Abstract
Fracturing behaviours are complex and involve complex interactions among the agents of separation: mechanical forces and distortions, activity of the environment upon the surface of the metal, and the inherent metallurgical structure leading to the nucleation and growth of fractures. When we succeed in isolating any one of these three, or characterising interactions between any two, our understanding of the processes leading to structural failure is enhanced. Indeed, to isolate one effect, the other two must be known or held constant. It is for this reason that the mechanics of fracturing, as one agent, is so essential to studies of corrosive environmental influences, as another agent. Fracture mechanics provides a way to normalise out the effects of the mechanical conditions peculiar to variations in cracksize and shape and the stress which this material discontinuity refuses to support. To the extent that linear elasticity describes the mechanical 'environment', the principle of superposition permits the re-situation of the crack into a real elastic structure, thus enabling the results of small laboratory tests to predict the response of large structures to various stress conditions.
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