Dynamic Behavior and Stiffness Tuning in Solenoid Based

Ferromagnetic shape memory nickel-manganese-gallium (Ni-Mn-Ga) has shown tremendous promise as an actu-ator material due to its large strain and high bandwidth. However, current Ni-Mn-Ga devices are electromagnet based as this configuration allows for an externally applied force perpendicular to the applied field, and are therefore bulky, energy inefficient, and narrowband. We investigate the dynamic response of Ni-Mn-Ga driven by a solenoid transducer in which the magnetic field is aligned collinearly with the loading stress. The work fo-cusses on the quasistatic and dynamic testing of a Ni50Mn28.7Ga21.3 sample which is believed to have an internal stress field which plays the role of the restoring force necessary for reversible strains. This sample is shown to exhibit reversible compressive strains of-0.41 % with no external forces applied. Several experimental apparatus are used in order to verify these results. The measurements demonstrate a 231 % change in stiffness with applied dc magnetic fields. 1