Elasto-plasticity behavior of high strength steel sheet in biaxial stress path change

The elasto-plasticity behavior of a high-strength steel sheet of 980 MPa-TS was investigated by performing biaxial tension experiments. In order to evaluate the accuracy of constitutive models of plasticity in describing such elasto-plasticity behavior, numerical simulations of stressstrain responses were conducted for the same stress patfis as those in the experiments using two types of constitutive models: the isotropic hardening model (IH model) and the kinematic hardening model proposed by the present authors (Yoshida-Uemori model). In this work, special emphasis is placed in the cases of stress-path change. In experiments on radial loadings after equi-balanced tension preloading, it was found that flow stresses are considerably lower than uniaxial tension flow stress. The IH model can hardly describe this phenomenon, although it is sufficient for stress-strain analysis of proportional loading cases. In contrast to this, the Yoshida-Uemori model can well predict every stress-strain response in biaxial stress-path changes.