Modeling of Thin Layer Extensional Thermoelectric Sma Actuators

As a rst step towards the design of a high frequency, high force, large strain shape memory alloy(SMA) actuator, we model in this work a thermoelectrically cooled thin SMA layer linear actuator. The SMA is subjected to cyclic phase transition between the martensitic and austenitic phases by alternate heating/cooling, achieved with the thermoelectric Peltier e ect of a pair of P/N semiconductors. The e ect of variable actuating load and constant load applied as boundary conditions on the SMA actuator are considered. The thermomechanical boundary value problem involves strongly coupled thermal and mechanical elds. The evolution equations for the eld variables are integrated using the fourth-order Runge Kutta method and the coupling between the elds is accounted for by implementing an interative scheme. The primary parameters of interest in this work are the frequency response and evolution of the variable load. The performance of the actuator is compared with various commercially available actuators based on energy conversion e ciencies and energy output per unit volume of active material. Results of the analysis indicate that thin SMA layers( 6 thick) under partial phase transformation are capable of delivering frequencies of about 30 Hz at peak stresses of about 145 MPa.