Research On Sealing Performance And Material Of Rotary Shaft Lip Seal For Axle Box Of Railway

As one of the most important components of railway vehicle axle box,oil seal has an important influence on the reliability,service life and maintenance cost of vehicle operation department.For the high temperature,high speed,heavy load and harsh environment of railway vehicles,the rubber oil seal of the axle box of the high-speed train has high friction resistance and poor wear resistance,while it is difficult to withstand high or low temperature.In this paper,polytetrafluoroethylene?PTFE?oil seal is used in the railway vehicle axle box instead of traditional rubber skeleton oil seal,and the performance parameters and contact problems of PTFE oil seal are simulated by finite element ABAQUS/Standard.Combined with the sealing mechanism of PTFE,the sealing coefficient is taken as the objective function,the structure of the lip dynamic pressure return tank is taken as the parameter,and the corresponding boundary conditions are set to optimize the design through Matlab.Furthermore,PTFE modified materials were prepared by methods of sintering after pressing molding,and the friction and mechanical properties were studied.Finally,to improve the wear resistance of PTFE oil seals,a polyimide-based wear-resistant coating was designed and the related properties were studied.The results of the above studies are as follows:?1?The nonlinear finite element model of PTFE oil seal structure is established by using ABAQUS finite element analysis software to analyze the contact compressive stress and strain distribution of oil seal and shaft interference with different structural parameters.It is found that the lip thickness and contact width of oil seal have certain influence on the distribution of contact stress of seal lip.The results indicates that the wider the contact width,the more dispersed the stress is,while the greater the interference,the greater the contact stress will be.In addition,taking the interference amount of 0.5 mm,1mm,and 1.5 mm to study the lip stress,it is found that the maximum stress increases with the increase of the interference amount.On the basis of the sealing mechanism of PTFE oil seal,the relative width,depth and spiral angle of the oil return tank with PTFE oil seal dynamic pressure are established as functions of the sealing coefficient.The optimization design is carried out by Matlab.It proves that the structural parameters of the PTFE oil seal screw return tank are the key to affect the sealing performance.With the increase of relative width,relative depth and spiral angle,the sealing coefficient reaches the maximum value,and then begins to show a downward trend,and when the three increase at the same time,the rate of reaching the maximum value of the seal coefficient is faster.This indicates that the sealing effectiveness is closely related to the structure of the spiral return tank.?2?PTFE composites were prepared to investigate their friction,wear,tensile and compression properties.The study shows that the PTFE modified by filler exhibits lower friction coefficient and wear rate.Compared with pure PTFE,the modified PTFE exists lower tensile strength and stronger the compression strength,elastic modulus and compression modulus.As a result,modified PTFE material can be used either directly as the oil seal material to meet the sealing requirment.?3?Polyimide is widely used due to its advantages of low friction and wear,chemical resistance,high temperature resistance and excellent mechanical properties.The polyimide reinforced with graphene oxide and iron oxide composite filler demonstrate excellent wear resistance,which the minimum wear rate is only 9.67×10^-7 mm^3/N.m,far less than that of PTFE(3.42×10^-3 mm³/N.m)and has better tribological behavior.Therefore,the polyimide composite as a wear-resistant coating at the lip mouth of the PTFE oil seal can provide a new idea for the reasonable treatment of seal lip.