Characterization of the pseudoelastic damping capacity of shape memory alloy wire

The pseudoelastic hysteresis behavior of shape memory alloy (SMA) elements observed above the austenite finish temperature of the alloy, can be used to provide a large structural damping in different applications. In this work, the pseudoelastic damping capacity (SDC) of a NiTi SMA wire has been characterized using the complex modulus approach through testing under a dynamic tensile condition. A test setup has been specifically designed, built and validated for this measurement since a testing machine with the required performances was not available. Given the dynamic characteristic of the test the structure was designed to behave as a rigid body in the frequency range of interest. Different conditions have been tested, varying the excitation frequency, the amplitude of imposed deformation, and the pre-strain levels. Results show that the SDC has a nearly constant trend of 7.5% for low frequencies until 30 Hz. Moreover, variation of the amplitude of deformation, between 0.3% and 0.8%, causes an increasing of the damping capacity, which varies from 7.7% to 10.4%, respectively. Finally, the measured prestrain amplitude effect is in agreement with existing literature studies.