*Review* **Strain Rate Effect on the Thermomechanical Behavior of NiTi Shape Memory Alloys: A Literature Review**

**Zhengxiong Wang, Jiangyi Luo, Wangwang Kuang, Mingjiang Jin, Guisen Liu, Xuejun Jin \* and Yao Shen \***

The State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China **\*** Correspondence: jin@sjtu.edu.cn (X.J.); yaoshen@sjtu.edu.cn (Y.S.)

**Abstract:** A review of experiments and models for the strain rate effect of NiTi Shape Memory Alloys (SMAs) is presented in this paper. Experimental observations on the rate-dependent properties, such as stress responses, temperature evolutions, and phase nucleation and propagation, under uniaxial loads are classified and summarized based on the strain rate values. The strain rates are divided into five ranges and in each range the deformation mechanism is unique. For comparison, results under other loading modes are also reviewed; however, these are shorter in length due to a limited number of experiments. A brief discussion on the influences of the microstructure on the strain-rate responses is followed. Modeling the rate-dependent behaviors of NiTi SMAs focuses on incorporating the physical origins in the constitutive relationship. Thermal source models are the key rate-dependent constitutive models under quasi-static loading to account for the self-heating mechanism. Thermal kinetic models, evolving from thermal source models, address the kinetic relationship in dynamic deformation.

**Keywords:** NiTi; shape memory alloy; strain rate effect; thermomechanical
