EFFECT OF INITIAL VOLUME FRACTION OF VOIDS AND SPECIMEN SIZE ON DUCTILE FRACTURE.

Estimation of fracture strain of ductile round bar specimen, having a given initial volume fraction of voids, was attempted using the previously reported equation for the ductile fracture condition. As the equation involves four variables (volume fraction of voids, relative radial stress, relative work hardening ratio and specimen size), changes of these variables with strain were investigated. Densities of the necked region of tensile specimens of several materials (low-carbon steel, stainless steel, aluminum, etc. ) were measured. Using these results, experimental equations for the change in volume fraction of voids with the effect of work hardening and the difference in materials were obtained.