Thermoelectric shape memory alloy actuators and the issue of thermomechanical coupling

In this work, we model a thermoelectric shape memory alloy(SMA) actuator as part of a research effort to design high-force, high-frequency SMA actuators. Cyclic phase transformation in a SMA layer is achieved by alternately heating/cooling using the thermoelectric Peltier effect. The thermal and mechanical fields during phase transformation are, in general, highly coupled and the extent of this coupling in the light of different mechanical boundary conditions is examined. The primary parameters of design interest are the frequency response and the evolution of the actuation stress. The analysis resulting from the formulated boundary value problem indicates that thin SMA layers(approximate to 6 mu thick), under partial transformation, are capable of delivering frequencies of about 30 Hz at peak stresses of about 145 Mpa.