The role of homogeneous nucleation in planar dynamic discrete dislocation plasticity

Homogeneous nucleation of dislocations is the dominant dislocation generation mechanism at strain rates above 10⁸ s^-1; at those rates, homogeneous nucleation dominates the plastic relaxation of shock waves in the same way that Frank-Read sources control the onset of plastic flow at low strain rates. This article describes the implementation of homogeneous nucleation in dynamic discrete dislocation plasticity (D3P), a planar method of discrete dislocation dynamics (DDD) that offers a complete elastodynamic treatment of plasticity. The implemented methodology is put to the test by studying four materials - Al, Fe, Ni, and Mo - that are shock loaded with the same intensity and a strain rate of 10¹⁰ S^-1. It is found that, even for comparable dislocation densities, the lattice shear strength is fundamental in determining the amount of plastic relaxation a material displays when shock loaded.