An improved constitutive model based on two-surface theory considering strain-amplitude and loading-history dependence

Abstract

The mechanical behaviors of austenitic stainless steel S31608 were investigated under monotonic tensile and cyclic loading conditions with a wide range of strain amplitudes. Results indicated that it represented unsaturated long-range cyclic softening/hardening before fracture, pronounced strain-amplitude and loading-history dependence. First, the framework of combined hardening was applied to the experimental data to study the variations in a series of plastic state variables, including the elastic modulus and plastic hardening characteristics. Secondly, building on these insights, a comprehensive constitutive model was developed based on two-surface theory, consisting of a yield surface and boundary surface. Novel nonlinear isotropic and kinematic hardening rules were proposed to incorporate the complex properties mentioned above. Four major mechanisms of boundary evolution were proposed to reflect the influences of strain range and loading protocol. Finally, to benchmark the model’s predictive capability, the proposed model alongside the Updated Voce-Chaboche (UVC) model, YU model, and He model were implemented and compared their predictions against test results. The comparison results demonstrated that the complicated mechanical properties were beyond the ability of the UVC model. In contrast, the proposed model precisely predicted both stress evolution and the hysteretic loop shape change of S31608 under various loading schemes, achieving a narrow error band within ± 8 %.