Evolving hardening behaviors of high strength steel sheets under altered loading paths

In this work, the subsequent yield loci of the given DP steel sheets were experimentally determined by conducting biaxial tensile tests with pre-strained cruciform specimens. The results revealed that distortional hardening behavior, which has been previously discovered and calibrated under proportional loading conditions only, still exist in the complex loading conditions. Moreover, the expanding and translating of the yield loci was non-neglectable, which means the isotropic and kinematic hardening should be considered. Therefore, the combined isotropic-kinematic-distortional hardening model was proposed to calibrate the evolving hardening behaviors of the given sheet metals. Afterwards, the proposed model, together with other hardening models, were programmed as user subroutines UMAT and VUMAT in ABAQUS respectively. The V-bending tests and FE simulations were then conducted to evaluate the springback predicting precision with proposed model.