Micromechanical modeling on thermomechanical coupling of cyclically deformed superelastic NiTi shape memory alloy

The response of NiTi shape memory alloy (SMA) changes drastically with the loading rate. This paper presents a three-dimensional thermomechanically coupled constitutive model to describe the rate dependent cyclic performance of superelastic NiTi SMA. Two inelastic mechanisms, i.e. martensitic transformation and transformation-induced plasticity, are taken into account. The fully coupled heat equilibrium equation is deduced from the first law of thermodynamics. The thermodynamic driving forces of the internal variables are derived from the second law of thermodynamics (Clausius-Duhem inequality). The constitutive model is extended from single crystal scale to polycrystalline version via finite element approach. The validity of the model is verified through simulating thermomechanical response of cyclically tensioned superelastic NiTi SMA at various deformation rates. Moreover, the robustness of the model is checked by simulating the thermomechanical behavior of superelastic NiTi cantilever tube subjected to cyclic bending. The simulation results match with the experimental observation reasonably.