STUDIES ON THE DUCTILITY PREDICTIONS BY DIFFERENT LOCAL FAILURE CRITERIA

It is well known that the ductile fracture of metals has frequently be en observed to result from the growth and coalescence of microscopic v oids. Correspondingly, local approach methodologies have been develope d in the modelling of ductile fracture. Three local ductile fracture c riteria, a critical void volume fraction criterion based on a Gurson-t ype constitutive relation, a critical void growth criterion based on R ice-Tracey void growth equations, and Thomason's plastic limit-load cr iterion, have been studied and examined against the predictions of duc tility with respect to stress triaxiality. A calibration for the predi ctions 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 compariso ns of the criteria have been made. It has been found that there are co nsiderable differences in the predictions by the three criteria. Final ly, a method has been introduced which can correlate the predictions w ell using dual dilational constitutive models.