Analysis And Research On Load And Fatigue Life Of Pitch Bearing Of Large Wind Turbine

Pitch bearing is one of the special bearings for wind turbine.Because of its unique structural characteristic,it is widely used in the pitch system of wind turbine.When the wind turbine is running,The pitch bearing bears the huge gravitational load,aerodynamic load and centrifugal load from the blade,the force is complex and the working environment is harsh.The reliability,bearing capacity and service life of the pitch bearing play a vital role in the safe and efficient operation of the entire wind turbine;Therefore,In-depth research on the load and fatigue life of pitch bearing can provide a certain reference value for the design and optimization of pitch bearing.This thesis takes 6MW wind turbine pitch bearing as the research object,and analyzes its load and fatigue life.The main contents of this thesis are as follows:（1）Detailed analysis of the external load of the pitch bearing.According to the design load cases in the GL specification,analyze various wind models in the whole life cycle of wind turbine.The GH bladed software was used to build the unit dynamics model.Analyze the ultimate load and equivalent fatigue load of the pitch bearing during the whole life cycle of the unit.（2）A static analysis model was established and based on the hertzian contact theory,the distribution of the contact load of the pitch bearing under the extreme load and the load value of the maximum loaded rolling element were analyzed.Check the static strength of the pitch bearing,and establish the static load capacity curve of the pitch bearing.（3）For the steel ball with the largest load,the finite element analysis model of the contact between the steel ball and the raceway was established by ANSYS software,and the contact stress and distribution of the raceway were analyzed.Compared with the results calculated by hertzian contact theory,the rationality of the finite element model establishment is verified.And based on the sub-model,the influence of bolt pre-tightening force and structural parameters（contact angle,clearance,groove curvature radius coefficient）on the maximum contact stress of the raceway is studied.（4）Based on the analysis results of the finite element static model,combined with the bearing material fatigue performance parameters and load spectrum.Using ncode software,the simulation calculation of stress-fatigue life and strain-fatigue life of the pitch bearing was carried out,and the easily damaged area of the raceway was obtained.The analysis results of the two methods were compared.Finally,the effects of raceway hardening layer and raceway surface roughness on the fatigue life of pitch bearing are analyzed.