Loading of a metal results in the nucleation of voids around particles. Further deformation results in void growth and coalescence. This work combines mathematical models for void nucleation, growth, and coalescence into a simulation of a ductile fracture to examine the effects of stress triaxiality and constraint loss on ductile fracture.

Nucleation of voids from the particles is assumed to depend on the particle-matrix interface strength; subsequent void growth occurs according to equations developed by Rice and Tracey. The coalescence criterion involves a consideration of microstructural geometry.

Two types of loading are considered: proportional loading and near crack tip loading. In the latter case, a near crack tip region with a relatively large plastic zone and with significant constraint loss is considered. Results include a two-parameter failure locus for initiation of ductile fracture, which predicts the effect of constraint on ductile initiation.