Prediction And Optimization Of Bending Fatigue Life Of Variable Displacement Helical Gears For Subway Vehicle Transmission

In recent years,the overall scale of China’s cities continues to expand rapidly,travel by urban rail transit has become the choice of more and more people,including 223 subway lines,accounting for the major part of urban rail transit.The safety of subway vehicles is the bottom line for people to choose subway travel.Subway vehicle transmission gearbox is a key component of subway operation,and the reliability of the gears in the gearbox directly affects whether the subway vehicle can operate safely.The reliability of the gears also determines the maintenance strategy of the subway gearbox,which has a direct i MPact on the maintenance cost of the subway vehicle gearbox.The design of the gears with suitable displacement coefficients can improve the transmission quality and reliability,extend the maintenance cycle and reduce maintenance costs under suitable working conditions.In order to predict the bending fatigue life of the transmission helical gear of subway vehicles,it is necessary to accurately calculate the tooth root stress of the transmission helical gear.In this paper,we simulate and analyze the bending fatigue test of the transmission helical gear of a subway vehicle and its equivalent spur gear according to the operating conditions of a subway vehicle,and propose a suitable method for bending fatigue life prediction of a subway transmission helical gear.In order to make the subway vehicle transmission helical gear pair more economical,this paper optimized the variation coefficient parameters of a subway transmission gear pair by the folding line diagram method according to the principle of equal strength with fatigue performance as the target.The main research contents are as follows:(1)A finite element model of the helical gear pair is established according to the transmission gear parameters of a subway vehicle gearbox,and the transient dynamics simulation of the model under the operating conditions of the subway train is carried out by ABAQUS,and the tooth root stress clouds of the helical gear pair under different operating conditions and different meshing states are obtained.The location and time patterns of the maximum point of tooth root stress in the meshing process were obtained,and the working conditions that play a major role in the accumulation of bending fatigue damage of helical gears were determined.(2)By studying the bending fatigue test results of gears under single-stage load,it was found that the fatigue life corresponding to the large crack expansion stage is often less than10 %,and the conclusion that only the sprouting life of gears can be predicted and taken as the fatigue life of gears was obtained.Based on the test results,a bending fatigue life prediction model for cylindrical gears based on Miner’s linear cumulative damage theory and energy accumulation curve was proposed.The model predicts the bending fatigue life result lies within the 3 times life interval of the test life,which proves its validity and accuracy.(3)For a subway vehicle transmission helical gear pair,a finite element model of single tooth mesh of the gear pair with different displacement coefficients is established,and through finite element analysis,the tooth root stress distribution clouds of the major and minor gears of the gear pair are obtained,and the tooth root stress folding diagram of the gear pair with different displacement coefficients is drawn.By coMParing the finite element analysis results with the results calculated by the method in GB/T 3480,the stress error of the root of the small gear is only-1.127%,and the stress error of the root of the large gear is 5.387%,and the model can meet the accuracy requirements of the root stress calculation.Based on this,the fatigue life of this gear pair with different displacement coefficients was obtained by FE-Safe fatigue analysis software,and the fatigue life line graph was drawn.(4)Combined with the above research content,a subway vehicle transmission helical gear is optimized by the folding line diagram method according to the principle of equal strength,and the comprehensive fatigue life of the optimized gear pair is 3.29 times that of the prototype gear pair,and the optimized gear pair can meet the requirements of subway train operation with smooth meshing and low noise.