MODELING OF THERMOELECTRIC HEAT-TRANSFER IN SHAPE-MEMORY ALLOY ACTUATORS - TRANSIENT AND MULTIPLE CYCLE SOLUTIONS

In this paper we study the transient and multiple cycle solutions of o ne-dimensional symmetric thermoelectric shape memory alloy (SMA) actua tors. From the model proposed by Bhattacharyya et al. [1], an approxim ately equivalent simpler model governed by an integrodifferential equa tion is derived first, to describe the temperature distribution in SMA . Then a numerical algorithm is proposed to solve the integro-differen tial equation. It is found that for the transient cooling problem with constant electric current density of magnitude \J\ there is a critica l value J(0) of \J\ such that when \J\ > J(0), the temperature in SMA may not be always decreasing. The heat transfer problem and the result ing phase transition of SMA, induced by a piecewise constant electric current source, are also studied. It is found that there exist restric tions on the maximum and minimum values of the current density J for a repeated complete phase transition to take place in SMA. Explicit exp ressions for the critical values of J are derived and their physical i mplications are discussed.