Experimental Characterization of NiMnGa Magnetic Shape Memory Alloy Rods Under Dynamic Magnetic Fields

摘要

A comprehensive, experimental characterization of single crystal, NiMnGa rods is the current subject of study. Static tests aimed at characterizing the force-deflection behavior show that the actuator has two stiffnesses, a low stiffness associated with the region of twin boundary motion and a high stiffness when the material is in the fully twinned condition. For a 2 x 3 x 16 mm specimen, a block force of 4.35 N and a free strain of 5.02% were determined experimentally. Dynamic tests of the material exposed to a 0.85 T peak, AC, inductive field show that the strain and force generated by the actuator consist of mean and dynamic components. For peak performance, the recovery force acting on the NiMnGa actuator must be optimized. Experimental results indicate that NiMnGa has a maximum volumetric energy density of 12.15 kJ/m~3 and a maximum weight defined energy density of 1.45 J/kg. Using energy density by weight as a metric, NiMnGa has an energy output on the same order of magnitude as commercial piezostacks.