A method to construct the fracture locus in the range of high stress triaxiality when only a round tensile specimen is available

Our aim was to develop a method to construct a fracture locus for tensile loading with large positive values of stress triaxiality with only a round tensile specimen. Previously, at least three repetitions of tensile tests using a round tensile specimen, circumferentially notched tensile specimen and circumferentially cracked tensile specimen were required when we constructed the fracture locus. A fundamental idea considered in this study is to modify the Hancock and Mackenzie model by relating void nucleation strain to strain at necking and replacing the parameter in the model with a material constant depending on strain hardening coefficient. Validity of the proposed method was verified by comparing fracture loci constructed using the proposed method with data set measured by earlier researchers. Fracture loci constructed by the proposed method are in agreement with data set for ductile steels with yield stress in the range of 200-500 MPa and uniform strain of material is higher than 0.1.