Determination of Constitutive Equation Parameter Using Finite Element Polycrystalline Model

A plastic constitutive theory incorporating the directional dependence of the plastic strain increment dεp 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 nN, named "natural direction", in which the direction of the stress increment coincide with that of the plastic strain increment. In this report, a computer code for a finite element polycrystalline model is used for the numerical investigation of the variation of the two constitutive parameters μ(α) and β(α) of anisotropic plastic materials. The results show that the approximate functions for the two transition parameters are numerically determined and the direction dependence rule can be naturally extended for anisotropic plastic materials. It is also suggested that several quadratic functions used for classical plastic potential may be introduced for the natural direction potential whose normal is identical to the natural direction.