Viscoplastic constitutive modeling of anisotropic damage under nonproportional loading

Based on the theory of damage mechanics, a viscoplastic constitutive modeli ng of anisotropic damage for the prediction of forming limit curve (FLC) is developed. The model takes into account the effect of rotation of principa l damage coordinates on the deformation and damage behaviors. With the aid of the damage viscoplastic potential, the damage evolution equations are es tablished. Based on a proposed damage criterion for localized necking, the model is employed to predict the FLC of aluminum 6111-T4 sheet alloy. The p redicted results agree well with those determined experimentally.