| With the increasing development of modern rail transportation,wheel-rail rolling contact is inevitably affected by many complex factors,such as slip rate,axle load,speed,material properties of wheels and rails,external environmental factors of wheel-rail system and so on.These factors often influence wheel-rail rolling contact behavior,and thus influence particulate emissions.At home and abroad,the research mainly focuses on the damage and performance of the wheel and rail,but there is a lack of research on the particle morphology,particle size distribution and composition of the wheel and rail materials.Moreover,the emission and characteristics of particles have a significant impact on air pollution and human health,so it is necessary to conduct in-depth research on it.In this paper,a small scale rolling simulation test was carried out on a self-developed JDDRCF/M wheel-rail rolling contact fatigue/wear testing machine to study the characteristics of particles emitted from wheel-rail under different slip,load and speed conditions.Dust with a laser particle counter real-time collected the number of particles emitted from the wheel/rail interface,laser particle size instrument is used to measure the particle size distribution of abrasive dust,using scanning electron microscopy(SEM)analysis of the appearance of particle size,the wear surface morphology was analyzed with the help of three-dimensional profiler and scanning electron microscope,and draws the following conclusions:(1)Under different operating conditions,the morphologies of air particles are mostly lamellar with smooth edges,irregular spherical aggregates and smooth lamellar with irregular spherical aggregates.The morphology of grinding debris is mainly lamellar,irregular spheroid,irregular spheroid attached to lamellar particle surface and crushed particle powder.The morphology of air particles is basically similar to that of abrasive particles because they are related to wear mechanism.Almost all submicron particles are spherical,a property that is independent of test conditions.(2)As can be seen from the particle size distribution diagram,the peak particle size moves to the left with the increase of slip condition,and the slip difference changes from 3% to 10%,with an obvious shift to the left.Large slip difference will form more small particles,indicating that particles are broken,and fatigue wear changes to abrasive wear.(3)The roughness of rail,the contact width and depth of rail wear marks,and the wear amount all have the same trend with the number of small particles(0.3 μm,0.5 μm,1 μm),indicating that rail wear may be closely related to the number and morphology of small particles.The trend of large particle emission is basically consistent with wheel wear,and there is a close relationship between large particle emission and wheel wear.It may be because of the high hardness of the rail,the crack Angle is small,the crack expands slowly,and the crack is easy to accumulate,and the small particles are easy to form the spalling.(4)With the increase of slip,the total amount of small particle emission first increases,then decreases and then increases.When the load is changed,the total amount of small particles emission increases first and then decreases with the increase of the load.With the increase of velocity,the total amount of small particle emission firstly decreased and then increased.The amount of large particulate matter emission increases with the change of slip,load and velocity.It shows that the variation trend of small particulate matter quantity is greatly affected by service conditions,while the variation trend of large particulate matter quantity is basically unaffected.This is because the rail is closely related to the emission of small particles.The damage and wear amount of rail is small,and the relative change of working conditions has a significant impact on the number of particles. |
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