Project Details
Projekt
Coordination Funds
Applicant
Professor Dr.-Ing. Michael Schmidt
Subject Area
Joining and Separation Technology
Term
since 2021
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
