A damage-coupled viscoplastic constitutive model considering tension-compression asymmetry for modeling low cycle fatigue mechanical behaviors of Inconel 617 at elevated temperature

Abstract

Design and analysis based on the advanced constitutive models capable of simulating the complex mechanical behaviors of materials would improve the operational reliability and safety of high-temperature engineering components that experience thermo-mechanical fatigue loading in aerospace and power industries. Inspired by the experimental observations of a set of low cycle fatigue tests of nickel-based superalloy Inconel 617 at 700 °C, a damage-coupled unified viscoplastic constitutive model considering tension-compression asymmetry is proposed. For a better description of the hysteresis loop shape, the cyclic hardening behavior is modeled by the kinematic hardening rule. The damage is measured by the degradation of elastic modulus, and a low cycle fatigue damage model is employed to describe the cyclic softening behavior and predict the fatigue life. Due to the similarity in the evolution of damage and compressive hardening ratio, a compressive hardening factor, which is a function of damage, is incorporated into the kinematic hardening model to simulate the tension-compression asymmetry, i.e. the mean stress evolution. The strain-range dependence of cyclic hardening and tension-compression asymmetry is also considered. The simulation results show that the proposed model can effectively model the low cycle fatigue mechanical behaviors of the material at elevated temperatures.