Abstract:  The previous research mainly focused on the mechanical properties and design improvement of pitch bearing itself, but there was no systematic study on the influence of load change on the mechanical behavior of pitch bearing, which made it difficult to quantitatively predict the influence of load optimization on the reliability improvement of pitch bearing, and not conducive to the accurate formulation of pitch control strategy. Therefore, online test and numerical simulation techniques were introduced to study the influence of load optimization on mechanical behaviors of pitch bearing. Firstly, by using online test method based on strain-load measurement and displacement sensor before and after the load optimization, the blade root loads at different power levels and the corresponding radial and axial relative displacements between internal and external rings of pitch bearing were measured. Then, taking the flexibilities of pitch bearing and surrounding structures into account, a finite element analysis method was proposed to build the finite element model of pitch system. Finally, the simulations were performed by using the tested loads as inputs, and the influences of load optimization on deformation of pitch bearing, the maximum contact stress and the minimum margin angle of edge contact between rolling elements and raceways were analyzed. The research results indicate that with 3.46%~5.08% load reduction after load optimization, at the same power level the deformation of pitch bearing decreases, the maximum contact stress is reduced by more than 1.10%, and the minimum margin angle of edge contact increases by more than 0.47°, so that the reliability of pitch bearing is improved. The research results can provide guidance for accurate development of control strategy for load optimization.
Key words:  mechanical behavior of pitch bearing; load change; online test; control strategy for load optimization; maximum contact stress; minimum margin angle of edge contact