The Impact of Mesh Generation in Finite Element Simulations on Stress Gradient and Calculated Fatigue Strength

Rotors of permanent magnet electric motors, which are made of electrical steel, have sharp notches at the openings of the permanent magnets. In cyclic tests the electric steel NO30–15 shows a higher dynamic support effect compared to state-of-the-art literature values. To determine the calculated fatigue strength, both material parameters and the associated stress gradient need to be considered. Computational approaches, following the FKM-guideline and Schütz-criteria, are used to assess the influence of different meshing strategies on the stress gradient. For mildly notched geometries, global cross-links with element sizes of 0.3 mm are sufficient to adequately describe the gradient. However, sharp-notched geometries require finer mesh structures in the vicinity of the notch base. The key requirement to ensure a continuous stress curve can be accurately represented throughout the meshing of the notch base. By meeting this criterion, the calculated fatigue strength becomes less sensitive to gradient fluctuations.