Magnetic Material Deterioration of Non-Oriented Electrical Steels as a Result of Plastic Deformation Considering Residual Stress Distribution

For the application in the magnetic core of an electrical machine, electrical steel is cut, packaged, and fixed. The processes induce plastic deformation as well as residual stress. As a result, the magnetic material properties are deteriorated. Most of the effects act local, e.g., in the vicinity of the cut edge or welding line. In order to model the change in local magnetic properties, the effect mechanisms of plastic and elastic stress have to be understood and quantified. In this paper, rectangular samples of a conventional non-oriented 2.4 wt% FeSi with 0.35 mm thickness are stressed uniaxially beyond the elastic limit and characterized during loading, after deformation, and during reloading. A homogeneous stress distribution across the cross section is targeted by the experimental setup to enable a correlation between the global magnetic properties and mechanical finite-element simulations of the stress. As a result, separate physical effects, e.g., dislocation formation, global stress distribution, and residual stress after dislocation formation, on magnetic property change are analyzed. This knowledge is essential to understand the complex effects of processing on the local magnetic properties of rotors and stators in electrical machines.