The elastic interaction of a finite crack with a coherent interface was investigated. A planar distribution of continuous dislocations, and a planar array of discrete interface dislocations, were used to simulate the crack and the interface, respectively. It was found that a primary and secondary shielding/anti-shielding effect upon mode-I and mode-II fracture, respectively, were induced by the interface. As the interface was symmetrical with respect to the crack, the secondary effect vanished and only the primary effect persisted. If the interplanar spacing on one side of the interface where the crack was present, was larger than that on the other side, both crack tips were shielded from mode-I fracture simultaneously; and vice versa. Therefore, coherent precipitates with a smaller lattice constant than that of the matrix became effective barriers to crack propagation. The mode-I shielding/anti-shielding effect on both crack tips, which was linearly proportional to the lattice misfit, became significant as the crack came closer to the interface, or the interface became longer. With increasing crack length, the primary effect increased monotonically at the crack tip nearer to the interface. It increased, reached a maximum and then decreased at the other crack tip.

Elastic Interaction between a Coherent Interface and a Finite Crack. K.M.Lin, H.C.Lin, S.D.Wang: Physica Status Solidi A, 1996, 158[2], 481-92