Numerical analysis of joule heating in a Ni–Ti segmented wire used in sensing applications

Use of shape memory alloy (SMA) has been extensively increased to fabricate sensors and actuators. It is because of its inherently unique properties such as pseudo-elasticity and shape memory effect. Among various SMA's, Ni–Ti SMA has received a prime interest in various applications. However, Ni–Ti SMA-based sensors suffer from the Joule heating effect as their performance is impacted due to an increase in the temperature. This work presents a finite element analysis approach to estimate a rise in temperature in Ni–Ti SMA sensors. A numerical model was developed in COMSOL, considering a Ni–Ti with Cu segment. Electro-thermal boundary conditions were set to assess the thermal response of the segmented wire. Multiple simulation runs were carried out by varying material and geometric characteristics of segmented wire. The results are validated against the literature and quantitative estimation of thermal characteristics through physics driven analytical model. Simulation results show that the Joule heating effect has a significant effect on the properties of the material which can be considered while designing and selecting the sensor application. This study further brought a few mitigation actions which can minimize the Joule heating effect without hindering the performance of Ni–Ti SMA-based sensors.