Damage evolution and modeling of sintered metals under multi-axial loading conditions

Sintered powder metals have found extensive engineering applications in industry. The mechanical property of sintered metals is characterized by high porosity and micro-cracks. Inelastic behavior of the materials is coupled with micro-crack propagation and coalescence of open voids. In the present paper the damage evolution of the sintered iron under multi-axial monotonic loading conditions was investigated experimentally and computationally. The tests indicated that damage of the sintered iron initiated already at a stress level much lower than the macroscopic yield stress. The damage process can be divided into three stages: the primary stage with high growth rate in the elastic state, the secondary stage with stable growth rate in the elastic-plastic state and fracture where the growth rate is too large to measure. Based on the uniaxial tensile tests an elastic-plastic continuum damage model was developed which predicts both elastic damage and plastic damage in the sintered iron under general multi-axial monotonic loading conditions. Computational predictions agree with experiments with different multi-axial loading paths. The damage evolution in sintered metals can be reasonably predicted by the proposed damage model. (C) 2013 Elsevier B. V. All rights reserved.