A strain rate dependent anisotropic hardening model and its validation through deep drawing experiments

Abstract

In the present work, a modified version of the widely used Yld2000-2d yield function and its implementation into the commercial FE-code LS-Dyna is presented. The difference to the standard formulation lies in the dependency of the function parameters on the equivalent plastic strain. Furthermore, strain rate dependency is incorporated. After a detailed description of the model and the identification of the parameters, the numerical implementation i.e., the stress-update algorithm used for the implementation is explained. In order to validate the model, two different materials, namely Formalex™5x, a 5182-based aluminum alloy and a DC05 mild steel were characterized. The results of the tensile and hydraulic bulge tests are presented and used for the parameter identification. The experimental curves are reproduced by means of one element tests using the standard and modified model to demonstrate the benefit of the modifications. For validation purposes, cross die geometries were drawn with both materials. The outer surface strains were measured with an optical measurement system. The measured major and minor strains were compared to the results of simulations using the standard and the modified Yld2000-2d model. A significant improvement in prediction accuracy has been demonstrated.