Behavior of screw dislocations near phase boundaries in the gradient theory of elasticity

The solution of the boundary-value problem on a rectilinear screw dislocati on parallel to the interface between phases with different elastic moduli a nd gradient coefficients is obtained in one of the versions of the gradient theory of elasticity. The stress field of the dislocation and the force of its interaction with the interface (image force) are presented in integral form. Peculiarities of the short-range interaction between the dislocation and the interface are described, which is impossible in the classical line ar theory of elasticity. It is shown that neither component of the stress f ield has singularities on the dislocation line and remains continuous at th e interface in contrast to the classical solution, which has a singularity on the dislocation line and permits a discontinuity of one of the stress co mponents at the interface. This results in the removal of the classical sin gularity of the image force for the dislocation at the interface. An additi onal elastic image force associated with the difference in the gradient coe fficients of contacting phases is also determined. It is found that this fo rce, which has a short range and a maximum value at the interface, expels a screw dislocation into the material with a larger gradient coefficient. At the same time, new gradient solutions for the stress field and the image f orce coincide with the classical solutions at distances from the dislocatio n line and the interface, which exceed several atomic spacings. (C) 2000 MA IK "Nauka /Interperiodica".