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Large slewing bearings are designed to sustain axial, radial and tilting moments.
Due to their design and manufacturing process, a nonstandard approach has to be
used to calculate the fatigue life. First, a maximum contact force is obtained from
the load distribution in a bearing by means of analytical expressions of the
Hertzian contact theory. Then, a strain-life approach is used to calculate the
fatigue life on the basis of the subsurface stresses as obtained from the finite
element analysis. Experimentally determined depth-dependent elasto-plastic
material properties, which appear as a result of hardening, are taken into
consideration. The fatigue life largely depends on external bearing loads. For an
external loading, which results in 3200 MPa contact pressure on a bearing
raceway, the fatigue life is approximately 4.69e7 load cycles (1.54e6 revolutions).
The calculated fatigue life is in accordance with the requirements of the fatigue
life of wind turbines’ blade flange bearings.