TY - JOUR A1 - Kolkoori, Sanjeevareddy A1 - Rahman, Mehbub-Ur A1 - Chinta, P.K. A1 - Kreutzbruck, Marc A1 - Rethmeier, Michael A1 - Prager, Jens T1 - Ultrasonic field profile evaluation in acoustically inhomogeneous anisotropic materials using 2D ray tracing model: Numerical and experimental comparison N2 - Ultrasound propagation in inhomogeneous anisotropic materials is difficult to examine because of the directional dependency of elastic properties. Simulation tools play an important role in developing advanced reliable ultrasonic non destructive testing techniques for the inspection of anisotropic materials particularly austenitic cladded materials, austenitic welds and dissimilar welds. In this contribution we present an adapted 2D ray tracing model for evaluating ultrasonic wave fields quantitatively in inhomogeneous anisotropic materials. Inhomogeneity in the anisotropic material is represented by discretizing into several homogeneous layers. According to ray tracing model, ultrasonic ray paths are traced during its energy propagation through various discretized layers of the material and at each interface the problem of reflection and transmission is solved. The presented algorithm evaluates the transducer excited ultrasonic fields accurately by taking into account the directivity of the transducer, divergence of the ray bundle, density of rays and phase relations as well as transmission coefficients. The ray tracing model is able to calculate the ultrasonic wave fields generated by a point source as well as a finite dimension transducer. The ray tracing model results are validated quantitatively with the results obtained from 2D Elastodynamic Finite Integration Technique (EFIT) on several configurations generally occurring in the ultrasonic non destructive testing of anisotropic materials. Finally, the quantitative comparison of ray tracing model results with experiments on 32 mm thick austenitic weld material and 62 mm thick austenitic cladded material is discussed. KW - Ultrasonic field KW - 2D ray tracing KW - Directivity KW - Anisotropic austenitic weld KW - Non-destructive testing PY - 2013 DO - https://doi.org/10.1016/j.ultras.2012.07.006 VL - 53 IS - 2 SP - 396 EP - 411 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-27324 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kolkoori, Sanjeevareddy A1 - Höhne, Christian A1 - Prager, Jens A1 - Rethmeier, Michael A1 - Kreutzbruck, Marc T1 - Quantitative evaluation of ultrasonic C-scan image in acoustically homogeneous and layered anisotropic materials using three dimensional ray tracing method N2 - Quantitative evaluation of ultrasonic C-scan images in homogeneous and layered anisotropic austenitic materials is of general importance for understanding the influence of anisotropy on wave fields during ultrasonic non-destructive testing and evaluation of these materials. In this contribution, a three dimensional ray tracing method is presented for evaluating ultrasonic C-scan images quantitatively in general homogeneous and layered anisotropic austenitic materials. The directivity of the ultrasonic ray source in general homogeneous columnar grained anisotropic austenitic steel material (including layback orientation) is obtained in three dimensions based on Lamb's reciprocity theorem. As a prerequisite for ray tracing model, the problem of ultrasonic ray energy reflection and transmission coefficients at an interface between (a) isotropic base material and anisotropic austenitic weld material (including layback orientation), (b) two adjacent anisotropic weld metals and (c) anisotropic weld metal and isotropic base material is solved in three dimensions. The influence of columnar grain orientation and layback orientation on ultrasonic C-scan image is quantitatively analyzed in the context of ultrasonic testing of homogeneous and layered austenitic steel materials. The presented quantitative results provide valuable information during ultrasonic characterization of homogeneous and layered anisotropic austenitic steel materials. KW - Ultrasonic non-destructive evaluation KW - Ultrasonic C-scan image KW - Anisotropic austenitic steel KW - 3D ray tracing KW - Directivity PY - 2014 DO - https://doi.org/10.1016/j.ultras.2013.08.007 SN - 0041-624x VL - 54 IS - 2 SP - 551 EP - 562 PB - Elsevier CY - Amsterdam AN - OPUS4-29733 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brauser, Stephan A1 - Kromm, Arne A1 - Dabah, Eitan A1 - Kannengießer, Thomas A1 - Rethmeier, Michael T1 - Thermal stability of retained austenite in low alloyed TRIP-steel determined by high energy synchrotron radiation N2 - TRIP-steels offer a good combination between strength and ductility. Therefore TRIP-steels are widely used in the automobile industries. The aim of this work is to study the stability of involved phases during heating and to identify the kinetics of the occuring phase transformations. For that purpose, in-situ diffraction measurements, using high energy synchrotron radiation were conducted. The analysis revealed the decomposition of the metastable austenitic phase into carbide and ferrite along the heating process and the regeneration of the austenite by further heating of the sample. KW - Austenite stability KW - Phase transformation KW - TRIP steel KW - Energy dispersive synchrotron X-ray diffraction PY - 2014 DO - https://doi.org/10.4028/www.scientific.net/MSF.772.129 SN - 0255-5476 VL - 772 SP - 129 EP - 133 PB - Trans Tech Publications CY - Aedermannsdorf, Switzerland AN - OPUS4-29700 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 - Experimental and numerical investigation of an electromagnetic weld pool support system for high power laser beam wleidng of austenitic stainless steel N2 - A three-dimensional turbulent steady state numerical model was used to investigate the influence of an alternating current (AC) magnetic field during high power laser beam keyhole welding of 20 mm thick stainless steel AISI 304 being modeled as an ideal non-ferromagnetic material. Three-dimensional heat transfer and fluid dynamics as well as the electromagnetic field equations were solved with the finite element package COMSOL Multiphysics 4.2 taking into account the most important physical effects of the process. Namely, the thermo-capillary (Marangoni) convection at the weld pool boundaries, natural convection due to gravity and density differences in the melt volume as well as latent heat of solid–liquid phase transitions at the phase boundaries were included in the model. It is shown that the gravity drop-out associated with the welding of thick plates due to the hydrostatic pressure can be prevented by the application of AC magnetic field between 80 mT and 135 mT for corresponding oscillation frequencies between 1 kHz and 10 kHz below the weld specimen. Experimentally, a value of the magnetic flux density of around 230 mT was found to be necessary to allow for single-pass laser beam welding without sagging or drop-out of melt for a 20 mm thick combination of austenitic stainless steel AISI 304 and ferritic construction steel S235JRC at an oscillation frequency of around 2.6 kHz. KW - Electromagnetic weld pool control KW - Laser beam welding KW - Lorentz force KW - Marangoni flow KW - Natural convection PY - 2014 DO - https://doi.org/10.1016/j.jmatprotec.2013.11.013 SN - 0924-0136 SN - 1873-4774 VL - 214 IS - 3 SP - 578 EP - 591 PB - Elsevier CY - Amsterdam AN - OPUS4-29709 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Su, H. A1 - Wu, Chuan Song A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Simultaneous measurement of tool torque, traverse force and axial force in friction stir welding N2 - Simultaneous measurement of the tool torque, traverse force and axial force during friction stir welding process is of great significance to the understanding of the underlying process mechanism and the optimizing of the process parameters. Different from the traditional measurement methods using load cell or rotating component dynamometer, an indirect but economical methodology is used in this study for the simultaneous measurement of the traverse force, axial force and tool torque by monitoring the output torques of the servo motors and main spindle three-phase AC induction motor inside the FSW machine. The values of the traverse force, axial force and tool torque are determined under different welding conditions, and the influencing factors are examined. The measured results in friction stir welding of AA2024-T4 aluminum alloys at different combinations of tool rotation speed and welding speed lay foundation for process optimization. KW - Friction stir welding KW - Measurement KW - Traverse force KW - Axial force KW - Tool torque PY - 2013 DO - https://doi.org/10.1016/j.jmapro.2013.09.001 SN - 0278-6125 SN - 1526-6125 VL - 15 IS - 4 SP - 495 EP - 500 PB - Elsevier Ltd. CY - Dearborn, Mich., USA AN - OPUS4-29688 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heinze, Christoph A1 - Michael, Thomas A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Microcrack formation during gas metal arc welding of high-strength fine-grained structural steel N2 - The recent development of high-performance-modified spray arc processes in gas metal arc welding due to modern digital control technology and inverter power sources enables a focused spray arc, which results in higher penetration depths and welding speed. However, microcracks occurred in the weld metal while approaching the process limits of the modified spray arc, represented by a 20-mm double layer DV-groove butt-weld. These cracks were detected in structural steel exhibiting a yield strength level of up to 960 MPa and are neither dependent on the used weld power source nor a consequence of the modified spray arc process itself. The metallographic and fractographic investigations of the rather exceptional fracture surface lead to the classification of the microcracks as hot cracks. The effects of certain welding parameters on the crack probability are clarified using a statistical design of experiment. However, these microcracks do not impact the design specification for toughness in the Charpy V-notch test (absorbed energy at -40 °C for the present material is 30 J). KW - High-strength low-alloy steel KW - Welding KW - Fracture KW - Design of experiments KW - Microcracking PY - 2014 DO - https://doi.org/10.1007/s40195-013-0011-5 SN - 1006-7191 SN - 1000-9442 VL - 27 IS - 1 SP - 140 EP - 148 PB - Springer CY - Shenyang AN - OPUS4-30123 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rethmeier, Michael T1 - Influence of weld imperfections on the fatigue behaviour of resistance spot welded advanced high strength steels KW - Resistance spot welding KW - Gaps KW - Cracks KW - Fatigue life PY - 2014 DO - https://doi.org/10.4028/www.scientific.net/AMR.891-892.1445 SN - 1022-6680 SN - 1662-8985 VL - 891-892 SP - 1445 EP - 1450 PB - Trans Tech Publ. CY - Zurich AN - OPUS4-30099 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 KW - Laser beam welding KW - Hartmann effect KW - Marangoni flow PY - 2013 UR - http://weldingdesign.com/processes/magnets-improve-quality-high-power-laser-beam-welding SN - 0043-2253 SP - 1 EP - 3(?) PB - Penton/IPC CY - Cleveland, Ohio AN - OPUS4-29412 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid laser‑arc welding of laser‑ and plasma‑cut 20‑mm‑thick structural steels N2 - It is already known that the laser beam welding (LBW) or hybrid laser-arc welding (HLAW) processes are sensitive to manufacturing tolerances such as gaps and misalignment of the edges, especially at welding of thick-walled steels due to its narrow beam diameter. Therefore, the joining parts preferably have to be milled. The study deals with the influence of the edge quality, the gap and the misalignment of edges on the weld seam quality of hybrid laser-arc welded 20-mm-thick structural steel plates which were prepared by laser and plasma cutting. Single-pass welds were conducted in butt joint configuration. An AC magnet was used as a contactless backing. It was positioned under the workpiece during the welding process to prevent sagging. The profile of the edges and the gap between the workpieces were measured before welding by a profile scanner or a digital camera, respectively. With a laser beam power of just 13.7 kW, the single-pass welds could be performed. A gap bridgeability up to 1 mm at laser-cut and 2 mm at plasma-cut samples could be reached respectively. Furthermore, a misalignment of the edges up to 2 mm could be welded in a single pass. The new findings may eliminate the need for cost and time-consuming preparation of the edges. KW - Hybrid laser-arc welding KW - Thick-walled steel KW - Edge quality KW - Gap bridgeability KW - Laser cutting KW - Plasma cutting PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-552013 DO - https://doi.org/10.1007/s40194-022-01255-y SN - 0043-2288 VL - 66 SP - 507 EP - 514 PB - Springer AN - OPUS4-55201 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meng, Xiangmeng A1 - Artinov, Antoni A1 - Bachmann, Marcel A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - The detrimental molten pool narrowing phenomenon in wire feed laser beam welding and its suppression by magnetohydrodynamic technique N2 - Element transport in the wire feed laser beam welding (WFLBW) is directly determined by the molten pool shape and thermo-fluid flow therein. In this paper, an untypical molten pool profile, i.e., elongated at its top and bottom but narrowed at the middle, is found experimentally by real-time metal/glass observa- tion and numerically by multi-physical modeling. Ex-situ X-ray fluorescence element mapping is used to characterize the element dilution status in the fusion zone. For the first time, the detrimental influence of the molten pool narrowing on the element transport is identified and discussed, combining the exper- imental and numerical results. A magnetohydrodynamic technique is utilized to suppress the narrowing, aiming at a more homogenous element distribution. It is found that due to the interaction of the two dominant circulations from the top and bottom regions of the molten pool, a low-temperature region is formed. It leads to an untypical growth of the mushy zone, narrowing the molten pool in the middle re- gion. Its detrimental effect on material mixing is non-negligible considering the direct blocking effect on the downward flow and the premature solidification at the middle region. The Lorentz force from a trans- verse oscillating magnetic field can change the flow pattern into a single-circulation type. The downward transfer channel is widened, and its premature solidification is prevented because the low-temperature- gradient region is mitigated. This paper provides a supplementary reason regarding the common issue of insufficient material mixing during LBW, and a promising technique to optimize the process. KW - Thermo-fluid flow KW - Element transport KW - Laser beam welding KW - Magnetohydrodynamics KW - Multi-physical modeling PY - 2022 DO - https://doi.org/10.1016/j.ijheatmasstransfer.2022.122913 VL - 193 SP - 122913 PB - Elsevier B.V. AN - OPUS4-55006 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meng, Xiangmeng A1 - Putra, Stephen Nugraha A1 - Bachmann, Marcel A1 - Artinov, Antoni A1 - Rethmeier, Michael T1 - Influence of the free surface reconstruction on the spatial laser energy distribution in high power laser beam welding modeling N2 - An accurate and efficient description of the spatial distribution of laser energy is a crucial factor for the modeling of laser material processing, e.g., laser welding, laser cutting, or laser-based additive manufacturing. In this study, a 3D heat transfer and fluid flow model coupled with the volume-of-fluid algorithm for free surface tracking is developed for the simulation of molten pool dynamics in high-power laser beam welding. The underlying laser-material interactions, i.e., the multiple reflections and Fresnel absorption, are considered by a raytracing method. Two strategies of free surface reconstruction used in the ray-tracing method are investigated: a typical piecewise linear interface calculation (PLIC)-based method and a novel localized level-set method. The PLIC-based method is discrete, resulting in noncontinuous free surface reconstruction. In the localized level-set method, a continuous free surface is reconstructed, and, thus, the exact reflection points can be determined. The calculated spatial laser energy distribution and the corresponding molten pool dynamics from the two methods are analyzed and compared. The obtained numerical results are evaluated with experimental measurements to assure the validity of the proposed model. It is found that distinct patterns of the beam multiple reflections are obtained with the different free surface reconstructions, which shows significant influence not only on the molten pool behaviors but also on the localized keyhole dynamics. KW - Laser beam welding KW - Laser energy distribution KW - Weld pool dynamics KW - Ray teacing PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-562429 DO - https://doi.org/10.2351/7.0000739 SN - 1042-346X VL - 34 IS - 4 SP - 042023-1 EP - 042023-8 PB - Laser Institute of America CY - Orlando, Fla. AN - OPUS4-56242 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marko, A. A1 - Bähring, S. A1 - Raute, J. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Transferability of ANN-generated parameter sets from welding tracks to 3D-geometries in Directed Energy Deposition N2 - Directed energy deposition (DED) has been in industrial use as a coating process for many years. Modern applications include the repair of existing components and additive manufacturing. The main advantages of DED are high deposition rates and low energy input. However, the process is influenced by a variety of parameters affecting the component quality. Artificial neural networks (ANNs) offer the possibility of mapping complex processes such as DED. They can serve as a tool for predicting optimal process parameters and quality characteristics. Previous research only refers to weld beads: a transferability to additively manufactured three-dimensional components has not been investigated. In the context of this work, an ANN is generated based on 86 weld beads. Quality categories (poor, medium, and good) are chosen as target variables to combine several quality features. The applicability of this categorization compared to conventional characteristics is discussed in detail. The ANN predicts the quality category of weld beads with an average accuracy of 81.5%. Two randomly generated parameter sets predicted as “good” by the network are then used to build tracks, coatings,walls, and cubes. It is shown that ANN trained with weld beads are suitable for complex parameter predictions in a limited way. KW - Welding parameter KW - Quality assurance KW - DED KW - Artificial neural network KW - Additive manufacturing PY - 2022 DO - https://doi.org/10.1515/mt-2022-0054 SN - 0025-5300 VL - 64 IS - 11 SP - 1586 EP - 1596 PB - De Gruyter AN - OPUS4-56278 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marko, A. A1 - Bähring, S. A1 - Raute, J. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Prognose von Qualitätsmerkmalen durch Anwendung von KI-Methoden beim Directed 10 Energy Deposition N2 - Dieser Beitrag enthält die Ergebnisse eines im Rahmen der DVS Forschung entwickelten Ansatzes zur Qualitätssicherung im Directed Energy Deposition. Es basiert auf der Verarbeitung verschiedener während des Prozesses gesammelter Sensordaten unter Anwendung Künstlicher Neuronale Netze (KNN). So ließen sich die Qualitätsmerkmale Härte und Dichte auf der Datenbasis von 50 additiv gefertigten Probenwürfel mit einer Abweichung < 2 % vorhersagen. Des Weiteren wurde die Übertragbarkeit des KNN auf eine Schaufelgeometrie untersucht. Auch hier ließen sich Härte und Dichte hervorragend prognostizieren (Abweichung < 1,5 %), sodass der Ansatz als validiert betrachtet werden kann. KW - Kl KW - Directed Energy Depositio KW - Qualitätssicherung PY - 2022 SN - 0036-7184 VL - 74 IS - 10 SP - 672 EP - 679 PB - DVS Media CY - Düsseldorf AN - OPUS4-56284 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - El-Batahgy, A. A1 - Elkousy, M. A1 - Al-Rahman, A. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - Gook, S. T1 - Retaining Mechanical Properties of GMA-Welded Joints of 9%Ni Steel Using Experimentally Produced Matching Ferritic Filler Metal N2 - Motivated by the loss of tensile strength in 9%Ni steel arc-welded joints performed using commercially available Ni-based austenitic filler metals, the viability of retaining tensile strength using an experimentally produced matching ferritic filler metal was confirmed. Compared to the austenitic Ni-based filler metal (685 MPa), higher tensile strength in gas metal arc (GMA) welded joints was achieved using a ferritic filler metal (749 MPa) due to its microstructure being similar to the base metal (645 MPa). The microstructure of hard martensite resulted in an impact energy of 71 J (-196 °C), which was two times higher than the specified minimum value of _>34 J. The tensile and impact strength of the welded joint is affected not only by its microstructure, but also by the degree of its mechanical mismatch depending on the type of filler metal. Welds with a harder microstructure and less mechanical mismatch are important for achieving an adequate combination of tensile strength and notched impact strength. This is achievable with the cost-effective ferritic filler metal. A more desirable combination of mechanical properties is guaranteed by applying low preheating temperature (200 °C), which is a more practicable and economical solution compared to the high post-weld heat treatment (PWHT) temperature (580 °C) suggested by other research. KW - 9%Ni steel KW - Ni-based austenitic filler metal KW - Mechanical mismatching KW - Microstructure KW - Post-weld heat treatment KW - Preheating KW - Matching ferritic filler metal PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-564610 DO - https://doi.org/10.3390/ma15238538 SN - 1996-1944 VL - 15 IS - 23 SP - 1 EP - 14 PB - MDPI AN - OPUS4-56461 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Brunner-Schwer, C. A1 - Knöfel, F. A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Laserstrahlhybridschweissen von Türmen für Windkraftanlagen Ökonomische und ökologische Vorteile N2 - Das Laserstrahlhybridschweißen ist beim Schweißen von Türmen für Windkraftanlagen eine Alternative zum Unterpulverschweißen von Dickblechen in Mehrlagentechnik und bietet hier ökonomische und ökologische Vorteile. Der industrielle Einsatz des Verfahrens ist jedoch durch prozessspezifische Herausforderungen eingeschränkt. Die im Beitrag beschriebene kontaktlose elektromagnetische Badstütze dient zur Erweiterung des Verfahrenspotenzials im Dickblechbereich >15 mm. KW - Elektromagnetische Badstütze KW - Laserhybridschweißen KW - Windkraftanlagen KW - Ökonomische und ökologische Vorteile PY - 2022 VL - 7 SP - 340 EP - 347 PB - DVS Media GmbH AN - OPUS4-56372 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Improvement of Charpy impact toughness by using an AC magnet backing system for laser hybrid welding of thick S690QL steels N2 - The study deals with the influence of the heat input and the resulting cooling times on the microstructure and Charpy impact toughness of single-pass laser hybrid welded 20-mm thick high-strength steel S690QL. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured in-situ using a pyrometer and an optical fibre in three different depths of the seam where Charpy impact test specimens were also later taken. Thereby, three different heat inputs from 1.3 kJ/mm to 2 kJ/mm were investigated. Despite the observed decreased values of both t8/5-cooling time and the Charpy impact toughness in the root part of the seam, the required impact toughness of 38 J/cm2 could be reached in dependance on applied heat input, especially at the heat input of 1.6 kJ/mm. T2 - 12th CIRP conference on photonic technologies [lane 2022] CY - Fürth, Germany DA - 04.09.2022 KW - Thick-plate welding KW - Laser hybrid welding KW - Electromagnetic backing KW - Charpy impact toughness KW - Thermal cycles PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563731 DO - https://doi.org/10.1016/j.procir.2022.08.067 VL - 111 SP - 462 EP - 465 PB - Elsevier B.V. AN - OPUS4-56373 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jokisch, T. A1 - Gook, S. A1 - Marko, A. A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Laser beam welding of additive manufactured components: Applicability of existing valuation regulations N2 - With additive manufacturing in the powder bed, the component size is limited by the installation space. Joint welding of additively manufactured parts offers a possibility to remove this size limitation. However, due to the specific stress and microstructure state in the additively built material, it is unclear to what extent existing evaluation rules of joint welding are also suitable for welds on additive components. This is investigated using laser beam welding of additively manufactured pipe joints. The welds are evaluated by means of visual inspection, metallographic examinations as well as computed tomography. The types of defects found are comparable to conventional components. This is an indicator that existing evaluation regulations also map the possible defects occurring for weld seams on additive components. KW - Weld imperfections KW - Additive manufacturing KW - Weldability KW - Laser welding PY - 2022 VL - 2 SP - 109 EP - 113 PB - DVS Media GmbH AN - OPUS4-56374 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bakir, Nasim A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Influence of the weld pool geometry on solidification cracking in partial penetration high power laser beam welding N2 - Solidification cracking is still a serious problem in laser beam welding, especially in the welding of thick-walled plates. The influence of weld pool geometry on solidification cracking in partial penetration welding of thick plates is investigated within scope of this study. Therefore, a specific experimental setup of steel and quartz glass in butt configuration and on the side with high-speed camera were used to record the weld pool shape. In addition, the influence of laser inclination angle on the weld pool geometry and on solidification crack formation was investigated. The results show a bulge in the weld pool root, which is separated from an upper region by a necking region. This leads to a case where there are three different longitudinal region lengths with different solidification zones. This temporal sequence of solidification strongly promotes the formation of solidification cracks in the weld root. T2 - 12th CIRP Conference on photonic technologies (LANE 2022) CY - Fürth, Germany DA - 04.09.2022 KW - Laser beam welding KW - Partial penetration KW - Weld pool shape PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563940 DO - https://doi.org/10.1016/j.procir.2022.08.174 VL - 111 SP - 397 EP - 400 PB - Elsevier B.V. AN - OPUS4-56394 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Artinov, Antoni A1 - Meng, Xiangmeng A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Study on the transition behavior of the bulging effect during deep penetration laser beam welding N2 - The present work is devoted to the study of the transition behavior of the recently confirmed widening of the weld pool, known as the bulging effect, during high-power deep penetration laser beam welding of thick unalloyed steel sheets. A three-dimensional transient multi-physics numerical model is developed, allowing for the prediction of the bulge formation and the study of its temporal behavior. The model is generalized to account automatically for the transition from partial to complete penetration. Several experimental measurements and observations, such as drilling period, weld pool length, temperature, efficiency, and metallographic cross-sections are used to verify the model and assure the plausibility of the numerical results. The analysis of the calculated temperature and velocity distributions, as well as the evolution of the keyhole geometry, shows that the formation of a bulging region strongly depends on the penetration depth of the weld. Based on the numerical results, the bulge is found to occur transiently, having its transition from a slight bulge to a fully developed bulging between penetration depths of 6 mm and 9 mm, respectively. KW - Laser beam welding KW - Deep penetration KW - Bulge formation KW - Numerical modeling PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-545067 DO - https://doi.org/10.1016/j.ijheatmasstransfer.2021.122171 VL - 184 SP - 122171 PB - Elsevier Ltd. AN - OPUS4-54506 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 - Straße, Anne A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Study on Duplex Stainless Steel Powder Compositions for the Coating of thick Plates of Laser Beam Welding N2 - Duplex stainless steels combine the positive properties of its two phases, austenite and ferrite. Due to its good corrosion resistance, high tensile strength, and good ductility, it has multiple applications. But laser beam welding of duplex steels changes the balanced phase distribution in favor of ferrite. This results in a higher vulnerability to corrosion and a lower ductility. Herein, different powder combinations consisting of duplex and nickel for coating layers by laser metal deposition (LMD) are investigated. Afterward, laser tracks are welded, and the temperature cycles are measured. The ferrite content of the tracks is analyzed by feritscope, metallographic analysis, and electron backscatter diffraction. The goal is the development of a powder mixture allowing for a duplex microstructure in a two-step process, where first the edges of the weld partners are coated with the powder mixture by LMD and second those edges are laser beam welded. The powder mixture identified by the pretests is tested in the two-step process and analyzed by metallographic analysis, energy-dispersive X-ray spectroscopy, and Vickers hardness tests. The resulting weld seams show a balanced duplex microstructure with a homogenous nickel distribution and a hardness of the weld seam similar to the base material. KW - Duplex AISI 2205 KW - Laser metal deposition KW - Laser beam welding KW - Nickel KW - Stainless steels PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-547024 DO - https://doi.org/10.1002/adem.202101327 SN - 1438-1656 SP - 1 EP - 11 PB - Wiley-VCH CY - Weinheim AN - OPUS4-54702 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marko, A. A1 - Bähring, S. A1 - Raute, J. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Quality Prediction in Directed Energy Deposition Using Artificial Neural Networks Based on Process Signals N2 - The Directed Energy Deposition process is used in a wide range of applications including the repair, coating or modification of existing structures and the additive manufacturing of individual parts. As the process is frequently applied in the aerospace industry, the requirements for quality assurance are extremely high. Therefore, more and more sensor systems are being implemented for process monitoring. To evaluate the generated data, suitable methods must be developed. A solution, in this context, was the application of artificial neural networks (ANNs). This article demonstrates how measurement data can be used as input data for ANNs. The measurement data were generated using a pyrometer, an emission spectrometer, a camera (Charge-Coupled Device) and a laser scanner. First, a concept for the extraction of relevant features from dynamic measurement data series was presented. The developed method was then applied to generate a data set for the quality prediction of various geometries, including weld beads, coatings and cubes. The results were compared to ANNs trained with process parameters such as laser power, scan speed and powder mass flow. It was shown that the use of measurement data provides additional value. Neural networks trained with measurement data achieve significantly higher prediction accuracy, especially for more complex geometries. KW - DED KW - Artificial neural network KW - Process monitoring KW - Quality assurance KW - Data preparation PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-547039 DO - https://doi.org/10.3390/app12083955 VL - 12 IS - 8 SP - 1 EP - 13 PB - MDPI AN - OPUS4-54703 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Geisen, O. A1 - Müller, V. A1 - Graf, B. A1 - Rethmeier, Michael T1 - Integrated weld preparation designs for the joining of L‑PBF and conventional components via TIG welding N2 - size limitations and high production costs of L-PBF make it competitive for smaller, highly complex components, while the less complex elements of an assembly are manufactured conventionally. This leads to scenarios that use L-PBF only where it’s beneficial, and it require an integration and joining to form the final product. For example, L-PBF combustion swirlers are welded onto cast parts to produce combustion systems for stationary gas turbines. Today, the welding process requires complex welding fixtures and tack welds to ensure the correct alignment and positioning of the parts for repeatable weld results. In this paper, L-PBF and milled weld preparations are presented as a way to simplify the Tungsten inert gas (TIG) welding of rotationally symmetrical geometries using integrated features for alignment and fixation. Pipe specimens with the proposed designs are manufactured in Inconel 625 using L-PBF and milling. The pipe assembly is tested and TIG welding is performed for validation. 3D scans of the pipes before and after welding are evaluated, and the weld quality is examined via metallography and computed tomography (CT) scans. All welds produced in this study passed the highest evaluation group B according to DIN 5817. Thanks to good component alignment, safe handling, and a stable welding process, the developed designs eliminate the need for part-specific fixtures, simplify the process chain, and increase the process reliability. The results are applicable to a wide range of components with similar requirements. KW - L-PBF KW - AM feature integration KW - TIG welding KW - Integrated alignment features KW - Pipe weld preparation KW - Dissimilar joints KW - Inconel 625 PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-547042 DO - https://doi.org/10.1007/s40964-021-00221-2 SN - 2363-9512 SP - 1 EP - 11 PB - Springer AN - OPUS4-54704 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, S. A1 - El-Sari, B. A1 - Biegler, M. A1 - Rethmeier, Michael A1 - Lichtenthäler, F. A1 - Stark, M. T1 - Multiple-wire submerged arc welding of high-strength fine-grained steels N2 - Ensuring the required mechanical-technological properties of welds is a critical issue in the application of multi-wire submerged arc welding processes for welding high-strength fine-grained steels. Excessive heat input is one of the main causes for microstructural zones with deteriorated mechanical properties of the welded joint, such as a reduced notched impact strength and a lower structural robustness. A process variant is proposed which reduces the weld volume as well as the heat input by adjusting the welding wire configuration as well as the energetic parameters of the arcs, while retaining the advantages of multiwire submerged arc welding such as high process stability and production speed. KW - Submerged arc welding KW - High-strength fine-grained steels KW - Mechanical properties of the joints KW - Energy parameters of the arc PY - 2022 DO - https://doi.org/10.37434/tpwj2022.01.02 SN - 0957-798X IS - 1 SP - 9 EP - 13 PB - Paton Publishing House CY - Kiev AN - OPUS4-54701 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - El-Sari, B. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Verbesserung der Vorhersagegüte von künstlichen neuronalen Netzen zum Widerstandspunktschweißen durch Auswertung des dynamischen Widerstands N2 - Das Widerstandspunktschweißen ist ein etabliertes Fügeverfahren in der Automobilindustrie. Es wird vor allem bei der Herstellung sicherheitsrelevanter Bauteile, zum Beispiel der Karosserie, eingesetzt. Daher ist eine kontinuierliche Prozessüberwachung unerlässlich, um die hohen Qualitätsanforderungen zu erfüllen. Künstliche neuronale Netzalgorithmen können zur Auswertung der Prozessparameter und -signale eingesetzt werden, um die individuelle Schweißpunktqualität zu gewährleisten. Die Vorhersagegenauigkeit solcher Algorithmen hängt von dem zur Verfügung gestellten Trainingsdatensatz ab. In diesem Beitrag wird untersucht, inwieweit die Vorhersagegüte eines künstlichen neuronalen Netzes durch Auswertung einer Prozessgröße, dem dynamischen Widerstand, verbessert werden kann. KW - Künstliche Intelligenz KW - Qualität KW - Neuronales Netz KW - Widerstandspunktschweißen PY - 2021 SP - 785 EP - 789 AN - OPUS4-53976 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - El-Sari, B. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Investigation of the Extrapolation Capability of an Artificial Neural Network Algorithm in Combination with Process Signals in Resistance Spot Welding of Advanced High-Strength Steels N2 - Resistance spot welding is an established joining process for the production of safetyrelevant components in the automotive industry. Therefore, consecutive process monitoring is essential to meet the high quality requirements. Artificial neural networks can be used to evaluate the process parameters and signals, to ensure individual spot weld quality. The predictive accuracy of such algorithms depends on the provided training data set, and the prediction of untrained data is challenging. The aim of this paper was to investigate the extrapolation capability of a multi-layer perceptron model. That means, the predictive performance of the model was tested with data that clearly differed from the training data in terms of material and coating composition. Therefore, three multi-layer perceptron regression models were implemented to predict the nugget diameter from process data. The three models were able to predict the training datasets very well. The models, which were provided with features from the dynamic resistance curve predicted the new dataset better than the model with only process parameters. This study shows the beneficial influence of process signals on the predictive accuracy and robustness of artificial neural network algorithms. Especially, when predicting a data set from outside of the training space. KW - Automotive KW - Artificial intelligence KW - Quality monitoring KW - Resistance spot welding KW - Quality assurance PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-539783 DO - https://doi.org/10.3390/met11111874 VL - 11 IS - 11 SP - 1 EP - 11 PB - MDPI AN - OPUS4-53978 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Raute, J. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Elektronenstrahl schweißt additiv gefertigte Nickel-Superlegierungen N2 - Die Additive Fertigung ist ideal zur Herstellung und Reparatur komplexer Bauteile aus hochfesten Werkstoffen. Doch es fehlen Fügeverfahren, die Heißrisse vermeiden. Die Lösung heißt Elektronenstrahl. KW - Additive Fertigung PY - 2021 SP - 1 EP - 6 AN - OPUS4-53979 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Meng, Xiangmeng A1 - Artinov, Antoni A1 - Rethmeier, Michael T1 - Elucidation of the Bulging Effect by an Improved Ray-Tracing Algorithm in Deep Penetration Wire Feed Laser Beam Welding and its Influence on the Mixing Behavior N2 - Herein, an improved ray-tracing routine using a virtual mesh refinement approach is adopted in a 3D transientmultiphysics computational fluid Dynamics model for deep penetration wire feed laser beam welding. In a previous study, it was shown that the improved localization of the reflection points of the subrays within the keyhole leads to a more realistic development of the keyhole Depth being validated with experimental results. Another effect investigated in Detail herein is a drastic change in the flow behavior in the weld pool, which promotes the occurrence of a necking area in the solidification line and subsequent bulging under specific circumstances. This has a detrimental effect on the filler material element transport in the weld pool, leading to an inhomogeneous dilution of the added material. The numerical observations are backed up by experimentally obtained data, allowing to provide a clear physics-based explanation of the reduced mixing behavior of the filler wire in the melt pool. KW - Bulging effects KW - Numerical welding simulations KW - Ray-tracing methods KW - Wire feed laser beam welding PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543322 DO - https://doi.org/10.1002/adem.202101299 SP - 1 EP - 9 PB - Wiley AN - OPUS4-54332 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Artinov, Antoni A1 - Bachmann, Marcel A1 - Rethmeier, Michael A1 - Karkhin, V. A1 - Khomich, P. T1 - Modeling of hydrodynamic and thermal processes at laser welding with through penetration N2 - A mathematical model for physical processes in fusion welding has been developed. It is based on the equivalent heat source concept and consists of two parts: thermo-hydrodynamics of the weld pool and heat conduction in the weldment outside the pool. In thermo-hydrodynamic problem, temperature – dependent material properties, keyhole shape, thermo-capillary and natural convection, phase transformations and other physical phenomena are taken into consideration. Solution of the thermo-hydrodynamic problem by the finite element method is demonstrated with keyhole laser beam welding of a 15 mm thick steel plate. Thermo-capillary convection is primarily responsible for the intricate convex-concave melt pool shape and pool enlargement near the plate surfaces. The calculated and experimental molten pool dimensions are in close agreement. KW - Laser welding KW - Weld pool modeling KW - Heat conduction KW - Greens function method PY - 2021 DO - https://doi.org/10.1080/09507116.2021.1989209 SP - 1 EP - 12 PB - Taylor & Francis Group AN - OPUS4-54022 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rethmeier, Michael A1 - Gumenyuk, Andrey A1 - Bachmann, Marcel T1 - High-power laser beam welding for thick section steels – new perspectives using electromagnetic systems N2 - In recent years, it was shown that the introduction of additional oscillating and permanent magnetic fields to laser beam and laser-arc hybrid welding can bring several beneficial effects. Examples are a contactless weld pool support for metals of high thickness suffering from severe drop-out when being welded conventionally or an enhanced stirring to improve the mixing of added filler material in the depth of the weld pool to guarantee homogeneous resulting mechanical properties of the weld. The latest research results show the applicability to various metal types over a wide range of thicknesses and welding conditions. The observations made were demonstrated in numerous experimental studies and a deep understanding of the interaction of the underlying physical mechanisms was extracted from numerical calculations. KW - Laser beam welding KW - Numerical simulations KW - Electromagnetic support PY - 2021 DO - https://doi.org/10.1080/13621718.2021.1999763 VL - 27 IS - 1 SP - 43 EP - 51 PB - Taylor & Francis Group AN - OPUS4-53970 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Biegler, M. A1 - El-Sari, B. A1 - Rethmeier, Michael A1 - Finus, F. T1 - Schweißen unter Zug – LME-Eingangsprüfung für die Autoindustrie N2 - Der Trend zum Leichtbau und die Transformation zur E-Mobilität in der Automobilindustrie befeuern die Entwicklung neuer hochfester Stähle für den Karosseriebau. Derartige Werkstoffe sind beim Widerstandspunktschweißen besonders rissanfällig (LME). Das Schweißen unter Zug stellt eine effektive Methode um die LME-Anfälligkeit unterschiedlicher Werkstoffe qualitativ zu bestimmen. KW - Automobilindustrie KW - Widerstandspunktschweißen KW - Liquid Metal Embrittlement KW - Zinkbeschichtung KW - Hochfester Stahl PY - 2021 IS - 6 SP - 54 EP - 55 AN - OPUS4-54057 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Artinov, Antoni A1 - Meng, Xiangmeng A1 - Bakir, Nasim A1 - Üstündag, Ömer A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - The bulging effect and its relevance in high power laser beam welding N2 - The present work deals with the recently confirmed widening of the weld pool interface, known as a bulging effect, and its relevance in high power laser beam welding. A combined experimental and numerical approach is utilized to study the influence of the bulge on the hot cracking formation and the transport of alloying elements in the molten pool. A technique using a quartz glass, a direct-diode laser illumination, a high-speed camera, and an infrared camera is applied to visualize the weld pool geometry in the longitudinal section. The study examines the relevance of the bulging effect on both, partial and complete penetration, as well as for different sheet thicknesses ranging from 8 mm to 25 mm. The numerical analysis shows that the formation of a bulge region is highly dependent on the penetration depth and occurs more frequently during partial penetration above 6 mm and complete penetration above 8 mm penetration depth, respectively. The location of the bulge correlates strongly with the cracking location. The obtained experimental and numerical results reveal that the bulging effect increases the hot cracking susceptibility and limits the transfer of alloying elements from the top of the weld pool to the weld root. T2 - 18th Nordic Laser Materials Processing Conference (18th NOLAMP) KW - High-power laser beam welding KW - Bulge effect KW - Solidification cracking KW - Multi-physical modelling KW - Metal mixing PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-539149 DO - https://doi.org/10.1088/1757-899X/1135/1/012003 VL - 1135 IS - 012003 SP - 1 EP - 11 PB - IOP Publishing AN - OPUS4-53914 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Influence of an external applied AC magnetic field on the melt pool dynamics at high-power laser beam welding N2 - The study deals with the determination of the influence of an externally applied oscillating magnetic field on the melt pool dynamics in high power laser beam and hybrid laser arc welding processes. An AC magnet was positioned under the workpiece which is generating an upward directed electromagnetic force to counteract the formation of the droplets. To visualise the melt flow characteristics, several experiments were carried out using a special technique with mild steel from S355J2 with a plate thickness of up to 20 mm and a quartz glass in butt configuration. The profile of the keyhole and the melt flow were recorded with a highspeed camera from the glass side. Additionally, the influence of the magnetic field orientation to the welding direction on the filler material dilution on laser hybrid welding was studied with variating oscillation frequency. The element distribution over the whole seam thickness was measured with X-ray fluorescence (XRF). The oscillation frequency demonstrated a great influence on the melt pool dynamics and the mixing of the elements of the filler wire. The highspeed recordings showed, under the influence of the magnetic field, that the melt is affected under strong vortex at the weld root, which also avoids the formation of droplets. T2 - 18th Nordic Laser Materials Processing Conference (18th NOLAMP) KW - Laser beam welding KW - AC magnetic field KW - Melt pool dynamics KW - Filler wire mixing PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-539231 DO - https://doi.org/10.1088/1757-899X/1135/1/012017 VL - 1135 IS - 012017 SP - 1 EP - 10 PB - IOP Publishing AN - OPUS4-53923 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of the gap bridgeability at high-power laser hybrid welding of plasma-cut thick mild steels with AC magnetic support N2 - One of the challenges of the high-power hybrid laser welding of thick steels is the sensitivity of the process of the process to manufacturing tolerances. This usually leads to a time-consuming preparation of the welding edges, such as milling. The study deals with the influence of the edge quality of milled and plasma-cut steel made of S355J2 with a wall thickness of 20 mm on the laser hybrid welded seam quality. Furthermore, the gap bridgeability and the tolerances towards edge misalignment was investigated. An AC magnet was used as backing support to prevent sagging and positioned under the workpiece, to generate an upwards directed electromagnetic pressure. The profiles of the edges and the gap on the top and root side were measured using a digital camera. Single-pass laser hybrid welds of plasma-cut edges could be welded using a laser beam power of just 13.7 kW. A gap bridgeability up to 2 mm and misalignment of edges up to 2 mm could be achieved successful. Additionally, the independence of the cutting side and the welding side was shown, so that samples were welded to the opposite side to their cutting. For evaluation of internal defects or irregularities, X-ray images were carried out. Charpy impact strength tests were performed to determine the toughness of the welds. T2 - X International Conference «Beam Technologies & Laser Application» KW - Laser hybrid welding KW - Magnetic bath support KW - Plasma-cut samples KW - Thick plate welding PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-539248 DO - https://doi.org/10.1088/1742-6596/2077/1/012007 VL - 2077 IS - 012007 SP - 1 EP - 8 PB - IOP Publishing AN - OPUS4-53924 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Winterkorn, René A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Wire arc additive manufacturing with novel Al-Mg-Si filler wire - Assessment of weld quality and mechanical properties N2 - Wire arc additive manufacturing enables the production of near-net shape large-volume metallic components leveraging an established industrial base of welding and cladding technology and adapting it for layer-wise material deposition. However, the complex relationship between the process parameters and resulting mechanical properties of the components still remains challenging. In case of high-strength Al-Mg-Si aluminum alloys, no commercial filler wires are yet available due the high susceptibility of solidification cracking as well as the necessary efforts to obtain acceptable mechanical properties. To address this need, we evaluated a novel filler wire based on AlMg0.7Si doped with a Ti5B1 master alloy to foster fine equiaxed grains within the deposited metal. The correlation between the process parameters and component quality was examined by analyzing the size and distribution of pores as well as the grain morphology. Furthermore, we evaluated the influence of different post-weld heat treatment strategies to achieve mechanical properties corresponding to the reference wrought material. We demonstrated that fine equiaxed grains in the weld metal reduced the susceptibility of solidification cracking significantly. The novel AlMg0.7Si-TiB (S Al 6063-TiB) filler wire facilitated wire arc additive manufacturing of high-strength aluminum components with mechanical properties that were almost as superior as the corresponding wrought base material. KW - Wire arc additive manufacturing KW - Precipitation hardening aluminum alloys KW - AlMg0.7SiTiB filler wire KW - Grain refinement KW - Mechanical properties PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-538327 DO - https://doi.org/10.3390/met11081243 SN - 2075-4701 VL - 11 IS - 8 SP - 1 EP - 13 PB - MDPI CY - Basel AN - OPUS4-53832 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fu, B. A1 - Shen, J. A1 - Suhuddin, U. A1 - Pereira, A. A1 - Maawad, E. A1 - dos Santos, J. A1 - Klusemann, B. A1 - Rethmeier, Michael T1 - Revealing joining mechanism in refill friction stir spot welding of AZ31 magnesium alloy to galvanized DP600 steel N2 - 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. KW - Refill friction stir spot welding KW - Multi-materials joining KW - Magnesium alloy KW - Galvanized steel KW - Mechanical properties KW - Microstructure PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-536878 DO - https://doi.org/10.1016/j.matdes.2021.109997 SN - 0264-1275 VL - 209 SP - 109997 PB - Elsevier Ltd. AN - OPUS4-53687 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fu, B. A1 - Shen, J. A1 - Suhuddin, U. A1 - Chen, T. A1 - dos Santos, J. A1 - Klusemann, B. A1 - Rethmeier, Michael T1 - Improved mechanical properties of cast Mg alloy welds via texture weakening by differential rotation refill friction stir spot welding N2 - 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 pro- pose a novel process variant, the differential rotation refill FSSW (DR-refill FSSW). DR-refill FSSW stim- ulates 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. KW - Refill friction stir spot welding KW - Magnesium Alloy KW - Texture KW - EBSD KW - Plastic deformation PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-536885 DO - https://doi.org/10.1016/j.scriptamat.2021.114113 SN - 1359-6462 VL - 203 SP - 114113 PB - Elsevier Ltd. AN - OPUS4-53688 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Raute, J. A1 - Jokisch, T. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Effects on crack formation of additive manufactured Inconel 939 sheets during electron beam welding N2 - The potential of additive manufacturing for processing precipitation hardened nickel-base superalloys, such as Inconel 939 is considerable, but in order to fully exploit this potential, fusion welding capabilities for additive parts need to be explored. Currently, it is uncertain how the different properties from the additive manufacturing process will affect the weldability of materials susceptible to hot cracking. Therefore, this work investigates the possibility of joining additively manufactured nickel-based superalloys using electron beam welding. In particular, the influence of process parameters on crack formation is investigated. In addition, hardness measurements are performed on cross-sections of the welds. It is shown that cracks at the seam head are enhanced by Welding speed and energy per unit length and correlate with the hardness of the weld metal. Cracking parallel to the weld area shows no clear dependence on the process variables that have been investigated, but is related to the hardness of the heat-affected zone. KW - Electron beam welding KW - Hot Cracks KW - Superalloy KW - Inconel 939 PY - 2021 DO - https://doi.org/10.1016/j.vacuum.2021.110649 SN - 0042-207X VL - 195 SP - 10649 PB - Elsevier Ltd. AN - OPUS4-53689 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jokisch, T. A1 - Gook, S. A1 - Marko, A. A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Laserstrahlschweißen additiv gefertigter Bauteile: Einsetzbarkeit bestehender Bewertungsvorschriften N2 - Bei der additiven Fertigung im Pulverbett ist die Bauteilgröße durch den Bauraum begrenzt. Das Verbindungsschweißen additiv gefertigter Teile bietet eine Möglichkeit diese Größenbegrenzung aufzuheben. Aufgrund des spezifischen Spannungs- und Gefügezustands im additiv aufgebauten Teil ist jedoch unklar, inwiefern bestehende Bewertungsvorschriften des Verbindungsschweißens auch für Schweißnähte an additiv gefertigten Bauteilen geeignet sind. Dies wird anhand des Laserstrahlschweißens additiv gefertigter Rohrverbindungen untersucht. Die Schweißnähte werden mittels visueller Prüfung, metallografischer Untersuchungen sowie Computertomografie ausgewertet. Die festgestellten Fehlerarten sind vergleichbar zu konventionellen Bauteilen. Dies ist ein Indikator dafür, dass bestehende Bewertungsvorschriften die möglichen auftretenden Defekte auch für Schweißnähte an additiven Bauteilen abbilden. KW - Schweißunregelmäßigkeiten KW - Additive Fertigung KW - Laserstrahlschweißen KW - Schweißeignung PY - 2021 VL - 73 IS - 3 SP - 132 EP - 137 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-53575 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Churiaque, C. A1 - Sanchez-Amaya, J.M. A1 - Üstündag, Ömer A1 - Porrua-Lara, M. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Improvements of hybrid laser arc welding for shipbuilding T-joints with 2F position of 8 mm thick steel N2 - the joints throughout the structure. The flat units are constituted by butt welded flat plates, on which longitudinal T-welded reinforcements are placed to rigidize the structure. Among the different welding technologies, Hybrid Laser Arc Welding (HLAW) is becoming a mature process, profitable and highly productive. In addition, more innovative welding equipment are being developed nowadays, offering greater work flexibility, and raising expectations of achieving better quality, and economic viability. Another key point of HLAW to keep in mind is that structural distortions are reduced, resulting in decreasing the cost and time of straightening work. In the present contribution, the influence of HLAW parameters on the quality of fillet joints of naval steel has been analysed. Experimental HLAW tests were performed with a high power disk laser to join EH36 naval steel plates, with a T configuration. The influence of different processing parameters has been analysed, as the laser power, welding speed, wire feed rate and the configuration of the HLAW processes (including head angle and laser/arc leading process). In addition, FEM simulations were carried out in order to estimate residual stresses and distortion of welded part. The distortion values provided by FEM presented excellent agreement with the measured experimental results. To evaluate the welds, non destructive tests including X-ray tests, metallographic analysis of cross sections, and microhardness mapping tests were performed. Full penetration 8 mm T welds were obtained for the first time at an industrially applicable 2F position with a reasonable HLAW head angle, in one single step without sealing root, and using zero gap square groove Edge preparation. The present contribution presents welding rates up to 2.2 m/min for 2F T-joints of this steel thickness, a much higher processing velocity than previously reported for industrial applications. KW - Hybrid laser arc welding PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-528410 DO - https://doi.org/10.1016/j.optlastec.2021.107284 VL - 143 SP - 1 EP - 20 PB - Elsevier Ltd. AN - OPUS4-52841 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Ökologische Bilanzierung von Schmelzschweißverfahren unter Berücksichtigung vor- und nachgelagerter Prozessschritte N2 - Ein wesentliches Ziel der deutschen Industriepolitik besteht darin, Rahmenbedingungen zu schaffen, welche die Positionierung nachhaltiger Produkte und Prozesse innerhalb globaler Wertschöpfungsketten ermöglichen und ökoeffiziente Fertigungsprozesse langfristig sichern. In diesem Beitrag werden aktuelle Forschungsarbeiten zur Bewertung der Umweltwirkungen der schweißtechnischen Fertigungskette anhand ausgewählter Schmelzschweißverfahren unter Berücksichtigung vor- sowie nachgelagerter Fertigungsschritte dargestellt. Eine weit verbreitete und standardisierte Methode zur Abschätzung der Umweltwirkungen eines Produkts oder Prozesses ist die Ökobilanzierung. Hierbei stellen die Sachbilanzierung, das heißt die Ermittlung sämtlicher relevanter Energie- und Ressourcenverbräuche während der schweißtechnischen Fertigung, aufgrund des hohen Dokumentationsaufwands, sowie die Ableitung assoziierter Wirkkategorien das größte Hindernis für eine Etablierung und Akzeptanz der Ökobilanzierung in der Praxis dar. Gleichwohl wird seitens Unternehmen, welche als Zulieferer von OEM’s (engl.: original equipment manufacturer) agieren, die Dokumentation des fertigungsspezifischen CO2-Verbrauches gefordert. Ein weiterer Aspekt der Arbeiten beinhaltet Methoden zur automatisierten Erfassung von schweißtechnischen Produktionsdaten sowie deren Nachverfolgbarkeit. Anhand unterschiedlicher Schweißverfahren werden die aus den Produktionsdaten abgeleiteten Energie- und Ressourcenverbräuche automatisiert in die relevanten Umweltwirkungen überführt. Die analysierten Schweißprozesse umfassen dabei ein breites für kleine und mittlere Unternehmen (KMU) relevantes Spektrum. Durch die softwareseitige Bereitstellung der aufgestellten Umweltprofile ist der Anwender in der Lage, Schweißprozesse unter ökologischen Aspekten zu bewerten und die effizienteste Variante zu identifizieren. KW - Umweltschutz PY - 2021 VL - 73 IS - 5 SP - 276 EP - 282 PB - DVS Media GmbH AN - OPUS4-52842 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marko, A. A1 - Schafner, A. A1 - Raute, J. A1 - Rethmeier, Michael T1 - Relative density prognosis for directed energy deposition with the help of artificial neural networks N2 - Additive manufacturing, and therefore directed energy deposition, is gaining more and more interest from industrial users. However, quality assurance for the components produced is still a challenge. Machine learning, especially using artificial neuronal networks, is a potential method for ensuring a high-quality standard. Based on process Parameters and monitoring data, part quality can be predicted. A further advantage is the ability to constantly learn and adopt to slight process changes. First tests using artificial neural networks focus on the prediction of track geometry. The results show that even a small data set is enough to provide high accuracy in the predictions. In this work, an artificial neural network for the predictive analysis of relative density in laser powder cladding has been developed. A central composite experimental design is used to generate 19 data sets. Input variables are laser power, feed rate and powder mass flow. Cubes are built up where density is considered as a target value. Several neural networks are trained and evaluated with these data sets. Different topologies and initial weights are considered. The best network reaches a confidence level of around 90 % for the prediction of relative density based on the process parame� ters. Finally, the optimization of the generalization performance is investigated. To this purpose, methods of variation in error limit as well as cross-validation are applied. In this way, density is predictable by an artificial neural network with an accuracy of about 95 %. KW - Directed energy deposition KW - Artificial neural network PY - 2021 DO - https://doi.org/10.1515/mt-2020-0004 SN - 0025-5300 VL - 63 IS - 1 SP - 41 EP - 47 PB - DE Gruyter CY - Berlin AN - OPUS4-52690 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Artinov, Antoni A1 - Meng, Xiangmeng A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Numerical analysis of the partial penetration high power laser beam welding of thick sheets at high process speeds N2 - The present work is devoted to the numerical analysis of the high-power laser beam welding of thick sheets at different welding speeds. A three-dimensional transient multi-physics numerical model is developed, allowing for the prediction of the keyhole geometry and the final penetration depth. Two ray tracing algorithms are implemented and compared, namely a standard ray tracing approach and an approach using a virtual mesh refinement for a more accurate calculation of the reflection points. Both algorithms are found to provide sufficient accuracy for the prediction of the keyhole depth during laser beam welding with process speeds of up to 1.5 m/min. However, with the standard algorithm, the penetration depth is underestimated by the model for a process speed of 2.5 m/min due to a trapping effect of the laser energy in the top region. In contrast, the virtually refined ray tracing approach results in high accuracy results for process speeds of both 1.5 m/min and 2.5 m/min. A detailed study on the trapping effect is provided, accompanied by a benchmark including a predefined keyhole geometry with typical characteristics for the high-power laser beam welding of thick plates at high process speed, such as deep keyhole, inclined front keyhole wall, and a hump. KW - High-power laser beam welding KW - High process speeds KW - Deep penetration KW - Numerical modeling KW - Ray tracing PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-532170 DO - https://doi.org/10.3390/met11081319 SN - 2075-4701 VL - 11 IS - 8 SP - 1 EP - 16 PB - MDPI CY - Basel AN - OPUS4-53217 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Böhne, C. A1 - Meschut, G. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - The Influence of Electrode Indentation Rate on LME Formation during RSW N2 - During resistance spot welding of zinc-coated advanced high-strength steels (AHSSs) for automotive production, liquid metal embrittlement (LME) cracking may occur in the event of a combination of various unfavorable influences. In this study, the interactions of different welding current levels and weld times on the tendency for LME cracking in third-generation AHSSs were investigated. LME manifested itself as high penetration cracks around the circumference of the spot welds for welding currents closely below the expulsion limit. At the same time, the observed tendency for LME cracking showed no direct correlation with the overall heat input of the investigated welding processes. To identify a reliable indicator of the tendency for LME cracking, the local strain rate at the origin of the observed cracks was analyzed over the course of the welding process via finite element simulation. While the local strain rate showed a good correlation with the process-specific LME cracking tendency, it was difficult to interpret due to its discontinuous course. Therefore, based on the experimental measurement of electrode displacement during welding, electrode indentation velocity was proposed as a descriptive indicator for quantifying cracking tendency. KW - Liquid Metal Embrittlement (LME) KW - Crack KW - Resistance Spot Welding (RSW) KW - Advanced High-Strength Steel (AHSS) KW - Welding Current KW - Heat Input KW - Simulation PY - 2022 DO - https://doi.org/10.29391/2022.101.015 SN - 0043-2296 VL - 101 IS - 7 SP - 197-s EP - 207-s PB - American Welding Society CY - New York, NY [u.a.] AN - OPUS4-55600 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, S. A1 - Midik, A. A1 - Biegler, M. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Joining 30 mm Thick Shipbuilding Steel Plates EH36 Using a Process Combination of Hybrid Laser Arc Welding and Submerged Arc Welding N2 - This article presents a cost-effective and reliable method for welding 30 mm thick sheets of shipbuilding steel EH36. The method proposes to perform butt welding in a two-run technique using hybrid laser arc welding (HLAW) and submerged arc welding (SAW). The HLAW is performed as a partial penetration weld with a penetration depth of approximately 25 mm. The SAWis carried out as a second run on the opposite side. With a SAWpenetration depth of 8 mm, the weld cross-section is closed with the reliable intersection of both passes. The advantages of the proposed welding method are: no need for forming of the HLAW root; the SAW pass can effectively eliminate pores in the HLAWroot; the high stability of the welding process regarding the preparation quality of the weld edges. Plasma cut edges can be welded without lack of fusion defects. The weld quality achieved is confirmed by destructive tests. KW - Shipbuilding steel KW - Hybrid laser arc welding KW - Submerged arc welding KW - Hardness KW - Bending test KW - Two-run welding technique KW - Microstructure PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-556090 DO - https://doi.org/10.3390/jmmp6040084 SN - 2504-4494 VL - 6 IS - 4 SP - 1 EP - 11 PB - MDPI CY - Basel AN - OPUS4-55609 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marko, A. A1 - Bähring, S. A1 - Raute, J. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Quality Prediction in Directed Energy Deposition Using Artificial Neural Networks Based on Process Signals N2 - The Directed Energy Deposition process is used in a wide range of applications including the repair, coating or modification of existing structures and the additive manufacturing of individual parts. As the process is frequently applied in the aerospace industry, the requirements for quality assurance are extremely high. Therefore, more and more sensor systems are being implemented for process monitoring. To evaluate the generated data, suitable methods must be developed. A solution, in this context, was the application of artificial neural networks (ANNs). This article demonstrates how measurement data can be used as input data for ANNs. The measurement data were generated using a pyrometer, an emission spectrometer, a camera (Charge-Coupled Device) and a laser scanner. First, a concept for the extraction of relevant features from dynamic measurement data series was presented. The developed method was then applied to generate a data set for the quality prediction of various geometries, including weld beads, coatings and cubes. The results were compared to ANNs trained with process parameters such as laser power, scan speed and powder mass flow. It was shown that the use of measurement data provides additional value. Neural networks trained with measurement data achieve significantly higher prediction accuracy, especially for more complex geometries. KW - DED KW - Artificial neural network KW - Data preparation KW - Quality assurance KW - Process monitoring PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-555063 DO - https://doi.org/10.3390/app12083955 SN - 2076-3417 VL - 12 IS - 8 SP - 1 EP - 13 PB - MDPI CY - Basel AN - OPUS4-55506 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid Laser-Arc Welding of Thick-Walled, Closed, Circumferential Pipe Welds N2 - The application of hybrid laser-arc welding (HLAW) for joining closed circumferential welds is a challenge due to the high risk of forming a defective overlap area with a shrinkage void or solidification cracks in the material thickness. A series of HLAW experiments were performed to understand the development of a faulty overlap area when closing the circumferential weld. Welding trials on flat specimens and pipe segments were supported by numerical analyses in which the thermomechanical behavior of the welds in the overlap area was investigated. Different process control strategies were tested, including variations in defocusing levels and the overlap length. The newly developed HLAW head, including laser optics with a motor-driven collimation system, made it possible to defocus the laser beam during welding without disturbing the stability of the welding process. High-level defocusing of the laser beam of more than 40 mm relative to the specimen surface with a resulting beam diameter of > 2.9 mm, and in combination with a short overlap length of 15 mm, was promising with respect to the formation of a desired cup-shaped weld profile that is resistant to solidification cracks. KW - Hybrid Laser-Arc Welding KW - Thick-Walled Steel KW - High-Power Welding KW - Crater KW - Pipe Welding PY - 2022 DO - https://doi.org/10.29391/2022.101.002 SN - 0043-2296 VL - 101 IS - 1 SP - 15 EP - 26 PB - American Welding Society CY - New York, NY AN - OPUS4-55508 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Straße, Anne A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael ED - Schmidt, M. ED - Vollertsen, F. ED - Schmidt, B. M. T1 - Preliminary study to investigate the applicability of optical strain measurement technique for the detection of hot cracks in laser metal deposited layers N2 - Laser metal deposition (LMD) as an additive manufacturing technique became increasingly important in recent years and thus the demand for component safety. This is the reason, for the need for reliable in-situ defect detection techniques. For laser beam weld seams an optical measurement technique based on an optical flow algorithm was successfully used to define the critical straining conditions that lead to hot cracking. This algorithm was adapted for bead-on-plate weld seams on LMD deposited layers of IN718 alloy while performing external strain on the specimen in an externally loaded hot cacking test facility. The resulting transversal hot cracks along the weld seam were localized via X-Ray inspection and the type of cracking confirmed by Scanning Electron Microscopy (SEM). The strain distribution was measured in the vicinity of the solidification front and correlated to the detected hot cracks. Based on the results this technique could be adopted for LMD experiments. T2 - 12th CIRP Conference on Photonic Technologies [LANE 2022] CY - Fürth, Germany DA - 04.09.2022 KW - Laser Metal Deposition (LMD) KW - Strain measurement KW - Optical flow KW - Critical strain PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-556445 DO - https://doi.org/10.1016/j.procir.2022.08.034 VL - 111 SP - 335 EP - 339 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-55644 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Straße, Anne A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Study on Duplex Stainless Steel Powder Compositions forthe Coating of Thick Plates for Laser Beam Welding N2 - Duplex stainless steels combine the positive properties of its two phases, austenite and ferrite. Due to its good corrosion resistance, high tensile strength and good ductility it has multiple applications. But laser beam welding of duplex steels changes the balanced phase distribution in favor of ferrite. This results in a higher vulnerability to corrosion and a lower ductility. In this study different powder combinations consisting of duplex and nickel for coating layers by laser metal deposition are investigated. Afterwards laser tracks are welded, and the temperature cycles measured. The ferrite content of the tracks are analyzed by feritscope, metallographic analysis and Electron Backscatter Diffraction. The goal is the development of a powder mixture allowing for a duplex microstructure in a two-step process, where firstly the edges of the weld partners are coated with the powder mixture by LMD and secondly those edges are laser beam welded. The powder mixture identified by the pretests is tested in the two-step process and analyzed by metallographic analysis, energy dispersive X-ray spectroscopy and Vickers hardness tests. The resulting weld seams show a balanced duplex microstructure with a homogenous nickel distribution and a hardness of the weld seam similar to the base material. KW - Duplex AISI 2205 KW - Stainless Steel KW - Laser Beam Welding KW - Nickel KW - Laser Metal Deposition PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-554663 DO - https://doi.org/10.1002/adem.202101327 SN - 1438-1656 VL - 24 IS - 6 SP - 1 EP - 11 PB - Wiley-VCH CY - Weinheim AN - OPUS4-55466 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Meng, Xiangmeng A1 - Artinov, Antoni A1 - Rethmeier, Michael T1 - Evaluation of narrowed weld pool shapes and their effect on resulting potential defects during deep penetration laser beam welding N2 - This study presents mechanisms of the evolution of a narrowed region in the weld pool center during deep penetration laser beam welding. In numerous numerical studies presented in this study, it was also found that the local reduction of the weld pool size can cause detrimental effects on the melt flow behavior and the resulting properties of the welds. A particularly large influence of this effect was identified in three aspects. First, the local variation of the solidification sequence of the weld pool causes an increase in the hot-cracking susceptibility due to a locally delayed solidification. Second, it was proven that a change in the local length and width of the weld pool is associated with an adverse impact on the potential flow routes of the molten material that induces stronger local variations of its solidification. Thus, the element mixing, e.g., during the welding with filler materials, is blocked. This leads to a non-homogeneous chemical composition of the final weld and can cause undesired effects on the final material properties. Finally, another observed effect is related to the reduced ability of process pores to reach the top surface. As this type of porosity is usually produced around the keyhole tip, the change of the fluid flow regime above this area plays a significant role in determining the final path of the pores until the premature solidification in the middle of the weld pool captures them. This study summarizes mainly numerical results that were supported by selected experimental validation results. KW - Weld pool shape KW - Laser beam welding KW - Solidification KW - Porosity KW - Numerical process simulation PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-557759 DO - https://doi.org/10.2351/7.0000733 SN - 1042-346X VL - 34 IS - 4 SP - 1 EP - 7 PB - Laser Institute of America CY - Orlando, Fla. AN - OPUS4-55775 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Life Cycle Assessment of Fusion Welding Processes - A Case Study of Resistance Spot Welding Versus Laser Beam Welding N2 - The high amount of resource consumption of fusion welding processes offers the potential to reduce their environmental impact. While the driving forces are known froma qualitative perspective, the quantitative assessment of the crucial parameters is not a trivial task. Therefore, herein, a welding-specific methodology to utilize life cycle assessment as a tool for evaluating the environmental impact of fusion welding processes is presented. In this context, two welding processes, resistance spot welding and laser beam welding, are analyzed for two different use cases. These comprise the welding of shear test specimens and a cap profile made of electrogalvanized sheets of DC 05þ ZE (1.0312) as representative of an automotive application. For both welding processes, the main influences on the resulting environmental impact categories are evaluated and compared. The requirements for ecological efficient welding processes are discussed and implemented. KW - Resistance spot welding KW - Carbon dioxide footprint KW - Environmental impact categories KW - Laser beam welding KW - Life cycle assessment PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-566458 DO - https://doi.org/10.1002/adem.202101343 SN - 1438-1656 VL - 24 IS - 6 SP - 1 EP - 14 PB - Wiley-VCH CY - Weinheim AN - OPUS4-56645 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - El-Batahgy, A.M. T1 - Laser and hybrid laser-arc welding of cryogenic 9 % NI Steel N2 - Heat treated 9%Ni steel is considered the most suitable and economic material for construction of large-size liquefied natural gas (LNG) storage tanks which operate at cryogenic temperatures (-196°C). Strength above 700 MPa as well as a minimum impact value of 60 J are required to ensure reliable operation of the LNG tanks at operating temperature. Conventional arc welding processes, including shielded metal arc welding, gas metal arc welding, gas tungsten arc welding and submerged arc welding, are currently used in construction of LNG tanks. Ni based filler wire is the preferred filler metal of choice in LNG tank construction. The main problem with this choice is the lower mechanical properties, particularly tensile strength of the weld metal. To compensate, the wall thickness needs to be excessively thick to ensure the strength of the welded structures. Ni based filler material is expensive and a large quantity is needed to fill the multi-pass weld grooves. These factors significantly add to the cost in the fabrication of LNG storage tanks. For these reasons, exploration of new welding technologies is a priority. A big potential can be seen in laser based welding techniques. Laser beam welding results in much smaller fusion zone with chemical composition and mechanical properties similar to that of the base material. Laser welding is a much faster process and allows for a joint geometry which requires less filler material and fewer welding passes. The advantages of laser welding can help to overcome the problems pointed out above. Trials of autogenous laser welding, laser cold-wire welding and hybrid laser-arc welding conducted on the 9%Ni steel are presented in this paper. Chemical composition of the weld metal as well as effects of welding parameters on the weld formation, microstructure and tensile strength is discussed. Filler wire penetration depth as well as character of its distribution in the narrow laser welds was examined using EPMA - electron probe microanalysis. KW - hardness KW - cryogenic steel KW - laser welding KW - microstructure KW - tensile strength PY - 2016 UR - http://gns.mephi.ru/sites/default/files/journal/file/en.2016.1-4.pdf SN - 2499-9733 VL - 1 IS - 18 SP - 34 EP - 45 PB - Research Nuclear University MEPHl CY - Moskau, Russia AN - OPUS4-36553 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frei, J. A1 - Suwala, H. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Bestimmung der Rissanfälligkeit von hochfesten Stählen beim Widerstandspunktschweißen N2 - Die stetig zunehmenden Anforderungen an Kraftstoffverbrauch, Schadstoffemission, sowie passive Sicherheit haben die Automobilindustrie vor Herausforderungen gestellt, die nur durch einen konsequenten Einsatz moderner hochfester Stahlwerkstoffe zu bewältigen sind. Obgleich eine generelle Eignung dieser Stähle für das Widerstandspunktschweißen (WPS) gegeben ist, kann es durch verschiedene externe Einflüsse im betrieblichen Umfeld zur Rissbildung in der Schweißverbindung kommen. Der Einfluss dieser Risse auf die mechanischen Eigenschaften ist derzeit nicht hinreichend genau erfasst, so dass häufig die Vorgabe einer rissfreien Schweißverbindung besteht. Die Kenntnis der Rissanfälligkeit der verarbeiteten Materialkombinationen sowie von ungünstigen Schweißparametern ist daher für viele Unternehmen von erheblicher wirtschaftlicher Bedeutung. Im Rahmen des FOSTA Projekts P921 „Entwicklung eines Verfahrens zur Bestimmung der Rissanfälligkeit von hochfesten Stählen beim Widerstandspunktschweißen“ wurde ein Ansatz zur Bestimmung der Rissanfälligkeit von WPS-Verbindungen hochfester Stähle entwickelt. Mittels einer hydraulischen Vorrichtung unter Zugbelastung wurden geschweißte, rissbehaftete Proben optisch ausgewertet. Das Verfahren ist geeignet, um ein Werkstoffranking bezüglich der Rissanfälligkeit beim Widerstandspunktschweißen für Werkstoffe aufzustellen. KW - Widerstandspunktschweißen KW - Werkstoffranking KW - Rissanfälligkeit KW - hochfeste Stähle KW - Liquid Metal Embrittlement KW - Lötrissigkeit PY - 2016 DO - https://doi.org/10.3139/120.110904 VL - 58 IS - 7-8 SP - 612 EP - 616 PB - Carl Hanser Verlag CY - München AN - OPUS4-37161 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Neubert, Sebastian A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Experimental determination of TRIP parameter K for mild- and high strength low alloy steels and a super martensitic filler material N2 - A combined experimental numerical approach is applied to determine the transformation induced plasticity (TRIP)-parameter K for different strength low-alloy steels of grade S355J2+N and S960QL as well as the super martensitic filler CN13-4-IG containing 13 wt% chromium and 4 wt% nickel. The thermo-physical analyses were conducted using a Gleeble® 3500 facility. The thermal histories of the specimens to be tested were extracted from corresponding simulations of a real gas metal arc weldment. In contrast to common TRIP-experiments which are based on complex specimens a simple flat specimen was utilized together with an engineering evaluation method. The evaluation method was validated with literature values for the TRIP-parameter. It could be shown that the proposed approach enables a correct description of the TRIP behavior. KW - Transformation induced plasticity (TRIP) KW - Phase transformation KW - High-strength low-alloy steel KW - Super martensitic filler material KW - Thermo physical simulation KW - Gleeble experiments PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-367297 DO - https://doi.org/10.1186/s40064-016-2474-0 VL - 5 IS - 575 SP - Paper 754, 1 EP - 16 PB - SpringerPlus AN - OPUS4-36729 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Neubert, S. A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Influence of non-uniform martensitic transformation on residual stresses and distortion of GMA-welding N2 - A combined experimental and numerical approach is applied for a numerical analysis of the non-uniform martensitic transformation kinetic on welding residual stresses and distortion of a single pass weld. The (γ → α)-transformation kinetic within the weld pool region is governed by a non-uniform distribution of the elements chromium and nickel. The single-pass weld was performed by use of the low-alloyed high-strength steel S960QL with the high-alloyed high-strength filler wire CN 13/4-IG®. A thermo-mechanical FE model of the welding process was experimentally validated against temperature field, solid phase distribution, transformation behaviour, X-Ray stress measurements and transient optical distortion measurements. The experimentally determined and calculated weld residual stresses and transient distortion are in good agreement. It can be shown that the change on the (γ → α)-transformation kinetic driven by the inhomogeneous distribution of the chemical contents causes a strong influence on the weld residual stresses within the volume of the weld pool, which could promote crack propagation within the solidified weld pool by use of high-alloyed filler materials. Furthermore, a significant influence on the development of the transient welding distortion is visible. This influence should be respected during numerically calculation of welding distortion in case of multi-pass welding using interpass temperatures and high-alloyed filler materials. KW - Welding residual stresses KW - FEA KW - Welding simulation KW - Dissimilar welding KW - Transformable steels PY - 2017 DO - https://doi.org/10.1016/j.jcsr.2016.08.020 SN - 0143-974X SN - 1873-5983 VL - 128 SP - 193 EP - 200 PB - Elsevier Ltd. AN - OPUS4-37276 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Numerical simulation of solidification crack formation during laser beam welding of austenitic stainless steels under external load N2 - Solidification cracking phenomena taking place under controlled tensile weldability (CTW) test conditions have already been investigated both experimentally and numerically via FEA in order to get a better understanding of the mechanisms of hot crack formation during laser beam welding of austenitic steel grades. This paper develops a threedimensional finite element model employing the contact element technique to simulate the formation and propagation of solidification cracks during laser full penetration welding of fully austenitic stainless steel 1.4376. During the experimental procedure, the resulting strain and displacement directed to the laser beam in the close vicinity of the weld pool was measured at the surface of the workpiece using a digital image correlation (DIC) technique with an external diode laser as an illuminating source. Local strain fields, global loads and crack lengths predicted by the model are in good agreement with those observed in experiments. KW - Solidification cracking KW - Finite element analysis KW - Imaging KW - Laser welding KW - Austenitic stainless steels PY - 2016 DO - https://doi.org/10.1007/s40194-016-0357-1 SN - 0043-2288 SN - 1878-6669 VL - 60 IS - 5 SP - 1001 EP - 1008 PB - Springer CY - Berlin, Heidelberg AN - OPUS4-37287 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frei, J. A1 - Rethmeier, Michael A1 - Alexandrov, B. T. T1 - Low heat input gas metal arc welding for dissimilar metal weld overlays part I: the heat-affected zone N2 - Dissimilar metal weld overlays of nickel base alloys on low alloy steel components are commonly used in the oil and gas, petro-chemical, and power generation industries to provide corrosion and oxidation resistance in a wide range of service environments and temperatures. Traditionally, weld overlays are produced using cold or hot wire gas tungsten arc welding (GTAW). Potential advantages of cold metal Transfer (CMT) welding, a low heat input gas metal arc welding process, over the conventional GTAW in production of weld overlays were evaluated. Metallurgical characterization was performed on CMT overlays of Alloy 625 filler metal on Grade 11 and Grade 22 steels. Significant grain refinement was found in the high temperature HAZ compared to the traditional coarse-grained HAZ in arc welding. Evidences of incomplete carbide dissolution, limited carbon diffusion, and incomplete transformation to austenite were also found. These phenomena were related to high heating and cooling rates and short dwell times of the high-temperature HAZ in austenitic state. Tempering effects in the steel HAZ were identified, showing a potential for development of CMT temperbead procedures. Based on the results of this study, the steel HAZ regions in CMT overlays were classified as high-temperature HAZ and intercritical HAZ. KW - Clad steels KW - Nickel alloys KW - Low alloy steels KW - GMA surfacing KW - DIP transfer KW - Coarse-grained heat-affected zone KW - Microstructure PY - 2016 DO - https://doi.org/10.1007/s40194-016-0306-z SN - 0043-2288 SN - 1878-6669 VL - 60 IS - 3 SP - 459 EP - 473 PB - Springer CY - Heidelberg, Germany AN - OPUS4-36377 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schempp, Philipp A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Grain structure in aluminium TIG welds N2 - The microstructure of a fusion weld has great influences on the susceptibility of the base material to hot cracking and on the mechanical properties of the weld. Small, globulitic grains are necessary for increased strength, ductility and toughness and for a low inclination to hot cracking instead of large, oblong grains. This study reports on the factors which exert the main influences on such grain refinement in the weld. Thus, the influences of the thermal conditions, the chemical composition of the weld metal and the number and type of solidification nuclei on the microstructure were classified for the TIG welding of three different aluminium alloys. PY - 2014 SN - 1612-3433 VL - 13 IS - 3 SP - 177 EP - 181 PB - DVS - German Welding Society CY - Düsseldorf AN - OPUS4-30806 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schempp, Philipp A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Kornstruktur in Aluminium-WIG-Schweißnähten N2 - Die Mikrostruktur einer Schmelzschweißnaht hat großen Einfluss auf die Heißrissanfälligkeit des Grundwerkstoffs und die mechanischen Eigenschaften der Schweißnaht. Für eine erhöhte Festigkeit, Duktilität und Zähigkeit und eine geringe Heißrissneigung sind anstatt großer, länglicher Körner kleine, globulitische Körner notwendig. Diese Studie berichtet über die Faktoren, die eine solche Schweißnahtkornfeinung hauptsächlich beeinflussen. So wurde für das Wolfram-Intertgasschweißen (WIG-Schweißen) von drei verschiedenen Aluminiumlegierungen der Einfluss der thermischen Bedingungen, der chemischen Zusammensetzung des Schweißguts und der Anzahl und Art der Erstarrungskeime auf die Mikrostruktur klassifiziert.--------------------------------------------------------------------------------------------------------------------------------------------------------------------------- The microstructure of fusion welds has a significant influence on the susceptibility of the base material to hot cracking and on the mechanical properties of the weld. Small, globulitic grains are important for increased strength, ductility and toughness and for a low susceptibility to solidification cracking instead of large, columnar grains. This study shows the main influences on such weld metal grain refinement. Therefore, the influence of thermal conditions, the chemical composition of the weld metal and the number and type of solidification nuclei on the microstructure were classified for the TIG welding of three different aluminium alloys. KW - Aluminium/Aluminiumlegierungen KW - Festigkeit KW - Metallurgische Fragen KW - Rissbildung KW - Werkstofffragen PY - 2014 SN - 0036-7184 VL - 66 IS - 3 SP - 120 EP - 125 PB - Verl. für Schweißen u. Verwandte Verfahren, DVS-Verl. CY - Düsseldorf AN - OPUS4-30717 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Polami, S.M. A1 - Reinhardt, R. A1 - Rethmeier, Michael A1 - Schmid, A. T1 - Joint-site structure friction welding method as a tool for drive pinion light weighting in heavy-duty trucks N2 - To satisfy the applied compressive stresses of friction welded drive pinion fabricated by using the joint-site structure (JSS) method, three different variants were followed: (A) the initial design with two joints was carried out. Two different burn-off lengths were examined for this variant. (B) The optimum burn-off length was considered for only one weld zone. (C) The weld zone was moved radially from the initial location and two different gap sizes were compared. The smallest gap size for the third variant led to the largest weld length. The lack of structural welding defects for this variant was assessed by ultrasonic testing. Hardness of the material after friction welding (FW) was correlated to the Continuous Cooling Transformation (CCT) diagram of the used materials and revealed the phase/microstructure transformation of the material. The simulated applied stresses on the optimized friction welded design of the drive pinion showed suitable results. The new drive pinion friction welded by the JSS method reduced the weight of the component by approx. 14%. KW - Friction welding KW - Joint-site structure KW - Drive pinion KW - Lightweight design PY - 2014 DO - https://doi.org/10.1016/j.jmatprotec.2014.03.027 SN - 0924-0136 SN - 1873-4774 VL - 214 IS - 9 SP - 1921 EP - 1927 PB - Elsevier CY - Amsterdam AN - OPUS4-30718 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 - Müller, A. A1 - Goecke, S.F. A1 - Rethmeier, Michael T1 - Laser beam oscillation for fillet welding N2 - In today’s automotive frame-and-body construction, laser welds are typically carried out as square butt welds in lap joints. These welds are increasingly produced by remote laser welding optics with working distances of 500 mm and more. This enables simple path programming because clamping devices are traversed over and therefore low cycle times with improved productivity is achieved. However, workpiece tolerances lead to part displacements and varying joint positions over time. These displacements have to be acted against by appropriate flange length that contain for positioning deviations. Using this concept, aspired light-weight optimisations, e.g. reducing flange length, are difficult to achieve. By using seam tracking sensors, part tolerances are automatically detected and counteracted for. In addition, joint edge detection allows constructive changes on the type of weld. Fillet welds reduce flange lengths', improve force flow and open up possibilities for visual quality monitoring. Apart from that, vertical displacements in the form of height tolerances still occur. This needs consideration by adapting the set of welding parameter to the current welding situation. In this respect, one main welding parameter is the lateral beam offset to the upper sheet. Since body-in-white welding applications mainly comprise of zinc-coated steel sheets, special requirements for the welding process are given. Especially zero-gap-welding and welding of joints with gaps larger than 0.2 mm are critical. Using a laser beam oscillation process can stabilise these situations. Approaches to finding parameter sets are presented in this paper. KW - Laser beams KW - Welding KW - Fillet welds KW - Gap KW - Process procedures KW - Monitoring systems PY - 2014 DO - https://doi.org/10.1007/s40194-014-0165-4 SN - 0043-2288 SN - 1878-6669 VL - 58 IS - 6 SP - 865 EP - 872 PB - Springer CY - Oxford AN - OPUS4-32075 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Su, H. A1 - Wu, Chuan Song A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Thermal energy generation and distribution in friction stir welding of aluminum alloys N2 - The accurate prediction of the thermal energy generation and distribution in friction stir welding process is of great significance for the optimization of the process parameters and the understanding of the underlying mechanisms. In this study, a new method of integrative calculation and measurement is proposed to obtain the more reasonable values of the frictional coefficient and the slip rate, which are both used to characterize the heat generation rate at the tool-workpiece contact interfaces. A three-dimensional model is established to fully couple the energy generation, heat transfer and material flow in friction stir welding of aluminum alloys. The energy produced by both interfacial friction and plastic deformation are taken into consideration. The analysis accuracy of the thermal energy generation and distribution is improved, and the distribution features of thermal energy density in the vicinity of the tool are elucidated. The predicted peak temperature values at some locations are in agreement with the experimentally measured ones. KW - Thermal energy generation KW - Energy density distribution KW - Heat transfer KW - Material flow KW - Friction stir welding PY - 2014 DO - https://doi.org/10.1016/j.energy.2014.09.045 SN - 0360-5442 VL - 77 SP - 720 EP - 731 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-32076 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 - Welding is one of the most critical operations for the construction of reliable metal structures in everything from ships to reactor vessels. When welds fail, often the entire structure fails, and expectations on weld quality have never been higher. Any process that uses a localized heat source, such as welding, is likely to result in some distortion. The welding process of very thick metal components is not inherently stable and is barely controllable without external forces. KW - Electromagnetic weld pool control KW - Laser beam weliding KW - Marangoni effect PY - 2014 VL - 2013-2014 SP - 30 EP - 32 AN - OPUS4-30338 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sohail, M. A1 - Han, S.-W. A1 - Na, S.-J. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Characteristics of weld pool behavior in laser welding with various power inputs N2 - This paper investigates the numerical simulations of multi-kilowatt disk laser and fiber laser welding, ranging from 6 to 18 kW to study the behavior of molten pool in 20-mm-thick steel plate by using Volume-Of-Fluid (VOF) method and several mathematical models like Gaussian heat source, recoil pressure, Marangoni flow, buoyancy force, and additional shear stress and heat source due to the metallic vapor. Vortex flow pattern is observed for higher laser power except for 6-kW case, and the higher the laser power, the bigger the vortex flow pattern. Welding speed has an influence on molten pool in terms of depth of penetration and size of molten pool, but overall shape of molten pool remains the same. The reasons for the vortex flow pattern in high-power laser welding are the absorption of more energy at the bottom of keyhole, which promotes more liquid metal at the bottom, while for lower power with lower speed, the melt formation is more uniform in the thickness direction and most of the molten metal in the lower part of keyhole reaches the top of molten pool, and consequently, no vortex flow pattern is observed in the keyhole bottom. KW - Laser welding KW - Mathematical models KW - Simulating KW - Molten pool KW - Flow PY - 2014 DO - https://doi.org/10.1007/s40194-014-0112-4 SN - 0043-2288 SN - 1878-6669 VL - 58 IS - 3 SP - 269 EP - 277 PB - Springer CY - Oxford AN - OPUS4-30644 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Avilov, Vjaceslav A1 - Graf, J. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Anwendung von AC-Magnetfeldern zur Verbesserung der Nahtqualität laserstrahlgeschweißter Aluminiumverbindungen N2 - Im Rahmen eines AiF-Forschungsvorhabens wurde die Beeinflussung des Schweißprozesses mittels generierter Wechselstrom-Magnetfelder (ACMagnetfelder) beim Laserstrahlschweißen von Aluminiumlegierungen untersucht. Das vorrangige Augenmerk galt hierbei der Entfernung von Poren sowie der Stabilisierung der Schweißnahtoberfläche zur Vermeidung von rauen Schweißnähten. Das Schweißen mit Einsatz des AC-Magneten erzeugte im Vergleich zu den Referenznähten deutlich flachere Schweißnähte mit reduzierter Porenanzahl, die typische Schuppenstruktur wurde unterdrückt. Das Magnetfeld bewirkte bei entsprechenden Parametern der magnetischen Flussdichte und der Frequenz eine Halbierung der Rauigkeit der Schweißnahtoberfläche. Neben der Oberflächenberuhigung wurde auch die Verteilung von Poren in der Schmelze beeinflusst. Es konnte nachgewiesen werden, dass bei einer geeigneten Auswahl der Parameter von AC-Magnetfeldern die Porositätsanteile in der Schweißnaht auf ein Zehntel gegenüber den Referenzschweißnähten reduziert werden können.----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Within the framework of an AiF research project, investigations were conducted into the influences exerted on the welding process using generated alternating current (AC) magnetic fields during the laser beam welding of aluminium alloys. In this respect, attention was principally paid to removing pores and to stabilising the weld surface in order to avoid rough welds. In comparison with the reference welds, welding utilising the AC magnet produced considerably flatter welds with a reduced number of pores and the typical ripple structure was suppressed. With corresponding parameters for the magnetic flux density and the frequency, the roughness of the weld surface was halved using the magnetic field. In addition to the surface stabilisation, influences were also exerted on the distribution of pores in the molten metal. It was possible to prove that, by selecting suitable parameters for AC magnetic fields, the porosity proportions in the weld can be reduced to one tenth of those in the reference welds. KW - Aluminium KW - Laserstrahlschweißen KW - Magnetfelder KW - Poren KW - Schweißnahtimperfektionen KW - Werkstofffragen PY - 2014 SN - 0036-7184 VL - 66 IS - 9 SP - 524 EP - 529 PB - Verl. für Schweißen u. Verwandte Verfahren, DVS-Verl. CY - Düsseldorf AN - OPUS4-31441 LA - deu 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 - Ebert-Spiegel, M. A1 - Goecke, S.-F. A1 - Rethmeier, Michael T1 - Efficient gap filling in MAG welding using optical sensors N2 - MAG welding is widely used for thin sheet metal applications such as car body structures due to its ability to tolerate a fair amount of deviation of the components from the ideal shape. In MAG welding, the process window is sufficiently large to accommodate the expected component tolerances. In practice, however, quality control is an issue since most welds are produced with parameters outside of the optimum range, especially in the case of automated MAG welding. To ensure best performance, a robust real-time control law is needed that adapts critical process parameters to the changing conditions, most notably the variation in gap height. Here, the gap-dependent adaptive control algorithm for the deposition of filler material and the related energy input comes into play. With an optical sensor that is mounted in front of the torch, the system measures the actual position of the two components in real-time during the entire welding process and the controller adapts the relevant parameters accordingly using a dynamic process model. This optimization ensures that only the required filler material is used and the associated energy input is tightly controlled to assure best quality even in a fully automated welding process. KW - MAG welding KW - Sheet KW - Robots KW - Automation KW - Sensors KW - Adaptive control PY - 2014 DO - https://doi.org/10.1007/s40194-014-0145-8 SN - 0043-2288 SN - 1878-6669 VL - 58 IS - 5 SP - 637 EP - 647 PB - Springer CY - Oxford AN - OPUS4-31438 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schneider, André A1 - Gumenyuk, Andrey A1 - Lammers, Marco A1 - Malletschek, A. A1 - Rethmeier, Michael T1 - Laser beam welding of thick titanium sheets in the field of marine technology N2 - The ever larger requirements of the material selection in the range of maritime industry necessitate the application of high-tech materials. Titanium because of its excellent mechanical properties at low weight is an attractive alternative for the construction of ships. The goal of this investigation was to design a welding method for joining samples of 16 mm thick Ti3Al2.5 V. The welding experiments with a 20 kW Yb-fiber laser source and varying combinations of parameters were intended to qualify the laser beam welding process. The welding results were analyzed by non-destructive and destructive testing. In addition, the welding tests were recorded with two high-speed cameras to observe the weld pool and the vapor plume. The evaluation of the high-speed images in correlation with the results of non-destructive testing shows, that a significant improvement of process stability and weld quality can be achieved by the suppression of the vapor plume. KW - Titanium alloy KW - Maritime industry KW - Vapor plume KW - Laser beam welding KW - Ti3Al2.5V PY - 2014 DO - https://doi.org/10.1016/j.phpro.2014.08.046 SN - 1875-3892 VL - 56 SP - 582 EP - 590 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-31439 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 - Experimental and numerical investigation of an electromagnetic weld pool control for laser beam welding N2 - The objective of this study was to investigate the influence of externally applied magnetic fields on the weld quality in laser beam welding. The optimization of the process parameters was performed using the results of computer simulations. Welding tests were performed with up to 20 kW laser beam power. It was shown that the AC magnet with 3 kW power supply allows for a prevention of the gravity drop-out for full penetration welding of 20 mm thick stainless steel plates. For partial penetration welding it was shown that an0.5 T DC magnetic field is enough for a suppression of convective flows in the weld pool. Partial penetration welding tests with 4 kW beam power showed that the application of AC magnetic fields can reduce weld porosity by a factor of 10 compared to the reference joints. The weld surface roughness was improved by 50%. KW - Laser beam welding KW - Electromagnetic weld pool support KW - Hartmann effect KW - Electromagnetic rectification PY - 2014 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-314405 DO - https://doi.org/10.1016/j.phpro.2014.08.006 SN - 1875-3892 VL - 56 SP - 515 EP - 524 PB - Elsevier B.V. CY - Amsterdam [u.a.] AN - OPUS4-31440 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kannengießer, Thomas A1 - Kromm, Arne A1 - Rethmeier, Michael A1 - Gibmeier, J. A1 - Genzel, C. T1 - Residual stresses and in-situ measurement of phase transformation in low transformation temperature (LTT) welding materials PY - 2009 SN - 1097-0002 SN - 0069-8490 SN - 0376-0308 VL - 52 SP - 755 EP - 762 CY - Newtown Square, Pa., USA AN - OPUS4-19817 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pittner, Andreas A1 - Schwenk, Christopher A1 - Rethmeier, Michael A1 - Weiß, D. T1 - Automated generation of temperature fields for numerical welding simulation KW - Welding simulation KW - Temperature field generation KW - Optimization KW - Neural networks PY - 2009 SN - 0288-4771 VL - 27 IS - 2 SP - 219 EP - 224 CY - Tokyo, Japan AN - OPUS4-19826 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weber, Gert A1 - Thommes, H. A1 - Gaul, Holger A1 - Hahn, O. A1 - Rethmeier, Michael T1 - Resistance spot welding and weldbonding of advanced high strength steels KW - Resistance spot welding KW - High strength steel KW - Weldbonding KW - Widerstandspunktschweißen KW - Hochfester Stahl KW - Punktschweißkleben PY - 2010 DO - https://doi.org/10.1002/mawe.201000687 SN - 0933-5137 SN - 1521-4052 VL - 41 IS - 11 SP - 931 EP - 939 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-22948 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 - Rethmeier, Michael A1 - Gook, Sergej A1 - Lammers, Marco A1 - Gumenyuk, Andrey T1 - Laser-Hybrid Welding of Thick Plates up to 32 mm Using a 20 kW Fibre Laser N2 - New brilliant high-power lasers such as disc laser and fibre laser open up new fields of applications for laser-hybrid welding, e.g. power generation, shipbuilding and pipeline construction. For the use of laser-hybrid welding in pipe laying, insensibility towards tolerances and the possibility of orbital welding are very important factors in addition to the weld seam quality. Within the scope of a basic research project, first promising results for laser-hybrid welding of thick materials could be demonstrated. As base material, the typical pipeline steel API 5L X65 was selected. With the help of a 20 kW fibre laser in combination with an arc-welding process it was possible to produce high-quality welds in plates of up to 20 mm thickness in a single pass and of up to 32 mm in three to five passes, both welded in position PA. Various joint preparations were examined to weld 20 mm thick plates in one pass. Besides different welding positions, gap bridgeability and misalignment were studied. Results for microhardness and Charpy toughness are presented to proof the applicability of laser-hybrid welding for joining in pipe laying. KW - Laser beam welding KW - High power fibre laser KW - Laser-hybrid welding KW - Tick plates KW - Pipe laying PY - 2009 DO - https://doi.org/10.2207/qjjws.27.74s SN - 0288-4771 VL - 27 IS - 2 SP - 74 EP - 79 CY - Tokyo, Japan AN - OPUS4-20345 LA - eng 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 - 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 - Gaul, Holger A1 - Weber, Gert A1 - Rethmeier, Michael T1 - Influence of HAZ cracks on fatigue resistance of resistance spot welded joints made of advanced high strength steels N2 - A method is reported with which heat affected zone (HAZ) cracks in a specific region of spot welded joints, made of advanced high strength steels, could be realised. The influence of HAZ cracks on the fatigue behaviour, which is the focus of the contribution, was studied by evaluating the stiffness characteristics as a function of the number of cycles N in comparison with crack-free specimens, i.e. by analysing HAZ and fatigue cracks on the specimen surface and the surface of fatigue fractures containing beach marks. It was found that the fatigue cracks are not initiated at the HAZ cracks. The number of cycles to failure Nf is not significantly reduced for specimens with HAZ cracks. Overall, the examinations did not reveal any influence of HAZ cracks on the fatigue strength of resistance spot welded joints. KW - Discontinuities KW - AHSS KW - HAZ crack KW - Spot welding KW - Advanced high strength steels KW - Fatigue PY - 2011 DO - https://doi.org/10.1179/1362171810Y.0000000031 SN - 1362-1718 SN - 1743-2936 VL - 16 IS - 5 SP - 440 EP - 445 PB - Maney CY - London AN - OPUS4-24214 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 - Karkhin, Victor A1 - Pittner, Andreas A1 - Schwenk, Christopher A1 - Rethmeier, Michael T1 - Simulation of inverse heat conduction problems in fusion welding with extended analytical heat source models N2 - The paper presents bounded volume heat sources and the corresponding functional-analytical expressions for the temperature field. The power density distributions considered here are normal, exponential and parabolic. The sources model real heat sources like the welding arc, laser beam, electron beam, etc., the convection in the weld pool as well as the latent heat due to fusion and solidification. The parameters of the heat source models are unknown a priori and have to be evaluated by solving an inverse heat conduction problem. The functional-analytical technique for calculating 3D temperature fields in butt welding is developed. The proposed technique makes it possible to reduce considerably the total time for data input and solution. It is demonstrated with an example of laser beam welding of steel plates. KW - Laser beam welding KW - Volume heat source KW - Functional-analytical solution KW - Inverse modelling PY - 2011 DO - https://doi.org/10.1007/s11706-011-0137-1 SN - 2095-025X SN - 2095-0268 VL - 5 IS - 2 SP - 119 EP - 125 PB - Springer CY - Secaucus, N.J. AN - OPUS4-24164 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 - 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 - 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 - 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 - 0005-111x SN - 0005-2302 VL - 689 IS - 9 SP - 5 EP - 13 CY - Kiev, Ukraine AN - OPUS4-22979 LA - rus AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Quiroz, V. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Saldabilita di lamiere in acciaio inossidabile austenico ed austeno-ferritico ad alto contenuto di manganese con processo laser N2 - Manganese alloyed stainless steels represent a cost-effective alternative to conventional CrNi- stainless steels due to strong fl uctuations of the market prices for nickel seen during the last years. In CrMnNi steels, nickel is partially replaced by lower-cost manganese and small amounts of nitrogen for stabilization of the austenitic phase. This also brings benefi ts regarding the mechanical properties, as it results in an increased material strength. Laser beam welding of such materials was investigated for direct comparison with Standard CrNi steels. Main emphasis was laid on fi nding adequate process parameters to achieve a stable welding process and obtain a good weld quality. Two different laser sources, a 4.4 kW Nd:YAG and a 5 kW CO2 laser, were used to weld 1.5 mm stainless steel sheets in continuous wave mode. A high-Mn austenitic (1.4376) and a lean duplex (1.4162) steel, as well as the standard austenitic (1.4301) and duplex (1.4362) grades were selected as test materials. Both butt and lap joint confi gurations were studied. Experiments were carried out systematically, varying the welding speed, laser power and focal point position in order to determine adequate process windows. The infl uence of the shielding gas type and fl ow rate on the process stability and the weld quality were investigated. The effects of weld edge preparation on the weld appearance and quality levels attained were also examined. The obtained welded joints were subjected to radiographic tests for detection of internal imperfections. Also a metallurgical characterization of the samples regarding the resulting phase composition or balance and hardness depending on the welding process parameters was conducted. Furthermore, tensile and potentiodynamic tests were performed to evaluate the mechanical and corrosion properties, respectively. The results provide an insight into the advantages and limitations of the laser beam welding process for joining high-manganese alloyed stainless steels. Conditions for the production of defect-free and corrosion-resistant welds having good mechanical properties could be determined. KW - Weldability KW - Austenitic stainless steels KW - Corrosion KW - CO2 lasers KW - Duplex stainless steels KW - Laser welding KW - Manganese KW - Mechanical properties KW - Shielding gases KW - YAG lasers PY - 2016 SN - 0035-6794 VL - 68 IS - 1 SP - 33 EP - 43 AN - OPUS4-38100 LA - ita AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schempp, P. A1 - Rethmeier, Michael T1 - Understanding grain refinement in aluminium welding N2 - Grain refinement is an important opportunity to improve mechanical properties of fusion welds and the weldability (susceptibility to solidification cracking) of the base metal. In this study, grain refinement was achieved in aluminium welds through additions of grain refiner to the weld metal. Increasing grain refiner additions led to a decrease of the weld metal mean grain size (down to −86 %). The grain refinement efficiency was the highest in commercial pure Al (Alloy 1050A, Al 99.5), followed by Alloy 6082 (Al Si1MgMn) and Alloy 5083 (Al Mg4.5Mn0.7). To investigate this clear influence of alloy content on grain size, the undercooling parameters P and Q were calculated. Temperature measurements revealed that solidification parameters such as solidification growth rate or cooling rate vary significantly along the solidification front, dependent upon torch speed and alloy. On the basis of this comparison, an analytical approach was used to model the columnar to equiaxed transition (CET). Moreover, wavelength dispersive X-ray spectroscopy (WDS) and transmission electron microscopy (TEM) analyses revealed particles rich in Ti and B that are probably TiB2 particles coated by Al3Ti nucleating Al grains during solidification. Also, Ti/B contents needed in commercial filler wires to allow optimum weld metal grain refinement were calculated dependent upon base alloy and welding process. PY - 2015 DO - https://doi.org/10.1007/s40194-015-0251-2 SN - 0043-2288 SN - 1878-6669 VL - 59 IS - 6 SP - 767 EP - 784 PB - Springer CY - Oxford AN - OPUS4-34840 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Polami, S.M. A1 - Häfele, P. A1 - Rethmeier, Michael A1 - Schmid, A. T1 - Study on fatigue behavior of dissimilar materials and different methods of friction-welded joints for drive pinion in trucks N2 - This work addresses the fatigue strength of friction-welded joints for the drive pinion in heavy-duty trucks. Three different friction welding (FW) variants were tested for the joint between the pinion and the bevel of the shaft: (1) conventional FW using series materials, (2) conventional FW from dissimilar materials for every part, and (3) dissimilar joints by applying joint-site structure of FW. Each joint variant was compared to the series production part using a 4-point bending test. Results showed that the higher strength material slightly improved the fatigue strength of the conventional friction-welded joints. Despite the light weight of the component joined structurally at the site, the joint revealed a lower endurance limit compared to other variants. However, there has been little discussion on the weld zone position. The applied equivalent stresses on the weld zone of the joint-site structure are less similar to the position for the conventional FW. Characterization of the failure explains the extraordinary behaviors in relation to S-N curves. PY - 2015 DO - https://doi.org/10.1007/s40194-015-0258-8 SN - 0043-2288 SN - 1878-6669 VL - 59 IS - 6 SP - 917 EP - 926 PB - Springer CY - Oxford AN - OPUS4-34841 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thater, Raphael A1 - Wiethop, P. A1 - Rethmeier, Michael T1 - Welding simulation in car body construction N2 - Laser remote welding is a dynamic and flexible joining technology which enables various new approaches in welding sequence and weld position planning. However, the challenge is to find the optimal set-up within this large parameter space. In this article, numerical welding simulation is used to deal with this challenge. For a car door, different welding sequences and weld positions were numerically analyzed and compared with respect to its welding distortion behavior. PY - 2015 DO - https://doi.org/10.1002/latj.201500009 SN - 1613-7728 SN - 1863-9119 VL - 12 IS - 2 SP - 33 EP - 37 PB - Wiley-VCH CY - Weinheim AN - OPUS4-33110 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 - Welding is one of the most critical operations for the construction of reliable metal structures in everything from ships to reactor vessels. When welds fail, the entire structure often fails—so expectations on weld quality have never been higher. Any process that uses a localized heat source, such as welding, is likely to result in some distortion. The welding process of very thick metal components is not inherently stable and is barely controllable without external forces. KW - Laser beam welding KW - Hartmann effect KW - Electromagnetic weld control KW - Finite element simulation PY - 2015 UR - http://digital.industrial-lasers.com/industriallasers/20150304#pg1 SN - 1523-4266 SN - 0888-935X VL - 30/2 IS - March/April SP - 10 EP - 12 PB - Pennwell CY - Tulsa, Okla., USA AN - OPUS4-33037 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ebert-Spiegel, M. A1 - Goecke, S.-F. A1 - Rethmeier, Michael T1 - Possibilities for compensating a higher heat input, in particular by the torch offset relative to the top sheet at the fillet weld on a lap joint N2 - This paper deals with the use of an adaptive control system for compensating the variation in the gap height of a fillet welded lap joint. Gap bridging requires the input of additional filler material and is related to an increased energy input. Hence, the aim was a compensation of the effect of an increased heat input, in order to maintain the weld pool and excessive penetration, which can prevent consequently root reinforcement and burn-through. The findings achieved in this work show possibilities for a real-time controlled adjustments of the welding parameters in automated metal active gas (MAG) welding for compensating a higher heat input, in particular by means of the torch offset relative to the top sheet at the fillet weld on a lap joint. KW - MAG welding KW - Adaptive control KW - High strength steels KW - Gap KW - Energy input KW - Mathematical models PY - 2015 DO - https://doi.org/10.1007/s40194-015-0220-9 SN - 0043-2288 SN - 1878-6669 VL - 59 IS - 3 SP - 443 EP - 453 PB - Springer CY - Oxford AN - OPUS4-33079 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Su, H. A1 - Wu, Chuan Song A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Numerical modeling for the effect of pin profiles on thermal and material flow characteristics in friction stir welding N2 - Understanding the influence of tool/pin shapes on the thermal and material flow behaviors in friction stir welding is of great significance for the optimal design of tool/pin based on a scientific principle. In this study, a numerical method based on computational fluid dynamics is employed to quantitatively analyze the thermo-physical phenomena in friction stir welding with two tools of different pin shapes (axisymmetrical conical tool and asymmetrical triflat tool). Through combining a steady state model with a transient state model, both the computation efficiency and accuracy are ensured. The boundary conditions of heat transfer and material flow are determined with considering a partial sticking/sliding contact condition at the tool–workpiece interface. The total heat generation, heat density and temperature distribution during the welding process with triflat tool are elucidated and compared with that of conical tool, and the material flow patterns and deformation regions of various pin orientations are illustrated in detail. It is found that the deformation zone caused by triflat tool is larger than that by conical tool, which is validated by the weld macrographs. The computed thermal cycles and peak temperature values at some locations are in good agreement with the experimentally measured ones. KW - Friction stir welding KW - Pin profile KW - Heat generation KW - Material flow KW - Modeling PY - 2015 DO - https://doi.org/10.1016/j.matdes.2015.04.012 SN - 0261-3069 SN - 0264-1275 VL - 77 SP - 114 EP - 125 PB - Elsevier Ltd. CY - Oxford AN - OPUS4-33031 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jonietz, Florian A1 - Ziegler, Mathias A1 - Myrach, Philipp A1 - Suwala, H. A1 - Rethmeier, Michael T1 - Untersuchung von Punktschweißverbindungen mit aktiver Thermografie N2 - Widerstandspunktschweißen ist insbesondere im Automobilbau eine der wichtigsten Fügetechniken. Bislang erfolgt die Qualitätssicherung überwiegend durch stichprobenartige zerstörende Prüfung. Eine zerstörungsfreie Prüftechnik würde neben der Reduzierung der Prüfkosten auch eine Optimierung des Punktschweißverfahrens bedeuten, da prinzipiell jeder Schweißpunkt geprüft werden könnte und somit auch eine Reduzierung der Anzahl der Schweißpunkte möglich ist. Es wird ein Verfahren vorgestellt, bei dem die Punktschweißverbindung zwischen zwei Stahlblechen optisch auf einer Blechseite mittels Laser oder Blitzlicht erwärmt wird. Die aufgeschmolzene Zone, die sogenannte Schweißlinse, stellt dabei neben der mechanischen Verbindung auch eine Wärmebrücke zwischen den beiden verschweißten Blechen dar, die bei diesem Verfahren ausgenutzt wird. Durch den verbesserten thermischen Kontakt zwischen den verschweißten Blechen an der Schweißlinse kontrastiert diese deutlich mit dem umgebenden Blechmaterial, bei dem der Wärmeübertrag zwischen den Blechen vergleichsweise gering ist. Dieser Kontrast im thermischen Verhalten kann mittels zeitabhängiger Thermografie gemessen werden. Durch das hier vorgestellte Verfahren kann mittels aktiver Thermografie sowohl in Transmissions- als auch in Reflexionsanordnung die Größe des thermischen Kontaktes zwischen den beiden Blechen ermittelt werden, welche ein Maß für die Größe der Schweißlinse und damit für die qualitative Güte der Schweißung darstellt. Ein Vorteil des entwickelten Verfahrens ist seine Anwendbarkeit auf Bleche ohne Oberflächenbehandlung. T2 - DACH-Jahrestagung 2015 CY - Salzburg, Austria DA - 11.05.2015 PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-343476 UR - http://www.ndt.net/?id=19068 SN - 1435-4934 VL - 21 IS - 4 SP - 1 EP - 7 PB - NDT.net CY - Kirchwald AN - OPUS4-34347 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schneider, André A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Mobile vacuum in pocket format, mobile local low-pressure cap for high power laser beam welding of thick materials N2 - The presented apparatus enables laser beam welding of thick materials under local reduced pressure conditions, thus improving the quality of welds and reducing the laser beam power necessary for complete penetration welding. The vacuum cap presented in this article uses a local reduced ambient pressure environment in a tight zone around the welding area and, in contrast to a conventional vacuum chamber, it is movable in the welding direction. The mobile installation is very compact and reaches pressure values of around 200 mbar. The reduced pressure in the vacuum cap is sufficient to generate 50 % higher penetration depth in comparison to welding under ambient pressure conditions. The low pressure around the keyhole reduces the vapour-plasma plume and therefore prevents a defocusing and scattering of the laser radiation. This allows to raise the amount of laser beam power entering the keyhole as well as the effective power density. KW - High power laser beam welding KW - Mobile vacuum KW - Local reduced pressure KW - Vapor plume KW - Keyhole PY - 2015 DO - https://doi.org/10.1002/latj.201500025 SN - 1613-7728 SN - 1863-9119 VL - 12 IS - 4 SP - 43 EP - 44 PB - Wiley-VCH CY - Weinheim AN - OPUS4-34583 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schempp, Philipp A1 - Häcker, Ralf A1 - Pittner, Andreas A1 - Cross, C.E. A1 - Rethmeier, Michael T1 - Influence of grain size on mechanical properties of aluminium GTA weld metal N2 - Surface modification of mild steel was undertaken using two covered electrodes and two tubular electrodes. The two covered electrodes are DIN 8555: E6-UM-60 and E10-UM-60GR; however, the two tubular electrodes are E10-GF-60GR1 and E10-GF-60GR2. Chemical analysis for the weld metal and XRD of the flux covering for covered electrodes and flux core for tubular electrodes were conducted. The most important factor in determining the wear resistance is the microstructure of the deposit layers. In similar carbon equivalent electrodes E10-UM-60GR and E10-GF-60GR1, electrode E10-GF-60GR1 (tubular) shows larger carbides area fraction and better wear resistance than electrode E10-UM-60GR (covered). This could be attributed to a lower dilution associated with tubular electrode compared with covered electrode. The two tubular electrodes showed higher wear resistance than the covered electrodes which is mainly due to the larger Fe-Cr carbide precipitation area fraction. KW - GTA welding KW - Aluminium KW - Grain refinement KW - Tensile tests KW - Tear tests PY - 2014 DO - https://doi.org/10.1007/s40194-014-0132-0 SN - 0354-7965 VL - 58 IS - 4 SP - 491 EP - 497 PB - Drustvo za Unapredjivanje Zavarivanja u Srbiji CY - Beograd AN - OPUS4-35103 LA - srp AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pittner, Andreas A1 - Karkhin, Victor A1 - Rethmeier, Michael T1 - Reconstruction of 3D transient temperature field for fusion welding processes on basis of discrete experimental data N2 - This paper presents an approach to reconstruct the three-dimensional transient temperature field for fusion welding processes as input data for computational weld mechanics. The methodology to solve this inverse heat conduction problem fast and automatically focuses on analytical temperature field models for volumetric heat sources and application of global optimisation. The important issue addressed here is the question which experimental data is needed to guarantee a unique reconstruction of the experimental temperature field. Different computational-experimental test cases are executed to determine the influence of various sets of discrete experimental data on the solvability of the optimisation problem. The application of energy distributions utilised for laser beam welding allows reconstructing the temperature field efficiently. Furthermore, the heat input into the workpiece determined by the simulation contributes to the evaluation of the thermal efficiency of the welding process. KW - Welding KW - Temperature KW - Analysis techniques KW - Optimisation KW - Laser beams KW - Hybrid laser arc welding PY - 2015 DO - https://doi.org/10.1007/s40194-015-0225-4 SN - 0043-2288 SN - 1878-6669 VL - 59 IS - 4 SP - 497 EP - 512 PB - Springer CY - Oxford AN - OPUS4-33730 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Petrat, T. A1 - Rethmeier, Michael ED - Rethmeier, Michael T1 - Schicht für Schicht Auftragsschweißen dreidimensionaler Körper N2 - Die Anwendung der additiven Fertigung nimmt stark zu. Eine neue Designfreiheit erlaubt es hier den Konstrukteurinnen und Konstrukteuren, die Bauteilfunktion in den Vordergrund der Entwicklungen zu stellen. Leichtbaustrukturen sowie Funktionsintegration machen es möglich, vormals Bauteile aus vielen Einzelkomponenten jetzt in einem einzigen Bauteil zu vereinigen. Experten am Fraunhofer IPK qualifizieren das Laser-Pulver-Auftragschweißen für die additive Fertigung und legen dabei besonderen Wert auf die Automatisierung des Verfahrens. KW - Laser-Pulver-Auftragsschweißen PY - 2016 SN - 1438-1125 IS - 1 SP - 18 EP - 19 AN - OPUS4-38746 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frei, J. A1 - Rethmeier, Michael ED - Rethmeier, Michael T1 - Einfach anwenderfreundlich - Numerische Simulation von Fügestellen N2 - Ob in der Automobilindustrie, beim Rohrleitungs- oder beim Kraftwerksbau – anspruchsvolle und hochwertige Fügeverbindungen entscheiden oft über die Qualität des Endproduktes. Um z. B. das Verzugsverhalten von Karosseriebauteilen vorab einschätzen zu können, setzen Hersteller auf die numerische Simulation der geschweißten Komponenten. Besondere Aufmerksamkeit gilt hier den Fügestellen. Da diese oft nur wenige Millimeter klein sind, kommen konventionelle Prüfverfahren wie der Zugversuch hier jedoch nicht ohne weiteres in Frage. Forscher des Fraunhofer IPK untersuchen deshalb eine alternative Methode, um die negativen Begleiterscheinungen des thermischen Schweißens im Vorfeld am PC zu analysieren und nötige Gegenmaßnahmen ableiten zu können. KW - Numerische Simulation PY - 2016 SN - 1438-1125 IS - 2 SP - 14 EP - 15 AN - OPUS4-38747 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Graf, B. A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Combined laser additive manufacturing for complex turbine blades N2 - Laser beam processes are increasingly used in the field of additive manufacturing. Prominent methods are either powderbed-based like Laser Metal Fusion (LMF), or utilizing a powder nozzle like Laser Metal Deposition (LMD). While LMF allows the manufacturing of complex structures, build rate, part volumes and material flexibility are limited. In contrast, LMD is able to operate with high deposition rates on existing parts, and materials can be changed easily during the process. However LMD shape complexity is limited. Utilizing their respective strengths, a combination of these two additive technologies has the potential to produce complex parts with high deposition rates and increased material flexibility. In this paper, combined manufacturing with additive technologies LMF and LMD is described. Its benefit for industry with emphasis on turbomachinery is shown. As reality test for the innovation, an industrial turbine blade is manufactured. KW - Turbine blade KW - Additive manufacturing KW - Laser metal fusion KW - Laser metal deposition PY - 2016 SN - 2499-9733 VL - 3 IS - 20 SP - 34 EP - 42 AN - OPUS4-38709 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -