Bending Fatigue Life Prediction Of Gear Box Of Urban Rail Train Under Multistage Load

With the increasing problem of urban traffic congestion,traveling by public transportation has become the choice of more and more people.As an important part of the public transportation system,urban rail transit has the advantages of high punctuality rate and strong carrying capacity.However,while facilitating people’s efficient travel,the safety of trains is also a concern.The urban rail train gearbox is a key component of the train running part,and the reliability of the gear pair transmission is directly related to the safety of the train operation.The fatigue damage of the gear pair of the gearbox may cause abnormal noise in the gearbox,or damage the gearbox in severe cases,which will seriously affect the safe operation of the train.In order to predict the bending fatigue life of gear box gears of urban rail trains,this paper takes the gear box gears of urban rail trains as the research object.The life prediction model of gearbox gears escorts the safe operation of trains.The main research contents of this paper are as follows:(1)Based on the design parameters of the urban rail train,the finite element model of the train gear pair was established,and the characteristics of the stress change at the tooth root under the different running stages of the train were explored.Firstly,the threedimensional model of the gear pair is established.According to the data of the traction characteristics of the train motor and the running resistance of the train,the boundary condition data required for the finite element analysis of the gear pair under specific working conditions is calculated.Based on this,the finite element model of the gear pair is established,and the Stress contours of the gear pair during the traction,coasting and braking phases of the train.Through the analysis of the meshing process,the maximum stress value at the tooth root of the lower gear at each stage is obtained.(2)The influence of load interaction on the gear bending fatigue life is explored,and the damage scaling factor is proposed and applied to the improved gear bending fatigue life prediction model.In order to explore the influence of the ratio of the adjacent twolevel load amplitudes on the gear bending fatigue life,the two-level load amplitude ratios were selected as 0.90,0.95,1.05,and 1.10,respectively,and the gear specimens were subjected to bending fatigue tests under two-level loads.According to the test results,the damage scaling factor is fitted and applied to the improved life prediction model.By comparing the predicted life of the improved model with the actual life obtained from the test,the maximum deviation rate of the two reached 9.6 %.(3)The influence of the helix angle on the gear bending fatigue life was explored.In order to expand the applicable scope of the improved life prediction model,the design parameters of the urban rail train transmission were investigated.Considering the design characteristics of the gear box of urban rail trains,a single-tooth finite element model with the same normal phase parameters and different helix angles was established with the helix angle as the variable.The finite element calculation results are compared with the relevant standard calculation results to verify the correctness of the single-tooth finite element model.Using fatigue life analysis software,the fatigue life of gear teeth with different helix angles was analyzed.According to the bending fatigue life of gears with different helical angles,the helical angle bending fatigue life correction factor is fitted.Combined with this correction factor,the bending fatigue life of gears with different helix angle and the same phase parameters can be obtained only by performing bending fatigue tests on spur gears with the same phase parameters,which shortens the test period and reduces the test cost.(4)Combined with the previous research contents,a bending fatigue life prediction model suitable for urban rail train gears is proposed.According to the operating conditions of trains on a certain line,the damage of gears under different operating conditions is calculated,and the service life of gears is predicted according to the damages.By comparing the service life of the gear predicted by the model in this paper with the design service life of the gear,it is found that the two are relatively similar,which verifies the rationality of the fatigue life prediction model proposed in this paper.