Rolling contact fatigue life of large oscillating slewing bearings as used in wind turbines - Test results vs. calculations

Rolling contact fatigue tests are mostly done on small-scale bearings. For large slewing bearings, very few public results are available. The paper analyzes laboratory rolling contact fatigue test results of 32 large slewing bearings. Tests results of the Large Bearing Laboratory at Fraunhofer IWES and test results from the literature are combined for the analyses. Most bearings in the analysis are original-scale bearings that have been designed as pitch bearings for wind turbines, and some of the bearings have been designed to replicate such bearings. Based on an analysis of the test results, a corrective factor of 0.55 is proposed to adjust ISO 16281 calculations for large slewing bearings. The results can be generalized to other slewing bearings operating under similar conditions, both in wind turbines and in other applications.