Fretting wear in raceway-ball contact under wind turbine pitch bearing operating conditions

This paper investigates wear in wind turbine pitch bearings resulting from small-amplitude oscillations. The investigation focuses on assessing the impact of key parameters influencing wear damage. A new medium-scale test rig has been designed, enabling cost-efficient and accelerated tests to replicate fretting wear damage under simplified operating conditions of wind turbine pitch bearings. Through experimental result analysis, this study examines the influence of oscillation amplitude, contact force, oscillation frequency, presence of lubrication, and contact geometry on wear damage. A finite element model is also developed to obtain the frictional energy density to compare with experimentally measured wear depth to obtain new insights of the effect of the contact variables on wear damage. It has been found that most of the wear damage takes place at the location where the maximum sliding occurs but not at the location of the maximum contact pressure, while the contact geometry has an important impact on the wear damage. Controlling oscillation amplitude and contact pressure are effective ways to mitigate wear damage due to small-amplitude oscillations in wind turbine pitch bearings.