Thermomechanical Dynamic and Fatigue Behavior of CuAlNi Shape Memory Alloy Wires

This study evaluates the dynamic behavior and thermomechanical fatigue of a CuAlNi SMA wire subjected to cyclic tests using a DMA device under single cantilever bending mode, a highly relevant strain mode in applications such as vibration suppression. Analyses were conducted in two parts: first, to determine the damping capacity and stiffness of SMA wires as a function of bending deflection amplitude (proportional to strain on the sample surface) and loading frequency; second, to evaluate the structural fatigue life under strain control at different strain amplitudes and temperatures corresponding to the martensite phase, phase mixture, and austenite phase. A notable increase in damping capacity is observed during the martensitic phase transformation, although this increase is significantly influenced by the loading frequency. The storage modulus (stiffness) exhibits a notable decrease during transformation, but martensite and austenite reach similar modulus values. Bending fatigue tests and post-fatigue SEM analysis are used to assess how strain amplitude and temperature affect crack evolution and fracture mechanisms, revealing the low-cycle fatigue life of the CuAlNi wire, which can be adjusted by loading conditions.