Mode-III fracture was studied in terms of a discrete dislocation simulation. Under a remote mode-III stress, when the stress intensity factor at the crack tip was greater than that for dislocation emission, dislocations would be emitted from the tip. The magnitude of the stress intensity factor for dislocation emission did not depend only upon the dislocation core radius, frictional stress and shear modulus, but also upon the number of characteristic types of dislocation which were emitted in the vicinity of the crack tip. The velocity of the dislocations was assumed to be proportional to the third power of the effective stress. Dislocations which were dynamically and quasi-statically emitted from a static sharp surface crack tip during loading and unloading were investigated. The mechanical behavior of dislocations under dynamic emission exhibited an opposite trend to that for quasi-static emission. Dislocations which were dynamically emitted from a propagating sharp surface crack tip were also studied. The propagation rate of the crack tip was proportional to the third power of the stress intensity factor. When the emitted dislocations and the propagating crack tip had the same velocity, the system was in a steady state. Dislocations which were emitted in radial directions from the radial crack tips emanating from a circular hole were also considered.

Fundamentals of Mode-III Fracture - a Discrete Dislocation Simulation Approach. S.B.Lee: Key Engineering Materials, 1998, 145-149, 135-44