Application of micromechanical models to the analysis of ductile fracture resistance behaviour
A damage model introduced by Gurson and modified by Needleman and Tvergaard is used to investigate the effects of specimen geometry on the ductile fracture resistance behaviour. The parameters of the models are measured directly or determined from tension tests by matching the calculate load drop with the experimentally observed failure strain. For a steel ASTM A 710 at room temperature a complete set of parameters was determined from smooth tension tests and used to predict the experimental load vs. displacement and J resistance curves of a sidegrooved compact specimen. A satisfactory agreement of prediction and experiment could be found. In order to investigate the influence of constraint a series of numerical computations of different specimen geometries and loading situations was performed utilizing again the set parameters. The slopes of the predicted J resistance curves increase with increasing ratio of tension vs. bending load and with decreasing relative crack length.