TY - CONF A1 - Bachmann, Marcel A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Multi-physics process simulation of static magnetic fields in high power laser beam welding of aluminium T2 - COMSOL Conference 2012 (Proceedings) N2 - A three-dimensional turbulent steady state numerical model was used to investigate the influence of a stationary magnetic field during partial penetration high power laser beam keyhole welding of thick aluminum parts. COMSOL Multiphysics was used to calculate the three-dimensional heat transfer, fluid dynamics and electromagnetic field equations. Thermo-capillary (Marangoni) convection at the upper weld pool surface, natural convection due to gravity and latent heat of solid-liquid phase transition were taken into account. It shows that the application of steady magnetic fields produces a braking Lorentz force in the melt based on the Hartmann effect. The flow pattern in the weld pool and also the temperature distribution and associated weld pool geometry thus change significantly. Convective flows in the melt can effectively be suppressed and the influence of thermo-capillary flow is diminished to a thin surface layer. T2 - COMSOL Conference 2012 CY - Milan, Italy DA - 10.10.2012 KW - Electromagnetic weld pool control KW - Laser beam welding KW - Lorentz force KW - Marangoni convection KW - Buoyancy PY - 2012 SN - 978-0-9839688-7-0 SP - 1 EP - 7 AN - OPUS4-26993 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF 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 T2 - Proceedings of the ICALEO 2022, 41st International Congress on Applications of Lasers & Electro-Optics 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. Firstly, 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. Secondly, 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 which were supported by selected experimental validation results. T2 - International Congress of Applications of Lasers & Electro-Optics 2022 CY - Orlando, FL, USA DA - 17.10.2022 KW - Weld pool shape KW - Laser beam welding KW - Solidification KW - Porosity KW - Numerical process simulation PY - 2022 SP - 1 AN - OPUS4-56532 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Meng, Xiangmeng A1 - Putra, Stephen Nugraha A1 - Bachmann, Marcel A1 - Artinov, Antoni A1 - Rethmeier, Michael T1 - The influence of the free surface reconstruction on the spatial laser energy distribution in high power laser beam welding modeling T2 - Proceedings of the ICALEO 2022, 41st International Congress on Applications of Lasers & Electro-Optics 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 ray-tracing 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 non-continuous 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. T2 - International Congress of Applications of Lasers & Electro-Optics 2022 CY - Orlando, FL, USA DA - 17.10.2022 KW - Laser beam welding KW - laser energy distribution KW - Weld pool dynamics KW - Ray-tracing PY - 2022 SP - 1 EP - 9 AN - OPUS4-56533 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Heßmann, Jennifer A1 - Bachmann, Marcel A1 - Hilgenberg, Kai T1 - Joining dissimilar materials a new approach based on laser beam welding and melt displacement by electromagnetic forces T2 - Lasers in Manufacturing (LiM) 2021 N2 - In order to reduce weight of vehicles, the interest in multi-material-design has been growing within the last few years. For vehicles the combination of steel and aluminium alloys offers the most promising compromise between weight, strength and formability. Thermal joining of these dissimilar materials is still a challenge to overcome. A possible approach is a new joining technology, whereby a combination of laser beam welding and contactless induced electromagnetic forces are used to displace the generated melt of one joining partner into a notch of the other. This paper presents the working principle and shows numerical analyses to improve the understanding of this joining process. The simulations help to calculate the thermal development of the joining partners, which is important for the formation of intermetallic phases. Furthermore, the calculation of the time required for a complete displacement is possible. The numerical results are validated by experimental results. T2 - LiM 2021 CY - Online meeting DA - 21.06.2021 KW - Joining dissimilar materials KW - Laser beam welding KW - Electromagnetic forces KW - Steel and aluminium PY - 2021 SP - 1 EP - 9 PB - Wissenschaftliche Gesellschaft Lasertechnik e.V. (WLT) AN - OPUS4-52978 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Observation of the weld pool shape in partial penetration welding and its influence on solidification crack formation for high-power laser beam welding T2 - Lasers in Manufacturing Conference 2021 N2 - In this study, steel-glass experiments were conducted to observe the melt pool geometry using a high-speed camera. The high-speed recordings and optical flow analysis show that two main flows take place in form of vortices. The lower vortex drives the melt backwards from the front keyhole wall and thus causes an extension of the melt pool, which is called bulging. This bulging promotes solidification cracking by forming a closed area filled with melt and the accumulation of impurities in the final solidification phase, resulting in low-melting phases which are under tensile stress at the end of solidification. T2 - Lasers in Manufacturing Conference 2021 CY - Online meeting DA - 21.06.2021 KW - Laser beam welding KW - Weld pool shape KW - Solidification craking KW - Partial penetration PY - 2021 SP - 1 EP - 5 AN - OPUS4-53587 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Heßmann, Jennifer A1 - Hilgenberg, Kai ED - Hausmann, J. M. T1 - Meeting the challenge of thermal joining of steel and aluminum using a new approach based on melt displacement by electromagnetic forces T2 - 5th international conference on hybrid materials and structures 2022 - Book of abstracts N2 - Environmental protection, resource conservation and CO2 reduction require new joining concepts for effective multi-material design in automotive lightweight construction. The thermal joining of dissimilar materials, especially the combination of aluminum alloys and steel, is associated with difficulties. Different material properties, such as melting point and coefficient of thermal expansion, complicate joining processes. Furthermore, the insolubility between these materials results in the formation of intermetallic phases. These brittle phases reduce the load-bearing capacity and quality of the joints. The thickness of the intermetallic phases should not reach the critical value of 10 μm to ensure good mechanical properties of the joint. It is known that a two-phase reaction layer consisting of Al5Fe2 and Al3Fe (also known as Al13Fe4) forms at the interface between solid steel and liquid aluminum. Due to high cooling rates, as it is the case in laser beam welding, metastable intermetallic compounds can form different from the equilibrium state. The formation of the intermetallic reaction layer is a diffusion-controlled process. So, it is only possible to control the growth of these phases. This problem has led to use joining methods that do not require the melting of both joining partners. A promising joining method is laser beam welding-brazing, whereby only one joining partner is melted and wets the solid joining partner. Conventional laser beam welding-brazing only results in material-fit joints and often requires the use of expensive filler materials. An additional form-fit could optimize the mechanical performance of the joint. For this reason, a new joining method for overlap configurations of dissimilar materials was developed. A laser beam melts the lower joining partner through a cavity of the upper joining partner. The created melt pool is moved upwards into the cavity of the upper joining partner due to contactless induced Lorentz forces of an AC-magnetic system. The displaced melt creates a form- and material-fit joint after solidification. The advantage of this joining technology is the absence of filler materials, flux agents and expensive auxiliary joining elements. T2 - 5th International Conference Hybrid 2022 - Materials and Structures CY - Leoben, Austria DA - 20.07.2022 KW - Joining dissimilar materials KW - Laser beam welding KW - Electromagnetic forces KW - Steel and aluminium PY - 2022 SN - 978-3-88355-426-6 SP - 6 EP - 8 PB - Deutsche Gesellschaft für Materialkunde (DGM) CY - Sankt Augustin AN - OPUS4-55536 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of solidification cracking susceptibility of laser welded joints of austenitic stainless steels T2 - Welding and failure analysis of engineering materials (WAFA-2015) N2 - Laser welding is a widely established manufacturing process in many industry sectors. Solidification cracking represents one of the most inadequately solved problems in welding and has major economic implications. The avoidance of hot crack forms for most fusion welding processes poses a key challenge for an important range of metallic construction materials and affects not only the manufacturers of welding equipment and material manufacturers, but also a large number of customers using welding technologies, as well as welding technical standardization and research. Solidification cracking susceptibility was examined with the help of the Controlled Tensile Weldability Test (CTW) developed by Federal Institute for Materials Research and Testing (BAM), Berlin. The test is based on the fact that hot crack formation depends on a critical strain that emerges within a critical temperature range, the so called brittle temperature range (BTR). Using this test and defined investigation programme a centreline solidification crack was generated. By controlling the applied strain during the laser beam welding process, it was possible to determine the critical strain and strain rate that led to solidification cracking formation. The hot cracking susceptibility of the tested stainless steels was qualified and quantified. The results demonstrate that the crack length increases with increasing applied strain. Furthermore, the strain rate has a significant influence on the formation of the solidification crack. T2 - 3rd International conference in Africa and Asia CY - Luxor, Egypt DA - 02.11.2015 KW - Laser beam welding KW - Hot cracking KW - Solidification cracking KW - Hot cracking test PY - 2015 SP - A-29, 1 EP - A-29, 9 AN - OPUS4-36522 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of hot crack susceptibility of laser welded joints of four austenitic steels T2 - European Steel Technology and Application Days N2 - Laser welding is a widely established manufacturing process in many industry sectors. Solidification cracking represents one of the most inadequately solved problems in welding and has major economic implications. The avoidance of hot crack is for most fusion welding processes a key challenge for an important range of metallic construction materials and affects not only the manufacturers of welding equipment and material manufacturers, but also a large number of customers using welding technologies, as well as welding standardization and research. In this study a new investigation programme has been developed to qualify the hot cracking susceptibility of a variety of austenitic stainless steels. The results show the possibility of using this technique to determinate the critical values that occur with initiation of solidification cracking during laser beam welding T2 - The METEC and 2nd European Steel Technology and Application Days CY - Düsseldorf, Germany DA - 15.06.2015 KW - Laser beam welding KW - Hot cracking KW - Solidification cracking KW - Hot cracking test PY - 2015 SP - 1 EP - 5 AN - OPUS4-36525 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gumenyuk, Andrey A1 - Gook, Sergej A1 - Lammers, Marco A1 - Rethmeier, Michael T1 - High power fibre laser welding for pipeline applications T2 - LAMP2009 - 5th International congress on laser advanced materials processing (Proceedings) N2 - With an availability of the modern high power fibre lasers the application range of laser and laser hybrid welding can be significantly increased. For the implementation of this new technology in the economically extremely interesting application of pipeline construction it is necessary to fulfil a series of systematic research studies. As it has been shown in the past the fibre laser hybrid wielding of pipeline Steel X65 up to 32 mm thickness is possible with appropriate quality. For the use of laser-hybrid welding in pipe laying insensibility towards tolerances and the possibility of girth welding are very important factors in addition to the weld seam quality. The aim of a Research project carried out in the Federal Institute for Materials Research and Testing (BAM) was the development of a welding procedure using high power fibre laser in combination with GMAWProcess which could be applied for welding of pipelines. For tests segments of linepipes with an outer diameter of 914 mm and a wall thickness of 16 mm have been welded using specially designed equipment for girth welding of pipes. First promising results for the use of laser-hybrid welding of thick materials could be demonstrated. The gap-bridgeability and misalignement was studied. T2 - LAMP2009 - 5th International congress on laser advanced materials processing CY - Kobe, Japan DA - 29.06.2009 KW - High power fiber laser KW - Laser beam welding KW - Hybrid welding KW - Pipeline construction KW - Orbital welding PY - 2009 SP - 1 EP - 5 AN - OPUS4-19936 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Perret, William A1 - Alber, U. A1 - Schwenk, Christopher A1 - Rethmeier, Michael ED - Wieland, H.-J. T1 - Efficient welding simulation of an automotive sheet metal assembly T2 - SCT2011 - 3rd International conference on steels in cars and trucks - Future trends in steel development, processing technologies and applications N2 - Fusion welding is widely used in the automotive industry to join metal structures. It is well-known that distortions and residual stresses occur during and after the welding process. Many procedures exist to decrease these negative heat effects of welding, but are often coupled with highly cost intensive experiments. The implementation of a welding Simulation tool to reduce this very expensive experimental procedures is therefore of high interest. Despite the fact that the automotive industry is a key sector for Simulation procedures, welding Simulation Software is nevertheless not yet widely implemented. This is mainly due to the complexity of the Simulation tools requiring expert users and the resulting high time to Solution. In this study, a new fast thermo-mechanical Simulation of a complex and large laser beam welded automotive sheet metal assembly with several non linear welds is simulated. Assumptions and simplifications of the complex physical welding phenomenon, which are made to keep the computational cost and the complexity of the Simulation in an industrial frame, are discussed. The calibration time of the phenomenological heat source model has been optimized with a very fast analytical thermal model and the resulting simulated temperature fields match perfectly with the measured ones. Additionally, the user experience and the time-to-solution are kept within a reasonable time frame for arr industrial environment. All Simulation results are validated with experimental results. T2 - SCT2011 - 3rd International conference on steels in cars and trucks CY - Salzburg, Austria DA - 05.06.2011 KW - Welding simulation KW - Temperature field KW - Laser beam welding KW - Fast calculation PY - 2011 SN - 978-3-514-00783-3 SP - 704 EP - 713 PB - Stahleisen AN - OPUS4-24088 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Karkhin, Victor A1 - Pittner, Andreas A1 - Schwenk, Christopher A1 - Rethmeier, Michael ED - Halmoy, E. T1 - Simulation of the temperature field in laser beam welding by inverse technique T2 - 13th Conference on laser materials processing in the nordic countries N2 - This paper presents volume heat sources and the corresponding functional analytical Solutions for the transient temperature field. The considered energy distributions are normal, exponential and parabolic. The method follows the common approach in Computational Welding Mechanics (CWM) to account for the physics of the welding process and the resulting temperature field by phenomenological models for heat conduction. Therefore, the used heat source models are apparent heat sources that incorporate the real heat input as well as the fluid flow in the weld pool and the latent heat connected with phase transformations. The heat source models provide welding characteristics like thermal cycle and Fusion line in the cross section within short computational time. Consequently, inverse techniques on basis of optimisation algorithms enable the adaptation of the models to the experimental data efficiently. Furthermore, the direct evaluation of the energy distribution for the experimental fusion line in the cross section is demonstrated which enhances the numerical optimisation by reducing the number of unknown model Parameters and providing a reasonable initial guess within the model parameter space. The proposed temperature field models are validated with real laser beam welding experiments. T2 - 13th Conference on laser materials processing in the nordic countries CY - Trondheim, Norway DA - 27.06.2011 KW - Volume heat source KW - Inverse modelling KW - Functional analysis KW - Laser beam welding PY - 2011 SP - 223 EP - 234 AN - OPUS4-24165 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Experimental study and numerical simulation of hot crack formation for novel laser weldability test. T2 - BEAM TECHNOLOGIES & LASER APPLICATION Proceedings of the International scientific and technical Conference N2 - Laser beam welding is a widely established manufacturing process in several industries. The solidification cracking seriously effecting the safety of welded joints could arise during the beam welding of stainless steels caused by high solidification rates. In this study the controlled tensile weldability test (CTW) was used to investigate the solidification cracking susceptibility the fully austenitic stainless steels CrMnNi (1.4376), CrNi (1.4301), CrNiMo (1.4404) and CrNiSi (1.4828) during laser beam welding. The test facility allows welding of specimens with simultaneous application of tensile load along or cross to the welding direction while the speed of tensile force application is either constant or increases linearly. The tensile force increment and/or the displacement are set by means of a CNC controller. Trials were conducted by varying the ultimate tensile strain and cross-head speed while keeping the welding parameters constant. By observing the crack-no crack behaviour and estimating the generated crack length for each trail using a new optimized experimental procedure the influence of the two important conditions (the strain and the strain rate) for the formation of solidification cracks can be investigated, the critical values of strain and strain rate that are responsible for solidification cracking formation have been determined. In the present study a three-dimensional FEM using the contact element technique was developed to simulate the solidification cracking during laser full penetration welding under external load conditions for the steel 1.4376 in order to get a better understanding of the mechanisms of hot crack initiation and the theoretical results were compared to the experimental ones. By comparing the resulting solidification crack with simulated crack, it is possible to determine the critical condition of solidification crack formation in the region where the strains and the strain rates cannot be measured due to the high temperature. The results show a good agreement between numerical calculation and experiment. It is proposed that the solidification cracking susceptibility may be predicted by FEM analysis by using the correct mechanical and thermo-physical constants of the materials. T2 - BEAM TECHNOLOGIES & LASER APPLICATION CY - St. Petersburg, Russia DA - 21.09.2015 KW - Solidification cracking KW - Hot cracking test KW - FEM KW - Laser beam welding PY - 2015 SN - 978-5-7422-5150-7 SP - 55 EP - 68 AN - OPUS4-36615 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Avilov, Vjaceslav A1 - Fritzsche, André A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Full penetration laser beam welding of thick duplex steel plates with electromagnetic weld pool support T2 - ICALEO 2015 - 34th International congress on applications of lasers & electro-optics (Proceedings) N2 - Full penetration high power bead-on-plate laser beam welding tests of up to 20 mm thick 2205 duplex steel plates were performed in PA position. A contactless inductive electromagnetic (EM) weld pool support system was used to prevent gravity drop-out of the melt. Welding experiments with 15 mm thick plates were carried out using IPG fiber laser YLR 20000 and Yb:YAG thin disk laser TruDisk 16002. The laser power needed to achieve a full penetration was found to be 10.9 and 8.56kW for welding velocity of 1.0 and 0.5 m min(-1), respectively. Reference welds without weld pool support demonstrate excessive root sag. The optimal value of the alternating current (AC) power needed to completely compensate the sagging on the root side was found to be approximate to 1.6 kW for both values of the welding velocity. The same EM weld pool support system was used in welding tests with 20 mm thick plates. The laser beam power (TRUMPF Yb:YAG thin disk laser TruDisk 16002) needed to reach a full penetration for 0.5 m min(-1) was found to be 13.9 kW. Full penetration welding without EM weld pool support is not possible-the surface tension cannot stop the gravity drop-out of the melt. The AC power needed to completely compensate the gravity was found to be 2 kW. (C) 2016 Laser Institute of America T2 - ICALEO 2015 - 34th International congress on applications of lasers & electro-optics CY - Atlanta, GA, USA DA - 2015-10-18 KW - Electromagnetic weld pool support KW - Laser beam welding KW - Duplex stainless steel PY - 2015 SN - 978-1-940168-05-0 SP - 571 EP - 579 PB - Amer inst physics CY - Melville, NY, USA AN - OPUS4-35035 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bachmann, Marcel A1 - Kunze, R. A1 - Avilov, Vjaceslav A1 - Rethmeier, Michael T1 - Finite element modelling of an AC electromagnetic weld pool support in full penetration laser beam welding of thick duplex stainless steel plates T2 - ICALEO 2015 - 34th International congress on applications of lasers & electro-optics (Proceedings) N2 - An electromagnetic weld pool support system for 20 mm thick duplex stainless steel AISI 2205 was investigated numerically and compared to experiments. In our former publications, it was shown how an AC magnetic field below the process zone directed perpendicular to the welding direction can induce vertically directed Lorentz forces. These can counteract the gravitational forces and allow for a suppression of material drop-out for austenitic stainless steels and aluminum alloys. In this investigation, we additionally adopted a steady-state complex magnetic permeability model for the consideration of the magnetic hysteresis behavior due to the ferritic characteristics of the material. The model was calibrated against the Jiles-Atherton model. The material model was also successfully tested against an experimental configuration before welding with a 30 mm diameter cylinder of austenitic stainless steel surrounded by duplex stainless steel. Thereby, the effects of the Curie temperature on the magnetic characteristics in the vicinity of the later welding zone were simulated. The welding process was modelled with a 3D turbulent steady-state model including heat transfer and fluid dynamics as well as the electromagnetic field equations. Main physical effects, the thermo-capillary (Marangoni) convection at the weld pool boundaries, the natural convection due to gravity as well as latent heat of solid–liquid phase transitions at the phase boundaries were accounted for in the model. The feedback of the electromagnetic forces on the weld pool was described in terms of the electromagneticinduced pressure. The FE software COMSOL Multiphysics 4.2 was used in this investigation. It is shown that the gravity drop-out associated with the welding of 20 mm thick duplex stainless steel plates due to the hydrostatic pressure can be prevented by the application of AC magnetic fields between around 70 mT and 90 mT. The corresponding oscillation frequencies were between 1 kHz and 10 kHz and the electromagnetic AC powers were between 1 kW and 2.3 kW. In the experiments, values of the electromagnetic AC power between 1.6 kW and 2.4 kW at oscillation frequencies between 1.2 kHz and 2.5 kHz were found to be optimal to avoid melt sagging or drop-out of melt in single pass fullpenetration laser beam welding of 15 mm and 20 mm thick AISI 2205. T2 - ICALEO 2015 - 34th International congress on applications of lasers & electro-optics CY - Atlanta, GA, USA DA - 2015-10-18 KW - Electromagnetic weld pool support KW - Laser beam welding KW - FE simulation KW - Duplex stainless steel PY - 2015 SN - 978-1-940168-05-0 SP - 650 EP - 659 AN - OPUS4-35036 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Artinov, Antoni A1 - Bachmann, Marcel A1 - Karkhin, Victor A1 - Rethmeier, Michael ED - Sommertisch, C. ED - Enzinger, N. ED - Mayr, P. T1 - A novel approach for calculating the thermal cycle of a laser beam welding process using a stationary CFD model T2 - Mathematical Modelling of Weld Phenomena 12 N2 - This work aims to find the thermal cycles during and after fusion welding through simulation by first calculating the resulting local temperature field in the quasi-stationary part of the process. Here complete-penetration keyhole laser beam welding with a laser power of 18 kW on a 15 mm thick slab of a low-alloyed steel at a welding speed of 2 m/min is considered. In order to physically depict the laser material interaction a multi-physics numerical model including the effects of phase transformation, thermo-capillary convection, natural convection and temperature-dependent material properties up to evaporation temperature is developed. It uses a fixed keyhole geometry with a right truncated circular cone shape to introduce the laser beam energy to the workpiece. In a subsequent study, the resulting local temperature field is then used as an equivalent heat source in order to predict the unsteady thermal cycle during and after fusion welding. The translational movement of the laser beam through the workpiece is represented by a moving mesh approach. For the simulation, stationary heat transfer and fluid dynamics are described by a system of strongly coupled partial differential equations. These are solved with the commercial finite element software COMSOL Multiphysics 5.0. The results of the numerical simulation are validated by experiments, where the weld bead shapes and the thermal cycles show good correlation. T2 - 12th International Seminar "Numerical Analysis of Weldability" CY - Graz, Austria DA - 24.09.2018 KW - Equivalent heat source KW - Process simulation KW - Laser beam welding KW - Transient heat transfer KW - Moving mesh PY - 2019 SN - 978-3-85125-616-1 VL - 12 SP - Chapt. VI, 694 EP - 710 PB - Verlag der Technischen Universität Graz AN - OPUS4-48817 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Meng, Xiangmeng A1 - Artinov, Antoni A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - A theoretical study of influence o f electromagnetic stirring on transport phenomena in wire feed laser beam welding T2 - ICALEO 2019 - 38th International congress on applications of lasers & electro-optics (Proceedings) N2 - The additional element from the filler wire in the laser beam welding is usually distributed inhomogeneously in the final weld due to the high solidification rate of weld pool. It has been found that the electromagnetic stirring produced by an external oscillating magnetic field can enhance the material mixing in the weld pool to achieve a more uniform element distribution. However, the magnetic field has a highly non-linear and multi-coupled interaction with the weld pool behavior, which makes the quantitative explanation of the physical mechanism difficult. In this study, the effect of electromagnetic stirring on the transport phenomena in the wire feed laser beam welding is investigated by a numerical modelling. A 3D transient multi-physical model considering the magnetohydrodynamics, heat transfer, fluid flow, keyhole dynamics and element transport is developed. The multiple reflections and the Fresnel absorption of the laser on the keyhole wall are calculated using the ray tracing method. The numerical results show that a Lorentz force produced by the oscillating magnetic field and its induced eddy current gives significant influence on the transport phenomena in the molten pool. The forward and downward flow is enhanced by the electromagnetic stirring, which homogenizes the distribution of the additional elements from a nickel-based filler wire in a steel weld pool. The numerical results show a good agreement with the high-speed images of the molten pool, the fusion line from the optical micrograph and the element distribution from the energy dispersive X-ray spectroscopy. This work provides a physical base for the electromagnetic-controlled laser beam welding and some guidance for the selection of electromagnetic parameters. T2 - ICALEO 2019 - 38th International congress on applications of lasers & electro-optics CY - Orlando, FL, USA DA - 07.10.2019 KW - Magnetohydrodynamics KW - Molten pool dynamics KW - Element transport KW - Laser beam welding PY - 2019 SN - 978-1-940168-1-42 SP - Paper # Macro 403 AN - OPUS4-49664 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fritzsche, André A1 - Hilgenberg, Kai A1 - Teichmann, F. A1 - Pries, H. A1 - Rethmeier, Michael T1 - Electromagnetic porosity Reduction in Laser Beam Welding of Die-Cast Aluminum Alloy T2 - Lasers in Manufacturing Conference 2017 N2 - The present paper investigates the electromagnetic porosity reduction in partial penetration laser beam welding of 6 mm aluminum die casting AlSi9MnMg. Applying an electromagnetic field, a significant reduction of the porosity as well as smoothing of the surface of aluminum die casting can be observed. Starting from the reference case without an electromagnetic support, the porosity was reduced by 76 %. Especially big pores can be removed from the weld pool effectively due to their beneficial volume-to-area ratio whereas very small metallurgical pores tend to remain within the weld pool even when higher magnetic flux densities are applied. T2 - Lasers in Manufacturing Conference 2017 CY - Munich, Germany DA - 26.06.2017 KW - Laser beam welding KW - Die-cast aluminum KW - Porosity reduction KW - Electromagnetic influence PY - 2017 SP - 1 EP - 10 AN - OPUS4-41244 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Artinov, Antoni A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - About the origin of solidification cracking in laser welded thick-walled structures T2 - 4th International Conference on Welding and Failure Analysis of Engineering Materials N2 - In this study, a three-dimensional CFD-simulation model was developed to simulate the fluid flow in the weld pool. The CFD-model showed a bulging region in the middle of the depth, which is separated from the top surface and bottom surface by two narrowing regions. It can be concluded that the interaction of the movement of the laser source with the Marangoni vortex leads to a teardrop shape at the upper and bottom surface of the workpiece. Additionally, it shows that the bulging in the weld is a result of the backflows on the upper and lower sides due to the thermo-capillary-driven flows. The weld pool shape was used as a heat source in a two-dimensional thermomechanical model, which allows a highly accurate transformation of the weld pool dimensions obtained from the CFD model. This developed technique allows the consideration of physical aspects, which cannot be considered when using traditional heat sources. The mechanical model has shown that the chronological order of the solidification of the weld has a significant influence on the nature and distribution of the stresses in the weld. High tensile stress has been observed in the bulging region, i.e. in the susceptible region for solidification cracking, when compared to the other narrowing regions, which show compressive stress. T2 - 4th International Conference on Welding and Failure Analysis of Engineering Materials CY - Aswan, Egypt DA - 19.11.2018 KW - Laser beam welding KW - Solidification cracking KW - Numerical simulation KW - Weld pool geometry KW - CFD-model KW - FE-model PY - 2018 SP - W-6, 1 EP - 10 CY - Aswan, Egypt AN - OPUS4-46735 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Artinov, Antoni A1 - Meng, Xiangmeng A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Numerical study on the formation of a bulging region in partial penetration laser beam welding T2 - Mathematical Modelling of Weld Phenomena 13 N2 - A transient three-dimensional thermo-fluid dynamics numerical model was developed to study the formation of a bulging region in partial penetration laser beam welding. The model accounts for the coupling between the fluid flow, the heat transfer, and the keyhole dynamics by considering the effects of multiple reflections and Fresnel absorption of the laser beam in the keyhole, the phase transitions during melting and evaporating, the thermo-capillary convection, the natural convection, and the phase-specific and temperature-dependent material properties up to the evaporation temperature. The validity of the model was backed up by experimentally obtained data, including the drilling time, the weld pool length, the local temperature history outside the weld pool, the process efficiency, and a range of metallographic crosssections. The model was applied for the cases of partial penetration laser beam welding of 8 mm and 12 mm thick unalloyed steel sheets. The obtained experimental and numerical results reveal that the bulging region forms transiently depending on the penetration depth of the weld, showing a tendency to transition from a slight bulging to a fully developed bulging region between penetration depths of 6 mm and 9 mm, respectively. T2 - 13th International Seminar "Numerical Analysis of Weldability" CY - Seggau, Austria DA - 04.09.2022 KW - Laser beam welding KW - Deep penetration KW - Bulge formation KW - Numerical modeling PY - 2023 SN - 978-3-85125-968-1 SN - 978-3-85125-969-8 SN - 2410-0544 VL - 13 SP - 101 EP - 126 PB - Verlag der Technischen Universität Graz AN - OPUS4-58802 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Artinov, Antoni A1 - Kising, Pascal A1 - Bachmann, Marcel A1 - Meng, Xiangmeng A1 - Rethmeier, Michael T1 - Numerical analysis of the dependency of the weld pool shape on turbulence and thermodynamic activity of solutes in laser beam welding of unalloyed steels T2 - Mathematical Modelling of Weld Phenomena 13 N2 - A three-dimensional numerical model was developed to accurately predict the steady-state weld pool shape in full penetration laser beam welding. The model accounts for the coupling between the heat transfer and the fluid dynamics by considering the effects of solid/liquid phase transition, thermo-capillary convection, natural convection, and phase-specific and temperature-dependent material properties up to the evaporation temperature. A fixed right circular cone was utilized as a keyhole geometry to consider the heat absorbed from the laser beam. The model was used to analyze the influence of the thermodynamic activity of solutes and turbulence on the weld pool shape. A mesh sensitivity analysis was performed on a hybrid mesh combining hexahedral and tetrahedral elements. For the case of full penetration laser beam welding of 8 mm thick unalloyed steel sheets, the dependence of the weld pool shape on the surface-active element sulfur was found to be negligible. The analysis of the results showed that a laminar formulation is sufficient for accurately predicting the weld pool shape since the turbulence has a minor impact on the flow dynamics in the weld pool. The validity of the numerical results was backed up by experimental measurements and observations, including weld pool length, local temperature history, and a range of metallographic crosssections. T2 - 13th International Seminar Numerical Analysis of Weldability CY - Seggau, Austria DA - 04.09.2022 KW - Weld pool shape KW - Numerical modeling KW - Laser beam welding KW - Thermo-capillary convection KW - Turbulence PY - 2023 SN - 978-3-85125-968-1 SN - 978-3-85125-969-8 SN - 2410-0544 VL - 13 SP - 161 EP - 188 PB - Verlag der Technischen Universität Graz AN - OPUS4-58803 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -