Temperature profiles in a Ti-45Ni-5Cu (at%) shape memory alloy developed by the Joule heating

Spatially varying temperature profile generated by the Joule heating of a Ti-45Ni-5Cu (at%) alloy wire was investigated by experiment and analysis. The Joule heating is a simple and effective method to fabricate shape memory alloy (SMA) actuators for proportional control. By applying a voltage drop of 1.338 V, a temperature gradient between 504 K and 413 K was obtained experimentally over a length of 30 mm SMA wire. A closed-form expression derived from a simple analytic model was suggested to predict the temperature profile, and the result of the finite element analysis was also provided. Finally, it is demonstrated that the Joule heated specimen shows a low shape recovery rate of 0.02%/K and a unique Lüders-type deformation with a progressively increasing stress level from 340 MPa to 380 MPa.