TY - GEN A1 - Florian, Tobias A1 - Schricker, Klaus A1 - Zenz, Constantin A1 - Otto, Andreas A1 - Schmidt, Leander A1 - Diegel, Christian A1 - Friedmann, Hannes A1 - Seibold, Marc A1 - Hellwig, Peter A1 - Fröhlich, Fabian A1 - Nagel, Falk A1 - Kallage, Peter A1 - Buttazzoni, Michele A1 - Rack, Alexander A1 - Requardt, Herwig A1 - Chen, Yunhui A1 - Bergmann, Jean Pierre T1 - Combining in situ synchrotron X-ray imaging and multiphysics simulation to reveal pore formation dynamics in laser welding of copper T2 - International Journal of Machine Tools and Manufacture N2 - Laser beam welding has emerged as a powerful tool for manufacturing copper components in electrical vehicles, electronic devices or energy storage, owing to its rapid processing capabilities. Nonetheless, the material’s high thermal conductivity and low absorption of infrared light can introduce process instabilities, resulting in defects such as pores. This study employs a hybrid approach that combines in situ synchrotron X-ray imaging with compressible multiphysics process simulation to elucidate pore-forming mechanisms during laser beam welding of copper. High-speed synchrotron X-ray imaging with an acquisition rate of 20,000 images/second facilitates the identification of relevant process regimes concerning pore formation during laser beam welding of copper with a wavelength of 1070 nm. Furthermore, in situ observations with high temporal and spatial resolution present a unique database for extensive validation of a multi-physics process simulation based on welding processes using different concentric intensity distributions. These validated simulation results enable thorough comprehension of process-related pore formation based on the interaction between keyhole, melt pool and resulting flow field. The findings show that pore formation is driven by four different mechanisms: bulging, spiking, upwelling waves at the keyhole rear wall and melt pool ejections. The synergy of high- speed synchrotron X-ray imaging and multi-physics modeling provides a fundamental understanding of the chronological sequence of events leading to process-related pore formation during laser beam welding of copper. KW - In situ high-speed synchrotron X-ray imaging KW - Multi-physics simulation KW - Laser beam welding KW - Copper KW - Pore formation KW - Concentric intensity distributions Y1 - 2025 U6 - https://doi.org/10.1016/j.ijmachtools.2024.104224 SN - 0890-6955 VL - 204 SP - 1 EP - 22 PB - Elsevier BV ER - TY - GEN A1 - Diegel, Christian A1 - Schricker, Klaus A1 - Schmidt, Leander A1 - Seibold, Marc A1 - Friedmann, Hannes A1 - Hellwig, Peter A1 - Fröhlich, Fabian A1 - Nagel, Falk A1 - Kallage, Peter A1 - Rack, Alexander A1 - Requardt, Herwig A1 - Chen, Yunhui A1 - Bergmann, Jean Pierre T1 - In situ characterization of keyhole behavior and spatter formation in full penetration laser beam welding with local gas flow using high-speed synchrotron X-ray imaging T2 - Optics & laser technology N2 - Spatter formation is a major issue at welding speeds above 8 m/min for full penetration laser beam welding of high-alloyed steels. In experiments using a local gas flow directed at the keyhole rear wall, a reduction in spatter formation on the specimen top side was observed for welding of AISI 304. However, the interaction between gas flow and keyhole behavior with respect to the mechanisms and locations of spatter detachment, especially on the bottom side, is not yet fully understood. High-speed synchrotron X-ray imaging enables detailed insights into the keyhole behavior and the spatter formation to obtain a deeper understanding of the underlying mechanisms. During the reference experiments welding without shielding gas flow, the spatter detach from a melt pool swelling behind the keyhole aperture on both sides of the sheet. A gas flow with a low flow rate of 4.8 L/min reduces the spatter formation on the top side and the keyhole length due to the absence of oxygen affecting the surface tension. A swelling also forms on the keyhole front on the bottom side and small spatter detach undirected. Increasing the flow rate to 12.8 L/min elongates the keyhole, particularly on the specimen top side. The increased momentum transfer of the gas flow results in a periodic keyhole oscillation on the specimen top side. In combination with an elongated melt pool, the oscillation is directly correlated with the hump formation, caused by melt being pushed over the already solidified weld seam. In addition, spatter does not detach from the top side due to the changed melt flow and only detach from the keyhole front on the bottom side. KW - Laser welding KW - Spatter formation KW - Gas flow KW - High-speed X-ray imaging KW - Synchrotron KW - In situ Y1 - 2025 U6 - https://doi.org/10.1016/j.optlastec.2025.113367 SN - 0030-3992 VL - 191 SP - 1 EP - 17 PB - Elsevier BV CY - Amsterdam ER - TY - GEN A1 - Schricker, Klaus A1 - Schmidt, Leander A1 - Nagel, Falk A1 - Diegel, Christian A1 - Friedmann, Hannes A1 - Seibold, Marc A1 - Hellwig, Peter A1 - Fröhlich, Fabian A1 - Kallage, Peter A1 - Chen, Yunhui A1 - Requardt, Herwig A1 - Rack, Alexander A1 - Bergmann, Jean Pierre T1 - A comprehensive study on the influence of spatial power distribution on time-dependent keyhole behavior in laser beam welding of copper by means of high-speed synchrotron X-ray imaging T2 - Optics & laser technology N2 - This paper examines the impact of spatial power distributions on the time-dependent keyhole behavior during laser beam welding of copper using high-speed synchrotron X-ray imaging. The experimental setup utilized a COHERENT HighLight FL8000-ARM fiber laser with concentric intensity distribution created by an optical fiber cable. The European Synchrotron Radiation Facility (ESRF, beamline ID19) was used to conduct high-speed synchrotron imaging at 20,000 images per second to study the spatio-temporal keyhole behavior. Keyhole geometries were extracted through advanced image processing techniques, allowing quantification of parameters like depth, aperture, bulging, and determination of related oscillation frequencies. The results showed that core-dominated processes exhibit significant variations in keyhole geometry. In contrast, ring-dominated processes exhibited reduced penetration depths but increased melt pool dynamics due to altered absorption conditions and increased temperatures within the melt pool. A stabilized core-ring power distribution minimized fluctuations, resulting in improved process stability. The findings were summarized in a model concept describing three characteristic keyhole regimes: core-dominated, ring-dominated, and stabilized core-ring processes. KW - Laser welding KW - Synchrotron KW - In situ KW - Copper KW - Intensity, spatial power distribution Y1 - 2025 U6 - https://doi.org/10.1016/j.optlastec.2025.113999 SN - 0030-3992 VL - 192, Part E SP - 1 EP - 15 PB - Elsevier BV CY - Amsterdam ER -