Modelling of the magnetoelastic behaviour of a polycrystalline ferrimagnetic material
Résumé
The effect of stresses on the magnetic behaviour of polycrystalline ferrites has been investigated by the use of experiments and a multiscale model. This model is based upon 3 scales: the magnetic domain, the single crystal and the polycrystal. At the scale of the magnetic domain, a minimisation of the potential energy (composed of field energy, anisotropy energy and magneto-elastic energy) gives the orientation of magnetisation under the effect of magnetic field, stresses, and crystal orientation. At the scale of the single crystal, the volume fractions of domains of different orientations are computed from their respective energies through a balance equation that introduces two adjusting parameters. The isotropic polycrystalline behaviour is deduced from the averaging of the behaviour of a sufficient number of grains (of different crystallographic orientations). The adjusting parameters are identified from the magnetisation response of a ring subjected to two different levels of axial compressive stresses. The model is then used to predict the behaviour of the same ring subjected to different levels of radial compressive loading. The predictions are in good agreement with the experimental results.