Influence of the Latent Heat of Transformation and Thermomechanical Coupling on the Performance of Shape Memory Alloy Actuators

In this work, the influence of the latent heat of transformation and heat transfer on the performance of shape memory alloy (SMA) actuators is numerically explored. A 1D analytical model is first considered and used to perform parametric studies on the effects of geometry and heat transfer conditions on SMA wire responses. In order to consider the response of SMA structures, a recent SMA constitutive model is expanded to include the effects of the latent heat of transformation. The enhanced model is then implemented in a 3D finite element framework to solve the coupled and transient thermomechanical problems. The resultant model is used to explore the isothermal and adiabatic assumptions commonly used for quasi-static SMA modeling by considering the response of SMA structures. The responses of an axial SMA actuator heated from one end is evaluated and it is shown that the generation of latent heat during forward transformation and its absorption during reverse transformation decreases the actuation response when compared to a case neglecting thermal effects. It is concluded that the latent heat of transformation must be considered for the design of SMA components unless their operation can reasonably be approximated as isothermal.