Hoch belastete Großwälzlagerungen in Windenergieanlagen

The industrial application of wind power plants is gaining importance in face of strongly growing energy demands and limited capacities of fossil fuels. Increasing contact loads and corrosive wear processes -especially in case of offshore use- are setting highest requirements regarding lubricant performance as well as bearing layout and manufacturing to ensure operational capability. The investigations carried out are focussing on slewing blade and main rotor bearings of large diameter for wind turbines. With special regard to blade bearings a testrig is designed allowing grease lubricant testing under permanent-pitch operating conditions for on- and offshore use. The influence of lubricant on tribocorrosive wear, frictional torque and raceway damage is experimentally investigated by use of optical interferometric and metallographical analysis of contact area. The experimental results highlight significant differences in lubricant performance preventing fretting wear under on- and offshore operating conditions. To investigate tribocorrosive wear process in grease lubricated bearings in detail, an electrochemical measurement device is applied to a test rig for annular roller bearings. Results based on simultaneous recording of corrosion potential-time curves may form a base for further research activities on tribocorrosive wear in heavily loaded slewing bearing applications. In order to study the influence of geometry, frictional shear and mechanical loading for ball as well as roller bearings, a numerical algorithm for solid body contact based on half space theory is applied. Contact stress fields at and beneath the surface are evaluated using a 3d semianalytical model. Additionally a deterministic fatigue model, which is based on critical plane approach, is linked regarding fatigue process due to cyclic loading of raceway in detail. The calculations carried out on large simulation grids show exemplarily in how far tribological stress and fatigue damage at contact surface of blade bearings are affected by shear loading due to pitching. Finally theoretical investigations are extended to tapered main bearing under slowly turning as well as nominal EHL operating conditions taking roller profiling and misalignment into account. A numerical model linking Reynolds-PDE and contact elasticity is developed in order to optimize EHL solution procedure for heavily loaded bearings. Results comparing numerical and analytical solutions are shown and reveal the necessity of detailed investigations and advanced triboengineering in order to simulate contact conditions and to assess performance and finally lifetime of tribosystem under various influences.