Abstract
The evaluation of magnetic properties of fatigue-damaged specimens of electromagnetic steel sheets have been investigated. In low-cycle fatigue tests, plastic deformation occurred all over the specimen. In macro-magnetic measurement using B-H analyzer, magnetic properties such as iron loss were remarkably deteriorated. By observing magnetic domain structure using magneto-optical Kerr microscope, the width of magnetic domain decreased and the distribution of magnetic domain became random. In high-cycle fatigue tests, magnetic properties were also deteriorated in fatigue-damaged and especially in fatigue-cracked specimens. By observing specimen surface using laser scanning microscope some grains around notch or fatigue crack were plastically deformed. And in these plastically deformed grains, the width of magnetic domain decreased and the distribution of magnetic domain became random. Then the change of magnetic domain structure in plastically deformed region seems to be the main cause of deterioration of the magnetic properties both in low-cycle and high-cycle fatigue damaged specimens.
