The dislocation loop near a free surface

Abstract The solution for the displacements due to a point force in a semi-infinite isotropic elastic medium is used to obtain the displacements of an infinitesimal dislocation loop of arbitrary orientation. By integration these can be used to give the elastic field of a dislocation of arbitrary shape, orientation and Burgers vector. The equations are used to study the stability of a prismatic dislocation loop on a glide prism of square cross section near a free surface. Results are presented for the forces on the loop sides and the changes in loop energy during rotation for cases in which b is normal or parallel to the surface. The width of the denuded zone is discussed, and the results on loop orientation indicate why the equilibrium orientations of polygonal loops in thin films should be stabilized away from the pure edge orientation.