Residual stresses and magnetic material properties of embossed and cut magnetic flux barriers in non-oriented electrical steel under tensile load

In rotors of synchronous reluctance machines and permanent-magnet synchronous machines, magnetic flux barriers reduce stray fluxes and create the magnetic anisotropy of the rotor construction. Conventional flux barriers, fabricated as cutouts, diminish the mechanical strength, hence the rotor's maximum rotational speed and, accordingly the power density. An alternative design of magnetic flux barriers by targeted embossed residual stresses is analyzed to enhance electric drives' energy density and efficiency. As described by the Villari Effect, residual stresses influence the magnetic properties of soft magnetic materials, like non-oriented electrical steel. The functionality of embossed flux barriers is dependent on the residual stress distribution. During the application in the rotating electrical machine, centrifugal forces change the residual stress distribution and the mechanism of the magnetic flux barrier. This study focuses on the mechanical properties, the residual stress distribution, and the magnetic material properties of embossed electrical steel under unidirectional tensile load. The mechanical properties of the embossed and cut electrical steel sheets are analyzed in tensile tests and numerical evaluations. Single Sheet Tests are performed under unidirectional mechanical load to understand the magnetic material properties and evaluate the magnetic permeability. The results enable a better understanding of the interaction of mechanical stress and magnetic material properties, hence the magneto-elastic material behavior.