A PROPOSAL OF PREDICTING FORMULAS FOR INFLUENCE OF STRESS ON MAGNETOSTRICTION IN GRAIN-ORIENTED SILICON STEEL

Research has been carried out on the magnetostriction in grain oriented silicon steel, which is known to be one of main causes for noise problem and be crucially influenced by stress condition on the steel in either manufacturing or application process. Generalization of the formulation for the influence of the stress on the magnetostriction has been investigated, which enables computing design to evaluate an occurrence of the magnetostriction under various practical stress conditions, proposing a predictive formulae for the occurrence. The deteriorating influence on the magnetostriction of compressive stress applied to grain oriented silicon steel was attributed mainly to the formation of 90 degrees supplementary domains or triangular closure domains around grooves made on the surface. The supplementary domains or the triangular closure domains were found to occur under generalized condition that the strain elastic energy in easy magnetization axis [100], which is generally parallel to rolling direction in Goss orientation texture, is smaller than those in [010] and [001] (other easy magnetization axes). This result led to practical equation for the influence of the stress on the occurrence of the magnetostriction, having been substantiated by elaborate experimental results ranging from the effect of coating stress on the magnetostriction to the influence of residual internal tensile stress near scratched line on the surface. The obtained formulae were confirmed to be effective even for the magnetostriction under complicated state of superimpositon of bi-axial stresses experimented by Moses et al.