Thermomechanical response and elastocaloric effect of shape memory alloy wires

Abstract

Refrigeration technologies based on the elastocaloric effect of shape memory alloys (SMAs) have attracted much interest in recent years. To seek for schemes that can improve the temperature span and efficiency of elastocaloric devices, this work explores more practical loading conditions (between adiabatic and isothermal) of SMAs. To account for the smoothness of the martensite phase transformation of SMAs, a general polynomial form of hardening-like function is adopted in the phenomenological multi-physics coupling framework. The modeling framework is further calibrated by measurements of the thermomechanical responses of pre-trained Ni–Ti wires. Due to the hardening-like function, the martensitic volume fraction cannot be explicitly expressed. Accordingly, a new numerical scheme is also presented in this work. Moreover, an empirical function of the maximum transformation strain is proposed based on the experimental observation, which improves the capability of the model to capture experimental data. This work aims to provide a paradigm from material characterization to theoretical modeling and numerical simulation, and then to elastocaloric cooling performance analysis of SMAs.