On the role of thermoelectric heat transfer in the design of SMA actuators: theoretical modeling and experiment

A combined theoretical/experimental study of the heat transfer in thermoelectric shape memory alloy (SMA) actuators is undertaken in this paper. A one-dimensional model of a thermoelectric unit cell with a SMA junction is developed first and the transient temperatures in the SMA are evaluated for different applied electric current densities. As a first step towards the design of an actuator, a thermoelectric module is assembled in the laboratory for cooling/heating the SMA. Transient temperature profiles are recorded for the monotonic heating and cooling runs for two different materials-copper and SMA (with or without the phase transformation). These recorded profiles are then compared with the predictions from the model; the agreement is reasonable, particularly during the cooling process. Temperature profiles are also recorded for cyclic cooling and heating of copper at a frequency of 0.5 Hz and a good comparison is obtained. Theoretical predictions for thermal cycling of SMA show that it is possible to achieve a frequency of 2 Hz on full phase transformation and 17 Hz on partial transformation of 25%.