Dynamic Discrete Energy-Averaged Model for Magnetostrictive Materials

This study develops a rate-dependent constitutive model which includes pinning site loss and eddy current loss for magnetostrictive materials. The static pinning site loss is described by an energy-weighted averaging framework; the stress- and field-induced eddy current loss is defined by Maxwell’s equations. Due to the eddy currents, the magnetic field in magnetostrictive materials is inhomogeneous especially when the excitation frequency is beyond the cut-off frequency. The model developed in this study is able to capture the stress- and field-induced magnetic diffusion. Analytical solutions are derived for magnetostrictive rods and minor loop responses. However, numerical solutions can be found for other geometries and large input amplitudes using the same modeling algorithm. The model is used to interpret flux density versus stress measurements of a highly-textured, 100-oriented, polycrystalline Fe81.6Ga18.4 rod under constant current biasing. The model accurately and efficiently reproduces the nonlinear magnetostrictive behavior up to 800 Hz, which is much higher than the cut-off frequency