Springback Simulation with Complex Hardening Material Models

The rise in the light weight automotive design necessitates the usage of the high strength steels, which increase the springback tendency in the sheet metal forming. Contrary to the conventional steels, the high strength steels showing larger Bauschinger effect require complex hardening material models to predict the springback accurately. Nowadays lots of FEM material models regarding isotropic-kinematic hardening exist as well as a variety of complex measurements to determine the material parameters of these models. In this study, Yoshida-Uemori material model [1, 2] implemented into LS-DYNA via the user material interface is used to perform channel draw tests with various die radii for some steel grades. In order to detect the springback accuracy of this user model, the standard LS-DYNA material models Mat36 and Mat103 have been evaluated. Different test strategies to identify the material parameters by LS-OPT have been investigated to clarify that the test used to calibrate the material model is as important as the material model.