Experimental Study On Influencing Factors Of Friction Coefficient Of Wheel

After entering the 21 st century,China is in a period of rapid economic growth.The development of economy has led to the construction of China's railway.The friction between wheel and rail is a complex problem;it involves mechanics,chemistry,heat transfer and other disciplines.China's railway is developing to the direction of high-speed heavy-duty,which is undoubtedly put forward higher requirements of friction between wheel and rails.We all know that the start of the train,braking and normal driving are to rely on the interaction between the wheels and rail to achieve,as an important factors which impact the friction performance between wheel and rail,the friction coefficient will directly affect the value of the train brake and traction value.In the actual operation process,the movement of the wheels is very complex,in addition to along the rail creep movement,there also contains traversing and waving movement,that is,transverse and longitudinal sliding along the rail.It should be noted that,whether it is the wheels vertical,horizontal sliding,or creep movement when the train starts,the time of wheels' pure sliding along the rails is very short,that is,the phenomenon of instantaneous sliding.Especially the train's instantaneous creep moment when it starts,the value of sliding friction coefficient directly affects the value of friction between wheel and rail;it has a significant impact on the traction and acceleration of the train.When the train is braked,as the wheel slides on the rails,the wheel contact point remains constant and the contact area is kept at a higher temperature due to heat stacking,while the rail contact point is constantly changing,and the temperature of new rail contact point is lower than the wheel contact point,at this time,there is a temperature difference between the wheel and rail contact area.Therefore,it is very important to study on the friction coefficient of wheel and rail under instantaneous sliding state and temperature difference.In this paper,the friction coefficient of the wheel-rail friction zone at room temperature and high temperature is measured respectively.The main conclusions are as follows:(1)In the case of instantaneous sliding,the effect of velocity on the friction coefficient is obvious,and the friction coefficient decreases with the increase of the speed.At the moment wheel occurs creep when the train starts,reducing the wheel speed can obtain a larger friction coefficient and get a greater traction,which is beneficial to traffic safety.(2)In the instantaneous sliding state,the load on the friction coefficient has little effect;at the moment wheel occurs creep when the train starts,increasing the axle load,increasing the axle load of the train can increase the friction of the rail to the wheel,so that the traction is more traction.It is advantageous for traffic safety.(3)When the temperature,load and speed of the wheel specimen are constant,the friction coefficient varies with the rail temperature,and there are two poles when the rail temperature is 500 degrees Celsius and 1000 degrees Celsius respectively.(4)At the stage of 25 ? to 500 ?,the impact of rail temperature on the friction coefficient is small,the friction coefficient increases slowly with the increase of the rail temperature,where the friction coefficient of 500 degrees Celsius is 0.388.(5)500 ? to 1000 ? stage,the effect of rail temperature on the friction coefficient is larger than the first stage,the friction coefficient decreases with the increase of the rail temperature,the friction coefficient of the rail temperature is 1000 ?.(6)1000 ? to 1200 ? stage,the rail temperature on the friction coefficient of the larger coefficient of friction with the rail temperature increases sharply reduced,the rail temperature of 1200 degrees Celsius when the friction coefficient of the smallest 0.13.(7)the effect of temperature on the friction coefficient of friction zone is mainly reflected in two aspects: First,the temperature changes the mechanical properties and mechanical properties of the material,thus affecting the friction coefficient of the friction pair;Second,the temperature increases,changing the material molecules Of the degree of activity,exacerbate the oxidation of the surface of the material,thereby affecting the formation of oxide film speed,thus affecting the friction coefficient of friction.