Nonplanar Crack Growth Using the Surface Integral Method

Abstract

A surface integral formulation, based on representing a crack as a distribution of force dipoles, has been developed for modeling the propagation of a three-dimensional nonplanar fracture. The minimum strain energy density and maximum circumferential stress theories were used to determine the direction of crack growth. The extension of the fracture surface was based on the Paris law for fatigue. Remeshing of the fracture during growth was accomplished by adding a ring of elements to the existing mesh at the conclusion of each increment of crack growth. This promoted the efficiency of the algorithm by eliminating the need to recalculate the entire coefficient matrix. Use of the surface integral method, coupled with growth criteria, has yielded an accurate model for three-dimensional nonplanar crack growth under mixed mode loading conditions. The study of several penny-shaped precracks under mixed-mode loading conditions produced the expected growth trajectory, and compared favorably to existing two-dimensional, three-dimensional, and experimental results found in the literature.