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 (λDC) 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 λDC. 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.