Research On Strength Technology Of High Strength Bolt For Wind Turbine Yaw Drive Connection

Bolt connection is the most common and universal connection mode of wind turbine,especially the high strength bolt.The high strength bolt has the advantages of prestressing load,strong anti-alternating load and good stress performance.Therefore,it is widely used in wind turbine.With the development of wind turbine generator towards large scale,especially the sea fan has 6MW power fan installed operation,therefore,it is request higher and higher for the reliability of the parts of the wind turbine units.Yaw system is an indispensable part of wind turbine,it mainly depends on the control system's command to control the cabin position and the wind wheel to improve the efficiency of power generation.Yaw driver is the execution mechanism of yaw system and the stability of yaw system is closely related to the reliability of the yaw drive bolt.In recent years,due to the failure of bolts resulting damage accidents in endlessly,how to improve the joint strength and maintain the stability of bolt connection is the precondition of the stable operation of wind turbine.Therefore,it is necessary to analyze the strength characteristics of high strength bolts.The main research contents of the thesis are as follows:1)Using the engineering calculation method of VDI 2230 high strength bolt theory,the yaw driving machine and frame connecting bolt are reasonably simplified and the equivalent model of flange stiffness was established.The relationship between working load and pre-tightening force was studied and the influence of the residual pre-tightening force,the bolt and the clamping body flexibility,torque coefficient,the parameters of the bolt,stuffing loss force and the bolt pre-tightening torque was analysed.2)A Finite Element Model of bolt coupling for yaw driving machine and frame was established,considering the different contact relation between each contact surface.The relationship between the stress state distribution and displacement of the bolt under Pre-tightening and limiting conditions was analyzed by using ANSYS Workbench,comparing with the results of VDI 2230,the correctness of Finite Element Method was validated.At the same time,the change tendency of working stress with different prestressing force,different temperature and number of bolts was analyzed,the optimal pre-tightening force was determined according to the analysis results.3)Visual Basic 6.0 was applied as the exploitation platform and Visual Basic was the development tool,the design of the coupling bolt design for yaw driving machine is developed based on the method of VDI 2230,the parametric design of bolt is calculated.And the Access database is connected to implement custom parameters,the user only needs to enter or query the relevant parameters in the system according to the design requirements and the system can analyse the corresponding results automatically.