TY - JOUR A1 - Meng, Xiangmeng A1 - Bachmann, Marcel A1 - Artinov, Antoni A1 - Rethmier, Michael T1 - A study of the magnetohydrodynamic effect on keyhole dynamics and defect mitigation in laser beam welding N2 - In this paper, the highly transient keyhole dynamics, e.g., laser absorption, keyhole geometry, and fluctuation, etc., under a magnetic field are investigated using an experimental approach and multi-physical modeling. The model provides accurate predictions to the variation of penetration depth and weld pool profiles caused by the MHD effect, which is validated by the measurements of optical micrographs and in-situ metal/glass observation. The micro-X-ray computed tomography shows a remarkable reduction of keyhole-induced porosity with the magnetic field. The correlation between the porosity mitigation and the weld pool dynamics influenced by the magnetic field is built comprehensively. It is found that the magnetic field gives a direct impact on the laser energy absorption at the keyhole front wall by changing the protrusion movement. The porosity mitigation comes from multiple physical aspects, including keyhole stabilization, widening of the bubble floating channel, and the electromagnetic expulsive force. Their contributions vary according to the bubble size. The findings provide a deeper insight into the relationship between electromagnetic parameters, keyhole dynamics, and suppression of keyhole-relevant defects. KW - Laser beam welding (LBW) KW - Keyhole dynamics KW - Porosity KW - Magnetohydrodynamics (MHD) KW - X-ray computed tomography KW - Multi-physical modeling PY - 2022 DO - https://doi.org/10.1016/j.jmatprotec.2022.117636 SN - 0924-0136 VL - 307 SP - 117636 PB - Elsevier B.V. AN - OPUS4-55378 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 - Rethmier, Michael T1 - Influence of the spatial laser energy absorption on the molten pool dynamics in high-power laser beam welding N2 - The spatial laser energy absorption inside the keyhole is decisive for the dynamic molten pool behaviors and the resultant weld properties in high-power laser beam welding (LBW). In this paper, a numerical simulation of the LBW process, considering the 3D transient heat transfer, fluid flow, and keyhole dynamics, is implemented, in which the free surface is tracked by the volume-of-fluid algorithm. The underlying laser-material interactions, i.e., the multiple reflections and Fresnel absorption, are considered by an advanced ray-tracing method based on a localized level-set strategy and a temperature-dependent absorption coefficient. The laser energy absorption is analyzed from a time-averaged point of view for a better statistical representation. It is found for the first time that a significant drop in the time-averaged laser energy absorption occurs at the focus position of the laser beam and that the rest of the keyhole region has relatively homogeneous absorbed energy. This unique absorption pattern may lead to a certain keyhole instability and have a strong correlation with the detrimental bulging and narrowing phenomena in the molten pool. The influence of different focus positions of the laser beam on the keyhole dynamics and molten pool profile is also analyzed. The obtained numerical results are compared with experimental measurements to ensure the validity of the proposed model. KW - Laser beam welding KW - Laser energy absorption KW - Molten pool KW - Keyhole dynamics KW - Numerical modeling PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-587531 DO - https://doi.org/10.2351/7.0001078 SN - 1042-346X VL - 35 IS - 4 SP - 1 EP - 8 PB - AIP Publishing AN - OPUS4-58753 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 - Rethmier, Michael T1 - The influence of the spatial laser energy absorption on the molten pool dynamics in high power laser beam welding N2 - The spatial laser energy absorption inside the keyhole is decisive for the dynamic molten pool behaviors and the resultant weld properties in high-power laser beam welding (LBW). In this paper, a numerical simulation of the LBW process, considering the 3D transient heat transfer, fluid flow, and keyhole dynamics, is implemented, in which the free surface is tracked by the volume-of-fluid algorithm. The underlying laser-material interactions i.e., the multiple reflections and Fresnel absorption, are considered by an advanced ray-tracing method based on a localized Level-Set strategy and a temperature-dependent absorption coefficient. The laser energy absorption is analyzed from a time-averaged point of view for a better statistical representation. It is found for the first time that a noticeable drop of the time-averaged laser energy absorption occurs at the focus position of the laser beam, and the rest region of the keyhole has relatively homogenous absorbed energy. This unique absorption pattern may lead to a certain keyhole instability and have a strong correlation with the detrimental bulging and narrowing phenomena in the molten pool. The influence of the different focus positions of the laser beam on the keyhole dynamics and molten pool profile is also analyzed and compared. The obtained numerical results are compared with experimental measurements to assure the validity of the proposed model. T2 - International Congress of Applications of Lasers & Electro-Optics 2023 CY - Chicago, Illinois, USA DA - 16.10.2023 KW - Laser beam welding KW - Laser energy absorption KW - Molten pool KW - Keyhole dynamics KW - Numerical modeling PY - 2023 AN - OPUS4-58755 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Putra, Stephen Nugraha A1 - Meng, Xiangmeng A1 - Yang, Fan A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Numerical study on the temperature characteristic of material absorptivity and its significance in high-power laser beam welding N2 - The absorptivity of metallic materials plays an important role in high-power laser beam welding. It affects the amount of absorbed laser power leading to the heating and melting of the surfaces to be joined and is highly dependent on the temperature. Nonetheless, this key characteristic is often ignored in numerical simulations and an empirical parameter determined by trial-and-error approaches is rather implemented to calibrate the results. In the present work, the temperature dependence of laser absorption is included in a three-dimensional multiphase numerical model considering the coupled fluid flow and heat transfer. The calculated laser absorption is determined by the temperature-dependent material properties, laser characteristics, and incident angle of the laser beam. It is found that the temperature dependence of the laser absorption is crucial for accurately determining the keyhole and weld pool geometries, which is validated by experimental measurements using 304 austenitic steel. T2 - 13th CIRP Conference on Photonic Technologies [LANE 2024] CY - Fürth, Germany DA - 15.09.2024 KW - Laser beam welding KW - Temperature dependent absorption KW - Weld pool KW - Keyhole dynamics KW - Numerical modelling PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-616146 DO - https://doi.org/10.1016/j.procir.2024.08.179 VL - 124 SP - 585 EP - 589 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-61614 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Meng, Xiangmeng T1 - An investigation of keyhole dynamics and porosity mitigation in laser beam welding with external magnetic field N2 - The macro and micro benefits from a magnetic field have been well recognized in the laser beam welding, but the influence mechanism, especially on the local keyhole dynamics, is yet not fully understood. A combination of experimental approach and numerical modeling was conducted to study the highly transient keyhole dynamics under the magnetic field. It was found that the magnetic field gave a direct impact on the laser energy absorption at the keyhole front wall. The keyhole-induced porosity was suppressed under the influence of the magnetic field, which was confirmed by the micro-X-ray computed tomography. The porosity mitigation comes from multiple physical aspects, including keyhole stabilization, widening of the bubble floating channel, and the electromagnetic expulsive force. The predicted penetration depth and weld pool profiles with/without magnetic field show a good agreement with the experimental measurements, including optical micrographs and in-situ metal/glass observation. T2 - The 75th IIW Annual Assembly and International Conference CY - Tokyo, Japan DA - 17.07.2022 KW - Laser beam welding (LBW) KW - Keyhole dynamics KW - Porosity KW - Magnetic field KW - Multi-physical modeling PY - 2022 AN - OPUS4-55781 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bachmann, Marcel A1 - Putra, Stephen Nugraha A1 - Yang, Fan A1 - Meng, Xiangmeng A1 - Pusbatzkies, Pablo A1 - Rethmeier, Michael T1 - Elucidation of the Laser Beam Energy Attenuation by the Vapor Plume Formation during High Power Laser Beam Welding N2 - In high-power laser beam welding, a common phenomenon is the formation of a keyhole caused by the rapid evaporation of the material. Under atmospheric pressure, this evaporation generates a vapor plume that interacts with the laser beam, leading to energy attenuation and scattering of the laser radiation along its path. These interactions affect the stability of the process and the overall weld quality. This study investigates the influence of the vapor plume on the weld pool and keyhole dynamics during high-power laser beam welding of AlMg3 aluminum alloy through experimental and numerical approaches. The primary goal is to identify key vapor plume characteristics, particularly its length fluctuations, and to improve the accuracy of the numerical models. To achieve this, an algorithm was developed for the automated measurement of the vapor plume length using high-speed imaging and advanced data processing techniques. The measured plume length is then used to estimate the additional vapor heating and laser energy attenuation using the Beer–Lambert law. A refined numerical CFD model, incorporating 3D transient heat transfer, fluid flow, and ray tracing, was developed to evaluate the vapor plume’s impact. Results show that already the time-averaged plume length effectively captures its transient influence and aligns well with experimental weld seam geometries. Additionally, energy scattering and absorption caused by the vapor plume led to a wider weld pool at the top surface. The study also shows an increased percentage of keyhole collapses due to the reduced laser power absorption at the keyhole bottom, further highlighting the importance of accurately modeling vapor plume effects. T2 - International Congress of Applications of Lasers & Electro-Optics 2025 CY - Orlando, USA DA - 12.10.2025 KW - Laser beam welding KW - Vapor plume formation KW - Weld pool KW - Keyhole dynamics KW - Numerical modeling PY - 2025 SP - 1 EP - 10 AN - OPUS4-64817 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Putra, Stephen Nugraha T1 - Numerical study on the temperature characteristic of material absorptivity and its significance in high-power laser beam welding N2 - The absorptivity of metallic materials plays an important role in high-power laser beam welding. It affects the amount of absorbed laser power leading to the heating and melting of the surfaces to be joined and is highly dependent on the temperature. Nonetheless, this key characteristic is often ignored in numerical simulations and an empirical parameter determined by trial-and-error approaches is rather implemented to calibrate the results. In the present work, the temperature dependence of laser absorption is included in a three-dimensional multiphase numerical model considering the coupled fluid flow and heat transfer. The calculated laser absorption is determined by the temperature-dependent material properties, laser characteristics, and incident angle of the laser beam. It is found that the temperature dependence of the laser absorption is crucial for accurately determining the keyhole and weld pool geometries, which is validated by experimental measurements using 304 austenitic steel. T2 - 13th CIRP Conference on Photonic Technologies [LANE 2024] CY - Fürth, Germany DA - 15.09.2024 KW - Laser beam welding KW - Temperature dependent absorption KW - Weld pool KW - Keyhole dynamics KW - Numerical modelling PY - 2024 AN - OPUS4-61612 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bachmann, Marcel T1 - Elucidation of the Laser Beam Energy Attenuation by the Vapor Plume Formation during High Power Laser Beam Welding N2 - In high-power laser beam welding, a common phenomenon is the formation of a keyhole caused by the rapid evaporation of the material. Under atmospheric pressure, this evaporation generates a vapor plume that interacts with the laser beam, leading to energy attenuation and scattering of the laser radiation along its path. These interactions affect the stability of the process and the overall weld quality. This study investigates the influence of the vapor plume on the weld pool and keyhole dynamics during high-power laser beam welding of AlMg3 aluminum alloy through experimental and numerical approaches. The primary goal is to identify key vapor plume characteristics, particularly its length fluctuations, and to improve the accuracy of the numerical models. To achieve this, an algorithm was developed for the automated measurement of the vapor plume length using high-speed imaging and advanced data processing techniques. The measured plume length is then used to estimate the additional vapor heating and laser energy attenuation using the Beer–Lambert law. A refined numerical CFD model, incorporating 3D transient heat transfer, fluid flow, and ray tracing, was developed to evaluate the vapor plume’s impact. Results show that already the time-averaged plume length effectively captures its transient influence and aligns well with experimental weld seam geometries. Additionally, energy scattering and absorption caused by the vapor plume led to a wider weld pool at the top surface. The study also shows an increased percentage of keyhole collapses due to the reduced laser power absorption at the keyhole bottom, further highlighting the importance of accurately modeling vapor plume effects. T2 - International Congress of Applications of Lasers & Electro-Optics 2025 CY - Orlando, FL, USA DA - 12.10.2025 KW - Laser beam welding KW - Vapor plume formation KW - Weld pool KW - Keyhole dynamics KW - Numerical modeling PY - 2025 AN - OPUS4-64816 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Meng, Xiangmeng T1 - Prediction of weld pool and keyhole geometries in high-power laser beam welding through a physics-informed generative approach N2 - The weld pool and keyhole geometries are critical characteristics in evaluating the stability of the high-power laser beam welding (LBW) process and determining the resultant weld quality. However, obtaining these data through experimental or numerical methods remains challenging due to the difficulties in experimental measurements and the high computational demands of numerical modelling. This paper presents a physics-informed generative approach for predicting weld pool and keyhole geometries in the LBW process. With the help of a well experimentally validated numerical model considering the underlying physics in the LBW, the geometries of the weld pool and keyhole under various welding conditions are calculated, serving as the dataset of the generative model. A Conditional Variational Autoencoder (CVAE) model is employed to generate realistic 2D weld pool and keyhole geometries from the welding parameters. We utilize a β-VAE model with the Evidence Lower Bound (ELBO) loss function and include Kullback-Leibler divergence annealing to better optimize model performance and stability during training. The generated results show a good agreement with the ground truth from the numerical simulation. The proposed approach exhibits the potential of physics-informed generative models for a rapid and accurate prediction of the weld pool geometries across a diverse range of process parameters, offering a computationally efficient alternative to full numerical simulations for process optimization and control in laser beam welding processes. T2 - The 45th annual International Congress on Applications of Lasers & Electro-Optics CY - Orlando, FL, USA DA - 12.10.2025 KW - Laser beam welding KW - Generative artificial intelligence KW - Machine Learning KW - Numerical Simulation KW - Weld pool KW - Keyhole dynamics PY - 2025 AN - OPUS4-64812 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Putra, Stephen Nugraha A1 - Yang, Fan A1 - Meng, Xiangmeng A1 - Pusbatzkies, Pablo A1 - Rethmeier, Michael T1 - Elucidation of the laser beam energy attenuation by the vapor plume formation during high-power laser beam welding N2 - In high-power laser beam welding, a common phenomenon is the formation of a keyhole caused by the rapid evaporation of the material. Under atmospheric pressure, this evaporation generates a vapor plume that interacts with the laser beam, leading to energy attenuation and scattering of the laser radiation along its path. These interactions affect the stability of the process and the overall weld quality. This study investigates the influence of the vapor plume on the weld pool and keyhole dynamics during high-power laser beam welding of AlMg3 aluminum alloy through experimental and numerical approaches. The primary goal is to identify key vapor plume characteristics, particularly its length fluctuations, and to improve the accuracy of the numerical models. To achieve this, an algorithm was developed for the automated measurement of the vapor plume length using high-speed imaging and advanced data processing techniques. The measured plume length is then used to estimate additional vapor heating and laser energy attenuation using the Beer–Lambert law. A refined numerical CFD model, incorporating 3D transient heat transfer, fluid flow, and ray tracing, was developed to evaluate the vapor plume’s impact. Results show that already the time-averaged plume length effectively captures its transient influence and aligns well with experimental weld seam geometries. Additionally, energy scattering and absorption caused by the vapor plume led to a wider weld pool at the top surface. The study also shows an increased percentage of keyhole collapses due to the reduced laser power absorption at the keyhole bottom, further highlighting the importance of accurately modeling vapor plume effects. T2 - International Congress of Applications of Lasers & Electro-Optics 2025 CY - Orlando, USA DA - 12.10.2025 KW - Laser beam welding KW - Vapor plume formation KW - Weld pool KW - Keyhole dynamics KW - Numerical modeling PY - 2026 DO - https://doi.org/10.2351/7.0001863 SN - 1938-1387 IS - 38 SP - 012001-1 EP - 012001-9 PB - Laser Institute of America AN - OPUS4-64949 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -