Fatigue resistance of SMA-martensite bars subjected to flexural bending

The fatigue resistance of Ni–Ti Shape Memory Alloy (SMA)-martensite bars in bending subjected to large deformation cycles has been experimentally evaluated. Firstly, fatigue tests under constant displacement amplitude have been carried out, at two different frequencies of loading. Then, the cumulative fatigue damage and fatigue life prediction of specimens loaded under variable load conditions have been investigated. Finally, the effect of low-cycle-fatigue (LCF) and plastic deformations on subsequent high-cycle-fatigue (HCF) has been studied. The experimental results point out that the frequency of loading (i.e. temperature) significantly affects the fatigue life of the specimens. The damage accumulation process seems to follow the ‘‘Miner’’ linear damage theory for low-to-high (L–H) loading sequences, while the same does not hold for high-to-low (H–L) loading sequences. Surprisingly, a small fraction of LCF life consumption seems to enhance the subsequent HCF limits.