Effect of the anisotropic magnetostriction on Terfenol-D based fiber Bragg grating magnetic sensors

In this work, we study the effect of anisotropic magnetostriction on Terfenol-D based fiber Bragg grating magnetic sensors under different types of magneto-mechanical loading. We demonstrate that a Terfenol-D rod is subjected to axial strain also when the magnetic field is perpendicular to the rod axis and as consequence we question the hypothesis of uniaxial behavior that is normally found in the literature for this kind of sensors. In order to address this issue, we propose a calibration model that introduces transverse sensitivity coefficients in good agreement with the experimental data. Moreover, the dependence of the sensitivity coefficients on the magnetic field intensity and mechanical prestress has been retrieved revealing that accurate magnetic measurements are possible only taking into account the transversal magnetostriction of Terfenol D.