Fracture failure analysis and optimization of blade bolts in large wind turbine

YING Hua-dong1,2, LIU Hong-wei1, CHEN Zhong-ya2, HE Xian-zhao2
（1.Scool of Mechanical Engineering, Zhejiang University, Hangzhou 310000, China;
2.Zhejiang Windey Co., Ltd., Hangzhou 310012, China）

Abstract: Aiming at the problem of batch breaking of bolts at the blade root of wind turbine in a wind farm, to analyze whether the fracture was caused by fatigue damage, the method of finite element simulation and field test was used. The stiffness behavior of the blade bolt connection system and fatigue life of the blade bolt were studied. The fatigue life calculation results of blade bolts were combined with the fracture analysis of blade bolts to confirm that the fracture of blade bolt was caused by fatigue damage. A method of reducing the stiffness of blade bolts to improve their fatigue life was proposed, and the optimization scheme of fine bolt was designed,implemented and verified on site. The results show that the fatigue fracture location of blade bolt is mainly within ±45 degrees of leading edge，which is consistent with the simulation results. The improved fine-rod bolt scheme reduces the stress amplitude of the blade bolt by about 13%,which improves the fracture of blade bolt obviously in the field application.
Key words: fatigue break; preload monitoring; blade bolt; finite element analysis