| Abstract: | The governing finite element system for elastic-plastic analysis of fracture specimens in three dimensions is formulated. The formulation accounts for mixed material hardening, finite strains, finite rotations and plastic incompressibility. The implementation of these aspects into a computational formula is presented and alternative formulations are compared. Small strain theory is recovered as a special case of the present formulation. Analysis is performed on a finite thickness centre-cracked specimen. The grid characteristics required for converged solutions are discussed. The effects of material hardening model and specimen thickness are studied. The local yield state is examined as a gauge of the local deformation processes. The implications for the fracture behaviour of the specimen are discussed. Local surface displacements are compared to experimentally measured yield surfaces. The formulation is shown to predict extremely accurate local deformation in the neighbourhood of the crack front. Contrary to the few three-dimensional fracture studies carried out to date, this analysis concentrates on the local deformation behaviour which ultimately controls fracture. Accurate resolution of this behaviour is essential before meaningful fracture criteria in three dimensions can be developed. |
