Dislocation loop evolution from a source in a field of randomly distributed obstacles with a discrete strength spectrum

We have simulated dislocation loop emission by a Frank-Read source, and its evolution in a field of randomly distributed point obstacles with a discrete strength spectrum. The obstacles and their strengths are interpreted as the intersections of a dislocation loop with the base plane of the source. It is observed that behind the front of the expanding dislocation segment there remain islands of incomplete crystallographic slip that are hard-to-overcome regions of the glide plane that the dislocations bypass by the Orovan mechanism. We present the quantitative characteristics of the islands, and we classify them. We discuss the dynamical effects associated with pinching off a loop from a dislocation bounding the region of an expanding crystallographic glide. These effects must also be taken into account when describing the emission spectrum accompanying plastic deformation. © 1998 Plenum Publishing Corporation.