Shunted magnetostrictive devices in vibration control

Abstract

Structural vibrations in rotating machinery may lead to imprecise motion control, excessive noise, or even structural damage. Magnetostrictive materials can dissipate unwanted vibrations via hysteresis, eddy currents, and joule heating while exhibiting an electrically-tunable elastic modulus. Harnessing this feature, this article presents a shunted magnetostrictive device that includes an iron-gallium (Galfenol) rod, a permanent magnet array, a flux return path, and shunt circuits. The stiffness tunability and damping of this passive device are measured under a 750 Hz sinusoidal axial compression for resistive, capacitive, and inductive shunt circuits. The effect of eddy currents stiffness and damping is investigated for the first time by comparing results from laminated and solid Galfenol rods. Solid Galfenol produces larger eddy current-based damping, while laminated Galfenol enables larger stiffness variation and total damping. This device demonstrates a power density of 19.83 mW cm−3 for vibration energy harvesting. The frequency-dependent behavior of the shunted device is tested from 5 Hz to 1 kHz for selected electrical loads.

Review of magnetostrictive materials for structural vibration control

“…Denget al [83] later conducted a parametric study for a solidstate damper where the active component is a 6mm diameter and 10mm long Galfenol rod. The proposed damper was validated experimentally by Denget al [84], which demonstrated a maximum loss factor of 0.05 at 1kHz.…”

“…However, the bias magnetic field in this device was applied via an electromagnet requiring external power supply. Denget al [84] experimentally characterized the loss factor available from this shunted damper which was biased by permanent magnets. At 750Hz, the maximum loss factors from a Galfenol-based shunted damper are 0.06 and 1.34 for resistive shunt and capacitive shunt, respectively.…”

“…Scheidler and Asnani [92] derived a lumped parameter model and conducted parametric studies for the proposed tunable mount based on linearized constitutive models. The Terfenol-D mount and Galfenol mount were experimentally characterized in [93] and [84], respectively. Table 2 summarizes the relative stiffness variation under various electrical impedances.…”

“…Yooet al [94] first evaluated the impedancedependent loss factor of a Galfenol-based unimorph, as shown in figure 33. Deng [93] and Denget al [84] later characterized the damping capacity of Terfenol-D and Galfenol, respectively, by applying axial mechanical load to the mounts presented in figure 32. The loss factors under various types of electrical impedance are summarized in table 3.…”