Effect of principal damage plane rotation on anisotropic damage plastic model

Under nonproportional loading, the principal planes of material, stress and damage are expected to differ, producing a hysteretic effect on the resulting design and failure analysis. This paper describes the development of an anisotropic damage model taking into account the effect of the principal damage plane rotation. All of the required mathematical formulations to generalize the damage model are derived in the principal damage coordinate system. Numerical procedures to include the changing damage planes are described in details. Two example cases of AL6111-T4 sheet material are provided to demonstrate the importance of the rotational effects of the principal planes on the resulting material behaviors under nonproportional loading.