Stability of the Dislocation Dipole in Half‐Space

The stability of an edge dislocation dipole of infinite length lying parallel to the free surface of an isotropic, semi‐infinite medium has been investigated by determining the dipole orientation for which the stress on both poles is less than a chosen dislocation friction stress. It is found that the effects of the surface are considerable, despite the fact that the stress field of the dipole is short‐ranged. In particular, the surface can induce orientations of stability which are not expected from the infinite body behaviour. Similar results are likely to arise for prismatic dislocation loops in bounded media. Some aspects of the effect of an applied shear stress on the dipole are also studied.