Rolling contact fatigue calculation of a three-row roller pitch bearing in a wind turbine

Rolling contact fatigue calculations of wind turbine pitch bearings need to consider the oscillating operation and the complex dynamic load distribution in the bearing. The present work proposes a methodology to calculate the life of a pitch bearing that is a roller bearing, specifically a three-row roller bearing. Previous publications in this field have discussed the life calculation of ball pitch bearings. Methodologies applicable to any pitch rolling bearing are partly improved upon in the present work. Several aspects not applicable to roller bearings are re-thought. In comparison to ball bearings, the rolling contact fatigue calculation of roller bearings adds another level of complexity, since they have a long contact that is typically discretized if strong deformation is present, leading to significantly more degrees of freedom. Exemplary calculations are carried out using a slightly modified version of an extensively validated finite-element (FE) model of a three-row roller bearing of a wind turbine. This paper focuses on the methodology used to calculate the life. The axial rows were found to have a much lower fatigue life than the radial row, and thus the axial rows are the main determinant of the fatigue life of the bearing. They also were shown to have a much lower uncertainty than the radial row using the approach proposed in this paper.