A concurrent multiscale study of dynamic fracture

Abstract

Dynamic fracture is a complex multiscale physical phenomenon. The process occurs in multiple time and length scales. Macroscopic behaviors such as crack instability and brittle/ductile transition are consequences and combinations of a series of microscopic events such as dynamic dislocation motions and formation of nano voids. On the other hand, the atomistic bond breaking and the motion of dislocation are strongly affected by continuum stress field as well. Thus, delineating the underlining multiscale process is demanding to understand the fundamental physics. In this work, we employed previously proposed concurrent multiscale method between multiscale micromorphic molecular dynamics (MMMD) and peridynamics to simulate dynamic fracture. To achieve widely adaptive message translation, especially for heterogeneous messages, the coupling utilizes the recently developed MMMD which has an intrinsic multiscale structure to serve as the translator for the messages from different scales. The main innovations of this work are: (1) The proposed MMMD/Peridynamics coupling is a non-local to non-local multiscale method; (2) The coarse-scale peridynamic model is built based on an atomistic-informed Cauchy–Born material model that has minimum empiricism, and (3) The multiscale method has the consistent dynamic fracture criterion at all scales. We investigate the crack nucleation, branching and propagation under different loading rates, putting the emphasis on brittle/ductile transition and crack propagation through the atomistic–continuum interface. Quantitative results of nucleation, bifurcation and the crack speed under different loading rates are presented and discussed in the paper.