Energy dissipation associated with crack extension in an elastic-plastic material

Abstract

Crack extension in elastic-plastic material involves energy dissipation through the creation of new crack surfaces and additional yielding around the crack front. An analytical procedure, using a two-dimensional elastic-plastic finite element method, was developed to calculate the energy dissipation components during a quasi-static crack extension. The Fracture of an isotropic compact specimen was numerically simulated using the critical crack-tip-opening-displacement (CTOD) growth criterion. Two specimen sizes were analyzed for three values of critical CTOD. Results from the analysis showed that the total energy dissipation rate consisted of three components: (1) the crack separation energy rate G s , (2) the plastic energy dissipation rate G p and (3) the residual strain energy rate G rs . All three energy dissipation components and the total energy dissipation rate initially increased with crack extension and finally reached constant values. For ductile materials (larger CTOD), G p becomes dominant (more than 70% of the total), whereas G rs remained constant (about 6%). Furthermore. G p appeared to vary linearly with the plastic zone height. G s is linearly proportional to the critical CTOD.