Investigation On Adhesion Property Of Wheel/Rail Under Water Conditions

The high speed and heavy load railway and Urban Rail Transit are quickly developing all over the world. The wheel/rail interaction characteristics is called adhesion property as the traction,accelerating and braking force are translated by wheel/rail contact spot interaction.The adhesion property can be deemed as rolling friction force between wheel and rail when the wheel rolles on the rail.To investigate on wheel/rail adhesion problem is to master the changing law of stress condition which wheel/rail bears when the move statement of wheel changs and to obtain the adhesion-creepage curve so as to seek the optimal adhesion-creepage dot which can be used to control the locomotive to play its power fully on traction and braking.This text is mainly based on the theory of Carter's two dimensional rolling contact and the rough surface steady partial elasto-hydrodynamic lubrication,combined with numerical analysis to investigate the effect of rolling speed and axle load on the adhesion property under water condition between wheel and rail.The adhesion property of under dry condition between wheel and rail was investigaed on JD-1 wheel/rail simulation machine also. The following conclusions are obtained by the numerical analysis and the test investigation above. Based on the theory of Carter's two dimensional rolling contact and the rough surface steady partial elasto-hydrodynamic lubrication, this text apply average flow model between rough surfaces which was contributed by Patir and Cheng to found the two-dimensional adhesion numerical analysis mode under water condition which was solved by multigrid algorithm(BWMG).The effect of rolling speed and on adhesion between wheel and rail is investigated by this numerical analysis mode which can acquire different results when it input different parameters.The following results are acquired by the mode.When under the same axle load,if the wheel rolling speed gets higher,the adhesion coefficient declines as the ratio of the mean asperities contact pressure to the total pressure becomes smaller.When under the same speed, if the axle load gets weighter, the adhesion coefficient increases as the ratio of the mean asperities contact pressure to the total pressure becomes bigger.The adhesion property of under dry condition when suddenly adding water and under water condition between wheel and rail were tested separately on JD-1 wheel/rail simulation machine.The effect of speed,axle load and creepage on wheel/rail adhesion coefficient under water condition was mainly investigated.The results indicate that,compared with the dry conditon,the adhesion coefficient decreases fifty to sixty percent when adding water between wheel and rail under dry condition. When under water condition,the wheel speed maily effects on not only the maximum adhesion value but also the steady adhesion value(the adhesion section at which the locomotive runs),the adhesion coefficient declines while the wheel speed becomes higher,however, the axle load has less effected on it.As the creepage increases,the adhesion coefficient increases linearly before it reaches the maximum value(saturation value),after which the coefficient declines slightly and gradually becomes stable at last. When the creepage reachs to about 0.5%,the maximum adhesion coefficient appears.