Failure Analvsis And Optimization Of Blade Bolts In Wind Turbine

Most parts of wind turbines are connected by bolts,such as blades and pitch bearings,pitch bearings and hubs,hubs and main shafts,nacelles and towers,and towers and foundations.These connections are all connected by bolts.The safety and economy of the system design are directly related to the reliability and competitiveness of the wind turbine.This paper takes the blade connecting bolts as the object.Through theoretical research,finite element analysis,test plan design,field data collection and analysis,etc.,the mechanism of fracture failure and optimization and improvement methods are studied,and significant results have been achieved.The chapters of the thesis are summarized as follows.The first chapter introduces the research status of wind turbine technology at home and abroad in recent years and some main results in the research of high-strength bolt connection.The second chapter analyzes and introduces the bolt structure strength calculation theory,finite element analysis method and the method of obtaining the load spectrum of the blade bolt.The third chapter completed the finite element analysis of the blade screw.Use ANSYS software to establish a 1.5MW-class wind turbine blade bolt connection numerical model,and perform finite element analysis on the connection structure,including:modeling the thick rod and thin rod bolts respectively,and analyze the bolt stress increment under different angles and different loads.At the same time,combined with the load situation,the fatigue life of the bolt is analyzed.The fourth chapter designs a load measurement plan.By installing a washer-type pressure sensor under the blade nut,the data acquisition instrument is used to obtain the pre-tightening force data of the connecting bolt in real time,and then the use status of the blade bolt and the connection status of the system are obtained.The finite element simulation value and the measured data are analyzed and compared,and the error is less than 5%,which effectively verifies the accuracy of the simulation model.Chapter five analyzes the measured load data of bolts and combines the simulation results.It is believed that the root cause of bolt fracture is fatigue load.At the same time,the field bolts are improved.After the implementation of the improvement plan,the bolt fracture situation has been significantly reduced,and it is also verified from the side that the bolt fracture is caused by fatigue.The sixth chapter summarizes the research work of the thesis,and puts forward the prospect of follow-up research.