On perturbations of plane cracks

Asymptotic analysis is presented for elasticity problems concerning out-of-plane perturbations of plane cracks. Some of the subtleties are first illustrated through consideration of twodimensional problems ; we derive formulae that generalize slightly those already available. Solution of the more difficult three-dimensional problem is facilitated through novel use of an integral identity. The asymptotic formulae that are developed for the stress intensity factors are more flexible than those available previously, in that no special system of coordinates based on the perturbed crack edge is employed. © 1998 Elsevier Science Ltd. All rights reserved.