Abstract
A plastic constitutive theory incorporating the directional dependence of the plastic strain increment dε^P on the stress increment dσ was proposed by Goya and Ito. The expression was given in terms of two transition parameters μ(α) and β(α) which denote the magnitude and the direction angle of the plastic increment, where α denotes the direction angle of the stress increment measured from a particular direction n_N, named "natural direction", in which the direction of the stress increment coincide with that of the plastic strain increment. It was also suggested that several yield functions used for classical plastic potential may be introduced for the natural direction potential whose normal is identical to the natural direction. It was choose Hill's quadratic function for the natural direction potential to anisotropic material. In this report, the law is implemented in an F.E.M. code for deformation analysis for anisotropic materials.
