Crystal plasticity based finite element modeling and experimental study for high strain rate microscale laser shock clinching of copper foil

Abstract

Abstract The microscale laser shock clinching (LSC) is a promising micro-forming technology that enables the deformation-based joining of ultra-thin sheets. In this research, a numerical crystal plasticity model of the LSC process at ultra-high strain rates is established to incorporate the actual grain size of the material and the anisotropic characteristics caused by different initial grain orientations. The simulations are in good agreement with the experiments, indicating that the crystal plasticity finite element method (CPFEM) can be used to study plastic deformation and predict the joint geometry during the LSC process. The results show that different zones of the joint exhibit different material flow behaviors, which are accordingly divided into three zones, namely the material inflow zone, the interlock forming zone, and the material stacking zone. The material at the neck and underside experiences the most severe thinning and is prone to failure as being located at the junction, where the material flows in opposite directions on both sides. It is also found that the holes with different diameter-to-depth ratios in the perforated steel sheets greatly affect the neck thickness, a key mechanical strength factor in formed joints.