Extrinsic and intrinsic boundary dislocations

Some recent experimental results on boundary dislocations are discussed with reference to the concepts of extrinsic and intrinsic boundary dislocations and the associated stress and displacement fields. It is shown that the presence of a long-range stress field is not only dependent on the origin of the boundary dislocations, but also results from the external displacement conditions allowed at the outer limits of the crystals. The conditions for this long-range stress field to vanish are specified. The difficulties in experimental studies of the mechanical aspects of boundary dislocations arrays are commented on, and some suggestions are made to help in their analysis.