The effect of non-crack component on critical fracture energy of ductile material

Recently, Marie and Chapuliot have described ductile failure in terms of fracture energy which is associated with the local plasticity surrounding the crack tip. They introduced critical fracture energy, G(fr), as a new energy release term related to crack growth and also claimed that G(fr) is a material property. They also proposed several schemes for the determination of the value of G(fr) from specimens as well as from components. In all these methods the role of non-crack displacement in the crack growth process has not been considered. For the specimens or the components for which non-crack displacements are significant the proposed methods have some limitations in their application. In this paper an attempt has been taken to model the ductile crack growth phenomenon with the same approach of G(fr) considering the effect of non-crack displacement during crack growth. The necessary modifications in a graphical method for determination of G(fr) have been suggested. The expression for Ernest's J(M-Pl) from which G(fr) is calculated is also modified. The values of G(fr) have been determined using the modified schemes for CT specimens and pipes with circumferential cracks and checked for whether G(fr) is an intrinsic material property. (C) 2004 Elsevier Ltd. All rights reserved.