Fatigue analysis of shape memory alloys: energy approach

The purpose of this paper is to define a low cycle fatigue criterion for NiTi shape memory alloys (SMAs) in order to perform numerical calculations necessary for designing structures made of SMA and subjected to cyclic loading. For this purpose, fatigue tests are performed in a temperature and deformation regime in which the alloy exhibits pseudoelasticity. A behavior similar to plastic shakedown is observed; during the first cycles a hysteresis loop with a varying size which eventually stabilizes is obtained. Therefore, by analogy with plastic fatigue (low cycle fatigue), it is shown that the dissipated energy of the stabilized cycle is a relevant parameter for the estimation of lifetime.