An improved unified viscoplastic model is developed within the framework of the Chaboche model in order to simulate the mechanical behaviour of a martensitic steel under Low-Cycle Fatigue (LCF) and Low-Cycle Fatigue-Creep (LCFC) loadings at 550 °C. The effects of strain rate sensitivity, static recovery, strain range-dependent cyclic softening, along with the effect of additional hardening under non-proportional loading are incorporated into the constitutive equations. The non-linear kinematic hardening rule is modified in such a way that it enables the simulation of the evolutionary behaviour of mean stress and the effect of decelerating stress relaxation. Finally, the prediction capability of the proposed model is illustrated for the experimental data obtained from the various strain-controlled axial-torsional tests.

在 Chaboche 模型的框架内开发了一种改进的统一粘塑性模型，以模拟马氏体钢在 550 °C 下的低循环疲劳 (LCF) 和低循环疲劳蠕变 (LCFC) 载荷下的机械行为。应变率敏感性、静态恢复、应变范围相关的循环软化的影响，以及非比例加载下额外硬化的影响都被纳入本构方程。对非线性运动硬化规则进行了修改，使其能够模拟平均应力的演化行为和减速应力松弛的影响。最后，针对从各种应变控制的轴向扭转试验中获得的实验数据，说明了所提出模型的预测能力。