Fatigue behaviour of thin Fe-Si steel sheets for electric motor production

The on-going evolution toward electric/hybrid traction requires the development of high-performance electric motors. The rotor of electric motors is made from a stack of thin steel sheets and a complex configuration of magnets. Electric steels are typically Fe-Si alloys where Si addition controls grain size. Mechanical durability assessment of electric motors is based on the fatigue performance of Fe-Si steels. This contribution reports a thorough mechanical characterisation of a Fe-Si alloy in the form of thin (i.e. 0.2 mm) sheets. Numerous tensile tests were performed to characterize the reference static properties and their respective scatter. A suitable fatigue testing procedure for thin sheets was developed and used in an extensive campaign aimed at investigating the directional fatigue behaviour of the Fe-Si steel. Comparison with literature data confirms that the fatigue response of thin sheets is affected by different factors related especially to the method of extraction.