TY - JOUR A1 - Yang, Keke A1 - Sowada, Matthias A1 - Olfert, Viktoria A1 - Seitz, Georg A1 - Schreiber, Vincent A1 - Heitmann, Marcel A1 - Hein, David A1 - Biegler, Max A1 - Jüttner, Sven A1 - Rethmeier, Michael A1 - Meschut, Gerson T1 - Influence of liquid metal embrittlement on the failure behavior of dissimilar spot welds with advanced high-strength steel: A component study N2 - This study investigates the effects of liquid metal embrittlement (LME) cracks on the mechanical performance of resistance spot-welded joints in zinc-coated advanced high-strength steel (AHSS) at the component level. To this end, a novel component-level test specimen featuring a hat and L-shaped profile was developed to identify critical failure points under three-point bending loads. Load-bearing capacity tests were subsequently conducted under both quasi-static and impact loading conditions, specifically targeting LME cracks with an average depth reaching 63.6% of the sheet thickness. By monitoring the surface strain of spot welds affected by LME cracks, the study visualizes stress concentration effects at the crack tips and traces the propagation of these cracks into the base material, which ultimately leads to material tearing and joint failure. The findings reveal that the effect of LME cracks in reducing load-bearing capacity is more pronounced under impact loading than under quasi-static loading, highlighting a previously underexplored aspect of LME behavior under impact loading. Specifically, the peak load decreased by 3.9% and 10.8%, while energy absorption declined by 52.2% and 78.3% under quasistatic and impact loading, respectively. KW - Liquid metal embrittlement KW - Resistance spot welding KW - Impact loading KW - Crack propagation KW - Advanced high-strength steel PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-621727 DO - https://doi.org/10.1016/j.jmrt.2024.11.166 VL - 33 SP - 8321 EP - 8328 PB - Elsevier B.V. AN - OPUS4-62172 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lemke, Josefine A1 - Höfemann, Matthias A1 - Biegler, Max A1 - Rethmeier, Michael T1 - Process strategies for optimizing the cooling behaviour of laser-welded Tailor Welded Blanks made of advanced high strength steels (AHSS) N2 - AHSS with 1000 MPa tensile strength show promising properties for the use in Tailor Welded Blanks (TWBs) to locally strengthen car body parts. Challenges in laser beam welding of the sheets are hardness-drops and -peaks in the heat-affected zone (HAZ) and weld, which cause risks during cold-forming. This happens due to rapid cooling caused by laser welding. A numerical approach aiming for slower cooling rates in the weld region is presented in this article. Laser welded sheets served as reference for setting up a process simulation. Models for pre-heating and a coaxial setup with power split were set up. A correlation between cooling-rate and hardness in the joining zone was established and applied to the modelled strategy. Splitting the power led to a slightly narrower weld seam and experimental pre-heating of the sheets to 600 °C could lower total seam hardening. It achieved a homogenization of the fusion zone. KW - AHSS KW - Laser welding KW - Tailor Welded Blanks KW - Hardness KW - FEM KW - HAZ PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-622324 DO - https://doi.org/10.1016/j.procir.2024.08.176 VL - 124 SP - 570 EP - 573 PB - Elsevier B.V. AN - OPUS4-62232 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Akyel, Fatma A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Brunner-Schwer, Christian A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Influence of heat input on cooling rates and mechanical properties of laser hybrid welded thick structural steels N2 - Laser hybrid welding presents several challenges when used to weld thick steels. A typical weld is divided into the arcdominated and laser-dominated zone. These zones lead to variations in the mechanical properties of the weld. The laserdominated zone is of particular importance regarding mechanical properties, notably Charpy impact toughness, due to the high cooling rates and the absence of filler wire. The low heat input of the laser can lead to martensitic microstructure causing hardening and deterioration of impact toughness. The high heat input of the arc can lead to grain coarsening and even loss of impact toughness. This study examines the influence of heat input on the cooling rates, microstructure and mechanical properties of single-pass laser hybrid welded steels of S355J2 and EH36 with thicknesses up to 30 mm. The experiments were performed with a 20-kW fibre laser and a contactless electromagnetic weld backing in the butt-joint configuration in 1G welding position. The cooling time was measured in three different locations near the fusion lines corresponding to different heights of the seam using a special configuration with pyrometers, collimators and optical fibres. The test specimens for the Charpy impact testing and tensile testing were extracted in three different depths. The experiments indicated that a heat input of 1.6 kJ/mm–2 kJ/mm, 2 kJ/mm–2.4 kJ/mm and 3.7 kJ/mm were recommended when single-pass laser hybrid welding of 20-, 25-, and 30-mm-thick structural steels regarding the minimum requirements of the mechanical properties, respectively. KW - Laser hybrid welding KW - Heat input KW - Mechanical properties KW - Charpy impact toughness KW - Cooling rate PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-625282 DO - https://doi.org/10.1007/s40194-025-01924-8 SN - 1878-6669 SP - 1 EP - 15 PB - Springer CY - United Kingdom AN - OPUS4-62528 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yang, Chunliang A1 - Yang, Fan A1 - Meng, Xiangmeng A1 - Putra, Stephen Nugraha A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Multi-refining effects of an AC electromagnetic field on the microstructure in AA5754 laser beam welding N2 - Fine-grain structure is beneficial to the mechanical properties of the joint. Different kinds of grain and sub-grain structures refined by magnetic field during laser beam welding of AA5754 aluminum alloy are analyzed in this manuscript, and the influences of different magnetic field parameters (magnetic flux density and frequency) in these refining effects are also studied. Using the scanning electron microscope (SEM), the sub-grain structure near the fusion line was obtained, and it was found that the branching promotion and branches refinement can be achieved by the magnetic field. The branches become finer with the magnetic flux density or frequency increases, and this effect is stronger in the dendritic region than in the equiaxed region. The results of electron backscatter diffraction (EBSD) in the equiaxed region show that a high-frequency magnetic field can greatly reduce the average grain size, while a low-frequency one has little effect. A phenomenological nucleation model based on dendrite fragmentation theory was established, and it was introduced into the phase field model to analyze the equiaxed grains evolution process. In addition, another refinement mechanism was also observed. The periodic solidification pattern caused by the unstable solidification in the molten pool can refine the grains, and the magnetic field promotes this kind of grain refinement by promoting the solidification period. KW - Laser beam welding KW - Magnetic field KW - Aluminum alloy KW - Crystal branch development KW - Periodic solidification pattern KW - Grain refinement PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-637222 DO - https://doi.org/10.1016/j.ijheatmasstransfer.2025.127509 SN - 0017-9310 VL - 252 SP - 1 EP - 16 PB - Elsevier Ltd. AN - OPUS4-63722 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schempp, Philipp A1 - Cross, C.E. A1 - Häcker, Ralf A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Influence of grain size on mechanical properties of aluminium GTA weld metal N2 - Grain refinement is an important possibility to enhance the mechanical properties such as strength, ductility and toughness of aluminium weld metal. In this study, grain refinement was achieved through the addition of commercial grain refiner Al Ti5B1 to gas tungsten arc weld metal of the aluminium alloys 1050A (Al 99.5) and 5083 (Al Mg4.5Mn0.7). The grain refiner additions led to a significant reduction of the weld metal mean grain size (Alloy 1050A, 86 %; Alloy 5083, 44 %) with a change in grain shape from columnar to equiaxed. Tensile tests showed for Alloy 5083 that the weld metal's ductility can be increased through grain refinement. No improvement in weld metal strength (i.e. yield strength and ultimate tensile strength) was observed. Furthermore, tear tests with notched specimens revealed that the resistance against initiation and propagation of cracks in the weld metal can be enhanced through grain refinement. The toughness was observed to increase clearly by grain refinement in weld metal of commercial pure Al (Alloy 1050A). In Alloy 5083 weld metal, the toughness was not improved through grain refinement, likely because of a semi-continuous network of brittle intermetallic phases that facilitate crack propagation. KW - GTA welding KW - Aluminium KW - Grain size KW - Tensile tests KW - Dynamic fracture tests PY - 2013 DO - https://doi.org/10.1007/s40194-013-0026-6 SN - 0043-2288 SN - 1878-6669 VL - 57 IS - 3 SP - 293 EP - 304 PB - Springer CY - Oxford AN - OPUS4-28065 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, L. J. A1 - Zhang, J. X. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - Na, S.J. T1 - Numerical simulation of full penetration laser welding of thick steel plate with high power high brightness laser N2 - Full penetration laser welding was carried out on a 10 mm steel plate using a 16 kW maximum power continuous wave thin disk laser. Upper surface and lower surface of molten pool were observed synchronously with two high speed CCD cameras during the welding process. The lower surface was much longer and more unstable than the upper one. A three dimensional laser deep penetration welding model in which volume of fluid (VOF) method was combined with a ray-tracing algorithm was used to simulate the dynamic coupling between keyhole and molten pool in laser full penetration welding. The calculated weld cross-section morphology and molten pool length on both upper side and lower side agree well with experimental results. Evolution of molten pool in lower side during full penetration laser welding was analyzed, periodical features of energy coupling, molten pool behavior and keyhole dynamics in laser full penetration welding were identified and discussed. KW - Full penetration laser welding KW - Molten pool KW - Keyhole KW - Thick plate PY - 2014 DO - https://doi.org/10.1016/j.jmatprotec.2014.03.016 SN - 0924-0136 SN - 1873-4774 VL - 214 IS - 8 SP - 1710 EP - 1720 PB - Elsevier CY - Amsterdam AN - OPUS4-30549 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, Sergej A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid laser arc welding of X80 and X120 steel grade N2 - The aim of the present work was to investigate the possibilities of hybrid laser arc welding regarding reliable production of longitudinal welds of high strength pipe steels X80 and X120 and to evaluate achievable mechanical properties of laser hybrid welds. The study focused on weld toughness examination in low temperature range up to –60°C. Suitable filler materials were identified in the context of this task. It could be shown that metal cored electrodes guaranteed sufficient Charpy impact toughness at low temperature for both investigated materials. Modern arc welding technologies such as modified pulsed spray arc were used to promote deeper penetration of the filler material into the narrow laser welding gap. Edge preparation with a 14 mm deep root face was considered as optimum, because no penetration of the filler material could be detected beyond this depth limit, and therefore, any metallurgical influences on the weld metal properties through the welding wire could be excluded. KW - High strength steel KW - Laser hybrid welding KW - Modified spray arc KW - Longitudinal weld KW - Pipeline PY - 2014 UR - http://www.maneyonline.com/doi/full/10.1179/1362171813Y.0000000154 DO - https://doi.org/10.1179/1362171813Y.0000000154 SN - 1362-1718 SN - 1743-2936 VL - 19 IS - 1 SP - 15 EP - 24 PB - Maney CY - London AN - OPUS4-29593 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, Sergej A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Method for defect-free hybrid laser-arc welding of closed circumferential welds N2 - This paper presents investigation results of a process for defect-free hybrid laser arc welding (HLAW) of closed circumferential welds. The process aims to avoid weld imperfections in the overlap area of a HLAW circumferential weld. A process control strategy for closing the circumferential weld was developed to achieve a defect-free overlap region by controlling the solidification conditions at the end of the weld. The controlled heat flow is achieved by adjusting the parameters of both welding processes involved, the laser beam as well as gas metal arc welding (GMAW) process. Experimental investigations were carried out on 12 mm to 15 mm thick tube sections. The influence of process parameters such as the laser ramp time, the change in magnification scale and the defocusing of the laser beam on the solidifi-cation conditions at the end of the circumferential weld was investigated to find an optimum strategy for ramping out the process energy. Within the framework of the experimental studies, it was demonstrated that defocusing the laser beam in the range between 60 mm and 100 mm over a short run-out area of the weld of approximately 15 mm led to a significantly better weld formation in the overlap area. A favourable cup-shaped weld shape could be achieved without a tendency to crack. The laser optics with a motor-driven lens system made it possible to increase the laser beam diameter without changing the position of the GMAW arc relative to the component surface. KW - Weld defects KW - Hybrid welding KW - Laser beam welding KW - Pipe manufacturing KW - Gas shielded arc welding PY - 2021 VL - 20 IS - 4 SP - 334 EP - 339 PB - DVS Media AN - OPUS4-54665 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Vollertsen, F. A1 - Grünenwald, S. A1 - Rethmeier, Michael A1 - Gumenyuk, Andrey A1 - Reisgen, U. A1 - Olschok, S. T1 - Welding thick steel plates with fibre lasers and GMAW N2 - The results of a collaborative research project on laser beam weldability of carbon steels of high sheet thickness are presented. That includes single and multiple pass welding of 16 mm and 20 mm thick plates, as well as the investigation of acceptable tolerances i.e. gap bridgeability and edge misalignment. For the welding experiments fibre lasers with 8 kW, 20 kW laser power and different GMAW-techniques were used in various applications. With the 20 kW fibre laser 16 mm plates could be welded with a single pass, 20 mm required a seam preparation or alternatively preheating of the material. For multi pass welding with 8 kW laser power a joint preparation with a single V-butt joint with a broad root face (Y-groove) was applied. The root pass was always welded with a hybrid process, the filler passes with a hybrid process as well as a GMAW process which produced the best results. KW - Arc welding KW - Carbon steels KW - Combined processes KW - Fibre lasers KW - Gas shielded arc welding KW - GMA welding KW - Multirun welding KW - Reference lists KW - Steels KW - Unalloyed steels PY - 2010 SN - 0043-2288 SN - 1878-6669 VL - 54 IS - 3/4 SP - R62 EP - R70 PB - Springer CY - Oxford AN - OPUS4-21224 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gaul, Holger A1 - Weber, Gert A1 - Rethmeier, Michael T1 - Evaluation of fatigue crack propagation in spot welded joints by stiffness measurements N2 - Resistance spot welded joints made of two advanced high strength steels (AHSS) and one high strength steel (HSS) were examined. In the high cycle fatigue regime tests were realised for one loading condition, and the load and the displacement were measured. From the load and displacement range, the stiffness was calculated and in situ normalised to its value after 1000 cycles. It was thus possible to use the normalised stiffness evaluated during the experiment as failure criterion for the fatigue test of resistance spot welded joints. In order to evaluate this failure criterion, fatigue cracks were produced in the three different steel grades mentioned above according to user-specified levels of the normalised stiffness. It was found that the fatigue crack area increases linearly and the through-sheet-thickness crack length exponentially with decreasing stiffness. The comparison of the fatigue crack propagation during the fatigue test of the three different tested base metals showed very similar values. The comparability of fatigue tests performed on spot welded joints might thus be improved by the in situ evaluated stiffness as a failure criterion. This can be also used in further work to verify results of computer simulations of the stress intensity factor at spot welds with the help of experimental results. KW - Resistance spot welding KW - Fatigue KW - Frequency KW - Stiffness KW - Advanced high strength steels KW - Crack growth PY - 2011 DO - https://doi.org/10.1016/j.ijfatigue.2010.12.005 SN - 0142-1123 VL - 33 IS - 5 SP - 740 EP - 745 PB - Elsevier CY - Oxford AN - OPUS4-22207 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Perret, William A1 - Schwenk, Christopher A1 - Rethmeier, Michael T1 - Comparison of analytical and numerical welding temperature field calculation N2 - Analytical and numerical methods are used to estimate the temperature field due to the heat effects of welding. Numerical techniques are more adapted for industrial complex applications where analytical solutions do not exist yet. However, computational time is much lower with analytical models and a combination of both methods is investigated. Therefore, the two approaches are introduced and confronted in this paper. The finite-element software Ansys has been used for numerical simulations and Scilab for analytical simulations. In order to get a similar result quality, both methods have to be analysed and compared with respect to boundary conditions. These configurations are presented in this paper. Before starting any analysis, the analytical and numerical models have to be comparable. For the numerical simulation, every in- or output is given in discrete form and, for the analytical simulation, in continuous form. Thus, an analysis of the energy input distribution in both models is compulsory to ensure that the same amount of energy is applied. After this first study, a comparison of the analytical and numerical temperature field simulation is done from a fix point source in an infinite volume in steady state to a moving point source in a finite dimension in a transient state. A good agreement between the analytical and the numerical simulation results is found. However, some techniques, like a consideration of an image heat source for the analytical model or the selection of boundary conditions for the numerical model, need to be taken into consideration when the degree of complexity of the study (finite dimension or cooling time) increases. The limit of the comparison is reached when the geometry becomes too complex and when the effect of variable thermal properties with temperature cannot be neglected. KW - Welding simulation KW - Temperature field KW - Analytical approach KW - Numerical approach KW - Heat conduction PY - 2010 DO - https://doi.org/10.1016/j.commatsci.2009.11.032 SN - 0927-0256 VL - 47 IS - 4 SP - 1005 EP - 1015 PB - Elsevier CY - Amsterdam AN - OPUS4-20887 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kannengießer, Thomas A1 - Kromm, Arne A1 - Gibmeier, J. A1 - Rethmeier, Michael T1 - In-situ-Analyse der Phasenumwandlungskinetik während des Schweißens N2 - Zugeigenspannungen, wie sie beim Schweißprozess durch inhomogene Temperaturverteilungen und Schrumpfungen hervorgerufen werden, können die Lebensdauer geschweißter Verbindungen signifikant herabsetzen. Eine neue und außerordentlich attraktive Methode, um Druckeigenspannungen bereits während des Schweißens gezielt einzustellen, gelingt mit sogenannten LTT (Low Transformation Temperature)-Legierungen. LTT-Legierungen weisen eine martensitische Phasenumwandlung bei relativ niedrigen Temperaturen auf, wobei die damit verbundene Volumenexpansion zu einer Reduktion der Schrumpfeigenspannungen bzw. Erzeugung von Druckeigenspannungen führt. Zum direkten Nachweis der Phasenumwandlungen und der damit verbundenen resultierenden Schweißeigenspannungen wurden erstmals In-situ-Schweißexperimente unter Nutzung hoch energetischer, polychromatischer Synchrotronstrahlung (Weißstrahl) realisiert, um die Umwandlungskinetik während eines realen Schweißprozesses und die daraus resultierenden Schweißeigenspannungen zu analysieren. Es wird gezeigt, dass mit LTT-Legierungen signifikante Druckeigenspannungen in der Schweißnaht erreicht werden. PY - 2010 SN - 0025-5300 VL - 52 IS - 4 SP - 204 EP - 210 PB - Hanser CY - München AN - OPUS4-21219 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Caron, J. A1 - Heinze, Christoph A1 - Schwenk, Christopher A1 - Rethmeier, Michael A1 - Babu, S. S. A1 - Lippold, J. T1 - Effect of continuous cooling transformation variations on numerical calculation of welding-induced residual stresses N2 - Continuous cooling transformation (CCT) behavior affects the transient state of material properties employed in a numerical welding simulation, having a direct influence on the developing stress state. Three different CCT diagrams for S355J2 steel were employed to understand the influence of variations in CCT behavior on the numerical calculation of welding-induced residual stresses. The CCT diagrams were constructed from transformation data contained in the Sysweld software database, measured dilatometric data from Gleeble experiments, and transformation data calculated from the JMatPro software. The calculated transverse and longitudinal residual stress distributions provided a qualitative correction only in comparison to experimental measurements, with the largest deviation occurring near the weld interface. Overall, the results indicate a weak dependency of the calculated residual stresses due to anticipated CCT variations. The most significant effect on the calculated residual stresses was shown to be related to the proportion of formed martensite. It is suggested that CCT data of approximate accuracy is sufficient for reliable calculation of welding-induced residual stresses. KW - Continuous cooling transformation diagrams KW - Residual stresses KW - Gas metal arc welding KW - C-Mn steels KW - Welding simulation KW - Schweißsimulation KW - Eigenspannungen KW - Martensitbildung KW - Sensitivitätsanalyse KW - Sysweld KW - Martensite kinetic KW - Sensitivity analysis PY - 2010 SN - 0043-2296 SN - 0096-7629 VL - 89 SP - 151-s - 160-s PB - American Welding Society CY - New York, NY AN - OPUS4-21444 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brauser, Stephan A1 - Weber, Gert A1 - Rethmeier, Michael T1 - Potenzial optischer Dehnungsfeldmessung zur Charakterisierung der Eigenschaften von Widerstandspunktschweißverbindungen N2 - Die Ermittlung lokaler Werkstoffkennwerte im Schweißbereich ist für die Auslegung sicherheitsrelevanter Bauteile insbesondere durch Finite-Elemente-Berechnungen von großer Bedeutung. Konventionelle Prüfmethoden können lediglich globale Kennwerte bereitstellen, die jedoch gerade für die Berechnung widerstandspunktgeschweißter Bauteile häufig nicht ausreichen, da diese durch das Vorliegen örtlich eng begrenzter Fügezonen gekennzeichnet sind. Moderne Prüfmethoden wie die optische Dehnungsfeldmessung ermöglichen hingegen eine orts- und zeitkonkrete Bestimmung der Werkstoffkenndaten. Um das Potenzial optischer Dehnungsfeldmessungen für das Charakterisieren des lokalen Werkstoffverhaltens von Punktschweißverbindungen zu ermitteln, wurden Scherzugversuche sowie Zugversuche an widerstandspunktgeschweißten hochfesten Stählen durchgeführt. Die Ergebnisse zeigen das hohe Potenzial dieses Verfahrens sowohl für die Quantifizierung des lokalen Dehnungsverhaltens im Fügebereich als auch für die Ermittlung lokaler Werkstoffkenndaten. PY - 2010 SN - 0036-7184 VL - 62 IS - 9 SP - 496 EP - 500 PB - Verl. für Schweißen u. Verwandte Verfahren, DVS-Verl. CY - Düsseldorf AN - OPUS4-22163 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brauser, Stephan A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Rethmeier, Michael T1 - In-situ synchrotron diffraction and digital image correlation technique for characterizations of retained austenite stability in low-alloyed transformation induced plasticity steel N2 - Direct measurement and quantification of phase transformation in a low-alloyed transformation induced plasticity steels depending on the tensile load as well as determination of the real true stress and true strain values were carried out in-situ using high energy synchrotron radiation. Digital image correlation technique was used to quantify more precisely the true strain values. The aim of the work was to obtain a better understanding of the phase transformation of commercial low-alloyed transformation induced plasticity steel depending on the true strain and true stress values. KW - Transformation induced plasticity KW - In-situ synchrotron diffraction KW - Austenite stability KW - Digital image correlation PY - 2010 DO - https://doi.org/10.1016/j.scriptamat.2010.08.007 SN - 1359-6462 SN - 1872-8456 VL - 63 IS - 12 SP - 1149 EP - 1152 PB - Elsevier CY - Oxford AN - OPUS4-22164 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heinze, Christoph A1 - Kromm, Arne A1 - Schwenk, Christopher A1 - Kannengießer, Thomas A1 - Rethmeier, Michael T1 - Welding residual stresses depending on solid-state transformation behaviour studied by numerical and experimental methods N2 - The development of high-strength structural steels with yield strengths up to 1000 MPa results in the requirement of suitable filler materials for welding. Recently designed low transformation temperature (LTT) alloys offer appropriate strength. The martensitic phase transformation during welding induces compressive residual stress in the weld zone. Therefore, the mechanical properties of welded joints can be improved. The present paper illustrates numerical simulation of the residual stresses in LTT-welds taking into account the effect of varying Ms/Mf-temperatures, and therefore different retained austenite contents, on the residual stresses. Residual stress distributions measured by synchrotron diffraction are taken as evaluation basis. A numerical model for the simulation of transformation affected welds is established and can be used for identification of appropriate Ms-temperatures considering the content of retained austenite. KW - Welding simulation KW - Residual stress KW - Low transformation temperature filler material KW - Martensitic transformation KW - Retained austenite PY - 2011 DO - https://doi.org/10.4028/www.scientific.net/MSF.681.85 SN - 0255-5476 VL - 681 SP - 85 EP - 90 PB - Trans Tech Publications CY - Aedermannsdorf, Switzerland AN - OPUS4-23357 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rethmeier, Michael A1 - Brauser, Stephan A1 - Weber, Gert T1 - Potential of optical strain field measurement for the characterisation of the properties of resistance-spot-welded joints N2 - For the designing of safety-relevant components particularly by means of finite element calculations, great significance is attached to the determination of local material parameters in the welding region. Conventional test methods can merely provide global parameters which, however, are frequently not sufficient precisely for the calculation of resistance-spot-welded components since these are characterised by the existence of joining zones with tight local limitations. In contrast, modern test methods such as optical strain field measurement permit the determination of the characteristic material data for concrete locations and times. In order to establish the potential of optical strain field measurements for the characterisation of the local material behaviour of spotwelded joints, tensile shear tests as well as tensile tests were carried out on resistance-spot-welded high-strength steels. The results show the high potential of this procedure not only for the quantification of the local strain behaviour in the joining region but also for the determination of local characteristic material data. PY - 2011 SN - 1612-3433 VL - 10 IS - 1 SP - 48 EP - 52 PB - DVS - German Welding Society CY - Düsseldorf AN - OPUS4-23220 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, Sergej A1 - Gumenyuk, Andrey A1 - Lammers, Marco A1 - Rethmeier, Michael T1 - Peculiarities of the process of orbital laser-arc welding of thick-walled large-diameter pipes KW - Hybrid laser-arc welding KW - Orbital welding KW - High-pressure pipelines KW - Fibre-optic lasers PY - 2010 SN - 0957-798X VL - 9 SP - 2 EP - 8 PB - E. O. Paton Electric Welding Institute of the National Acad. of Sciences of Ukraine CY - Kyïv AN - OPUS4-22956 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weber, Gert A1 - Thommes, H. A1 - Gaul, H. A1 - Hahn, O. A1 - Rethmeier, Michael T1 - Mechanical properties of weldbonded joints of advanced high strength steels N2 - In lightweight car body shell mass production, due to requirements on vehicle weight reduction and carbon dioxide emissions, joining of advanced high strength steels (AHSS) with different joining procedures and especially hybrid bonding techniques is becoming more and more important. One of these hybrid bonding techniques is the combination of resistance spot welding and adhesive bonding called weldbonding. One of the important advantages of weldbonded joints in comparison to resistance spot welded joints are the enhanced mechanical properties. To guarantee sufficiently high quality conditions regarding the strength of the weldbonded joints, the influences of the applied adhesive systems and of different base metal combinations are studied. This is carried out for both non-corrosive and corrosive environments and for the choice of different joining parameters settings. In particular, the mechanical behaviour of the weldbonded joints is investigated under quasi-static, impact and fatigue loads. Furthermore, the energy absorption of the weldbonded joints for both non-corrosive and corrosive environments is studied. It is shown that the weldbonded joints possess higher mechanical strengths in all load cases (quasi-static, impact and fatigue). Corrosive attack affects weldbonded joints, and the quasi-static strength is reduced. Resistance spot welded joints are not affected by the corrosive attack, but even after several weeks of corrosive attack, the quasi-static strength of weldbonded joints remains higher than that of resistance spot welded joints. KW - Weldbonded joints KW - Corrosion KW - Mechanical strength KW - Fracture behaviour KW - Fatigue KW - Crash behaviour PY - 2011 DO - https://doi.org/10.1163/016942411X580090 SN - 0169-4243 SN - 1568-5616 VL - 25 IS - 18 SP - 2369 EP - 2389 PB - VNU Science Press CY - Utrecht AN - OPUS4-24513 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schwenk, Christopher A1 - Tikhomirov, D. A1 - Eßer, G. A1 - Rethmeier, Michael T1 - General standard for welding simulation N2 - Für die Abgrenzung der Anwendbarkeit verschiedener Methoden der numerischen Schweißsimulation sowie für die Vereinheitlichung der Voraussetzungen und der durchzuführenden Schritte bei der Simulation sind normative Regelwerke für den Anwender erforderlich. Da es derzeit noch keine normähnlichen Dokumente auf diesem Gebiet gibt, wurde vom Deutschen Institut für Normung e.V. DIN in Zusammenarbeit mit der Forschungsvereinigung des DVS Deutscher Verband für Schweißen und verwandte Verfahren e.V. ein Arbeitsausschuss gegründet, welcher sich mit der Erarbeitung der entsprechenden Dokumente befasst. Der vorliegende Beitrag konzentriert sich auf die Vorstellung der neuen DIN Spec 32534-1, welche die grundlegenden Simulations-Schritte erläutert und ihre Anwendungsfelder sowie die Schlüsselbegriffe spezifiziert. Des Weiteren wurde eine allgemein gültige Simulationsstruktur erarbeitet, welche als Empfehlung für den Auftraggeber und den Auftragnehmer bei der Formulierung und Abwicklung eines Dienstleistungsauftrages sowie für den Neueinstieg in die Schweißsimulation dienen soll. Schließlich wird ein Ausblick auf die weiteren Themenfelder des Arbeitsausschusses sowie auf die internationalen Aktivitäten auf diesem Gebiet gegeben. N2 - For differentiating the applicability of various numerical welding simulation methods as well as unifying the prerequisites and the steps to be taken in simulation, normative codes are required for the user. Since any standard-like documents are currently still lacking in this field, the DIN German Institute for Standardization in partnership with the Research Association of DVS German Welding Society have set up a standards committee dealing with the preparation of respective documents. This article focuses on the presentation of the new DIN Spec 32534-1 explaining the major simulation steps and specifying the application fields and the key terms of welding simulation. In addition, a generally valid simulation structure has been established which is intended to serve as a recommendation for customers and suppliers in formulating and handling a service order as well as for persons who start doing welding simulation for the first time. It additionally gives an overview of the other subject areas dealt with in the standards committee as well as of the international activities in this field. PY - 2011 UR - 10.3139/120.110257 SN - 0025-5300 VL - 53 IS - 9 SP - 522 EP - 527 PB - Hanser CY - München AN - OPUS4-24355 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thater, Raphael A1 - Perret, William A1 - Schwenk, Christopher A1 - Alber, U. A1 - Rethmeier, Michael T1 - Industrial application of welding temperature field and distortion visualization using FEA KW - Numerical welding simulation KW - Temperature field KW - Distortion KW - Industrial application KW - Automotive assembly PY - 2010 SN - 0387-4508 VL - 39 IS - 2 SP - 232 EP - 234 CY - Osaka, Japan AN - OPUS4-24354 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schwenk, Christopher A1 - Rethmeier, Michael T1 - Material properties for welding simulation - measurement, analysis, and exemplary data N2 - Welding is a key technology in the area of industrial production due to its flexibility and efficiency. However, new materials and welding techniques necessitate permanent research activities in order to keep up with the demands. A detailed knowledge about the process itself and the heat effects of welding, e.g., temperatures, distortions, and stresses, is the basis for a target-oriented optimization instead of a trial-and-error approach. Numerical welding simulation is a powerful tool to meet these demands. Complementary to an experimental investigation, it enables the analysis of the specimen during the welding process, commonly known as computational welding mechanics (CWM). Whereas simulation is nowadays a common tool in different development processes, the modeling of welding still remains difficult because of the multiple physical effects taking place. One of the most important problems for the user is the lack of knowledge about the material properties as input data for the simulation. Furthermore, any scattering of the data causes uncertainties that can have major effects on the calculations. The objective of this paper is to give an overview about the experimental determination and analysis of the material properties needed as input data for a welding simulation. The measurement techniques and the occurring deviations of the results are discussed. Additionally, the collected data for three representative alloys (dual-phase steel, austenitic steel, precipitation-hardenable aluminum alloy) are analyzed. Finally, the temperature-dependent thermophysical and thermomechanical material properties for these three alloys are given in a ready-to-use format for a numerical welding simulation. KW - Thermophysical material properties KW - Thermomechanical material properties KW - Experimental determination KW - Numerical welding simulation PY - 2011 SN - 0043-2296 SN - 0096-7629 VL - 90 SP - 220-s EP - 227-s PB - American Welding Society CY - New York, NY AN - OPUS4-25028 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gaul, Holger A1 - Brauser, Stephan A1 - Weber, Gert A1 - Rethmeier, Michael T1 - Methods to obtain weld discontinuities in spot-welded joints made of advanced high-strength steels N2 - Resistance spot welding is the major joining technique in mass car production. This applies in particular to high-strength steel and advanced high-strength steel (AHSS) joining of thin sheet steel components for lightweight body shell structures. Joining of AHSS in mass production might lead to weld discontinuities under certain circumstances. Those discontinuities in form of cracks might be an initial start of cracking in the spot-welded joints regarding fatigue loads. It is of great interest to figure out, if, in comparison to specimens without weld discontinuities, the crack initiating point changes and if the fatigue resistance might be reduced by the discontinuities. In this contribution, an overview of potential discontinuities is given. Their possible causes are discussed and means for their detection are highlighted. Among the possible causes of weld discontinuities, two major groups are distinguished: the welding parameters as primary influences in the welding process, and the production-specific influences as secondary ones. With emphasis on major cracks penetrating the weld nugget, these influences are analysed. Finally, a combination of extreme welding parameters with production-specific influences is chosen in order to establish a method which enables the preparation of fatigue test specimens with reproducible major cracks in different locations of the spot-welded joints. This method is than applied in order to prepare spot weld specimens for fatigue tests. KW - Cracking KW - Defects KW - Fatigue loading KW - High strength steels KW - Resistance spot welding PY - 2011 SN - 0043-2288 SN - 1878-6669 VL - 55 IS - 11/12 SP - 99 EP - 106 PB - Springer CY - Oxford AN - OPUS4-25026 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brauser, Stephan A1 - Pepke, Lutz-Alexander A1 - Weber, Gert A1 - Rethmeier, Michael T1 - Deformation behaviour of spot-welded high strength steels for automotive applications N2 - Numerical simulation of component and assembly behaviour under different loading conditions is a main tool for safety design in automobile body shell mass production. Knowledge of local material behaviour is fundamental to such simulation tests. As a contribution to the verification of simulation results, the local deformation properties of spot-welded similar and dissimilar material joints in shear tension tests were investigated in this study for a TRIP steel (HCT690T) and a micro-alloyed steel (HX340LAD). For this reason, the local strain distribution was calculated by the digital image correlation technique (DIC). On the basis of the hardness values and microstructure of the spot welds, the differences in local strain between the selected material combinations are discussed. Additionally, the retained austenite content in the TRIP steel was analysed to explain the local strain values. Results obtained in this study regarding similar material welds suggest significant lower local strain values of the TRIP steel HCT690T compared to HX340LAD. One reason could be the decrease of retained austenite in the welded area. Furthermore, it has been ascertained that the local strain in dissimilar material welds decreases for each component compared with the corresponding similar material weld. KW - Resistance spot welding KW - Deformation behaviour KW - Advanced high strength steel KW - TRIP steel KW - Similar and dissimilar material spot weld KW - EBSD KW - SEM KW - Strain field PY - 2010 DO - https://doi.org/10.1016/j.msea.2010.07.091 SN - 0921-5093 SN - 1873-4936 VL - 527 IS - 26 SP - 7099 EP - 7108 PB - Elsevier CY - Amsterdam AN - OPUS4-21921 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heinze, Christoph A1 - Schwenk, Christopher A1 - Rethmeier, Michael T1 - Influences of mesh density and transformation behavior on the result quality of numerical calculation of welding induced distortion N2 - Welding simulation is a powerful, cost-efficient tool to predict welding induced distortion. Nevertheless, effects on calculation result quality are often unknown, thus, sensitivity analyses should be performed to evaluate the influences of certain parameters on distortion development. In the present paper, a single-layer gas metal arc (GMA) weld of 5 mm thick structural steel S355J2+N is experimentally and numerically investigated. Subsequent to welding, the numerical modeling begins with a mesh analysis based on modal analyses. Hereby, the influence of different coarsening methods and element edge length (EEL) in welding direction on the deformation behavior or the stiffness of the discrete geometry is the focus of the analysis. Secondly, phase transformations in structural steels such as S355J2+N are decisive for final product properties. The sensitivity of welding-induced distortion is examined regarding different continuous cooling transformation (CCT) diagrams for S355J2+N. The present investigations deal with different relevant influences on numerical calculation of welding-induced distortion. The quality and quantity of these effects are clarified based on the experimental and numerical set-up employed. Consequently, prediction of welding-induced distortion is possible and potential for pre-production optimization is present. KW - Welding simulation KW - Gas metal arc welding KW - Welding-induced distortion KW - Mesh analysis KW - CCT sensitivity PY - 2011 DO - https://doi.org/10.1016/j.simpat.2011.05.001 SN - 1569-190X VL - 19 IS - 9 SP - 1847 EP - 1859 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-23874 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Petrovskii, V.N. A1 - Uspenskii, S.A. A1 - Shcheglov, Pavel A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of a vapor-plasma welding torch induced by a high-power ytterbium fiber laser KW - Laser welding KW - Condensation KW - Diagnostic of the torch PY - 2011 SN - 2079-5629 VL - 2 IS - 2 SP - 159 EP - 165 PB - MAIK Nauka AN - OPUS4-24811 LA - rus AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tölle, Florian A1 - Gumenyuk, Andrey A1 - Backhaus, A. A1 - Olschok, S. A1 - Rethmeier, Michael A1 - Reisgen, U. T1 - Welding residual stress reduction by scanning of a defocused beam N2 - The residual stresses in narrow electron or laser beam welds with high stress gradients are decreased without any contact surfaces or additional equipment by applying the welding beam after welding in a defocused mode for heating the material regions in a certain distance from the weld on both sides. In case of electron beam application, the beam is positioned and focused by the electromagnetic coil with high frequency. In case of laser beam application a laser scanner optics enables fast positioning by an optomechanic beam deflection, while defocusing of the laser beam is obtained by increasing the distance between scanner optics and workpiece. Dependent on the component geometry and on the beam power different process parameters are used. The adjustable process parameters are the radius and the power of the defocused beam and the transversal and longitudinal distances between the welding and the defocused beam. The mechanism and the influence of the process parameters are investigated by FEM-simulation and a number of experiments on a ferritic steel S355J2+N with 5 mm thickness. FEM-simulation is used to reduce the matrix of process parameters for the experiments. The best experimental result shows a stress reduction of about 70%. KW - Residual stresses KW - Stress reduction KW - High energy beam welding KW - Post-weld heat treatment KW - Laser scanner optics PY - 2012 DO - https://doi.org/10.1016/j.jmatprotec.2011.07.019 SN - 0924-0136 SN - 1873-4774 VL - 212 IS - 1 SP - 19 EP - 26 PB - Elsevier CY - Amsterdam AN - OPUS4-24787 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shcheglov, Pavel A1 - Uspenskii, S.A. A1 - Gumenyuk, Andrey A1 - Petrovskii, V.N. A1 - Rethmeier, Michael A1 - Yermachenko, V. M. T1 - Plume attenuation of laser radiation during high power fiber laser welding N2 - The results of an in-situ plume-laser interaction measurement during welding of mild steel with a 5 kW ytterbium fiber laser are reported. A measurement of the attenuation of probe laser beam passing through the plume has allowed to estimate the plume characteristics like the size of the extinction area and the spatial distribution of the extinction coefficient. The power loss of the fiber laser radiation propagating through the whole plume length was calculated. Together with a measured temporal characteristics of extinction the result indicates a significant decreasing of the laser radiation stability, which can lead to the formation of the macroscopic welding defects. KW - Laser welding KW - Plume KW - Beam attenuation KW - Particles PY - 2011 DO - https://doi.org/10.1002/lapl.201110010 SN - 1612-2011 VL - 8 IS - 6 SP - 475 EP - 480 PB - Wiley-VCH CY - Berlin AN - OPUS4-24812 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heinze, Christoph A1 - Schwenk, Christopher A1 - Rethmeier, Michael T1 - The effect of tack welding on numerically calculated welding-induced distortion N2 - A single-layer pulsed gas metal arc weld of structural steel S355J2+N with a thickness of 5 mm is experimentally and numerically investigated. Two tack welds are considered in the numerical simulation into two different ways. First, the tack welds are represented by elements belonging to the initial material. This implies that the 'tack weld material' was not exposed to any thermal load or phase transformation before actual welding was performed. The weld seam is shortened and there is an influence on the stiffness of the whole structure affecting the calculation result. Secondly, the tack welds were simulated as conducted in the experimental welding procedure. The cases considering tack welding are compared to a simulation neglecting tack welding and to the experimental results. The influence of tack welds on the calculated welding-induced distortion is clarified and a contribution to an improved simulation-based prediction of welding-induced distortion is possible by modeling tack welding according to the realistic fabrication procedure. KW - Welding simulation KW - Welding-induced distortion KW - Gas metal arc welding KW - Tack welding PY - 2012 DO - https://doi.org/10.1016/j.jmatprotec.2011.09.016 SN - 0924-0136 SN - 1873-4774 VL - 212 IS - 1 SP - 308 EP - 314 PB - Elsevier CY - Amsterdam AN - OPUS4-24820 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brauser, Stephan A1 - Schwenk, Christopher A1 - Rethmeier, Michael A1 - Noack, T. A1 - Jüttner, S. T1 - Einfluss von schweißbedingten Rissen auf die Schwingfestigkeit von Widerstandspunktschweißverbindungen aus hochfestem austenitischen Stahl N2 - Unter den rauen Bedingungen in der Automobilkarosseriefertigung lassen sich schweißbedingte Imperfektionen wie Risse beim Widerstandspunktschweißen von hochfesten Stählen nicht immer vermeiden. Dabei ist der Einfluss solcher Risse auf die Schwingfestigkeit insbesondere von modernen hochfesten austenitischen Stählen derzeit nicht hinreichend bekannt. Im Rahmen dieser Arbeit wurde daher der Einfluss von Schweißrissen verschiedener Lage und Ausbildung untersucht. Dabei konnte durch die Analyse der normierten Steifigkeitsverläufe von Proben sowie durch die Gegenüberstellung der Versagensschwingspielzahlen nachgewiesen werden, dass die spritzerfrei erzeugten Oberflächenrisse im Zentrum, im Übergangsbereich sowie im Randbereich der Schweißlinse keinen negativen Einfluss auf die Schwingfestigkeit des hier untersuchten hochfesten austenitischen Werkstoffs haben. Proben, die mit Schweißspritzern hergestellt wurden und Risse im Randbereich aufweisen, zeigen deutliche höhere Versagensschwingspielzahlen als rissfreie Referenzproben. ---------------------------------------------------------------------------------------------------------------------------------------------- In the rough conditions in the fabrication of automobile bodies, it is not always possible to avoid welding-induced imperfections such as cracks during the resistance spot welding of highstrength steels. In this respect, the influence of such cracks on the fatigue strength particularly of modern high-strength austenitic steels is not sufficiently well-known at present. The influence of welding cracks with various positions and formations was therefore investigated within the framework of this paper. In this case, the analysis of the standardised stiffness courses of specimens and the comparison of the numbers of failure stress cycles served to prove that the surface cracks produced without any spatter in the centre, interfacial region and peripheral region of the weld nugget do not have any negative influence on the fatigue strength of the high-strength austenitic material investigated here. Specimens which were manufactured with welding spatter and exhibit cracks in the peripheral region show considerably higher numbers of failure stress cycles than crack-free reference specimens. KW - Festigkeit KW - Hochfester Stahl KW - Rissbildung KW - Widerstandspressschweißen KW - Werkstofffragen KW - Fahrzeugbau PY - 2012 SN - 0036-7184 VL - 64 IS - 1-2 SP - 28 EP - 31 PB - Verl. für Schweißen u. Verwandte Verfahren, DVS-Verl. CY - Düsseldorf AN - OPUS4-25623 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Biegler, Max A1 - Yang, Keke A1 - Meschut, Gerson A1 - Rethmeier, Michael T1 - Occurrence and avoidance of liquid metal embrittlement in resistance spot welding of springback-afflicted deep-drawn components N2 - This study investigates the occurrence and mitigation of liquid metal embrittlement occurring during resistance spot welding in deep-drawn automotive components, specifically focusing on an S-Rail made from advanced high-strength steel. A simulation-based liquid metal embrittlement risk criterion based on local major component stresses was established and used to quantify and compare liquid metal embrittlement risks between different tests. Experimental and numerical analyses were conducted, revealing that springback significantly impacts liquid metal embrittlement formation. Adjustments in electrode geometry and hold time post-welding were found to mitigate liquid metal embrittlement risks. The effects of stack-up configuration and related parameter settings on liquid metal embrittlement occurrence were identified and liquid metal embrittlement was effectively prevented across both stack-up configurations. These findings advance the understanding of liquid metal embrittlement mechanisms and provide practical approaches to enhance the spot weld quality in AHSS-based body-in-whites. KW - Liquid metal embrittlement KW - Crack KW - Advanced high-strength steels KW - Resistance spot welding KW - Weld current KW - Heat input KW - Simulation KW - Springback KW - Deep drawing KW - S-Rail PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-636577 DO - https://doi.org/10.1177/13621718251340452 SN - 1362-1718 SP - 1 EP - 9 PB - SAGE Publications AN - OPUS4-63657 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chang, Y.-J. A1 - Sproesser, G. A1 - Neugebauer, S. A1 - Wolf, K. A1 - Scheumann, R. A1 - Pittner, Andreas A1 - Rethmeier, Michael A1 - Finkbeiner, M. T1 - Environmental and social life cycle assessment of welding technologies N2 - Life Cycle Assessment (LCA) and Social Life Cycle Assessment (SLCA) are applied in evaluating possible social and environmental impacts of the state-of-art welding technologies, such as Manual Metal Arc Welding (MMAW), Manual Gas Metal Arc Welding (GMAW), Automatic GMAW and Automatic Laser-Arc Hybrid Welding (LAHW). The LCA results indicate that for 1 meter weld seam, MMAW consumes the largest amount of resources (like filler material and coating on electrodes) and energy, which contributes to comparatively higher environmental impacts in global warming potential, acidification, photochemical ozone creation potential and eutrophication than other chosen processes. With regard to social aspects, the health issues and fair salary are under survey to compare the relative potential risk on human health caused by fumes in different welding technologies, and to indicate the sufficiency of current salary of welders in Germany. The results reflect that the wage status of welders is still fair and sufficient. The manual processes bring much higher potential risk of welders’ health than the automatic processes, especially MMAW. KW - Fair salary KW - Human health KW - Life Cycle Assessment (LCA) KW - Social Life Cycle Assessment (SLCA) KW - Welding PY - 2015 DO - https://doi.org/10.1016/j.procir.2014.07.084 SN - 2212-8271 VL - 26 SP - 293 EP - 298 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-33036 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Magnets improve quality of high-power laser beam welding N2 - High-power laser beam welding uses a localized heat source to achieve narrow deep welds and high welding rates. Engineers run into some difficulties because the use of a localized heat source often results in the distortion of metal components; spattering and the ejection of droplets from the weld pool results in underfills, undercuts, craters, blowholes, or blowouts. A stationary magnetic field is applied to the laser welding process to improve its quality and counteract effects such as spattering. BAM Federal Institute For Materials Research and Testing in Germany are working to improve the quality of high-power laser beam welding using COMSOL Multiphysics. To model and simulate the laser beam welding, heat transfer, fluid dynamics, and electromagnetics were coupled and solved. This allowed BAM to accurately model the process by including Marangoni effects, gravity, latent heats of fusion, and Lorentz forces. KW - Laser beam welding KW - Electromagnetic weld pool control KW - Marangoni effect PY - 2013 SP - 30 EP - 32 AN - OPUS4-28655 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, A. A1 - Goecke, S.-F. A1 - Sievi, P. A1 - Albert, F. A1 - Rethmeier, Michael T1 - Laser beam oscillation strategies for fillet welds in lap joints N2 - Laser beam oscillation opens up new possibilities of influencing the welding process in terms of compensation of tolerances and reduction of process emissions that occur in industrial applications, such as in body-in-white manufacturing. The approaches are to adapt the melt pool width in order to generate sufficient melt volume or to influence melt pool dynamics, e.g. for a better degassing. Welding results are highly dependent on the natural frequency of the melt pool, the used spot diameter and the oscillation speed of the laser beam. The conducted investigations with an oscillated 300 µm laser spot show that oscillation strategies, which are adjusted to the joining situation improve welding result for zero-gap welding as well as for bridging gaps to approximately 0.8 mm. However, a complex set of parameters has to be considered in order to generate proper welding results. This work puts emphasize on introducing them. KW - Laser beam welding KW - Gap compensation KW - Process monitoring and control KW - System technology KW - Automotive application PY - 2014 DO - https://doi.org/10.1016/j.phpro.2014.08.149 SN - 1875-3892 VL - 56 SP - 458 EP - 466 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-31437 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schempp, Philipp A1 - Cross, C.E. A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Influence of solute content and solidification parameters on grain refinement of aluminum weld metal N2 - Grain refinement provides an important possibility to enhance the mechanical properties (e.g., strength and ductility) and the weldability (susceptibility to solidification cracking) of aluminum weld metal. In the current study, a filler metal consisting of aluminum base metal and different amounts of commercial grain refiner Al Ti5B1 was produced. The filler metal was then deposited in the base metal and fused in a GTA welding process. Additions of titanium and boron reduced the weld metal mean grain size considerably and resulted in a transition from columnar to equiaxed grain shape (CET). In commercial pure aluminum (Alloy 1050A), the grain-refining efficiency was higher than that in the Al alloys 6082 and 5083. Different welding and solidification parameters influenced the grain size response only slightly. Furthermore, the observed grain-size reduction was analyzed by means of the undercooling parameter P and the growth restriction parameter Q, which revealed the influence of solute elements and nucleant particles on grain size. KW - Aluminium KW - GTA welding KW - Grain refinement KW - Alloy 1050A KW - Alloy 5083 KW - Alloy 6082 KW - Al Ti5B1 PY - 2013 DO - https://doi.org/10.1007/s11661-013-1649-3 SN - 1073-5623 SN - 1543-1940 VL - 44A IS - 7 SP - 3198 EP - 3210 PB - The Minerals, Metals and Materials Society CY - Warrendale AN - OPUS4-28656 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heinze, Christoph A1 - Schwenk, Christopher A1 - Rethmeier, Michael T1 - Effect of heat source configuration on the result quality of numerical calculation of welding-induced distortion N2 - The results of numerical welding simulations strongly depend on its temperature field. In the present paper, the temperature field of a pulsed gas metal arc weld of structural steel S355J2+N (ASTM A572 Gr. 50) with a thickness of 5 mm is experimentally and numerically investigated. In the case of temperature field validation, volumetric Gauss and double-ellipsoid Goldak heat sources are applied. Additionally, different heat source configurations, including adaptations of thermal conductivity, are analyzed regarding their influence on the calculation of welding-induced distortion. The investigations clarify the influence of heat source configurations on the calculated results, thus, contribute to an improved prediction of welding-induced distortion. KW - Welding simulation KW - Heat source calibration KW - Gas metal arc welding KW - Sensitivity analysis KW - Distortion KW - Schweißsimulation KW - Verzug KW - Wärmequellenkonfiguration KW - Sysweld KW - Heat source configuration PY - 2011 DO - https://doi.org/10.1016/j.simpat.2011.09.004 SN - 1569-190X VL - 20 IS - 1 SP - 112 EP - 123 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-24684 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brauser, Stephan A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Rethmeier, Michael T1 - In-situ analysis of solid state phase transformation in TRIP-aided steels by synchrotron diffraction N2 - Energy dispersive synchrotron diffraction (EDXRD) analysis and 3 dimensional digital image correlations were conducted to investigate the stress and strain effected transformation behavior during tensile loading of low alloyed TRansformation Induced Plasticity (TRIP) steel. This technique allowed for phase specific stress measurement during certain tensile load steps in the elastic and also plastic regime. Additionally the simultaneous determination of the load dependent phase content was realized. The results show that the martensite transformation starts only after exceeding the overall yield point and is finished before reaching the uniform elongation, whereas a large portion of the austenite remains unchanged in the structure. Furthermore, the martensite transformation related to the stress in the γ-phase and α-phase was analyzed and quantified. KW - Synchrotron KW - EDXRD KW - Phase transformation KW - TRIP steel KW - Digital image correlation KW - Residual stress PY - 2011 UR - https://www.jstage.jst.go.jp/article/qjjws/29/3/29_3_81s/_pdf DO - https://doi.org/10.2207/qjjws.29.81s SN - 0288-4771 VL - 29 IS - 3 SP - 81 EP - 85 CY - Tokyo, Japan AN - OPUS4-24693 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schwenk, Christopher A1 - Rethmeier, Michael T1 - Standards and guidelines for numerical welding simulation PY - 2011 SN - 1001-1382 VL - 459 IS - 9 SP - 5 EP - 8 PB - Jixie Dianzi Gongye Bu * Harbin Hanjie Yanjiusuo AN - OPUS4-24644 LA - zho AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Perret, William A1 - Thater, R. A1 - Alber, U. A1 - Schwenk, Christopher A1 - Rethmeier, Michael T1 - Approach to assess a fast welding simulation in an industrial envrionment - application for an automotive welded part N2 - Fusion welding processes are widely used for joining metal structures, such as pipes, ships, and cars. In general, these joining processes offer a very good compromise between reliability, safety, cost and maintenance which are important issues in the current economical context. The negative heat effects of welding, i.e. distortions and residual stresses of the welded parts, are well known and many researches in this field have already been done in the last decades in order to minimize them. On the experimental side, many sophisticated procedures have become state of the art to deal with this problem. On the computational side, the improvement of the simulation algorithms and the computing power enables the simulations of many physical phenomena occurring during the welding process. The implementation of welding simulation techniques is nevertheless not an easy task and often associated with expert knowledge which hinders their global application in an industrial environment. This paper is focused on the industrial requirements of a welding simulation software with special respect to the needs of the automotive industry. The necessary information to run a welding simulation and the expectations of a weld specialist without deep knowledge in numerical methods are investigated. These expectations are tested on an automotive welded assembly with a commercially available welding simulation software designed especially for the needs of the automotive industry. A welding experiment is done and the measured temperature distributions and distortions serve as reference to validate the simulation results. The result quality of the simulations of temperature fields and distortions is in best agreement with experimental data. The workflow is well adapted for the considered industrial requirements and the time-tosolution as well as the computational costs are acceptable, whereas the efficient calibration of the heat input model is still a point which will be further investigated in current and future research works. KW - Welding simulation KW - Distortion KW - Automotive industry KW - Work-flow KW - Time-to-solution KW - Simufact.welding PY - 2011 DO - https://doi.org/10.1007/s12239-011-0102-0 SN - 1229-9138 VL - 12 IS - 6 SP - 895 EP - 901 PB - KSAE / Springer CY - Seoul / Berlin ; Heidelberg AN - OPUS4-25139 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Numerical simulation of full-penetration laser beam welding of thick aluminium plates with inductive support N2 - A three-dimensional laminar steady-state numerical model was developed to investigate the influence of an alternating current (ac) magnetic field during high-power full-penetration laser welding on the weld pool dynamics and weld cross section of a 20 mm thick aluminium plate in flat position. Three-dimensional heat transfer, fluid dynamics including phase transition and electromagnetic field partial differential equations were solved iteratively with the commercial finite element software COMSOL Multiphysics using temperature-dependent material properties up to evaporation temperature. Thermocapillary convection at the weld pool surfaces, natural convection and latent heat of solid–liquid phase transition were taken into account in this model. Solidification was modelled by the Carman–Kozeny equation for porous media morphology. The ac magnet was mounted on the root side of the weld specimen. The magnetic field was aligned perpendicular to the welding direction. The flow pattern in the melt and thus also the temperature distribution were significantly changed by the application of oscillating magnetic fields. It was shown that the application of an ac magnetic field to laser beam welding allows for a prevention of the gravity drop-out. The simulation results are in good qualitative agreement with the experimental observations. KW - Electromagnetic weld pool support KW - Laser beam welding KW - Lorentz force KW - Marangoni stresses KW - Natural convection PY - 2012 DO - https://doi.org/10.1088/0022-3727/45/3/035201 SN - 0022-3727 SN - 1361-6463 VL - 45 IS - 3 SP - 035201-1 - EP - 035201-13 PB - IOP Publ. CY - Bristol AN - OPUS4-25286 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Perret, William A1 - Thater, Raphael A1 - Alber, U. A1 - Schwenk, Christopher A1 - Rethmeier, Michael T1 - Case study for welding simulation in the automotive industry N2 - Welding is one of the most widely used joining processes in structural applications, like in car body production in the automotive industry. It is well-known that distortions and residual stresses occur during and after the welding process. Many procedures exist to decrease these negative heat effects of welding, but are often coupled with highly cost intensive experiments. For several decades, simulation models have been developed to understand and predict the heat effects of welding and to reduce experimental effort. In the production planning of various Original Equipment Manufacturers (OEM), some simulation tools are already well established, e.g. for crash test, forming or casting simulations. For welding, the demand is high but the implementation of welding simulation software is still not established yet. Welding is a complex process and the development of a flexible simulation tool, which produces good simulation results without expert knowledge in simulation, is not an easy task. In this paper, a welded assembly from the automotive industry has been simulated and compared to experimental data. Temperature fields and transient distortion distributions have been measured with thermocouples and with an optical 3D deformations analysis tool, respectively. The simulation has been run with a commercially available welding simulation software. The simulated temperature fields match the numerical ones perfectly. The simulated distortions are also qualitatively in best agreement with the experimental ones. Quantitatively, a difference of approximately 20 % between the simulated and the measured distortions is visible; this is acceptable considering the simplifications and assumptions of the simulation model. The global time to solution to get these results without expert knowledge in welding simulation was between 4 and 6 weeks, which is a reasonable time frame for an industrial application of welding simulation. KW - Automobiles KW - Distortion KW - Simulating KW - Temperature KW - Welding KW - Aluminium alloys KW - Al Mg Si alloys KW - Automobile engineering KW - Finite elements analysis KW - Mathematical models KW - MIG welding KW - Residual stresses KW - Vehicle bodies PY - 2011 DO - https://doi.org/10.1007/BF03321546 SN - 0043-2288 SN - 1878-6669 VL - 55 IS - 11/12 SP - 89 EP - 98 PB - Springer CY - Oxford AN - OPUS4-25029 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heinze, Christoph A1 - Schwenk, Christopher A1 - Rethmeier, Michael T1 - Numerical calculation of residual stress development of multi-pass gas metal arc welding under high restraint conditions N2 - During welding, residual stresses build-up created by the steep thermal gradient that occurs in the weld zone from localized heating and cooling, and phase transformations appearing in low-alloyed structural steel is inevitable. Welding of rather simple test plates do not cover the actual structural effects, which have to be considered during real component welding. However, the resulting welding-induced residual stress state is highly influenced by the structural characteristics, i.e. restraint conditions, of the welded construction. Therefore, a unique large-scale testing facility providing a specific shrinkage restraint while welding and subsequent cooling was used for the present investigations. Hereby, a six bead multi-pass gas metal arc weld of 20 mm thick structural steel S355J2 + N was welded under shrinkage restraint. The residual stresses were experimentally and numerically investigated, and compared to an analysis of plates welded under force-free support and free shrinkage conditions. The experimentally determined and calculated residual stresses using both 2D and 3D numerical models are in a good agreement. Furthermore, the influence of a shrinkage restraint on the residual stress distribution is both experimentally and numerically shown for the present test set-up. KW - Welding KW - Shrinkage KW - Ferrous metals and alloys PY - 2011 DO - https://doi.org/10.1016/j.matdes.2011.09.021 SN - 0261-3069 SN - 0264-1275 VL - 35 SP - 201 EP - 209 PB - Elsevier Science CY - Oxford AN - OPUS4-25036 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Lammers, Marco A1 - Rethmeier, Michael T1 - PA position full penetration high power laser beam welding of up to 30 mm thick AlMg3 plates using electromagnetic weld pool support N2 - Full penetration 15 kW Yb fibre laser butt welding of thick AlMg3 (AW 5754) plates was performed in PA position. A contactless inductive electromagnetic weld pool support system was used to prevent gravity dropout of the melt. The welding speed needed to achieve 20 mm penetration was ~0·5 m min-1. An ac power supply of ~244 W at 460 Hz was necessary to completely suppress gravity dropout of the melt and eliminate sagging of the weld pool root side surface. The oscillating magnetic field can suppress the Marangoni convection in the lower part of the weld pool. The system was also successfully used in the full penetration welding of 30 mm thick AlMg3 plates. KW - High power laser beam welding KW - Electromagnetic weld pool support KW - Full penetration PY - 2012 DO - https://doi.org/10.1179/1362171811Y.0000000085 SN - 1362-1718 SN - 1743-2936 VL - 17 IS - 2 SP - 128 EP - 133 PB - Maney CY - London AN - OPUS4-25888 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tölle, Florian A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Reduction of residual stresses in laser beam welds by means of defocused laser beams N2 - Longitudinal residual stresses in beam welds ranging at the value of the local yield strength can diminish the lifespan of components. To extend the service life of welds special methods of welding residual stress reduction were developed earlier which are however not effective for beam welds in complex component geometries. Application of beam welding sources for postwelding heat treatment of components has become a flexible tool for reducing longitudinal stresses in beam welds. Such heat treatment in a specific transversal distance to the weld by a defocused beam results in huge stress reductions depending on the used process parameters. Experimental results for ferritic and austenitic steels reveal weld stress reductions to up to compressive stresses. For different materials and diverse material thicknesses special process parameter regions have to be used in this procedure. At a transmission component this procedure shows a stress reduction by >300 MPa. KW - Post-welding heat treatment KW - Stress reduction KW - Residual stress KW - Beam welding PY - 2012 DO - https://doi.org/10.1179/1362171812Y.0000000019 SN - 1362-1718 SN - 1743-2936 VL - 17 IS - 5 SP - 381 EP - 385 PB - Maney CY - London AN - OPUS4-26000 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gebhardt, Moritz Oliver A1 - Gumenyuk, Andrey A1 - Quiroz Penaranda, Vanessa A1 - Rethmeier, Michael T1 - Laserstrahl-MSG-Hybridschweißen dickwandiger Präzisionsrohre N2 - Dickwandige Rohre aus Stahl sind die Basis einer Vielzahl von Komponenten im Maschinen- und Anlagenbau, zum Beispiel bei Hydraulikkomponenten, in der Kraftwerkstechnik oder der Petroindustrie. Insbesondere, wenn hohe Lage- und Formtoleranzen gefordert werden, ist das klassische Herstellungsverfahren ein Zerspanen aus dem Vollmaterial. Dies ist jedoch zeit- und materialintensiv. Als Alternative bieten sich die Laserstrahl-MSGHybridverfahren mit modernen Hochleistungslasern an. Mit diesen Verfahren ist es derzeit möglich, Bauteile bis zu etwa 15 mm Wanddicke verzugsarm und einlagig zu verschweißen. In ersten Experimenten wurden bei Schweißungen an Rohren jedoch in Bezug auf die Schweißrichtung längs und vertikal orientierte Erstarrungsrisse, so genannte Mittelrippendefekte, festgestellt. Im Rahmen eines Forschungsprojekts konnte die Ursache der Rissentstehung ermittelt und Maßnahmen zur Vermeidung gefunden werden. Dabei ließen sich die technischen Randbedingungen einhalten. Der Artikel gibt einen Überblick über das Forschungsprojekt und die wesentlichen Ergebnisse. --------------------------------------------------------------------------------------------------------------------------------------- Thick-walled pipes made of steel are the basis of a large number of components in mechanical and installation engineering, e.g. for hydraulic components, in power station technology or in the petroleum industry. Particularly when strict positional and shape tolerances are demanded, the classical manufacturing process is chip-producing machining from the solid material. However, this is time-intensive and material- intensive. The laser/GMA hybrid processes with modern high-power lasers are a suitable alternative. With these processes, it is currently possible to weld components with a wall thickness up to approx. 15 mm with little distortion in one pass. However, in initial experiments, solidification cracks with longitudinal and vertical orientations in relation to the welding direction, so-called central rib defects, were established in welds on pipes. Within the framework of a research project, it was possible to determine the cause of the cracking and to find measures in order to avoid it. The technical boundary conditions could be complied with in this respect. The article gives an overview of the research project and the essential results. KW - Laserstrahlschweißen KW - Prozesskombinationen KW - Rissbildung KW - Schutzgasschweißen KW - Schweißnahtfehler KW - Laser welding KW - Process combinations KW - Crack formation KW - Gas-shielded arc welding KW - Weld defects PY - 2012 SN - 0036-7184 VL - 64 IS - 5 SP - 254 EP - 259 PB - Verl. für Schweißen u. Verwandte Verfahren, DVS-Verl. CY - Düsseldorf AN - OPUS4-26054 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chen, Ji A1 - Schwenk, Christopher A1 - Wu, Chuan Song A1 - Rethmeier, Michael T1 - Predicting the influence of groove angle on heat transfer and fluid flow for new gas metal arc welding processes N2 - This article studies the three dimensional transient weld pool dynamics and the influence of groove angle on welding of low carbon structural steel plates using the ForceArc® process. The deformation of the weld bead is also calculated with an accurate coupling of the heat transfer with fluid flow through continuity, momentum and the energy equations combined with the effect of droplet impingement, gravity, electromagnetic force, buoyancy, drag forces and surface tension force (Marangoni effect). Different angles of V groove are employed under the same welding parameters and their influence on the weld pool behavior and weld bead geometry is calculated and analyzed, which is needed for subsequent calculations of residual stress and distortion of the workpiece. Such a simulation is an effective way to study welding processes because the influence of all welding parameters can be analyzed separately with respect to heat transfer, weld pool dynamic, and microstructure of the weld. Good agreement is found between the predicted and experimentally determined weld bead cross-section and temperature cycles. It is found that the main flow pattern is more or less the same although the groove angle increases, but it will evoke larger amount of fluid to flow downward to get deeper penetration. KW - Numerical simulation KW - Gas metal arc welding KW - Weld pool dynamics KW - Fluid flow KW - V groove PY - 2012 DO - https://doi.org/10.1016/j.ijheatmasstransfer.2011.08.046 SN - 0017-9310 VL - 55 IS - 1-3 SP - 102 EP - 111 PB - Elsevier CY - Amsterdam AN - OPUS4-26001 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tölle, Florian A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - Backhaus, A. A1 - Olschok, S. A1 - Reisgen, U. T1 - Mechanische Entlastung zur Eigenspannungsreduzierung in Strahlschweißnähten durch Anwendung eines defokussierten Strahls - Teil 2: Qualifizierung für komplexe Nahtgeometrien N2 - Schweißzugeigenspannungen in Strahlschweißnähten auf Höhe der lokalen Werkstoffstreckgrenze können die Bauteileigenschaften sowie deren Lebensdauer negativ beeinflussen. Die Nutzung der Schweißquelle für eine nachträgliche Behandlung der geschweißten Bauteile bietet eine kostengünstige und flexible Methode zur Reduzierung dieser Spannungen. Dabei wird durch einen oszillierenden defokussierten Elektronen- bzw. Laserstrahl, der Werkstoff beidseitig der Schweißnaht auf mehrere hundert Grad Celsius erwärmt, um dort zusätzliche Zugspannungsbereiche hervorzurufen. Die so erzeugten Längszugspannungszonen führen zu einer mechanischen Entlastung der Schweißnaht. Experimentelle Messungen der Längseigenspannungen an linearen Elektronen- und Laserstrahlschweißnähten im ersten Teil des Beitrags zeigten, dass die Spannungen mit diesem Verfahren um bis zu 70% reduziert werden können. In weiteren experimentellen Untersuchungen wird dieses Verfahren für kompliziertere Schweißnahtgeometrien getestet. An axialen sowie radialen Rundnähten an ferritischen Werkstoffen konnten ebenfalls hohe Spannungsreduktionen von über 50% erzielt werden. Zudem wurde dieses Verfahren mit einer für das Schweißen üblichen Laserstrahlschweißoptik ohne Scan-Funktion geprüft. Hierbei zeigte das Wärmebehandeln in zwei Arbeitsschritten noch größere Spannungsreduktionen im Vergleich zur Anwendung einer Laserstrahlscanneroptik zur quasisimultanen Wärmebehandlung auf beiden Seiten der Schweißnaht. ------------------------------------------------------------------------------------------------------------------------------------------- Residual tensile welding stresses in beam welds at the level of the local yield strength of the material may influence the properties of components as well as their service lives. The utilisation of the welding source for the subsequent treatment of the welded components offers a cost-favourable and flexible method of reducing these stresses. In this respect, an oscillating defocused electron or laser beam serves to heat the material on both sides of the weld up to several hundred degrees Celsius in order to induce additional tensile stress regions there. The longitudinal tensile stress zones produced in this way lead to the mechanical relief of the weld. Experimental measurements of the longitudinal residual stresses on linear electron and laser beam welds in the first part of the article showed that the stresses can be reduced by up to 70% with this process. In further experimental investigations, this process is tested for more complicated weld geometries. It was also possible to achieve great reductions in the stresses (over 50%) on both axial and radial circular welds on ferritic materials. Moreover, this process was tested with laser beam welding optics which are customary for welding and do not perform a scanning function. In this respect, the heat treatment in two work steps showed even greater reductions in the stresses in comparison with the application of laser beam scanner optics for quasi-simultaneous heat treatment on both sides of the weld. KW - Elektronenstrahlschweißen KW - Laserstrahlschweißen KW - Simulation und Berechnung KW - Spannungen KW - Wärmebehandlung KW - Electron beam welding KW - Laser welding KW - Simulation and calculation KW - Stresses KW - Heat treatment PY - 2012 SN - 0036-7184 VL - 64 IS - 7 SP - 406 EP - 411 PB - Verl. für Schweißen u. Verwandte Verfahren, DVS-Verl. CY - Düsseldorf AN - OPUS4-26339 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brauser, Stephan A1 - Schwenk, Christopher A1 - Rethmeier, Michael A1 - Noack, T. A1 - Jüttner, S. T1 - Influence of welding-induced cracks on the fatigue strength of resistance-spot-welded joints made of high-strength austenitic steel N2 - In the rough conditions in the fabrication of automobile bodies, it is not always possible to avoid welding-induced imperfections such as cracks during the resistance spot welding of high-strength steels. In this respect, the influence of such cracks on the fatigue strength particularly of modern high-strength austenitic steels is not sufficiently well-known at present. The influence of welding cracks with various positions and formations was therefore investigated within the framework of this paper. In this case, the analysis of the standardised stiffness courses of specimens and the comparison of the numbers of failure stress cycles served to prove that the surface cracks produced without any spatter in the centre, interfacial region and peripheral region of the weld nugget do not have any negative influence on the fatigue strength of the high-strength austenitic material investigated here. Specimens which were manufactured with welding spatter and exhibit cracks in the peripheral region show considerably higher numbers of failure stress cycles than crack-free reference specimens. PY - 2012 SN - 1612-3433 VL - 11 IS - 4 SP - 232 EP - 235 PB - DVS - German Welding Society CY - Düsseldorf AN - OPUS4-26346 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gebhardt, Moritz Oliver A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid process welds thick-walled tubes PY - 2012 SN - 0043-2296 SN - 0096-7629 VL - 91 IS - 6 SP - 55 EP - 61 PB - American Welding Society CY - New York, NY AN - OPUS4-26120 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brauser, Stephan A1 - Subaric-Leitis, Andreas A1 - Ullner, Christian A1 - Rethmeier, Michael T1 - Instrumentierte Eindringprüfung zur Bestimmung lokaler Festigkeitskennwerte an Punktschweißverbindungen N2 - Die lokalen Festigkeiten im Bereich einer Schweißverbindung sind maßgebend für deren Widerstandsfähigkeit gegenüber mechanischen Beanspruchungen. Im Gegensatz zu anderen präparationsaufwendigen Methoden, z. B. die Untersuchung von Mikro-Zugproben, liefert die instrumentierte Eindringprüfung mit deutlich geringerem Aufwand Verläufe von Festigkeiten mit sehr guter Ortsauflösung. Im Rahmen dieser Arbeit werden wahre Spannungs-Dehnungskurven aus zyklischen Eindringversuchen mittels Auswertungen auf der Basis repräsentativer Spannungen und Dehnungen und auf der Basis neuronaler Netze an Punktschweißverbindungen aus hochfesten Stählen, jeweils im Bereich des Grundwerkstoffs und der Schweißlinse, bestimmt. Die Ergebnisse werden exemplarisch für einen Stahltyp mit Ergebnissen von Zugversuchen am Grundwerkstoff und am thermisch behandelten Werkstoff mit Schweißgut ähnlicher Struktur verglichen und diskutiert. KW - Lokale Festigkeit KW - Spannungs-Dehnungskurve KW - Instrumentierte Eindringprüfung KW - Punktschweißverbindung PY - 2012 SN - 0025-5300 VL - 54 IS - 9 SP - 597 EP - 604 PB - Hanser CY - München AN - OPUS4-26432 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -