Simulations of dislocation nucleation and glide, ahead of a crystallographic mode-II crack, were performed for push-pull and reversed torsion fatigue conditions. An effect of the normal stress upon the friction of crack flanks, as well as upon the conditions for dislocation emission, was introduced. Crack growth-rates were deduced from the dislocation fluxes at the crack tip. By taking account of the presence of grain boundaries, the repeated decelerations (and sometimes arrests) which characterized stage-I crack growth could be described by the model.

A Discrete Dislocation Model of Stage-I Fatigue Crack Growth and an Analysis of Mode-I to mode-II Transition at Low ΔKI. V.Doquet: Journal de Physique IV, 2000, 10[6], 145-50