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Estimation model for magnetic properties of stamped electrical steel sheet

Less deterioration in the magnetic properties of electrical steel sheets in the process of stamping out the iron core is necessary in order to maintain performance. First, the influence of plastic strain and stress on the magnetic properties is studied using test pieces, in which plastic strain is added uniformly and residual stress is not induced. Because the influence of plastic strain is expressed using the equivalent plastic strain, at each equivalent plastic strain state the influence of the load stress is investigated. Second, the elastic limit is determined to be about 60% of the macroscopic yield point (MYP), and this agrees with the stress limit inducing irreversible deterioration in the magnetic properties. Therefore, simulation models, in which excess elastic limit plastic deformation begins and the magnetic properties deteriorate sharply, are proposed. Additional points taken into consideration in the deformation analysis are the strain rate sensitivity of flow stress, the anisotropy under deformation, and the influence of stress triaxiality on fracture. Finally, the proposed models are shown to be valid because the magnetic properties of rectangular sheets 5 mm wide stamped out from a nonoriented electrical steel sheet (35A250 JIS grade) can be estimated with good accuracy. It is concluded that the elastic limit must be taken into account in both the stamping process simulation and magnetic field calculation. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(2): 1–11, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22269