| With the rapid development of high-speed/heavy-haul rail, studies on the adhesion between wheel and rail required for higher level. In particular, due to the increasing speed, the research on adhesion in wheel-rail has become more complex. Sufficient wheel-rail adhesion can effectively improve the capacity of the wheel-rail system, extend the life of wheel and rail, reduce costs of railway equipment maintenance. Thus, it can bring great economic benefits. Above all, only in-depth and thorough analysis of this issue, can we guarantee safe operation of trains and ensure passenger safety.This paper studies the wheel-rail adhesion properties under the dry conditions and with a variety of media, as well as theoretical research on the old methods to increase viscosity and proposes new methods. The results of paper provide an important reference basis for the development of heavy-haul and high-speed rail and research on characteristics of wheel-rail adhesion, with great scientific significance. This main results and conclusions obtained of paper are as follows:1、When under the dry conditions, when the creepage is less than1.5%, the adhesion coefficient increases rapidly. When creepage is about1.5%, adhesion coefficient reaches the maximum value, and then, As the creepage increases, the adhesion coefficient declines slightly and gradually becomes stable at last. Adhesion coefficient decreases with the increasing of speed. With the axle load decreased, adhesion coefficient increases. The adhesion coefficient obtained by new simulating wheel is smaller than that obtained by old simulating wheel, meanwhile, There is no difference between the adhesion coefficient obtained by new simulating wheel and that obtained by rusted simulating wheel.with the decrease of the radius of curve, while the lateral adhesion coefficient increases but longitudinal adhesive coefficient decreases.2、The adhesion coefficient decreases fifty to sixty percent when adding water between wheel and rail under dry condition compared with dry conditon.When under water conditions,speed is the main factor causing adhesion coefficient decreasing and the adhesion coefficient becomes smaller when speed is higher. As the creepage increases, the adhesion coefficient increases before it reaches the maximum value, after that the coefficient declines slightly and gradually becomes stable at last. As far as influence degree of three testing factors which have effect on adhesion coefficient is concerned, axle load is the fires one, then speed, finally track curve radius under dry condition, and speed is the first one, then axle load, finally track curve radius under water medium condition.3、The adhesion coefficient under waste oil, oil-water mixture, oil-water-sand mixture condition is smaller than the adhesion coefficient under dry condtion. By comparing the surface of the rail-wheel after experiment under three kinds of mixtures of oil dielectric, the wear of rail-wheel surface after experiment under oil-water-sand mixture is the most obvious and the wear scar is the widest; while under waste oil dielectric conditions the wear is the smallest and the wear scar is the narrowest; and under oil-water medium the wear is the mediate. The adhesion coefficient of wheel-rail under oil-water-sand media is the largest, under the oil-water media the adhesion coefficient of wheel-rail is the smallest.4、With the ramp condition, the adhesion coefficient between0.23and0.33under dry condition and the adhesion coefficient between0.08and0.llunder water condition; By comparing the surface of the rail-wheel after experiment under three kinds of mixtures of oil dielectric, the wear of rail-wheel surface after experiment under oil sand is the most obvious and the wear scar is the widest; while under waste oil dielectric conditions the wear is the smallest and the wear scar is the narrowest; and under oil-water medium the wear is the mediate. The adhesion coefficient of wheel-rail under oil-water-sand media is the largest, under the oil-water media the adhesion coefficient of wheel-rail is the smallest.5、The adhesion coefficient of wheel/rail increases by35-65%when sand was sprayed into contact surface under wet condition. However, the adhesion coefficient increases slightly when sand was sprayed under dry condition. The adhesion improving properties of sand mainly depend on diameter of sand particle and sand volume under water medium conditions, and the sand with bigger diameter would contribute to better adhesion improving properties, which means that the adhension coefficient of wheel/rail increase with sand volume sprayed increasing. Additionally, the adhesion improving properties of sand reduced with speed increasing, Inner and external track appeared on simulating specimen surface after experiment under water medium conditons, while the wear degree of inner track was more serious that external track. Results also showed wear degree of specimen surface which sprayed coarse sand on was more serious than that sprayed fine sand on; accordingly, hardness of specimen surface sprayed coarse sand on was bigger than that sprayed fine sand on.6、the magnetic field can increase obviously adhesion coefficient of wheel/rail under water and oil conditions. The increase rate of adhesion coefficient under water condition exceeds20%and the increase rate of adhesion coefficient under oil condition is50%. Under water and oil conditions, the speed has no obvious effecton adhesion coefficient of wheel/rail when magnetic field is used. Different magnetic field strength of the wheel-rail adhesion have a certain influence, as the magnetic field strength increases, a corresponding increase in wheel-rail adhesion; and some of the strongest magnetic field on both sides of the wheel-rail wear can be produced by adsorption of iron, thereby reducing the third body between the wheel and rail wear.7、Numerical methods CONTACT has been employed that study the effect of slip ratio to wheel/rail adhesive coefficient. When the slip ratio is among0-1.38%, with the increases of the slip ratio,the adhesion area in the contact area decreases, the slip area increases, longitudinal adhesive force density increases,and the adhesion coefficient increases too. When the slip ratio is1.38%,to the a boundary station, then the contact area is completely slip, longitudinal adhesive force density go to the biggest, also the adhesion coefficient.While the slip ratio is more than1.38%,the contact area is macroscopic area, longitudinal adhesive force density decreases a little,that adhesion decreases and gradually becomes stable. |
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