The effect of rail corrugation on the vertical dynamics of railway vehicle coupled with a curved track is investigated in detail with a numerical method when a wheelset is steadily curving. In the calculation of rail ...The effect of rail corrugation on the vertical dynamics of railway vehicle coupled with a curved track is investigated in detail with a numerical method when a wheelset is steadily curving. In the calculation of rail corrugation we consider the combination of Kalkers rolling contact theory modified, a model of material loss on rail running surface, and a dynamics model of railway vehicle coupled with a curved track. In the establishment of the dynamic model, for simplicity, one fourth of the freight car without lateral motions, namely a wheelset and the equivalent one fourth freight car body above it, is considered. The Euler beam is used to model the rails and the track structure under the rails is replaced with equivalent springs, dampers and mass bodies. The numerical results show the great influence of the rail corrugation on the vibration of the parts of the vehicle and the track, and the some characters of rail corrugation in development.展开更多
The effect of discrete support of rail on the formation and evolution of railcorrugation is primarily investigated with numerical method in the situation of wheelset curvingsteadily and repeatedly. In the numerical an...The effect of discrete support of rail on the formation and evolution of railcorrugation is primarily investigated with numerical method in the situation of wheelset curvingsteadily and repeatedly. In the numerical analysis of corrugation it is considered that acombination of Kalker's rolling contact theory with non-Hertzian to be modified, a linear frictionalwork model and a vertical dynamics model of railway vehicle coupled with a curved track. And theuneven support stiffness of rail in the vertical direction due to discrete sleeper support and thedifferent running speed of the wheelset are taken into consideration. The damage on the runningsurface of rail, concerning rail corrugation formation, is restricted to wear mechanism of railmaterial. The numerical results obtained indicate that the discrete supports of rail by sleepershave a great influence on the formation of the corrugation under the condition of non-zero andstable creepages of wheelset and track.展开更多
This paper had investigated the effects of surface wettability on the frictional resistance of turbulent horizontal flow for tap water in five pipes made of various materials and four kinds of liquids in a polytetrafl...This paper had investigated the effects of surface wettability on the frictional resistance of turbulent horizontal flow for tap water in five pipes made of various materials and four kinds of liquids in a polytetrafluoroethylene(PTFE) pipe,with the same inner diameter of 14 mm. Pressure drops were measured under different flow rates through an experimental flow loop. The contact angles and adhesion work of liquids in contact with pipe surfaces were determined using a contact angle meter. Based on the dimension and regression analyses, two kinds of modified relationships between the frictional coefficient and the surface wettability were established according to the measured results corresponding to tap water in five pipes and four liquids in PTFE pipe. The experimental results show that the surface wettability has some influence on frictional coefficient of the studied liquids flowing in macroscale pipes, and the frictional coefficient decreases with the increase of the contact angle at the same Reynolds number. Meanwhile the effect of wettability on the hydrophobic surface is greater than that on the hydrophilic one. The frictional coefficients predicted by the modified formulas have verified to be in good agreement with the experimental values, the relative errors of which are within ±6% and ±3% for the tap water flowing in five different pipes and four kinds of liquids flowing in PTFE pipe, respectively.展开更多
The effect of high-frequency curved track vibrations in the vertical direction on the formation and development of rail corrugation was analyzed. Kalker抯 non-Hertzian rolling contact theory was modified and used to c...The effect of high-frequency curved track vibrations in the vertical direction on the formation and development of rail corrugation was analyzed. Kalker抯 non-Hertzian rolling contact theory was modified and used to calculate the frictional work density on the contact area of the wheel and rail in rolling when a wheelset is steadily curving. The material loss unit area was assumed to be proportional to the frictional work density to determine the wear depth of the contact surface of the rail. The combined influences of the corrugation and the coupled dynamics of the railway vehicle and track were taken into consideration in the numerical simulation. For simplicity, the model considered one fourth of freight car without lateral motion, namely, a wheelset and the equivalent one fourth freight car body above it. The Euler beam was used to model the rails with the track structure under the rails replaced with equivalent springs, dumpers, and mass bodies. The numerical results show that the high-frequency track vibration causes formation of the initial corrugation on the smooth contact surface of the rail when a wheelset is steadily curving. The corrugation wave length depends on the frequencies and the rolling speed of the wheelset. The vibration frequencies also affect the depth and increase the corrugation.展开更多
基金The project supported by the National Natural Science Foundation of China(59935100)the Foundation of Ph.D Student Education of China(20020613001)the Foundation of the Author of National Excellent Doctoral Dissertation of China(2000048,2002048)
文摘The effect of rail corrugation on the vertical dynamics of railway vehicle coupled with a curved track is investigated in detail with a numerical method when a wheelset is steadily curving. In the calculation of rail corrugation we consider the combination of Kalkers rolling contact theory modified, a model of material loss on rail running surface, and a dynamics model of railway vehicle coupled with a curved track. In the establishment of the dynamic model, for simplicity, one fourth of the freight car without lateral motions, namely a wheelset and the equivalent one fourth freight car body above it, is considered. The Euler beam is used to model the rails and the track structure under the rails is replaced with equivalent springs, dampers and mass bodies. The numerical results show the great influence of the rail corrugation on the vibration of the parts of the vehicle and the track, and the some characters of rail corrugation in development.
基金This project is supported by National Natural Science Foundation of China (No.599355100) Foundation of PhD Student Education Ministry of China (No.20020613001) Foundation for the Author of National Excellant Doctoral Dissertation of China (FANEDD) (No.200048, No.200248).
文摘The effect of discrete support of rail on the formation and evolution of railcorrugation is primarily investigated with numerical method in the situation of wheelset curvingsteadily and repeatedly. In the numerical analysis of corrugation it is considered that acombination of Kalker's rolling contact theory with non-Hertzian to be modified, a linear frictionalwork model and a vertical dynamics model of railway vehicle coupled with a curved track. And theuneven support stiffness of rail in the vertical direction due to discrete sleeper support and thedifferent running speed of the wheelset are taken into consideration. The damage on the runningsurface of rail, concerning rail corrugation formation, is restricted to wear mechanism of railmaterial. The numerical results obtained indicate that the discrete supports of rail by sleepershave a great influence on the formation of the corrugation under the condition of non-zero andstable creepages of wheelset and track.
基金supported by the National Major Science&Technology Project of China(No.2016ZX05025004-005)the Science&Technology Project of Sichuan Province(Grant No.2015JY0099)
文摘This paper had investigated the effects of surface wettability on the frictional resistance of turbulent horizontal flow for tap water in five pipes made of various materials and four kinds of liquids in a polytetrafluoroethylene(PTFE) pipe,with the same inner diameter of 14 mm. Pressure drops were measured under different flow rates through an experimental flow loop. The contact angles and adhesion work of liquids in contact with pipe surfaces were determined using a contact angle meter. Based on the dimension and regression analyses, two kinds of modified relationships between the frictional coefficient and the surface wettability were established according to the measured results corresponding to tap water in five pipes and four liquids in PTFE pipe. The experimental results show that the surface wettability has some influence on frictional coefficient of the studied liquids flowing in macroscale pipes, and the frictional coefficient decreases with the increase of the contact angle at the same Reynolds number. Meanwhile the effect of wettability on the hydrophobic surface is greater than that on the hydrophilic one. The frictional coefficients predicted by the modified formulas have verified to be in good agreement with the experimental values, the relative errors of which are within ±6% and ±3% for the tap water flowing in five different pipes and four kinds of liquids flowing in PTFE pipe, respectively.
基金Supported by the National Natural Science Foundation of China (No. 59935100) and the Foundation of the Ministry of Education China (No. 20020613001) and the Foundation for the Author for National Excellent Doctoral Dissertation China (Nos. 200048 a
文摘The effect of high-frequency curved track vibrations in the vertical direction on the formation and development of rail corrugation was analyzed. Kalker抯 non-Hertzian rolling contact theory was modified and used to calculate the frictional work density on the contact area of the wheel and rail in rolling when a wheelset is steadily curving. The material loss unit area was assumed to be proportional to the frictional work density to determine the wear depth of the contact surface of the rail. The combined influences of the corrugation and the coupled dynamics of the railway vehicle and track were taken into consideration in the numerical simulation. For simplicity, the model considered one fourth of freight car without lateral motion, namely, a wheelset and the equivalent one fourth freight car body above it. The Euler beam was used to model the rails with the track structure under the rails replaced with equivalent springs, dumpers, and mass bodies. The numerical results show that the high-frequency track vibration causes formation of the initial corrugation on the smooth contact surface of the rail when a wheelset is steadily curving. The corrugation wave length depends on the frequencies and the rolling speed of the wheelset. The vibration frequencies also affect the depth and increase the corrugation.
