A two-parameter criterion for predicting the fracture location along a surface crack

Abstract

The fracture prediction for materials containing surface cracks is not well established. In this paper, a new two-parameter fracture criterion which can predict the location of maximum crack extension along a surface crack front was presented. The surface-cracked specimens with different crack sizes and loads were selected, and the finite element method (FEM) was used to model the J-integral and the equivalent plastic strain (εp) distributions along the crack front for different specimens. And then, in succession, the areas APEEQ surrounded by the εp isoline ahead of crack tips under different J-integrals and the unified constraint parameter Ap were calculated. Based on the parameter Ap, J-integral and the fracture toughness Jref measured in a standard test, the J/(JrefAp), which considered the combined effects of crack driving force and material resistance force, was determined. The critical fracture location is the location for which the J/(JrefAp) is a maximum. The results show that for all the specimens, the prediction results obtained by two-parameter criterion are consistent with the measured results obtained by experiments. The J/(JrefAp) is a suitable prediction criterion to model the location of the maximum crack extension of surface crack. For comparison, similar predictions were also made using a single-parameter J-integral and Ap.