Frequency-dependent, dynamic sensing properties of polycrystalline Galfenol (Fe81.6Ga18.4)

Abstract

This paper presents the first measurement of Galfenol's frequency-dependent strain and magnetic flux density responses to controlled dynamic stress, from which frequency-dependent, effective material properties relating these quantities are calculated. Solid and laminated Galfenol (Fe 81.6 Ga 18.4) rods were excited by 2.88 MPa compressive stresses up to 1 kHz under constant field and constant current conditions. Due to magnetic diffusion cutoff frequencies of only 59.3 to 145.7 Hz, the dynamic properties of the solid rod are found to vary significantly; this illustrates the inaccuracy of frequency-independent dynamic properties calculated via linear piezomagnetic models from experimental responses to electrical excitation. Conversely, the sensing properties of the laminated rod exhibit a weak dependence on frequency over the measurement range (i.e., a cutoff >1 kHz). The data are used to validate an existing model for mechanically induced magnetic diffusion. Loss factors and magnetomechanical energy densities are also presented and discussed in terms of loss separation, magnetic diffusion, and energy conservation. Published by AIP Publishing.

Validated linear dynamic model of electrically-shunted magnetostrictive transducers with application to structural vibration control

“…The strongest of these assumptions are that the eddy currents in the transducer are negligible and the magnetostrictive material behaves linearly. It has been shown analytically [2,31] and experimentally [23] that the eddy currents induced in a magnetostrictive material by dynamic axial stress can be significant if the stress frequency is too high or if the material is not sufficiently laminated. It is expected that these eddy currents will reduce the influence of the shunt on the transducer's modulus, but it is unclear how the total mechanical energy loss will be affected.…”

“…The iron powder cores were used to reduce eddy current losses, which are not included in the model. To reduce the influence of eddy currents in the magnetostrictive material, the Galfenol rod was laminated with 6 laminates [23]. The total axial displacement of the magnetostrictive transducer was measured by two capacitive displacement probes.…”

Review of magnetostrictive materials for structural vibration control

“…Deng [27] and Scheidler and Dapino [28] have developed analytical constitutive models describing the eddy current loss in magnetostrictive materials. Scheidleret al [82] experimentally characterized the eddy current loss up to 1kHz by comparing the strain versus stress curves measured from a solid and a laminated Galfenol sample (Φ6.35 mm). 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.…”

A rate-dependent constitutive model incorporated in two-dimensional PolyFEM for Galfenol sensors

“…The major and minor loop changes in flux density and strain for varying stresses with biased magnetic field were measured at different frequencies. Scheidler et al [40] also studied the variations of material properties, piezomagnetic co-efficient and elasticity modulus, based on changes in frequency. Various approaches to predict the experimental observations of magnetostrictive materials were also attempted from different modelling perspectives.…”