Study On Failure Mechanism And Countermeasure Of CRH5 Drive System Universal Shaft

In recent years,the Ministry of Railway imported four kinds of electric multiple units(EMU),of them only CRH5 used the body suspension structure for its drive system.During the initial stage of operation,this structure exposed a few problems and mainly expressed by the universal shaft,the gear box pinion shaft connected with it and the traction motor output shaft.The universal shaft's length is 1945mm.It was fixed between the car body and the bogie.The falling off of the universal shaft will result in "pole vault"of the car body,which seriously affected the safety of train operation.This thesis takes CRH5 drive system universal shaft as research object,analyses the failure mechanism of universal shaft from different angles,and puts forward the optimization plan for universal shaft and drive system.The actual circuit test and the data from the test proved that the optimized plan is available.The main contents of this thesis are as follows:(1)The typical faults of drive system and universal shaft are calculated and analysed.The fault tree of drive system is constructed.The typical faults of universal shaft are emphatically analysed by FMECA method.(2)The movement characteristics of double cross universal shaft are studied.The additional load,additional moment and volatility of shaft are analysed when the universal shaft is decorated at Z-W type.A movement analysis diagram of CRH5 drive system is built up.The limit position of universal shaft and the additional moment,additional inertia moment at corresponding positions are calculated.(3)A dynamic model of CRH5 drive system is simulated by SIMPACK according to the structure of gear box and the suspension mode of traction motor.The influence caused by drive system on EMU nonlinear stability is analysed.The gyroscopic moment,angle velocity and angular acceleration of drive system and the displacement and acceleration of traction motor when the train is at straight and curve conditions are analysed.The influence on the drive system caused by the change of vibration frequency and inertia moment of drive system is analysed.According to the analysis above,we get that by changing the drive system ratio from 2.5 to 2.2 and reducing the revolving speed,the additional moment and rotating angular acceleration of universal shaft could be reduced by 8%-11.2%.By adjusting the arrangement angle of the drive system from 4.41° to 2.91°,the additional moment and rotating angular acceleration of universal shaft could be reduced by 2%-3%.(4)A rigid-flexible coupling modal analysis model of CRH5 drive system is established by ANSYS.The critical rotational speed of universal shaft corresponding to its first-order bending frequency is 5360rpm while the frequency is 89.34Hz.According to the engine bench test,the natural frequency of universal shaft in the drive system is 74Hz and the corresponding critical rotational speed is 4440rpm.We also can get a critical rotational speed 5610rpm according to the traditional formula.Based on the comparative analysis,we deduce that the critical rotional speed of universal shaft got by the bench test is about 82%of the speed calculated by finite element method and 79%of the speed calculated by traditional formula.(5)The influence factors of universal shaft failure caused by its structure are analysed:1)It was demonstrated that the vibration amplitude of ends of universal shaft can be reduced by decreasing the dynamic-unbalance value,which could decrease the failure probability of universal shaft.2)The needle roller bearing is the weak link of universal shaft,therefore,the compressive stress between the bearing bush and the needle roller should be considered while doing structure design.3)Design of lubrication and sealing needs to be emphasized while designing and manufacturing the universal shaft.(6)The optimization plan of CRH5 universal shaft drive system are put forward by multi-objective function optimization method:1)Adjust the arrangement angle of the drive system from 4.41° to 2.91°;2)Change the drive system ratio from 2.5 to 2.2;3)Optimize the stiffness of the suspention parts of the drive system;4)Use a new structural universal shaft.The data gathered by actual circuit test and analysis of the universal shaft proved that the optimized plan is available.