FOR 5134:  Solidification Cracks during Laser Beam Welding: High Performance Computing for High Performance Processing

• Subject Area: Mechanical and Industrial Engineering ; Computer Science, Systems and Electrical Engineering ; Materials Science and Engineering ; Mathematics
• Term: since 2021
• Website: Homepage
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 434946896

Lasers as tools in production technology are gaining increasing importance due to their ability to join workpieces contact-free and highly automated. One of the largest obstacles for the further pervasion of this process is the formation of solidification cracks during the joining procedure. Superficial solidification cracks can be detected easily by sensory measures. Solidification cracks within the weld seam, however, can only be detected with considerable effort and might lead to premature failure of the workpiece. There are various phenomenological explanatory approaches in the literature which all rely on empiric measures. With these models no quantitative statements on cracking probabilities can be made without prior experimental investigations. Thus, change of material, joining geometry or processing parameters always requires substantial effort. Therefore, quantitative understanding of the mechanisms responsible for the formation of solidification cracks is indispensable to reach the full potential of laser as a tool.Aim of this research group is to develop a quantitative understanding of these mechanisms. To this purpose the relationship between material, processing parameters, workpiece and cracking probability will be described quantitatively on all relevant length scales using a predictive and highly parallelized simulation framework. On the microscale the developing microstructure will be predicted for different processing parameters using strongly coupled chemo-thermomechanical solidification simulations. On the mesoscale the interaction between laser and material in the process zone will be modelled with extremely high spatial and temporal resolution in order to determine temperature gradients, solidification velocities, and local chemical composition of the alloy in the melt pool depending on the processing parameters. With this resolution the resolidifying area –the so-called mushy zone– can be reproduced explicitly for the first time. This area will also be modelled thermomechanically while taking microstructural effects into account. On the macroscale local strain and cracking probabilities will be predicted using thermal and microstructural information derived from the micro- and mesoscale. With this, quantitative investigations of the relationship between material and processing parameters on the different length scales involved will be facilitated for the first time.The realization of this aim necessitates the collaboration of scientists from production technology, materials science and mechanics. To implement and interconnect these models efficiently, scientists from computer science and mathematics are also involved in the research group.

• DFG Programme: Research Units
• International Connection: Russia, USA

Projects

• Coordination Funds (Applicant Schmidt, Michael )
• Efficient, robust, and highly scalable implicit solver for the simulation of thermoplastic solidification processes (Applicants Klawonn, Axel ;  Lanser, Martin )
• Macro-mechanical modelling of the material behavior during laser beam welding under mechanical load (Applicant Rethmeier, Michael )
• Massively Parallel Simulation of the Melt Pool Area during Laser Beam Welding using the Lattice Boltzmann Method (Applicant Rüde, Ulrich )
• Microstructure simulation of solidification in the weld (Applicants Nestler, Britta ;  Schneider, Daniel )
• Multiscale thermoplastic analysis in the solidification zone (Applicants Scheunemann, Lisa ;  Schröder, Jörg )
• Sustainable data and software management for research software to simulate solidification cracking during laser beam welding (Applicants Köstler, Harald ;  Selzer, Michael )
• Thermo-Fluiddynamical Investigation of the Melt Pool Area (Applicant Schmidt, Michael )

• Spokesperson: Professor Dr.-Ing. Michael Schmidt