Interaction of a screw dislocation with a thin-film-covered mode III crack

Abstract

The present work models stress corrosion cracking by considering the interaction of a screw dislocation with a thin-film-covered mode III crack under an applied remote load. Exact solutions are derived from the proposed model. The results show that the crack stress field due to the applied load is enhanced by a harder film or abated by a softer film. When the crack length is much larger than the film thickness, the local stress intensity factor approximately equals the product of the nominal applied stress intensity factor times the ratio of the shear modulus of the film over that of the substrate. The critical stress intensity factor for dislocation emission from the crack tip is greatly influenced by the film stiffness and the film thickness. It is easier for a dislocation to be emitted from the crack tip if the covered film has a larger shear modulus than the substrate. The opposite is also true, a softer film makes the dislocation emission more difficult.