Damage and Fracture Model under Multi-axial Stress Conditions Based on Damage Mechanics

Abstract

In various press forming and deep drawing processes, it is important to predict the forming limit under multiaxial stress conditions. Even in the uniaxial tension test, it is necessary to consider stress triaxiality to accurately predict failure strain, because after necking occurs, the neck portion, which is locally deformed by loading, is in a multiaxial stress state due to the change in the local cross-sectional area. In recent years, some damage and fracture models have been proposed focusing on the effect of stress triaxiality, while most of them are simple phenomenological models that do not consider the mechanical framework. In this study, the constitutive equation and damage evolution equation, which are based on a second-order symmetric damage tensor within the framework of the continuum damage mechanics, are constructed as a function of stress triaxiality to analyze damage and fracture of materials under multiaxial stress conditions. FEM analysis of an example problem was also performed, and the occurrence of anisotropic damage and the correlation between damage and equivalent plastic strain were confirmed.