Variation of mechanical properties of shape memory alloy bars in tension under cyclic loadings

It is well-known that the behavior of shape memory alloys (SMAs) depends on varying the temperature and dynamic loading frequency. However, the relationship between SMA behavior and cyclic loads has not been clearly discussed. This relationship is very important in the field of seismic application of SMAs. Therefore, this study arranges several dynamic tensile tests of martensitic and austenitic SMA bars. The parameters of the tests are the initial strain of the SMA bars, the number of cycles, and the loading frequency. The hysteretic curves of the stress–strain relation are measured, and the mechanical properties of the residual strain, Youngʹs modulus is varied at first, but becomes stable after 250 cyclic loading. However, the damping ratio decreases continuously when the number of loading cycles increased. It is found that the initial strain and loading frequency do not affect the mechanical properties significantly. Only the residual strain is influenced by the amount of initial strain but not the loading frequency.