Effect of local elastic softening on crack extension

Abstract

Elastic softening materials are brittle materials such that crack extension is associated with a softening zone behind the crack tip, with the material elements within this zone exerting a restraining effect on the crack tip. Crack extension is sometimes characterised in terms of the stress intensity K F, due to the applied loadings, at the front of the softening zone, i.e. the actual crack tip. This paper is concerned with the determination of the maximum load K F value for a general positive geometrical configuration, for the case where the softening zone size is small compared with a solid's characteristic dimension. The resulting expression for K F is compared with the maximum load stress intensity value K T measured with regard to the initial crack position, i.e. the trailing edge of the softening zone.