The non-local stresses due to a screw dislocation near to a free surface in such a medium were investigated by using a surface dislocation model. The non-local image force on a dislocation, due to the free surface, was also obtained. All of the classical singularities in the stresses and image forces were removed. A zero point of the stress was found which predicted that differing states of the shear stress existed simultaneously near to the dislocation. The appearance of a zero at the free surface, and a maximum in the dislocation image force was used to explain the existence of a dislocation-free zone.

K.L.Pan: Radiation Effects and Defects in Solids, 1995, 133[2], 167-78