A concurrent atomistic-crystal plasticity multiscale model for crack propagation in crystalline metallic materials

Abstract

This paper develops a coupled concurrent atomistic–continuum multiscale model for analyzing crack propagation and associated mechanisms in crystalline metallic materials. This modeling framework can be used to develop effective continuum-scale constitutive models for crack evolution in deforming domains characterized by crystal plasticity. The atomistic region is modeled by the molecular dynamics (MD) code LAMMPS, while the continuum region is modeled by a dislocation density crystal plasticity FE model. A novel method is developed to transfer discrete dislocations in the atomistic domains to dislocation densities in the continuum domain. Propagation of dislocation densities in the continuum domain is modeled by the advection equation of a conserved quantity using the reproducing kernel particle method (RKPM) in conjunction with the collocation method. Validation studies are conducted by comparing results of the concurrent model with those by MD for nickel single crystal specimen with an embedded crack. An analytical model of the crack tip nucleated dislocation density evolution is developed for inclusion in crystal plasticity models. The effect of applied strain-rate and temperature on the parameters of this model are studied.