Mechanical Response of Shape Memory Alloys Under a Rapid Heating Pulse - Part II

We report on a new experimental system for exploring the thermo-mechanical response of shape memory wires under a rapid heating pulse. The new setup enables the force and displacement generated by the phase transforming wire to be measured with a μs time resolution. In addition, part of the tests incorporated high-speed infrared and visible light photography. The experimental system enables exploring several unique dynamic effects. In particular, stress levels of 1.6 GPa with negligible plastic deformation and elastic strain rates of 10 3 s −1 are observed. Force measurements reveal a dead time of ~20 μs between the end of the electric pulse and the onset of the stress rise in the SMA wire. The high strain rate, generated by the phase transformation, induces string-like vibrations of the SMA wire that result in strong stress vibrations. The developed experimental system opens the way for studying the kinetics of the phase transformation.