A numerical study of void distribution effects on dynamic, ductile crack growth

Abstract

Rapid crack propagation through a material containing two populations of second phase particles is analysed numerically. An elastic-viscoplastic model of a ductile porous material is used to represent small second phase particles that nucleate cavities at large strains as well as larger inclusions with low strength, which result in large voids near the crack tip at an early stage. Various random distributions of the larger inclusions in front of the crack tip are considered, while the small second phase particles are taken to be uniformly distributed. Analyses are carried out for a plane strain double edge cracked specimen under symmetric impulsive loading at the ends and adiabatic heating and the resulting thermal softening are accounted for. The predicted crack growth velocities are entirely based on the ductile failure criterion incorporated in the material model, and thus the present results give a direct estimate of the effect of various random inclusion distributions, compared to results for a uniform distribution. The resistance to crack growth increases and the average crack speed decays with increasing deviation from a uniform inclusion spacing. The dependence of the average crack speed on the root mean square particle spacing is found to be approximately linear over the range considered.