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Abstract In this study, the cyclic mechanical characters of 316L stainless steel at elevated temperature are extensively investigated by the experimental and cyclic constitutive models. The experiments include the monotonic tensile tests with different loading rates and the low cycle fatigue tests considering the effect of strain amplitudes, strain rates and loading sequences. The evolution of cyclic stress amplitudes, hysteresis loops and elastic modulus under various loading conditions are comprehensively analyzed. The experimental results show that the 316L steel at elevated temperature performs a typical three-stage cyclic mechanical response, i.e., initial hardening, subsequent saturation and final accelerated softening. The cyclic softening in both stiffness and flow stress is mainly caused by the nucleation of micro-voids or micro-cracks, and the subsequent coalesce and propagation. Furthermore, although the nearly rate-independent mechanical behavior is observed at monotonic tensile and first several fatigue cycles due to the DSA effect, the cyclic hardening/softening behavior shows a significant strain-rate and loading history dependence. Finally, inspired by the experimental observations and analyses, a damage-coupled cyclic elastic-viscoplastic constitutive model involving strain-range, strain-rate and loading history dependence is proposed to predict the complex cyclic behaviors of the material at elevated temperature. A hardening factor is incorporated into the Chaboche kinematic hardening equations to model the kinematic-induced hardening behavior. And the plastic strain memory surface and the maximum plastic strain rate are introduced to model the strain-range, strain-rate and loading history dependence of cyclic behavior. The proposed model is proved to effectively describe the complex evolution of not only cyclic stress amplitude but also hysteresis loops for the 316L steel at elevated temperature. Highlights • The cyclic response and fatigue mechanism for the 316L steel at room and elevated temperature were compared. • The various tensile and LCF tests considering the effect of strain range, strain rate and loading sequence were carried out. • The fatigue damage was determined experimentally, and incorporated into the cyclic elastic-viscoplastic constitutive model. • The relationship between strain rate, DSA effect and cyclic behavior were investigated and realized by the proposed model. • The proposed model can predict the evolution of not only cyclic stress amplitude but also hysteresis loops accurately. [ABSTRACT FROM AUTHOR]

In this paper, the relaxation of weld residual stress in a 316L stainless steel weld joint under cyclic loading was researched by experimental and finite element method (FEM). Initially, the as-weld residual stresses were calculated by a sequential coupling thermo-mechanical FEM. Subsequently, a cyclic plasticity constitutive model was proposed to study the redistribution of the residual stress by the cyclic load. Significant residual stresses are released during the first few cycles. Especially, about 45–60% of the maximum residual stresses are released during the first cycle because of the plastic deformation caused by the superposition between the as-weld residual stress and the applied load. More residual stresses are released with the increase of the stress amplitude and cyclic number. An analytical model, which considers the effects of the initial residual stress, yield stress, stress amplitude, and number of cycles, was proposed to predict the relaxation of the weld residual stress by the cyclic load. In addition, experimental measurements were also performed to validate this model. Experimental results prove that the proposed model can be used as a valid tool to predict the relaxation of residual stress by the fatigue load. [ABSTRACT FROM AUTHOR]