A continuum damage model for multi-axial low cycle fatigue of porous sintered metals based on the critical plane concept

Experimental investigations reveal very different damage mechanisms in porous sintered metals from those of conventional dense materials. Interactions between the inherent porosity and heterogeneous matrix result in complicated deformation behavior and fatigue damage processes. In the present work, the damage evolution in the sintered metal under multi-axial cyclic loading conditions is studied experimentally and computationally. The total damage is divided into the stress-related elastic damage, the plastic damage induced by the plastic deformations and the fatigue damage driven by cyclic loading. To predict the cyclic deformation behavior as well as the fatigue damage evolution, a nonlinear fatigue damage model coupled with the critical plane concept is proposed, embedded into the Ohno-Wang cyclic plasticity and implemented into the FEM software ABAQUS based on an implicit integration algorithm. The proposed damage model is computationally and experimentally verified under multi-axial cyclic loading paths with different strain amplitudes. A good agreement between experimental and computational results shows that the present model is able to describe cyclic mechanical behavior and fatigue damage of porous metals.