Frequency-dependent temperature evolution in NiTi shape memory alloy under cyclic loading

We present a simple analytical model to study the temperature evolution of a superelastic NiTi shape memory alloy (SMA) bar under cyclic tensile loading. By dividing the cycle into five characteristic stages and solving the heat transfer equations for each of the stages, we obtain the analytical expressions of the temperature evolution under the cyclic loading of different frequencies (cycle period t_p) in different convective ambients (characterized by heat transfer time t_h). It is found that, due to latent-heat release/absorption, the specimen's temperature oscillates during the cyclic loading, and the oscillation amplitude (δ_stable) increases with the loading frequency and reaches a saturated value in the high-frequency range (t_p/t_p < 0.1). Moreover, due to the heat accumulated from the intrinsic mechanical dissipation (internal friction), the mean-temperature of the specimen increases with the loading frequency. The temperature rise becomes significant in the high-frequency range. These predictions quantitatively agree well with experiments.