Non-linear features of dislocation emission under mode-II loading were explored at the atomic scale. Crack-tip atomic string models were coupled with a continuum mechanics analysis. The dynamics showed that the atomic motion at the crack tip changed from periodic to chaotic as the mode-II stress intensity factor was increased. The chaotic atomic motion governed dislocation nucleation at the crack tip. A study of the dislocation emission band revealed a cloud-like drifting of the dislocation core ahead of the crack tip. When considered more quantitatively, this meant that the dislocation emission potential lost all local minima when KII reached a value: Kemit. The nucleated dislocations then escaped from the crack tip without stopping. Chaotic motion of the crack-tip atom string was observed at a remote stress intensity factor, Kchaos, which was less than 50% of Kemit. The onset of chaos initiated the emission of a dislocation.

Non-Linear Motion of Crack-Tip Atoms during Dislocation Emission Processes. H.Tan, W.Yang: Journal of Applied Physics, 1995, 78[12], 7026-34