Critical ductile fracture criterion based on first principal stress and stress triaxiality

A series of quasi-static fracture tests on ten types of specimens for six types of materials were performed to investigate the ductile fracture failure behavior of materials. The full-range equivalent stress-strain relations of materials were obtained by using finite-element-analysis aided testing method. The critical failure behavior was discussed in detail by the analysis of the local stress and strain distributions on the cross-sections of specimens and fractographic observation of specimens. The results show that the first principal stress is the dominant factor of ductile fracture failure. A novel critical fracture criterion of ductile materials represented by the critical first principal stress and critical stress triaxiality is proposed, and the validity of the proposed criterion has been successfully examined.