Thermal response of SMA wires under electrical actuation

In this paper a 1-D continuum-based thermomechanical model for linear SMA actuators is proposed. Zero-stress condition of a wire, which is electrically-heated andcooled in free convection condition, is modeled.This model is able to take into account both the shapememory effect and the pseudoelasticity as well aschanges in length affecting the dynamic response ofSMA actuators. The boundary value problem developedbased on the present thermomechanical model issolved by means of the finite difference method.Time variations of temperature profile along the length andthe relationship between these variations and theevolution of austenite or martensite is studied. The movement of phase transformation front close to the endof the wire is also studied during heating. The influence of wire radius on heating and cooling time and also thetotal time of a thermal cycle which are importantparameters in designing SMA linear actuators areinvestigated and an optimum wire radius is found toreduce the total time of a thermal cycle as an importantfactor for increasing the frequency in the actuators ofhigh frequency. For verifying the results, a comparisonis made with other researcher’s work, and good agreement between two approaches is found.

Thermal response of SMA wires under electrical actuation Keywords:

SMA , thermomechanical