Model to evaluate the AC–DC magnetostriction characteristics of SiFe electrical steels

Abstract

A simple model, describing the polarization dependence of the amplitude of AC peak-to-peak ( λ (p–p)) and zero-to-peak ( λ (0–p)), and of the DC ( λ DC) magnetostriction of electrical steels, based on some well-known mechanisms governing the domain structure of these materials is proposed. Three main features of the domain structure were considered in relation to the increase of polarization: At low polarization level (Part I of Fig. 1), a slight exponential increase of the magnetostrictive signal occurs according to the increase of volume fraction of sub-domain structure. Further on, owing to the annihilation of main 180° walls, the sub-structure is suppressed and its collapse can be described by a Dirac-type function (Part II). Almost at the same time, rotation of domains start to dominate (Part III), resulting in a sharp increase of the magnetostriction. These relationships can be formulated for the polarization dependence of the λ (p–p), the λ (0–p) and λ DC. Excellent fit of the experimental data was obtained by means of least squares, not only for different grades of grain-oriented but also for non-oriented steels, in wide range of thickness and Si content. In some cases, close relation of the fitted parameters to the materials properties were found.