Fully coupled discrete energy-averaged model for Terfenol-D

A fully coupled 3D energy-avaraged model is presented which describes the magnetomechanical behavior of Terfenol-D. Conventional energy averaging with eight easy axis orientations yields an unphysical kink in the magnetization response and fails to describe the gradual approach to saturation present in Terfenol-D magnetostriction. Superposition of an empirically weighted global anisotropy energy onto an anisotropy energy locally defined around each easy axis eliminates the unphysical kink in the response, while an implicit definition of the domain volume fraction describes the gradual approach to saturation. Anhysteretic bulk material response is described through a weighted sum of individual domains; the weights (or domain volume fractions) are calculated using Boltzmann-type energy averaging. A hysteretic extension is built from an evolution equation for the domain volume fractions. Although solution of the implicit equation for the anhysteretic domain volume fractions requires iteration, the model takes only 20% longer than its original non-iterative version because of the small size of the iteration loop. Comparison of the model with sensing and actuation measurements reveals an average modeling error below 3%. A reduced version of the model, proposed by eliminating certain easy axis orientations, has a 30% lower computational time, with an average modeling error below 6%. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3687372]