamento de 35 MPa (2196 N), com,fratura predominante na placa superior de PA6. %0 journal article %@ 0261-3069 %A Junior, W.S.,Handge, U.A.,dos Santos, J.F.,Abetz, V.,Amancio-Filho, S.T. %D 2014 %J Materials and Design %N %P 246-250 %R doi:10.1016/j.matdes.2014.07.050 %T Feasibility study of friction spot welding of dissimilar single-lap joint between poly(methyl methacrylate) and poly(methyl methacrylate)-SiO2 nanocomposite %U https://doi.org/10.1016/j.matdes.2014.07.050 %X In this work, the feasibility of friction spot welding (FSpW) of a commercial poly(methyl methacrylate) (PMMA) GS grade and a PMMA 6 N/2 wt% silica (SiO2) nanocomposite was investigated. Single-lap joints welded at rotational speeds of 1000, 2000 and 3000 rpm were produced. The analysis of the joint microstructure and material flow pattern indicated that joints could be produced using all of the tested welding conditions. However, the joint produced at 1000 rpm displayed sharp weld lines (weak links), indicating insufficient heat input, while the welds produced at 3000 rpm displayed excessive plastic deformation (bulging of the bottom plate), volumetric defects and a lack of material mixing in the welded area, associated with higher heat input. The weld produced at a rotational speed of 2000 rpm resulted in improved material mixing, which was indicated by the absence of weld lines and volumetric defects due to the more correct heat input. This welding condition was selected for further mechanical testing. Lap shear testing of PMMA GS/PMMA 6 N/2 wt% SiO2 nanocomposite single lap joints welded at 2000 rpm resulted in an average ultimate lap shear strength of 3.9 ± 0.05 MPa. These weld strength values are equal to or better than those obtained using state-of-the-art welding techniques for PMMA materials, thereby demonstrating the potential of friction spot welding for thermoplastic nanocomposites. %0 journal article %@ 0924-0136 %A Campanelli, L.C.,Suhuddin, U.F.H.,Antonialli, A.I.S.,dos Santos, J.F.,Alcantara, N.G.,Bolfarini, C. %D 2013 %J Journal of Materials Processing Technology %N 4 %P 515-521 %R doi:10.1016/j.jmatprotec.2012.11.002 %T Metallurgy and Mechanical Performance of AZ31 Magnesium Alloy Friction Spot Welds %U https://doi.org/10.1016/j.jmatprotec.2012.11.002 4 %X Microstructural features were studied along the cross-section of AZ31 magnesium alloy friction spot welded joints made using different combinations of welding parameters. Static lap shear testing was performed to evaluate the mechanical properties of the welded joints, and the resulting fracture mechanisms and crack propagation paths were fully examined. Failure load is optimized when the welding procedure is performed with the combination of parameters that maximizes the material mixing, the size of fully metallurgical bonding and simultaneously minimizes the vertical displacement of hook region. The welds demonstrate three failure modes during lap shear testing: through the weld and non-circumferential pull-out modes, in which crack propagation crosses the recrystallized zone, and circumferential pull-out mode, around this zone. %0 journal article %@ 0927-0256 %A Wang, H.,Colegrove, P.A.,dos Santos, J.F. %D 2013 %J Computational Materials Science %N %P 101-108 %R doi:10.1016/j.commatsci.2013.01.021 %T Numerical investigation of the tool contact condition during friction stir welding of aerospace aluminium alloy %U https://doi.org/10.1016/j.commatsci.2013.01.021 %X The contact condition between the welding tool and the workpiece in friction stir welding (FSW) is believed to be critically important to understand the heat generation and material flow behaviour. Both of these are difficult to study experimentally. In previous simulation studies, the contact conditions that occur during FSW are generally described as stick and/or slip, according to different methodologies but these descriptions have their limitations. In the study described in this paper, the thermal and mechanical outcomes from models with prescribed stick and slip conditions were compared to identify the results and drawbacks of assuming different contact conditions. This paper presents a new combination method for characterising the contact conditions that occur during FSW. This new method yields more reasonable heat generation estimates, as validated by the experimental thermal measurements. %0 journal article %@ 0261-3069 %A Abibe, A.B.,Amancio-Filho, S.T.,dos Santos, J.F.,Hage, E.jr. %D 2013 %J Materials and Design %N %P 338-347 %R doi:10.1016/j.matdes.2012.10.043 %T Mechanical and failure behaviour of hybrid polymer–metal staked joints %U https://doi.org/10.1016/j.matdes.2012.10.043 %X Structural applications that use multi-material structures in the transportation industry have increased in recent years. Weight reduction in order to avoid excessive emissions is the driving force of this trend. The current joining technologies for such complex structures have potential for engineering and performance improvement. This preliminary study shows an alternative joining method for hybrid structures, the so-called Injection Clinching Joining (ICJ) [Abibe et al., J Thermoplast Compos 2011;24(2): 233–49], based on the principles of staking, injection moulding, and mechanical fastening. The main objectives of the paper are to exploit the mechanical behaviour of overlap joints produced by this proposed method and assess its potential as an applicable technology. The measurements used in this research are optical and scanning electron microscopy, X-ray computer microtomography, lap-shear strength testing and in situ strain distribution. Different failure modes were found, depending on the joining conditions. Net tension failure had a brittle and catastrophic nature, while rivet pull-out presented a more desirable slow ductile failure mode. The joint strengths were good, ranging from 35.9% to 88.5% of the base material’s experimental ultimate tensile stress. Although there is a lack of studies on structural staking applications, this paper shows potential for these joining techniques and introduces ICJ as a potential focus of future research. %0 journal article %@ 0921-5093 %A Rao, D.,Huber, K.,Heerens, J.,dos Santos, J.F.,Huber, N. %D 2013 %J Materials Science and Engineering A %N %P 44-50 %R doi:10.1016/j.msea.2012.12.014 %T Asymmetric mechanical properties and tensile behaviour prediction of aluminium alloy 5083 friction stir welding joints %U https://doi.org/10.1016/j.msea.2012.12.014 %X The asymmetric material flow, severe plastic deformation and thermal cycle imposed on the base material during friction stir welding (FSW) result in unique microstructural development, which causes a gradient in local mechanical properties in the weld region. Micro-tensile and indentation testing were applied to determine the local mechanical properties in a friction stir welded joint. The local stress–strain curves exhibited a drastic change at the advancing side (AS) due to a steep gradient of mechanical properties. Finite Element Model (FEM) predictions of the tensile performance of the welded joints, based on the local mechanical properties measured by micro-tensile testing, were in very good agreement with the macro-tensile test data. %0 journal article %@ 0936-7195 %A Klusemann, B.,Svendsen, B.,Bargmann, S. %D 2013 %J GAMM-Mitteilungen %N 2 %P 219-238 %R doi:10.1002/gamm.201310013 %T Analysis and comparison of two finite element algorithms for dislocation density based crystal plasticity %U https://doi.org/10.1002/gamm.201310013 2 %X The purpose of the current work is the formulation and comparison of two finite element algorithms for a dislocation density based crystal plasticity model. We study multiscale inelastic materials whose behavior is influenced by the evolution of inelastic microstructure and the corresponding material or internal lengthscales. The work is an extension of the first investigation in Klusemann et al. [1] which was limited to a one-dimensional bar. In the γ -algorithm, the displacement u and glide system slips γα are global unknowns and determined via weak field relations. The non-dimensional densities of geometrically necessary dislocations ∼α are local quantities and solved for via a strong field relation. In the Q -algorithm, both the displacement uand dislocation densities ∼α are modeled as global, and the glide system slips γα as local. As it turns out, both algorithms generally predict the same microstructural behavior on a single crystal level. However, for a polycrystal the two solution strategies predict different material behaviors due to the formulation-dependent representation of the boundary conditions. The introduction of a boundary layer in the model leads to good agreement between both algorithms for single and polycrystal simulations. %0 journal article %@ 2191-0243 %A Klusemann, B.,Bargmann, S. %D 2013 %J Journal of the Mechanical Behavior of Materials %N 1-2 %P 51-66 %R doi:10.1515/jmbm-2013-0009 %T Modeling and simulation of size effects in metallic glasses with a non-local continuum mechanics theory %U https://doi.org/10.1515/jmbm-2013-0009 1-2 %X The present contribution is concerned with the modeling and computation of size effects in metallic glasses. For the underlying model description, we resort to a thermodynamically consistent, gradient-extended continuum mechanics approach. The numerical implementation is carried out with the help of the finite element method. Numerical examples are presented and compared with existing experimental findings to illustrate the performance of the constitutive model. In this regard, the influence of the material length scale is investigated. It is shown that with decreasing sample size or decreasing material length scale, a delay of the shear localization is obtained. In addition, the tension-compression asymmetry observed in experiments is captured by the proposed model. Further, the rate-dependent behavior as well as the influence of the results to initial local defects are investigated. %0 journal article %@ 0255-5476 %A Suhuddin, U.,Fischer, V.,dos Santos, J.F. %D 2013 %J Materials Science Forum, Light Metals Technology Conference, LMT 2013 %N %P 731-735 %R doi:10.4028/www.scientific.net/MSF.765.731 %T Formation of Intermetallic Compounds in Dissimilar Friction Spot Weld of Al to Mg Alloys %U https://doi.org/10.4028/www.scientific.net/MSF.765.731 %X In the present study, friction spot welding has been used for joining dissimilar AA5754 aluminum to AZ31 magnesium alloys. To get more insight into the microstructure, stop-action experimentation was employed. The welding cycle was forced to stop during the dwell time, and subsequently, the weld was quenched by pouring a mixed solution of ice and water to freeze the microstructure. Formation of the liquid phase leading to a formation of brittle intermetallic compound has been studied. Microstructural analyses reveal that formation of intercalated layers and a high density of grain boundaries induced by plastic deformation enhance the formation of eutectic structure during the welding process. %0 journal article %@ 1362-1718 %A Wang, H.,Colegrove, P.A.,dos Santos, J.F. %D 2013 %J Science and Technology of Welding and Joining %N 2 %P 147-153 %R doi:10.1179/1362171812Y.0000000078 %T Hybrid modelling of 7449-T7 aluminium alloy friction stir welded joints %U https://doi.org/10.1179/1362171812Y.0000000078 2 %X Many finite element models use adjustable parameters that control the heat loss to the backing bar, as well as the heat input to the weld. In this paper, we describe a method for determining these parameters with a hybrid artificial neural network (ANN) coupled thermal flow process model of the friction stir welding process. The method successfully determined temperature dependent boundary condition parameters for a series of friction stir welds in 3·2 mm thick 7449 aluminium alloy. The success of the technique depended on the method used to input thermal data into the ANN and the ANN topology. Using this technique to obtain the adjustable parameters of a model is more efficient than the conventional trial and error approach, especially where complex boundary conditions are implemented. %0 journal article %@ 0043-1648 %A Hanke, S.,Beyer, M.,Silvonen, A.,dos Santos, J.F.,Fischer, A. %D 2013 %J Wear %N 1-2 %P 415-423 %R doi:10.1016/j.wear.2012.11.016 %T Cavitation erosion of Cr60Ni40 coatings generated by friction surfacing %U https://doi.org/10.1016/j.wear.2012.11.016 1-2 %X CrNi-alloys with high Cr-content generally are quite brittle and, therefore, only available as castings and regarded as neither weldable nor deformable. The process of friction surfacing offers a possibility to generate Cr60Ni40 coatings e.g. on steel or Ni-base substrates. Cavitation tests were carried out using an ultrasonic vibratory test rig (∼ASTM G32) with cast specimens and friction surfaced coatings. The coatings show less deformation and smaller disruptions, and wear rates in steady state were found to be three times higher for the cast and heat treated samples than for the coatings, caused by a highly wear resistant Cr-rich phase. The results of this study show that it is possible to generate defect free coatings of Cr60Ni40 with a thickness of about 250 μm by friction surfacing, which under cavitation show a better wear behavior than the cast material. Thus, in combination with a ductile substrate, these coatings are likely to extend the range of applicability of such high-temperature corrosion resistant alloys. %0 journal article %@ 1453-0384 %A Amancio-Filho, S.T.,Blaga, L.,dos Santos, J.F.,Bancila, R. %D 2013 %J Sudura : Romanian Welding Society´s Review %N 1 %P 14-16 %T Friction riveting (FricRiveting) – An innovative technology for joining hybrid polymer-metal and composite-metal structures / Nituirea prin frecare (FricRiveting) – O tehnologie inovativă pentru îmbinarea structurilor hibride polimer-metal și compozit-metal %U 1 %X Hybrid polymer-metal and composite-metal structures are increasingly used in applications in the most branches of industry. The joining of these structures is one of the hot topics in research at the moment. Friction riveting (FricRiveting) is an innovative joining solution for hybrid structures. This paper presents the general aspects of FricRiveting, its principles, advantages and potential applications. Finally, some of the recent research work on FricRiveting is presented, its feasibility for glass fiber reinforced polymers and titanium grade 2. This research proved the applicability of the technology and a case study for an emergency bridge reveiled the potential of this solution for the construction of lightweight bridges.,Structurile hibride polimer-metal și compozit-metal cunosc o răspândire din ce în ce mai largă în toate ramurile industriei. Problematica îmbinărilor acestor structuri este o temă de actualitate. Nituirea prin frecare constituie o alternativă viabilă pentru astfel de structuri. Lucrarea de față prezintă aspectele generale ale nituirii prin frecare, principiile procesului, avantajele și potențialele aplicații ale acestuia. În final sunt prezente scurt cele mai recente cercetări referitoare la nituirea prin frecare, fezabilitatea acestei tehnologii moderne pentru polimeri armați cu fibră de sticlă și titan de gradul 2. Aceste cercetări au relevat aplicabilitatea tehnologiei iar un studiu de caz pentru un pod pentru situații de urgență a relevat potențialul acestei soluții pentru construcția de poduri ușoare. %0 journal article %@ 0261-3069 %A Blaga, L.,Bancila, R.,dos Santos, J.F.,Amancio-Filho, S.T. %D 2013 %J Materials and Design %N %P 825-829 %R doi:10.1016/j.matdes.2013.03.061 %T Friction Riveting of glass-fibre-reinforced polyetherimide composite and titanium grade 2 hybrid joints %U https://doi.org/10.1016/j.matdes.2013.03.061 %X In this work, the feasibility of Friction Riveting on thermoplastic composite laminates with metals was investigated on glass–fibre-reinforced polyetherimide with titanium grade 2. Microscopy analysis (light optical and laser scanning confocal microscopy), temperature monitoring (infrared thermometry) and quasi-static mechanical testing (T-pull tensile testing) were used to investigate joint properties. Joints with reduced amounts of thermo-mechanically modified composite material with moderate to high tensile strengths (1.9–4.0 kN) were achieved. The average process temperatures (430–464 °C) of the molten matrix were below the range inducing the extensive thermal degradation of the polyetherimide matrix and out of the range inducing the plasticising of titanium grade 2. The Volumetric Ratio, a simplified analytical model describing the anchoring efficiency of the rivet, was demonstrated to be directly proportional to the tensile strength of the joint and therefore an adequate analytical model to describe the mechanical performance of joints. Finally, a correlation between the rotational speed, heat input, process temperature and rivet plasticising was observed. The higher the rotational speed was, the higher the heat input, temperature and deformation of the plasticised rivet tip became, leading to higher rivet anchoring performances. %0 journal article %@ 1453-0392 %A Szabo, R.,Bergmann, L.,dos Santos, J.F. %D 2013 %J Welding and Material Testing %N 4 %P 3-7 %T Friction stir welding of structural steel S235 and S355 %U 4 %X High-quality, defect-free welds were successfully produced in S235 and S355 structural steels by friction stir welding. To explore the potential advantages injoining structural steels by FSW, the present study focuses on basic characterization of friction stir welded S235JR and S235JR plates. A remarkably fine-grained microstructure was observed in the stir zone for both materials by optical microscopy. Hardness measurements across the specific zones of the cross-section of the welds indicated higher values compared with base materials ones. The objective of this work was to demonstrate the feasibility of friction stir welding (FSW) for joining of structural steel. %0 journal article %@ 2176-1523 %A Campanelli, L.C.,Antonialli, A.I.S.,de.Alcantara, N.G.,Bolfarini, C.,Suhuddin, U.F.H.,dos Santos, J.F. %D 2013 %J Tecnologia em Metalurgia, Materiais e Mineracao %N 2 %P 97-102 %R doi:10.4322/tmm.2013.014 %T Lap Shear Test of a Magnesium Friction Spot Joint: Numeric Modeling %U https://doi.org/10.4322/tmm.2013.014 2 %X Friction spot welding (FSpW) is one of the most recently developed solid state joining technologies. In this work, based on former publications, a computer aided draft and engineering resource is used to model a FSpW joint on AZ31 magnesium alloy sheets and subsequently submit the assembly to a typical shear test loading, using a linear elastic model, in order to conceive mechanical tests results. Finite element analysis shows that the plastic flow is concentrated on the welded zone periphery where yield strength is reached. It is supposed that "through the weld" and "circumferential pull-out" variants should be the main failure behaviors, although mechanical testing may provide other types of fracture due to metallurgical features. %0 journal article %@ 0924-0136 %A Tier, M.D,Rosendo, T.S,dos Santos, J.F.,Huber, N.,Mazzaferro, J.A.,Mazzaferro, C.P.,Strohaecker, T.R. %D 2013 %J Journal of Materials Processing Technology %N 6 %P 997-1005 %R doi:10.1016/j.jmatprotec.2012.12.009 %T The influence of refill FSSW parameters on the microstructure and shear strength of 5042 aluminium welds %U https://doi.org/10.1016/j.jmatprotec.2012.12.009 6 %X Refill friction stir spot welding (FSSW-Refill) was used to produce solid-state joints in an automotive 5042 aluminium alloy. The influence of plunge depth, rotational speed, plunge rate and time on the microstructure and shear strength was investigated. The Statistica software package was used to correlate process parameters with the mechanical properties of the joints. The most significant variables are plunge depth and tool rotational speed, while volumetric defects have a small influence on the mechanical performance of the welds. Reducing the rotational speed from 1900 rpm to 900 rpm increased the bonding ligament length. For joints produced at a higher tool rotational speed (1900 rpm) the material flow was more vertical, i.e., towards the surface of the joint, the bonding ligament length was reduced and the shear strength was impaired. %0 journal article %@ 0268-3768 %A Richter-Trummer, V.,Koch, D.,Witte, A.,dos Santos, J.F.,de Castro, P.M.S.T. %D 2013 %J The International Journal of Advanced Manufacturing Technology %N 9-12 %P 2271-2281 %R doi:10.1007/s00170-013-4828-x %T Methodology for prediction of distortion of workpieces manufactured by high speed machining based on an accurate through-the-thickness residual stress determination %U https://doi.org/10.1007/s00170-013-4828-x 9-12 %X After high-speed machining of rolled and stretch straightened aluminium sheets, out-of-plane distortion is found. This is especially true for complex machined shapes in thin-gauge and high-strength aluminium alloys. This kind of sheets are mostly found in the aeronautical industry, where thin-weight-optimised aluminium shell designs are used for skin applications. Usually, in the aeronautical sector, low-thickness sections are used wherever possible, and higher thicknesses are used only where additional strength is required. In the present work, a methodology of predicting workpiece distortion based on the residual stress present in the workpiece is presented, which can be applied by machining companies without further investment in measurement equipment. A method for accurately determining through-the-thickness residual stresses was adapted to the special requirements of this industrial sector. The measured residual stresses were used in a finite element model capable of approximately calculating the shape distortion of simple and complex high-speed machined parts. Promising results have been obtained. %0 journal article %@ 1454-9069 %A Gabor, R.,dos Santos, J.F. %D 2013 %J Proceedings of the Romanian Academy : Series A %N 1 %P 64-71 %T Friction stir welding development of aluminium alloys for structural connections %U 1 %X Since its development in ’90, Friction Stir Welding (FSW) had known an important growth,,especially for the hard to weld aluminium alloys. For these FSW,has been shown to produce welds of,high quality with no defects, reduced cost and lower environmental impact when compared to,traditional fusion welding. The process parameters influence on,the connection formation is related.,An experimental program realized,by HZG of FSW, applied on two,aluminium alloys recommended,to be used in the field of civil engineering is presented. Detailed characterisations are presented,aiming to emphasize the performance of the process for the analysed alloys. %0 journal article %@ 1359-6462 %A Suhuddin, U.F.H.,Fischer, V.,dos Santos, J.F. %D 2013 %J Scripta Materialia %N 1 %P 87-90 %R doi:10.1016/j.scriptamat.2012.09.008 %T The thermal cycle during the dissimilar friction spot welding of aluminum and magnesium alloy %U https://doi.org/10.1016/j.scriptamat.2012.09.008 1 %X The thermal cycle during dissimilar friction spot welding of Al alloy AA5754 to Mg alloy AZ31 was measured by thermocouples located in the weld region. The results revealed that the weld is exposed to a non-equilibrium solidus temperature induced by rapid heating and cooling. Microstructural analyses showed that the grain structure development in the stir zone was affected by grain boundary diffusion, interfacial diffusion and dynamic recrystallization, which resulted in fine equiaxed grains of Al12Mg17 in the weld center. %0 journal article %@ 1438-1656 %A Huetsch, L.L.,Hilgert, J.,Herzberg, K.,dos Santos, J.,Huber, N. %D 2012 %J Advanced Engineering Materials %N 9 %P 762-771 %R doi:10.1002/adem.201200112 %T Temperature and Texture Development during High Speed Friction Stir Processing of Magnesium AZ31 %U https://doi.org/10.1002/adem.201200112 9 %X The increasing demand for low weight structural materials yields a growing interest in Mg alloys processed at industrially interesting speeds. One aim of this study is to develop defect free welds in the velocity range of 1–10 m · min−1. The resulting welds are subjected to temperature, microstructure and texture investigations. Energy input as well as temperature development under the tool are predicted using numerical models. Image correlation is used to evaluate distortion. The results show that while ensuring constant weld quality, the energy input, sample distortion and grain size can be decreased reaching a threshold at 5 m · min−1. Thermal analysis reveal an asymmetry between AS and RS. The basal planes exhibits a shift from 0 to 45° into processing direction. %0 journal article %@ 0104-9224 %A de Oliveira, P.H.F.,Amancio Filho, S.T,dos Santos, J.F.,Hage, E.jr. %D 2012 %J Soldagem & Inspecao %N 2 %P 96-103 %R doi:10.1590/S0104-92242012000200003 %T Feasibility study of the Friction Spot Welding (FSpW) process in thermoplastics - Estudo de viabilidade da soldagem de termoplásticos por "Friction Spot Welding" (FSpW) %U https://doi.org/10.1590/S0104-92242012000200003 2 %X The modern thermoplastics show a wide range of engineering applications, mainly due to its good processability and properties, such as stress-to-weight ratio and toughness. However, the manufacturing of larger products with complex geometries require advanced polymer welding techniques. Friction Spot Welding (FSpW) is a joining technique allowing the fabrication of joint with good mechanical properties. In this work, the feasibility of the FSpW of thermoplastics was investigated in polymethyl-methacrilate (PMMA), an amorphous thermoplastic with increasing importance in the airspace and automotive industry due to its good processability, weldability, aging and chemical resistance. The welded samples were analyzed by optical microscopy and Vickers microhardness measurements and mechanically tested. Lap-shear testing showed ultimate shear resistance values of about 9,5 MPa, which were similar or higher than values obtained through current PMMA welding techniques, such as microwave welding, ultrasonic welding and thermal bonding. Therefore, the present work was able to demonstrate the potential of FSpW as an alternative welding process for thermoplastics.,Os plásticos apresentam boa processabilidade, oferecendo uma grande liberdade de design. Porém, a fabricação de peças cada vez maiores e mais complexas tem exigido a busca por melhorias e desenvolvimento dos atuais processos de união e soldagem de polímeros. Friction Spot Welding (FSpW) é uma técnica de soldagem pontual por fricção inicialmente desenvolvida para ligas de alumínio, possibilitando soldas com excelentes propriedades mecânicas. Nesse trabalho a soldagem de termoplásticos através da técnica FSpW foi analisada. Para tal, utilizaram-se placas de polimetacrilato de metila (PMMA), um termoplástico amorfo com crescente importância na indústria automotiva e aeronáutica por seu bom balanço de propriedades, como baixa densidade, boa processabilidade, soldabilidade e resistência química e ao envelhecimento. As amostras soldadas foram analisadas por microscopia ótica, medições de microdureza Vickers e ensaio de resistência ao cisalhamento. Os resultados mostraram que a resistência mecânica ao cisalhamento alcançada (cerca de 9,5 MPa) é igual ou maior que a resistência de juntas sobrepostas de PMMA obtidas por outras técnicas convencionais como soldagem por ultra-som, por microondas e thermal bonding. O presente trabalho comprovou, dessa forma, a potencialidade da técnica FSpW para soldar termoplásticos. %0 journal article %@ 0921-5093 %A Coelho, R.S.,Kostka, A.,dos Santos, J.F.,Kaysser-Pyzalla, A. %D 2012 %J Materials Science and Engineering A %N %P 175-183 %R doi:10.1016/j.msea.2012.06.076 %T Friction-stir dissimilar welding of aluminium alloy to high strength steels: Mechanical properties and their relation to microstructure %U https://doi.org/10.1016/j.msea.2012.06.076 %X The use of light-weight materials for industrial applications is a driving force for the development of joining techniques. Friction stir welding (FSW) inspired joints of dissimilar materials because it does not involve bulk melting of the basic components. Here, two different grades of high strength steel (HSS), with different microstructures and strengths, were joined to AA6181-T4 Al alloy by FSW. The purpose of this study is to clarify the influence of the distinct HSS base material on the joint efficiency. The joints were produced using the same welding parameter/setup and characterised regarding microstructure and mechanical properties. Both joints could be produced without any defects. Microstructure investigations reveal similar microstructure developments in both joints, although there are differences e.g. in the size and amount of detached steel particles in the aluminium alloy (heat and thermomechanical affected zone). The weld strengths are similar, showing that the joint efficiency depends foremost on the mechanical properties of the heat and the thermomechanical affected zone of the aluminium alloy. %0 journal article %@ 0921-5093 %A Richter-Trummer, V.,Suzano, E.,Beltrao, M.,Roos, A.,dos Santos, J.F.,de Castro, P.M.S.T. %D 2012 %J Materials Science and Engineering A %N %P 81-88 %R doi:10.1016/j.msea.2012.01.016 %T Influence of the FSW clamping force on the final distortion and residual stress field %U https://doi.org/10.1016/j.msea.2012.01.016 %X Friction stir welding (FSW) is a solid state process, leading to joints with good mechanical performance. Low residual stresses and distortions are generally mentioned as further advantages, leading to the current high interest of the aeronautical industry in this process.,In order to achieve these beneficial properties, the welding process requires clamping of the parts to be welded. To the authors knowledge clamping forces in FSW have not been studied in detail yet, neither their influence on residual stress and distortion.,In the present work the clamping forces, both initially applied and their evolution during the welding process, were studied. Furthermore the influence of different clamping forces on the distortion and residual stress of the welded plates was analysed. The joints were subjected to mechanical testing and microstructural analysis in order to guarantee defect free joints in all cases and in order to be able to detect influences of the clamping process on joint performance.,It was found that higher clamping forces lead to lower distortion and a more uniform residual stress distribution through the thickness. Higher clamping forces also lead to a lower defect probability through the creation of gaps between the plate halves. %0 journal article %@ 1073-5623 %A Suhuddin, U.,Mironow, S.,Krohn, H.,Beyer, M.,dos Santos, J.F. %D 2012 %J Metallurgical and Materials Transactions A %N 13 %P 5224-5231 %R doi:10.1007/s11661-012-1345-8 %T Microstructural Evolution During Friction Surfacing of Dissimilar Aluminum Alloys %U https://doi.org/10.1007/s11661-012-1345-8 13 %X The microstructural evolution during friction surfacing of an aluminum alloy 6082-T6 rod on an aluminum alloy 2024-T351 substrate was characterized using the electron backscatter diffraction technique. Crystallographic data were obtained from several regions in the consumable material and in the deposited material. From the results, it can be deduced that the grain structure formation was a complex process governed by the geometrical effect of strain and the superposition of continuous and discontinuous dynamic recrystallizations. %0 journal article %@ 0104-9224 %A Campanelli, L.C.,Suhuddin, U.F.H.,dos Santos, J.F.Alcantara, N.G. %D 2012 %J Soldagem & Inspecao %N 1 %P 26-31 %R doi:10.1590/S0104-92242012000100005 %T Parameters optimization for friction spot welding of AZ31 magnesium alloy by Taguchi method - Otimizacao dos parametros de soldagem por friccao por ponto da liga de magnesio AZ31 pelo metodo de Taguchi %U https://doi.org/10.1590/S0104-92242012000100005 1 %X Friction spot welding (FSpW) is a solid state welding process suitable for producing spot-like joints, especially in lightweight materials, which are particularly interesting due to the weight saving potential. The plunging of an especially designed non-consumable and rotating tool creates a connection between overlapped sheets through frictional heat and plastic deformation. Minimum material loss is observed, and therefore a fully consolidated joint with flat surface (no keyhole) is obtained. In the current study, the effect of FSpW parameters, such as rotational speed, plunge depth and dwell time, on lap shear strength of AZ31 magnesium alloy joints was investigated. The optimization of input process parameters was carried out through Taguchi approach of DOE. Analysis of variance was applied to determine the individual importance of each parameter. Main effect plots were used to indicate the best levels for maximizing lap shear strength. The results show that tool plunge depth has the higher effect on the weld strength, followed by rotational speed and dwell time.,A soldagem por fricção por ponto (FSpW) é um processo de soldagem no estado sólido adequado para a produção de juntas pontuais, especialmente em materiais leves, que são particularmente interessantes devido ao potencial de redução de peso. A penetração de uma ferramenta não-consumível e rotacional especialmente desenvolvida cria uma junção entre as placas sobrepostas através de calor por fricção e deformação plástica. A perda de material é mínima, obtendo-se, portanto, uma junta totalmente consolidada com superfície plana (sem furo). Neste trabalho, investigou-se o efeito dos parâmetros do FSpW, tais como velocidade de rotação, profundidade de penetração e tempo de residência, na resistência ao cisalhamento das juntas de liga de magnésio AZ31. A otimização dos parâmetros de entrada do processo foi realizada através do método de Taguchi de DOE. A análise de variância foi aplicada para determinar a importância individual de cada parâmetro. Os gráficos dos efeitos principais foram utilizados para indicar os melhores níveis que maximizam a resistência ao cisalhamento. Os resultados mostram que a profundidade de penetração da ferramenta possui a maior influência sobre a resistência da solda, seguida da velocidade de rotação e tempo de residência. %0 journal article %@ 1362-1718 %A Hilgert, J.,dos Santos, J.F.,Huber, N. %D 2012 %J Science and Technology of Welding and Joining %N 6 %P 454-459 %R doi:10.1179/1362171812Y.0000000034 %T Shear layer modelling for bobbin tool friction stir welding %U https://doi.org/10.1179/1362171812Y.0000000034 6 %X This study presents an approach to model the shear layer in bobbin tool friction stir welding. The proposed CFD model treats the material in the weld zone as a highly viscous non-Newtonian shear thinning liquid. A customised parametric solver is used to solve the highly non-linear Navier‐Stokes equations. The contact state between tool and workpiece is determined by coupling the torque within the CFD model to a thermal pseudomechanical model. An existing analytic shear layer model is calibrated using artificial neural networks trained with the predictions of the CFD model. Validation experiments have been carried out using 4 mm thick sheets of AA 2024. The results show that the predicted torque and the shear layer shape are accurate. The combination of numerical and analytical modelling can reduce the computational effort significantly. It allows use of the calibrated analytic model inside an iterative process optimisation procedure. %0 journal article %@ 0255-5476 %A Campanelli, L.C.,Suhuddin, U.F.H.,dos Santos, J.F.,Alcantara, N.G. %D 2012 %J Materials Science Forum, THERMEC 2011 %N %P 3016-3021 %R doi:10.4028/www.scientific.net/MSF.706-709.3016 %T Preliminary Investigation on Friction Spot Welding of AZ31 Magnesium Alloy %U https://doi.org/10.4028/www.scientific.net/MSF.706-709.3016 %X Friction spot welding (FSpW) is a recent solid state welding process developed and patented by GKSS Forschungszentrum (now Helmholtz-Zentrum Geesthacht), Germany. A spot-like connection is produced by means of an especially designed non-consumable tool consisting of pin, sleeve and clamping ring that creates a joint between sheets in overlap configuration through frictional heat and plastic deformation. FSpW offers many advantages over conventional spot joining techniques including high energy efficiency, surface quality and environmental compatibility. Comparing with friction stir spot welding, FSpW produces a weld without keyhole on the surface at the end of the joining process. In the present study, the possibility of joining AZ31 magnesium alloy by FSpW technique was evaluated by using different welding parameters (rotational speed, plunge depth and dwell time), aiming to produce high quality connections. Microstructural features were analyzed by light optical microscope and mechanical performance was investigated by microhardness test and lap shear test. Microstructure analysis revealed that defects free welds could be produced. A slight decrease in grain size of the stir zone was observed causing a slight increase in the microhardness of this region. The preliminary lap shear data demonstrated that the weld strength is comparable to other welding process. %0 journal article %@ 0927-0256 %A Borges, M.F.,Amancio-Filho, S.T.,dos Santos, J.F.,Strohaecker, T.R.,Mezzaferro, J.A.E. %D 2012 %J Computational Materials Science %N %P 7-15 %R doi:10.1016/j.commatsci.2011.10.031 %T Development of computational models to predict the mechanical behavior of Friction Riveting joints %U https://doi.org/10.1016/j.commatsci.2011.10.031 %X Friction Riveting (FricRiveting) is a new, friction based, spot joining process for polymer–metal hybrid structures that has been studied experimentally in recent years. The process provides a cost effective and fast alternative to conventional joining methods, such as riveting and adhesive bonding. In this work, finite element analysis was performed to predict the behavior of overlap and point-on-plate FricRiveting joints with the objective of supporting the further development of the process. Additionally, it is intended to provide a better understanding of the mechanical behavior of the joint. The analyses were performed by simulating joints made of polyetherimide extruded plaques and high-strength aluminum alloy AA2024-T351 rivets using an FEA package. Model validation was carried out with three different types of mechanical tests: tensile, lap shear and T-pull. The results obtained in this preliminary work were most encouraging since the developed models were able to predict experimental behavior with accuracy.