Mechanisms discontinuous cleavage

Fracture A general term to include any kind of discontinuity in a body of rock if produced by mechanical failure, whether by shear stress or tensile stress. Fractures include faults, shears, joints, and planes of fracture cleavage. 

Chakrapani and Pugh [118] inferred that the mechanism for crack growth was repeated cycles of H diffusion to the crack tip region followed by brittle fracture. This was supported by discontinuous acoustic emission signals. It was also suggested that the role of H in the brittle fracture could be in the formation of brittle hydrides or to produce decohesion. They inferred that since SCC fractures tend to occur on 3140 planes, these may correspond to the habit or cleavage planes of a hydride. Fracture surfaces for SCC and pure-HE systems were different the latter tended to be flatter and without the pleated/stepped structure. It was speculated that this could be related to H fugacity and H entry kinetics, and the fact that, for SCC conditions, dissolution occurs at the crack tip. 

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