On the micromechanics of void growth by prismatic-dislocation loop emission

Experimental evidence and recent molecular dynamics simulations of void growth indicate that prismatic dislocation loop emission by externally applied stresses is a viable mechanism of void growth under shock loading conditions when diffusive processes are given no time to operate. In this paper, the process of growth by loop emission is studied in a model system comprised of a void in an infinite linearly elastic and isotropic solid loaded axisymmetrically by remote applied stresses. First, the interaction between applied stresses, the stress field of a single dislocation loop or a pile-up of loops next to the void, the surface energy expenditure on void surface change, and the lattice resistance to the motion of loops is reviewed. The necessary condition for interstitial loop emission is used to determine the equilibrium positions of the loops as well as the maximum number of loops in a pile-up under given applied stresses. For the parameters of the model-material with purely hydrostatic loading, the numerical results yield a volume change for the void, which when normalized by the initial undeformed volume, exhibits a strong dependence on the size of the void for radii less than ∼400 times the lattice Burgers vector. For larger voids, the normalized volume change was found to be independent of the void radius.