Ductile crack initiation assessment using strain hardening exponent

Ductile crack initiation behaviors were experimentally and analytically investigated using 400 MPa class structural steel, high strength steel and aluminum alloy. Ductile limit curves, which are the relationships between equivalent plastic strain and stress triaxiality factor, were obtained. It was shown that the limit curves were different for each material. Ductile crack initiation of carbon steels is considered to be caused by shear deformation between voids and Mohr - Coulomb criteria, which is related to normal stress and shear stress, was employed. As a result, it was found that strain hardening exponent can be a parameter for ductile crack initiation limit. It was shown that ductile crack initiation can be evaluated by one regression curve for various steels using strain hardening exponent.