Microcrack Interaction and Shear Fault Failure

The method of pseudo-tractions is used to solve the problem of interacting cracks which are arbitrarily distributed and are loaded by concentrated forces. The effect of interaction on the crack tip stress intensity factors is obtained for a set of equally spaced, parallel cracks which are loaded by both concentrated forces and uniform farfield stresses. For the special case when the cracks are collinear, the results are compared with those of the closed-form exact solution to check the accuracy of the method. The method is then applied to an array of dynamically growing wing cracks, and the growth regime of a periodic array of wing cracks of arbitrary orientation is studied. The shear fault failure mechanism is discussed in terms of such a model. The direction of the shear fault is related to the direction of a periodically distributed wing-crack array, in which tension cracks grow to a length equal to their spacing at a minimum applied load. The effect of confining pressure on the shear fault direction is discussed.