Brittle and ductile crack propagation using automatic finite element crack box technique

In this paper, a numerical automatic crack box technique (CBT) is developed to perform fine fracture mechanics calculations in various structures without complete re-meshing. This technique aims to simulate the fatigue crack growth under mixed mode loading in 2D medium and shell structures calculated with the ABAQUS code, for elastic and for elastic–plastic materials. Using this method, series of numerical calculations by FEM of the mixed mode crack growth are carried out and compared with experimental tests such as a special cracked specimen subjected to different mixed mode loads. The crack growth paths are determined by using different elastic and elastic–plastic crack extension criteria. It is shown that the proposed technique is an efficient tool to simulate the crack extension angle in elastic and elastic–plastic materials. Nevertheless further experiments are needed to confirm conclusions deduced from elastic–plastic calculations. this technique, several phenomena influencing the crack extension are analyzed: the overload during fatigue, the fracture toughness of the material in relation with its critical J integral and its behaviour law.