Connecting molecular dynamics and dislocation dynamics to continuum in hierarchical simulations of microcracks in solids

Multiscale approach to crack tip plasticity involves length scales from electronic structure to the continuum, as well as deformation behavior from single dislocation nucleation to plastic-zone shielding. A current challenge is to connect the different levels and methods of simulation in order to study ductile fracture in a more holistic fashion, a goal that cannot be accomplished through any one single simulation. We present two specific examples of potentially useful connections, (1) using molecular dynamics to determine a stress-displacement relation for direct use in continuum-level analysis, and (2) a comparative study of dislocation microstructure evolution by discrete dislocation dynamics and finite-element method. Applications to understanding brittle-ductile behavior in an important metal, alpha-Fe, are particularly emphasized.