Stress corrosion cracking was modelled by considering the interaction of a screw dislocation, with a film-covered mode-III crack, under an applied remote load. Exact solutions were obtained, and the results showed that the crack stress field that was due to the applied load was enhanced by a harder film or weakened by a softer film. When the crack length was much greater than the film thickness, the local stress intensity factor was approximately equal to the product of the nominal applied stress intensity factor and the ratio of the shear modulus of the film to that of the substrate. The critical stress intensity factor for dislocation emission from the crack tip was markedly affected by the stiffness and thickness of the film. A dislocation was more easily emitted from the crack tip if the covered film had a higher shear modulus than that of the substrate. A softer film made dislocation emission more difficult.

Interaction of a Screw Dislocation with a Thin Film-Covered Mode-III Crack. T.Y.Zhang, C.F.Qian: Acta Materialia, 1996, 44[11], 4513-20