Wind Power Pitch Bearing Based On Load Spectrum And Structure Research On Fatigue Life Prediction

As an important part of variable rotor system for wind turbine,variable rotor bearing is subjected to complex alternating loads during its service,which directly affects the safety operation of the whole machine.Therefore,it is urgent to carry out in-depth research on the fatigue life prediction of variable rotor bearing.Based on a certain level of 3.4 MW wind power variant OARS bearing as the research object,the integrated application of bearing mechanics theory,the Hertz contact theory,fatigue life analysis method and the finite element method(fem),the variable blade bearing load spectrum analysis,the multi-body contact model and fatigue life prediction,is analyzed.studying for bearing fatigue life of study provides scientific theory basis,has important engineering significance.The main reseach content of the paper includes:(1)The process of compiling the load spectrum under the actual service condition of the pitch bearing was investigated,and the actual load spectrum was processed by sampling,filtering,rain counting and other processes to obtain the fatigue load spectrum for fatigue life analysis.(2)Based on the Hertz contact theory,a multi-body model of "blade-bearing-hub" pitch bearing is established using finite element equivalence modeling method,in which non-linear spring unit and rigid rod unit are used to simulate the ball-roller contact,and the bolt connection in the pitch bearing is simulated by the beam unit and rod unit,forming a relatively perfect digital parameter modeling means and method.(3)The bearing contact loads were studied separately by the theoretical static model and the finite element model,and the difference between the two contact load distribution laws was analyzed and compared to obtain the maximum bearing contact load position.Based on the azimuthal position,a sub-model of local contact between the bearing balls and the raceway was established,and the laws of contact stress,equal effect force,raceway secondary surface stress and strain with contact depth were analyzed.The effect of process parameters on the contact stress performance of the bearings was investigated.(4)Fatigue analysis was performed on the pitch bearing structure under extreme load and fatigue load,respectively,introducing stress life and strain life fatigue analysis,and analyzing the bearing life under wire elastic and elastoplastic materials.The effect of different process parameters on bearing life was explored.A life analysis process suitable for solving the actual service fatigue load is proposed:the relationship between external load and contact stress is fitted by the overall multi-body structural model,the average stress is corrected by the Goodman model,the cumulative damage under the actual fatigue load is solved based on the corrected S-N curve and Miner damage theory.Guided by the actual works.