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 - Tognoli, Emanuele A1 - Schricker, Klaus A1 - Bassolini, Elena A1 - Bergmann, Jean Pierre T1 - Influence of the eutectic interface on the fatigue behavior of friction stir spot welds of aluminum with copper T2 - International Journal of Fatigue N2 - The development of hybrid bonds between copper and aluminum is being pursued for reasons of cost, functionality, and weight, particularly in the field of electromobility, to achieve near net-zero emissions. Joining aluminum to copper is a challenge, as interfacial intermetallic compounds have a negative impact on the strength, ductility, and electrical properties of the joint. The development of brittle intermetallic compounds can be limited by targeted temperature control, making solid-phase joining processes particularly suitable. In this article, the fatigue behaviour of friction stir spot welded joints of copper CW004A and aluminum alloy AA1050A with probeless tools is studied. A melt film forms between the metals and the axial force displaces this film laterally, creating an intermediate layer of eutectic and Al2Cu in the joint area. The effect of this layer on the fatigue behaviour of the joint was investigated in this study. At high loads, failure occurs by a combination of Modes I and II with crack propagation in as well as around the bonding area, while at low loads only Mode I is observed. Typically, cracks origin at the spot outer diameter in aluminum, propagate at first in the laterally expelled melt and then through the aluminum sheet, causing unbuttoning. KW - friction stir spot welding KW - aluminum-copper welding KW - fatigue behavior KW - fracture propagation KW - intermetallic compound Y1 - 2025 U6 - https://doi.org/10.1016/j.ijfatigue.2025.108834 SN - 0142-1123 SN - 1879-3452 VL - 194 IS - May 2025 PB - Elsevier ER - TY - GEN A1 - Walther, Dominik A1 - Schmidt, Leander A1 - Räth, Timo A1 - Schricker, Klaus A1 - Bergmann, Jean Pierre A1 - Sattler, Kai-Uwe A1 - Mäder, Patrick T1 - Deep learning-driven active sheet positioning using linear actuators in laser beam butt welding of thin steel sheets T2 - Journal of advanced joining processes N2 - Welding thin steel sheets in industrial applications is difficult because joint gaps occur during the process, which can lead to weld interruptions. Such welds are considered a reject and in order to avoid the weld to interrupt it is crucial to hinder the formation of joint gaps. Especially laser beam welding is affected by the emergence of gaps. Due to the narrow laser spot, product quality is highly dependent on the alignment and positioning of the sheets. This is typically done by clamping devices, which hold the workpieces in place. However, these clamps are suited for a specific workpiece geometry and require manual redesign every time the process changes. Adaptive clamping devices instead are designed to realize a time-dependent workpiece adjustment. Modeling the joint gap behavior to realize a controller for adaptive clamps can be difficult as the influence of heating, melting, and cooling on the joint gap formation is unknown and varies due to temperature dependent physical properties. Instead, the control parameters and actions can be derived using data-driven methods. In this paper, we present a novel data-driven approach how deep learning can be utilized to manipulate the sheet position during the weld with two actuators that apply force. A temporal convolution neural network (TCN) analyzes the change of the joint gap and predicts the required force to adapt the workpiece position. The developed method has been integrated into the welding process and improves the length of the average weld seam by 39.5% compared to welds without an active adjustment and 1.4% to welds that have been adapted with a constant force. KW - Laser beam welding KW - Temporal convolutional neural network KW - Thin steel sheets KW - Inductive probes KW - Gap adjustment KW - Deep learning Y1 - 2025 U6 - https://doi.org/10.1016/j.jajp.2025.100303 SN - 2666-3309 VL - 11 SP - 1 EP - 12 PB - Elsevier BV CY - Amsterdam ER - TY - GEN A1 - Walther, Dominik A1 - Schmidt, Leander A1 - Schricker, Klaus A1 - Junger, Christina A1 - Bergmann, Jean Pierre A1 - Notni, Gunther A1 - Mäder, Patrick T1 - Dataset for weld seam analysis and discontinuity prediction in laser beam welding scenarios T2 - Data in brief N2 - Laser beam welding can produce narrow, high-quality welds in various industrial joining processes. The thermal expansion and contraction of the metal during the weld results in the displacement of the sheets. That leads to the formation of joint gaps and subsequent to a process interruption. This behavior has only been analyzed to a limited extent and causes manufacturers to rely on heavy clamping systems rather than using more flexible fixtureless approaches. Due to the time-consuming and costly nature of recording and producing erroneous weld seams, such recordings and datasets are rarely available in this area. This often limits the research towards adaptable fixtureless welding setups. Because of this, we present a multi-modal dataset consisting of 100 recorded welds that tracks the metal sheets movement. The developed setup enables the determination of boundary conditions for fixtureless welding. Two types of sensors record the welding process. First, three inductive probes are applied to record the metal sheets` movement and second, a long-wave infrared (LWIR) camera records changes in the thermal radiation field. Two different welding speeds and laser powers were used to produce a variety of welds. The dataset can be used for data-driven algorithms to predict the metal movement, analyze the thermal radiation field, or develop quality control methodologies. KW - Laser Beam Butt Welding KW - Inductive Probes KW - LWIR Camera KW - Time Series KW - Images KW - Thin Steel Sheets KW - Classification KW - Regression Y1 - 2025 U6 - https://doi.org/10.1016/j.dib.2025.111381 SN - 2352-3409 VL - 59 SP - 1 EP - 8 PB - Elsevier BV CY - Amsterdam 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 -