<div class="section abstract"><div class="htmlview paragraph">Electrical steels are silicon alloyed steels that possess great magnetic properties, making them the ideal material choice for the stator and rotor cores of electric motors. They are typically comprised of laminated stacks of thin electrical steel sheets. An electric motor can reach high temperatures under a heavy load, and it is important to understand the combined effect of temperature and load on the electrical steel’s performance to ensure the long life and safety of electric vehicles.</div><div class="htmlview paragraph">This study investigated the fatigue strength and failure behavior of a 0.27mm thick electrical steel sheet, where the samples were prepared by a stamping process. Stress-control fatigue tests were performed at both room temperature and 150°C. The S-N curve indicated a decrease in the fatigue strength of the samples at the elevated temperature compared to the room temperature by 15-25 MPa in the LCF and HCF regimes, respectively. Looking at the fracture surface, the room temperature samples at both the low- and high-cycle regimes showed some intergranular cleavage facets along with predominant transgranular facets in the crack initiation zone and transitioned to only transgranular cleavage facets in the crack propagation zone. In contrast, the high-temperature samples showed a smaller fatigue damage zone, and outside of this zone, the main failure mechanism was severe necking for both the low- and high-cycle samples. An important finding here was that the crack always initiated from the breakaway zone on the stamped edge of the samples. The higher temperature adversely affected the fatigue strength, as the higher temperature releases residual stresses and annihilates dislocation density induced during the sheet manufacturing and sample preparation, resulting in shorter fatigue life.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Strict environmental regulations are driving the automotive industry toward electric vehicles as they offer zero emissions. A key component in electric vehicles is the electric motor, where the stator and rotor are manufactured from stacks of thin electrical steel sheets. The electrical steel sheets can be cut in different ways, and the cutting methods may significantly affect the fatigue strength of the component. It is important to understand the effect of the cutting processes on the fatigue properties of electrical steel to ensure there is no premature failure of the electric motor resulting from an improper cutting process.</div><div class="htmlview paragraph">This investigation compared the effect of three different edge preparation methods (stamping, CNC machining, and waterjet cutting) on the fatigue performance of 0.27mm thick electrical steel sheets. To investigate the effect of the edge finish on fatigue behavior, surface roughness was measured for these different samples. It was determined that the CNC machined samples had the lowest overall roughness over the cut edge, followed by the stamped samples, and the waterjet samples with the worst finish. The fatigue life followed a similar trend where CNC machined samples had the longest life, and the waterjet samples had the lowest life under the same stress amplitude. While the CNC samples had the greatest overall life, the stamped samples could withstand the largest alternating stress out of the three cutting processes because of the residual stresses induced by the stamping process. Additionally, the stamped samples had very close life to the CNC machines samples in the high cycle regime. An investigation was carried out to determine the relationship between surface roughness and residual stress to the fatigue life of the electrical steel.</div></div>