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, k₃₃, is found to have a maximum value of 0.509±0.002 at 25 kAM^-1. In comparison a resonance technique which only employs values for the resonance (f_R) and antiresonance (f_A) frequencies, with a correction for the skin effect, yields values for k₃₃ which are 15% larger. The difference is attributable to frequency dependent losses which influence not only f_R and f_A but the shape of the whole resonance curve