The formation of dislocation rings at crack tips was considered for the case where the glide plane was tilted against the crack plane and did not contain the crack front. The emanating ring was described in the Peierls model as a distribution of infinitesimal dislocations, and the effect of the interplanar potential in the glide plane upon the emission process was studied. The magnitude of the displacement, the radius of the ring and the profile of the displacement were allowed to vary during emission in order to minimize the energy. The formation of rings in tilted glide planes could avoid the formation of ledges, which had to occur when the dislocation was emitted in a plane which contained the crack front. Since ledge formation severely obstructed dislocation emission, it was suggested that ring formation was the more favorable process.

The Formation of Dislocation Rings on a Crack Front. G.Schoeck: Philosophical Magazine A, 1996, 74[2], 419-30