1. (A) Counterclockwise contour Γ around a crack tip showing an element of path length ds, with unit vector n normal to the path and with stress and displacement vectors, P and u, respectively, also shown.
(A) Counterclockwise contour Γ around a crack tip showing an element of path length ds, with unit vector n normal to the path and with stress and displacement vectors, P and u, respectively, also shown. Crack length is a. (B) An element of material experiencing two-dimensional stress. Not all three stress components need be active; often only one or two components are active. (C) Rectangular pathΓ surrounding a crack tip, used to illustrate evaluation of a J-integral.
Katharine J. Mach et al. J Exp Biol 2007;210:
© The Company of Biologists Limited 2007