Fatigue Life Prediction for NiTi Shape Memory Alloy Micro-tubes Under Uniaxial Stress-Controlled One-Way Shape Memory Cyclic Loading

By choosing the dissipation energy as the damage variable, corresponding damage evolution equations are established, respectively, for the mechanical cyclic loading part and the thermal one during the thermo-mechanical cyclic loading of NiTi shape memory alloys (SMAs) involving one-way shape memory effect (simply denoted as the OWSME cycling). And then, the evolution law of total damage is obtained by a superposition of such two damage parts. Finally, the uniaxial OWSME fatigue lives of NiTi SMA micro-tubes are predicted by combining the proposed damage model with an adopted failure criterion. The results show that all the predicted fatigue lives are located within the twice scatter band with regard to the experimental ones, and most of them are located within a scatter band of 1.5 times. It is indicated that the predicted OWSME fatigue lives are in good agreement with the experimental ones.