Influence of material microvoids and heterogeneities on fatigue crack propagation

The evaluation of crack initiation, short-crack growth as well as crack path at microscopic scale is a crucial issue for the safety assessment of macroscopically fracture-free structural components. In the present paper, the crack propagation at the material microscale is modeled by taking into account the spatial variability of mechanical characteristics of the material as well as the local multiaxial stress field disturbance induced by inhomogeneities (inclusions or voids). By adopting some crack extension criteria under mixed mode, the short-crack path is determined. A microstructure dependence of the crack path arises in the short-crack regime, while the microstructure of the material does not influence the crack propagation for sufficiently long cracks. A mean weighted equivalent stress-intensity factor (SIF) is computed for kinked short cracks, where the range of such a SIF can be used as a key parameter dictating their fatigue crack growth rate.