Emulation of interface stiffness for full scale tests on wind turbine blade bearings

Typical damage modes of rotor blade bearings are mainly related to oscillating movements with small angles under high loads. Under these conditions, the lubrication film between rollers and raceways of the bearings tends to collapse, which causes metal to metal contact and surface induced damage. Since established calculation methods for lifetime prediction are unsuitable for wind turbine blade bearings, full-scale test rigs are developed to close this particular knowledge gap. To generate realistic boundary conditions for bearing tests, the stiffness of the interfaces such as blade and hub have to be investigated. Because of the disadvantages of using real components within these test rigs, a possible solution is to use substitute components which aim to emulate the interface behaviour of the real components. This paper presents a method to derive a substitute of a rotor hub based on a FE-model of the virtual IWT7.5-164 research turbine. The results indicate that it is feasible to match the interface stiffness of the considered rotor hub with a corresponding substitute with only minor limitations.