Effect of magnetic anisotropy on Villari Effect in non-oriented FeSi electrical steel

Abstract

The Villari Effect (inverse magnetostrictive effect), which describes the sensitivity of magnetic properties of ferromagnetic materials to mechanical stress is pivotal for actual operational characteristics of electrical machines. In rotating electrical machines mechanical stress is inevitable. It is inherent in processed parts from processing and manufacturing as well as induced by operation of the machine (e.g. centrifugal force). Consequently, magnetic behavior of non-oriented (NO) electrical steel (ES) needs to be characterized not only in its unstressed state as determined by standardized testing, but also considered with regard to its stress dependency. Due to non-uniform distributions of crystallographic orientations within the material, interdependencies between stress and occurring anisotropies have to be identified in order to explain magnetic properties in the entire sheet plane of NO laminations. In this paper the effect of tensile and compressive stress on the magnetic properties of a conventional 2.4 wt% Si electrical steel is studied. Particular attention is paid to the comparison between different directions of applied mechanical stress with respect to the rolling direction. Therewith, the initial anisotropy and interrelating effects due to mechanical stress are evaluated.