Horst Gunther Delorenzi

Energy release rate calculations by the finite element method

Abstract The present paper outlines a finite element method for calculating the energy release rate. The method is based on a continuum mechanics formulation of the virtual crack extension principle and can be used with linear elastic materials as well as materials following the deformation theory of plasticity. The formulation is easily incorporated into a finite element program, but can also conveniently be used as part of a post-processing program, which uses stress and displacement data from a finite element analysis to calculate the energy release rate. The present formulation can be used as a unified approach for 2-D and 3-D fracture problems and includes the effect of body forces and traction loading on the crack faces.

Three-dimensional elastic-plastic finite element analysis of small surface cracks

Abstract Three-dimensional, elastic and elastic-plastic finite element analysis of small surface cracks was performed. The elastic analysis is in good agreement with other solutions. For a round surface with a radius equal to six times the crack depth, the K at the surface is about 4% higher than the K for a flat surface. The results of the elastic-plastic analyses show a unique variation of the effective K (J-integral) along the crack front with a decrease in K at the surface due to a lack of plane strain constraint and an increase in the effective K at the maximum depth point with increasing plasticity. Similar behavior was observed for a semielliptical crack. Increasing the strain hardening exponent from 10 to 20 produced similar results with slightly higher effective As for high applied strains. These results are useful in understanding the fracture behavior of small surface cracks.