Elastic Behaviors of Twist Disclination Loops near a Free Surface

For a twist disclination loop situated in an infinite homogeneous elastic medium or in a nonhomogeneous medium where the loop plane is parallel to the interface, its elastic field involves only shear stresses. However, when the plane of the loop is in some arbitrary orientation with respect to the interface of a two-phase system, there is a dilatational field associated with the loop. Consequently, it is likely to interact not only with screw dislocations but also with edge dislocations, point defects, and wedge disclinations. To demonstrate this point, we examined the interaction between a free surface and a disclination loop. Equilibrium orientations of disclination loops have been obtained. Interaction energies of loops and image forces acting on them also have been determined. They are affected by the Poisson's ratios of the elastic media. Some comparison between the behaviors of dislocation and disclination loops are discussed.