Interface microcrack nucleation

The Zener-Stroh mechanism of microcrack nucleation by a dislocation pile-up or band impinging upon an interface has been believed to be one of the basic mechanisms of microcrack nucleation in polycrystalline materials. In the case of different elastic properties of composite constituents, this problem is accurately solved in the present paper. The minimum number of elementary dislocations in the band necessary to form a microcrack, as well as the interface microcrack length are found in terms of physical properties and the number of elementary dislocations in the band. A band bears a stronger singularity than a pile-up, and therefore the obtained solution can serve as an upper bound estimate of the solution for the pile-up. The results of the paper may be used for the direct measurement of the true interface surface energy by an experimental observation of the nucleation of an interface microcrack.