Three-dimensional dynamic perturbation of a propagating crack

Asymptotic formulae are derived for the perturbations to the stress intensity factors induced by a small three-dimensional dynamic perturbation of a propagating, nominally plane, crack. The crack propagates through an infinite isotropic uniform medium and full account is taken of the equations of elastodynamics. Previous work by the authors treated the case in which the edge of the crack was subject to an in-plane perturbation, so that the crack remained plane, but with a wavy edge. The present work completes the study, by allowing for out-of-plane perturbations. (C) 1997 Elsevier Science Ltd.