Evaluation of Contact Stress and Fatigue Life for Roller Crowning Profiles in Triple Roller Pitch Bearings

ABSTRACT This study investigates the contact stress and rating life of a three‐row pitch bearing for wind turbines, considering the effects of roller crowning. All crowning profiles were logarithmic, and a total of six profiles were examined based on the Romax, ISO 16281, and Fujiwara equations. Finite element analysis (FEA) was employed to evaluate the contact stress in the bearing elements induced by different crowning profiles. To improve numerical convergence and accurately calculate contact stresses, the rollers in the full bearing model were replaced with spring elements. The reaction forces obtained from the full model were then mapped onto a sub‐model, where detailed contact stress analyses of the rollers were performed. The contact stress magnitudes for each profile were compared under extreme load conditions. For fatigue loading conditions, the modified rating life was calculated in accordance with ISO 16281 using the reaction forces derived from the spring elements. The stress analysis results indicated that the ISO 16281 profile exhibited no edge stress concentration and yielded the lowest stress at the roller contact because it mathematically induces a uniform load distribution. In parallel, the fatigue life calculation showed that the bearing life was longest for the ISO 16281 profile, followed by the Fujiwara and Romax profiles. This indicates that a longer life was achieved with the ISO 16281 profile rather than the Fujiwara profile, despite the latter having a lower roller reaction force distribution per bearing angle. These findings demonstrate that both the overall bearing reaction force distribution, local contact stresses, and bearing life should be comprehensively considered when selecting crowning profiles for wind turbine pitch bearings.