Analysis of a magnetostrictive actuator equipped for the electromagnetic and mechanical dynamic characterization

Abstract

The accurate assessment of the dynamic characteristics of a magnetostrictive material or device is a difficult task, since the behavior is affected by significant phenomena like dynamic mechanical and magnetic hysteresis. From the experimental point of view, up to now, setups for specific purposes and for static or very low-frequency regime have been realized. This paper proposes a device for dynamic characterization of Terfenol-D rods. This system is derived from a commercial actuator. So it can be reproduced in every laboratory. The peculiar elements of this equipment are a load cell, to assess the rod preload, a non-inductive strain-gage, to evaluate the dynamic rod displacement inside the device, a pickup coil and a tensiometer, to measure the magnetic induction and the magnetic field relative to the rods, whose reliability has been validated through a finite element model of the contrivance. This paper shows the ability of the proposed equipment to measure both the magnetic hysteresis cycles of the magnetostrictive material and the magnetomechanical characteristics. Measurements are presented concerning static and dynamic hysteresis cycles for different applied preloads and different supply frequencies. Moreover, strain–magnetic field characteristics are shown varying the same parameters. Finally, the previous results obtained with a bulk Terfenol-D rod have been briefly compared with those obtained with a laminated one.