Strength assessment of pitch bearing bolt connection of MW wind turbine based on periodic symmetric model

DONG Shuyan, YANG Yang, QI Tao, SU Fengyu, CHAO Guanliang, HE Haijian

（Xuchang XJ Group Wind Power Technology Company, Xuchang 461000，China）

Abstract: Aiming at the problems of strength assessment on the pitch bearing bolt connection of MW level wind turbine, the ultimate strength and fatigue strength were calculated based on the periodic symmetric model and GL guideline. The minimum ultimate safety factors were calculated by using the maximum extreme loads for the maximum bolt pretension level. Then, the maximum ultimate fatigue loads were calculated by comparing with the ultimate fatigue loads of three blades and the bolt loadstress nonlinear curves were obtained for the minimum bolt pretension level. A new load spectrum was constructed and was transformed to stress spectrum according to the interpolation of bolt loadstress nonlinear curves. The minimum fatigue safety factor were calculated by the rainflow method and PalmgrenMiner criterion. The results show that the ultimate and fatigue strength safety factor meet the design requirements. The method reduces the calculation amount and provides a new approach for the strength assessment of bolt.

Key words: wind turbine; pitch bearing; bolt connection; strength assessment