Effect of the amplitude of the training stress on the fatigue lifetime of NiTi shape memory alloys

This paper presents a mechanical training process that allows enhancing resistance to low cycle fatigue of shape memory alloys. To this end, three training stresses were tested (0–509.6 MPa, 0–637.0 MPa, 0–764.3 MPa); for each case, NiTi wires were first subjected to the corresponding load during first 20 cycles, and then tested to failure under strain-controlled fatigue loading. Results show that fatigue lifetime is training-dependent in the sense that specimens with higher training stresses present a better fatigue lifetime. Indeed, for sufficiently high training stress, fatigue lifetime can be 10 times extended.