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.

中文翻译：

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316L 不锈钢在高温下的循环硬化/软化行为，包括应变率和应变范围依赖性：实验和损伤耦合本构建模

摘要 在这项研究中，通过实验和循环本构模型广泛研究了 316L 不锈钢在高温下的循环力学特性。实验包括不同加载速率的单调拉伸试验和考虑应变幅度、应变速率和加载顺序影响的低周疲劳试验。综合分析了各种加载条件下的循环应力幅值、滞后回线和弹性模量的演变。实验结果表明，316L钢在高温下执行典型的三级循环机械响应，即初始硬化、随后的饱和和最终加速软化。刚度和流变应力的循环软化主要是由微孔洞或微裂纹的形核引起的，以及随后的合并和传播。此外，尽管由于 DSA 效应在单调拉伸和前几个疲劳循环中观察到几乎与速率无关的机械行为，但循环硬化/软化行为显示出显着的应变速率和加载历史依赖性。最后，受实验观察和分析的启发，提出了一种涉及应变范围、应变率和加载历史依赖性的损伤耦合循环弹粘塑性本构模型，以预测材料在高温下的复杂循环行为。将硬化因子纳入 Chaboche 运动硬化方程以模拟运动诱发硬化行为。并引入塑性应变记忆面和最大塑性应变率来模拟应变范围，循环行为的应变率和加载历史依赖性。证明所提出的模型不仅可以有效地描述 316L 钢在高温下的循环应力幅值和滞后回线的复杂演变。