A Constitutive Theory for the Damage of Materials with Dynamic Micro Void Evolution Processes

Abstract

A rigid plastic constitutive model for porous ductile materials is constructed in this paper. Because of its solid physical basis and dispensability of experimental curve-fitting parameters, Gurson-type yield function is widely applied to investigate the effects of void nucleation, growth and coalescence on the damage behaviors of porous materials. However, it is extremely difficult to use this kind of yield condition for rigid plastic analysis. To solve this problem, a few concepts, parameters and formulations such as effective stress, effective strain rate, generalized triaxiality ratio and generalized triaxiality function, are defined. With the aid of these parameters and formulas, the stress-strain rate type constitutive model on the basis of modified Gurson's yield function is established. Brief discussions are carried out to manifest the characteristics of the present model. The reasonability of the new model is demonstrated by the comparisons with the theoretical systems of conventional models.