  Damage nucleation from repeated dislocation absorption at a grain boundary is
simulated with molecular dynamics. At the grain boundary-dislocation
intersection site, atomic shuffling events determine how the free volume
brought by the incoming dislocation is accommodated. This process in turn
determines the crack nucleation mechanism, as well as the critical strain and
number of dislocations that can be absorbed before cracking. Slower strain
rates promote earlier crack nucleation and a damage nucleation mode where
cracking is preceded by dislocation emission. The simulation methodology
presented here can be used to probe other types of boundaries as well, although
multiple thermodynamically equivalent starting configurations are required to
quantify the damage resistance of a given grain boundary.
