Studies on the ductility predictions by different local failure criteria

Abstract

It is well known that the ductile fracture of metals has frequently been observed to result from the growth and coalescence of microscopic voids. Correspondingly, local approach methodologies have been developed in the modelling of ductile fracture. Three local ductile fracture criteria, a critical void volume fraction criterion based on a Gurson-type constitutive relation, a critical void growth criterion based on Rice-Tracey void growth equations, and Thomason's plastic limit-load criterion, have been studied and examined against the predictions of ductility with respect to stress triaxiality. A calibration for the predictions of the plastic limit-load criterion has been made, which yields a modification to the criterion to give more realistic predictions at low stress triaxiality than the original criterion. Various comparisons of the criteria have been made. It has been found that there are considerable differences in the predictions by the three criteria. Finally, a method has been introduced which can correlate the predictions well using dual dilational constitutive models.