Research On The Wear Mechanism And Sealing Performance Of The Oil Seal Of The Traction Gear Box Of An EMU

This article takes the rotating shaft oil seal of the gear box of an EMU as the research object.Based on the current research status,relevant research is carried out on two major aspects of the current oil seal research.One is to use finite element simulation software to compare the structure of the oil seal to optimize the oil seal lip and shaft diameter interference.The other is to conduct tribological and mechanical experimental research on the base material of the oil seal to analyze its friction mechanism and mechanical characteristics.In this paper,the main base material of analog oil seals is polytetrafluoroethylene（PTFE）.In order to further enhance the wear resistance of the oil seal lip,it is proposed to prepare a wear-resistant coating on the oil seal lip to increase its wear resistance and reduce the frictional heat loss of the lip.The main contents and results of this research are as follows:（1）ABAQUS finite element simulation software was chosen to compare and simulate the lip length,lip angle,and shaft diameter of the PTFE oil seal,and the controlled variable method was used to study the relationship between these three elements and the interference.Results have shown that when the length of the oil seal lip remains unchanged,the contact lip width between the oil seal lip and the rotating shaft gradually decreases as the bending angle increases,and the contact stress gradually increases,which will aggravate the lip and shaft diameter.The maximum contact stress on the lip decreases as the length of the lip increases,and the maximum stress point on the lip also moves away from the oil storage side as the length of the lip increases.Furthermore,the length also increases as the shaft diameter increases,and when the shaft diameter reaches 16mm,warping occurs at the lip.Then,MATLAB numerical calculation software was used to numerically calculate the sealing coefficient of the spiral return groove of the PTFE oil seal lip according to the sealing mechanism.Combined with previous studies,the relationship between depth,relative width,and width of the spiral groove are revealed.The objective function of the spiral groove of the oil seal is numerically analyzed by MATLAB.When the relative groove depthk₂ is small,the increase of the relative groove width₁k can increase the sealing coefficient K.When the relative groove depth is large,the change trend of the sealing coefficient K is more severe.Appropriately increasing the helix angleαcan obviously increase the sealing coefficient.（2）Modified PTFE lip material is formulated with four different inorganic fillers.Friction and wear tests were carried out on the modified lip material and the wear mechanism was explained.The mechanical performance test was simultaneously conducted and the performance parameters were analyzed and compared.Studies have shown that the friction and wear performance of the modified lip material is significantly improved,which demonstrate that the friction coefficient and wear rate are significantly lower than those of pure PTFE materials.Under oil lubrication conditions,the minimum wear rate is 8.3×10^-8mm³/Nm,which is one order of magnitude lower than that of pure PTFE and shows amazing wear resistance.At the same time,the relevant parameters of the tensile test and the compression test have also been significantly improved,which can meet the requirements of mining oil seals and increase its the service life.（3）Polyimide is a kind of wear-resistant high-performance polymer with excellent performance,which has a wide range of applications in the engineering field.The pure polyimide was modified with reduced graphene oxide and zinc oxide composite additives to fabric a wear-resistant coating in order to meet the requirement of high wear-resistant lip.The tribological and thermodynamic properties of the wear-resistant coating were studied.Resultes have shown that wear-resistant coatings have better tribological properties than pure polyimide.Friction and wear tests show that the friction coefficient and wear rate of the wear-resistant coating are far lower than those of pure polyimide.When the filler content is 0.8wt%under a load of 300N,the volume wear rate is at least 1.1×10^-8mm³/Nm.Compared with pure polyimide,it is reduced by 90%,which mean its remarkable wear resistance.In addition,the corresponding oil-lubricated friction and wear properites were also carried out,and the tribological performance of the non-lubricated condition and the oil-lubricated condition were compared.The wear rates under lubrication conditions show two orders of magnitude lower than that under dry sliding condition.Finally,the thermodynamic test of the wear-resistant coating also showed better thermal decomposition stability.