Image force on a straight dislocation emitted from a cylindrical void

The image force exerted by the free surface of a cylindrical circular void on a nearby straight dislocation depends on whether the dislocation has arrived at its location by the emission from the surface of the void, or by the glide from infinity. In the context of elasticity theory, in the first case, the dislocation has been created by imposing the displacement discontinuity along the cut from the free surface of the void to the center of the dislocation, and, in the second case, from the center of the dislocation to infinity. The explicit expressions for the two corresponding image forces are derived and compared. It is shown that the attraction from the free surface of the void is stronger in the first case, particularly for smaller voids. Furthermore, in the case of dislocation emitted from the surface of the void, the interaction energy depends on the cut used to impose the displacement discontinuity, but not in the case of a dislocation approaching the void from infinity. The relevance of the obtained results for the materials science problems is discussed.