Study on cyclic constitutive model and ultra low cycle fracture prediction model of duplex stainless steel

Abstract This paper calibrates micromechanical fracture models for duplex stainless steel in order to study its fracture behaviour under seismic loading, characterized by large strain ultra low cyclic conditions. In this investigation, smooth round bars and notched round bars were subject to monotonic and cyclic loading. Monotonic and cyclic loading constitutive models were calibrated against smooth round bar test tests. The fracture toughness parameters of the void growth model (VGM), the stress modified critical strain (SMCS) model and the cyclic void growth model (CVGM) were calibrated against the notched round bar tests. Furthermore, the skeleton curve, hysteresis loop and characteristic length of duplex stainless steel were also investigated. The test results indicate that duplex stainless steel exhibits cyclic hardening behaviour under cyclic loading, and the subsequent numerical simulation successfully captured this behaviour. The toughness parameters of duplex stainless steel are generally higher than those for carbon steel grades Q345B and Q460, which demonstrates that duplex stainless steel has better toughness. All the experimental results provide useful data for the prediction of ultra low cycle fatigue (ULCF) fracture of duplex stainless steel.