FATIGUE BEHAVIOUR OF A SHAPE MEMORY ALLOY

In the present paper, the fatigue behaviour and the phase transition mechanisms of an equiatomic pseudo-elastic NiTi Shape Memory Alloy are examined by means of tensile cyclic tests (up to 100 loading cycles). More precisely, miniaturised dog-bone specimens are tested by using a customised testing machine, which allows in situ X-Ray diffraction (XRD) analyses in order to measure the contents of both austenite and martensite phase. On the basis of such experimental results in terms of martensite content, an analytical model is here proposed to correlate the stress-strain relationship to the phase transition mechanisms. Finally, analytical and experimental results are compared in terms of stress-strain relationship.