with simplified relations between the state of deformation and their histories. In terms of the anisotropy

Magnesium alloy sheets have been extending their field of applications to automotive and elec-tronic industries taking advantage of their excellent light weight property. In addition to well-known lower formability, magnesium alloys have unique mechanical properties which have not been thor-oughly studied: high in-plane anisotropy/asymmetry of yield stress and hardening response. The rea-son of the unusual mechanical behavior of magnesium alloys has been understood by the limited symmetry crystal structure of HCP metals and thus by deformation twinning. In this paper, the phenomenological continuum plasticity models considering the unusual plastic behavior of magne-sium alloy sheet were developed for a finite element analysis. A hardening law based on two-surface model was further extended to consider the general stress–strain response of metal sheets including Bauschinger effect, transient behavior and the unusual asymmetry. Three deformation modes observed during the continuous in-plane tension/compression tests were mathematically formulatedConstitutive modeling for anisotropic/asymmetri