Differential equation model of shape memory alloy spring and its application in heat engines

In order to use low-grade thermal sources more efficiently, different types of Shape Memory Alloy (SMA) heat engines have been proposed and studied, but the lack of a robust constitutive model is still an open issue. In the current paper, the SMA spring model is constructed by combining the mechanical spring theory and the SMA differential equation model. This model can describe the characteristics of SMA springs well, so it is used for SMA heat engine modeling. The state of the SMA heat engine under different loads is calculated, and the output of the SMA heat engine can also be calculated and compared with its experimental value. The calculated rotation speed and output power of the SMA heat engine are in good agreement with the experimental values, which illustrates the superiority of the proposed model and provides a method for the simulation, design, and optimization of the SMA heat engine.