Experimental Investigation of the Pseudoelastic Hysteresis Damping Characteristics of Shape Memory Alloy Wires

An experimental investigation was conducted to determine the pseudoelastic hysteresis damping characteristics of Ni-Ti Shape Memory Alloy (SMA) wires. The comprehensive study examines the effects of cycling, oscillation frequency, strain amplitude, temperature, and static strain offset on the pseudoelastic stress-strain hysteresis of SMA wires under axial loading. Experimental data are obtained for complete austenite-martensite transformation hysteresis as well as partial transformation hysteresis. The results indicate that as the frequency of excitation increases, the reverse phase transformation from detwinned martensite to austenite commences at higher stress levels, and the area of the hysteresis loop decreases. This results in a rapid initial decrease in energy dissipation, but approaches a stable level by about 10 Hz. The energy dissipation at 10 Hz was found to be about 50% of that observed at very low frequencies. The energy dissipated at higher temperatures was found to be up to 40% lower than that observed at 90'F. The energy dissipated per cycle was found to be larger when lower values of static strain offset were used.