Nonlinearities, harmonics, and trends in dynamic applications of Terfenol-D

We are working to understand Terfenol-D's behavior in dynamic applications. Experimental results demonstrate that the amplitudes of harmonics present in Terfenol-D transducer output displacement spectra increase with increasing drive-current amplitude. An empirical mathematical model which predicts harmonics is presented. The model approximates both the nonlinear strain versus magnetic flux density behavior (c vs B), and the magnetic hysteresis (B vs H) of the material. Trends are shown for displacement versus drive-current amplitude as a function of frequency. Generally, displacements increase with increasing drive-current amplitude, and decrease with increasing drive frequency (when operated away from mechanical resonance). Single frequency drive-current results are compared with the trends predicted by the mathematical model.