A microstructure-based constitutive model accounting for rate dependence of superelastic NiTi alloy under cyclic deformation

Abstract

In this work, a micromechanical constitutive model based on single crystal is proposed to account for the rate dependence and functional degradation of superelastic NiTi. Correspondence variant pair is treated as ellipsoid inclusion embedded in austenite matrix, and the stress distribution is obtained through Mori–Tanaka homogenization. Two inelastic mechanisms, that is, martensitic transformation and transformation-induced plasticity, are taken into consideration. Slipping is modeled to originate from austenite–martensite interface and is transferred between austenite and martensite. The heat equilibrium equation and thermodynamic driving force are deduced from the first law of thermodynamics and Clausius–Duhem inequality, respectively. Via the introduction of dominant <111> texture and Taylor approximation, the single crystal model is extended to polycrystalline version. The calibration and numerical implementation procedures for the model are systemized. The effects of key prescribed material parameters are discussed. Simulation results are validated against the experimental data. It is found that simulated thermomechanical responses agree with experimental observations reasonably.