AC MAGNETOSTRICTION OF 3.25-PERCENT GRAIN-ORIENTED SILICON-IRON UNDER COMBINED LONGITUDINAL AND NORMAL COMPRESSIVE STRESS

The ac magnetostriction of transformer sheet has been measured with longitudinal compression up to 2000 lbf/in2 /in> (13 800 kN-m-2). kN-m-2). Longitudinal stress causes a sudden increase in magnetostriction, while normal stress smooths out the step-like change. Si-Fe sheet from three different manufacturers is shown to have widely varying stress sensitivities, which are due entirely to differences in the insulating coatings on the laminations. Application of a glass coating greatly reduces the stress sensitivity, such that longitudinal stresses over 1100 lbf/in2 (7600 kN-m-2) kN-m-2) are needed to produce any increase in magnetostriction. Both longitudinal and normal compression change the domain structure from simple 180-degree walls to a more complicated structure where most of the magnetization is at 90 degrees to the rolling direction. This stress structure is conducive to high positive magnetostriction. © 1969, IEEE. All rights reserved.