Application of micromechanical models to the prediction of ductile fracture
Abstract
The effect of the specimen geometry on the ductile fracture behaviour is investigated by continuum damage mechanics techniques. A model introduced by Gurson and modified by Needleman and Tavergaard has been implemented in the Finite Element program package ADINA. The damege parameters of the model are measured and calculated from smooth tension test and the characteristic material distance is estimated from compact tension experiments. For a steel ASTM A 710 at room temperature a complete set of parameters is determined and used to precdict the experimental load vs. displacement curves of notched round bars and of a sidegrooved compact specimen as well as the J - resistance curve. A satisfactory agreement of prediction and and experiment is observed. In order to investigate the influence of the stress state (constraint) in cracked specimens a series a of numerical computations of different specimen geometries and loading situations is performed utilizing again the same set of parameter s. The slopes of the predicted J resistance curves increase with increasing ratio of tensin vs. bending load and with decreasing relative crack length.
