Characterisation of magnetostrictive materials with computer modelling

A plane wave model (PWM) which enables magnetostriction parameters to be determined is fitted to simulated and experimental impedance curves, including an analysis of the inaccuracies due to random and systematic error. The PWM method is applied to a free standing rod of Terfenol-D. The magnetomechanical coupling coefficient, k/sub 33/, is found to have a maximum value of 0.509+or-0.002 at 25 kAM/sup -1/. In comparison a resonance technique which only employs values for the resonance (f/sub R/) and antiresonance (f/sub A/) frequencies, with a correction for the skin effect, yields values for k/sub 33/ which are 15% larger. The difference is attributable to frequency dependent losses which influence not only f/sub R/ and f/sub A/ but the shape of the whole resonance curve.<
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