CYCLIC DEFORMATION AND FATIGUE OF A TINI SHAPE-MEMORY ALLOY WIRE SUBJECTED TO ROTATING BENDING

The cyclic deformation and fatigue of a TiNi shape-memory alloy wire w ere studied by carrying our rotating-bending fatigue tests at various strain amplitudes, temperatures, and rotational speeds in air and in w ater. The results were summarized as follows: (1) for strain amplitude s in the rhombohedral-phase transformation region, the fatigue life wa s longer than 10(7) cycles and the deformation properties did not chan ge under cyclic deformation; (2) for-the strain amplitudes in the mart ensitic transformation region, the fatigue life was shorter than 10(5) cycles and the higher the temperature, the shorter was the fatigue li fe, (3) the rotational speed did not affect the fatigue life in water but a higher rotational speed led to a shorter fatigue life in air.