Investigation of magneto-mechanical interactions of non-grain oriented electrical steel – analysis of mechanical and magnetic fatigue using the effect of the Barkhausen noise

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The fatigue of material properties has a significant influence on the application’s properties when components and parts constructed with this material are present. While mechanical fatigue is a key application criterion for structural materials, the fatigue of other technological properties, such as the magnetic properties of electrical steel, is generally not considered. The aim of the proposed project is therefore to initially produce new types of non-grain-oriented electrical steel grades using Cu and Nb as alloying elements, which are characterized by a higher mechanical strength compared to conventional electrical steel grades. High mechanical strength electrical steel is required for high speed electrical machines to acquire the resulting centrifugal forces. The higher the speed, the larger the power density of the electric motor will be. Despite of the increasing rotational demands and possible dynamic changes of the electric motor’s rotor speed during operation nowadays, this topic is not very thoroughly studied or discussed in literature. The magnetic properties of electrical steel are very sensitive to mechanical stress. The main goal of the project is to correlate the mechanic fatigue to the change in magnetic properties as a result of cyclic loading in order to understand and quantify the effects. The differently alloyed manufactured electrical steel strips are rolled and subjected to different final annealing processes before being subjected to mechanical fatigue loading. The method of Barkhausen noise analysis is utilized to quantify the magnetic deterioration, whereas it is an established method to usually characterize the mechanic properties and fatigue of components. A “magnetic” Wöhler Curve is deduced from the obtained experimental data of the characterization of the magnetic property change as a result of cyclic loading. The data is additionally used to enable an estimation of magnetic deterioration as a result of cyclic loading by modeling of the magnetic Wöhler curve. The project is comprised of three main objectives: Study and modeling of the magnetic and mechanic fatigue of electrical steel, a quantification of effects by expanding the measurement spectrum of the Barkhausen noise analysis and a fatigue-resistent material design of non-oriented electrical steels.