The method of caustics in environmental cracking

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A simple and powerful crack growth criterion under combined environmental conditions and applied loads is formulated for mixed-mode situations based on the method of caustics. It is established that the axis of symmetry of the caustic represents the crack growth direction, while the crack growth condition is expressed in terms of the diameter of the caustic. Caustics can easily be obtained by illuminating the specimen in the vicinity of the crack tip by a laser light beam and recording the optical pattern on a viewing screen at some distance from the specimen. An elegant procedure for the experimental study of environmental cracking is thus developed. © 1986.

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Engineering Fracture Mechanics