Experimental Evaluation of Microvoid Characteristics and Relationship with Stress and Strain for Ductile Fracture

The present study aims to characterize the microvoid sizes and their statistical distribution at the instance of fracture from the fracture surface of steel specimens. To this end, uniaxial tensile tests are conducted on circumferentially notched specimens made of 17-4 PH stainless steel and ASTM A992 high-strength structural steel. The fracture surfaces of the steel test specimens are studied using a digital microscope to quantify the statistical microvoid size distribution. Furthermore, the evaluated microvoid sizes of different fracture locations are mapped with the stress and strain fields. Finally, based on the experimentally evaluated microvoid sizes, an uncoupled fracture model was adopted to predict the fracture displacement and location of ductile fracture initiation in the fractured specimens. The fracture displacements predicted using the calibrated uncoupled fracture model are within the acceptable limit. The fracture initiation locations coincided with the peak strain-averaged stress triaxiality in the fracture specimens.