Influence of compressive stress on magnetic properties of laminated electrical steel sheets

In a practical motor, the compressive stress of more than 100 MPa is sometimes impressed by a shrink fitting etc, as a result, the magnetic properties of iron core deteriorate. Therefore, it is necessary to measure magnetic properties under the compressive stress. However, the measurement under the compressive stress of more than 100 MPa is difficult if a single sheet tester is used, because of the buckling of a single sheet specimen. Then, we measured the magnetic properties under the compressive stress up to 150 MPa without buckling by using a laminated specimen. It is shown that the permeability rapidly decreases even by small stress in both cases of rolling and transverse directions. The iron loss is increased by the stress, but it almost does not increase when the stress is larger than about 50 MPa. Furthermore, the permeability and iron losses of the rolling direction and transverse direction become the same values, and the anisotropy disappears when the stress is larger than about 50 MPa.