Experimental Study Of Wheel/Rail Adhesion Characteristic Under Ramp Conditions

In the recent years, the high-speed railway develops rapidly in China, and the trend of high-speed and heavy-haul is more and more significant. Wheel-rail adhesion is becoming one of the most important factors for the locomotive traction and braking performance. As the application of the high speed technology, the research of the issue of wheel-rail adhesion is more and more complicated. Ramp line is one of the regular line types. For the ramp section in both existing and new lines, how to use the wheel-rail adhesion more efficiently is of great significance to the safety of train's operation. Thus, the study of the wheel/rail adhesion udner the ramp condition has an important signification.The adhesion characteristic of wheel/rail has been investigated using a JD-1 wheel/rail simulation testing machine and Hertz simulation rules under the ramp condition. The effect of ramp on adhesion coefficient of wheel/rail has been studied under dieffrent medium (dry cond, water and oil)conditons in details. Main conclusions are draw as follows: 1. Under the ascent condition:(1) The adhesion coefficient of wheel/rail udner different mediums and ascent conditions have a significant drop compared with the straight level track condition. The decrease rate is about 30%.(2) The adhesion coefficient in the ascent track under dry condition are all above 0.25. The difference of adhesion coefficients under different speed condition is samll.(3) The water medium would decrease adhesion coefficient of wheel/rail in the ascent track. The difference of adhesion coefficients under different water volume condition is samll and the adhesion coefficient is about 0.1.(4) The surface damge of wheel/rail in the ascent track is more severe than in the straight level track under oil condition.(5) The adhesion coefficient in the experiments udner the ascent condition is close to the calculated results.2. Under the descent condition: (1) The adhesion coefficients of wheel/rail under and dry and water conditions decreased obviously compared with the results in the condition of straight level track. The adhesion coefficient is about 50-60% of that in the straight level condition. But the adhesion coefficients of wheel/rail under oil ondition is taller than straight level.(2) The adhesion coefficients in the experiments under the descent conditon are smaller than the calculated results. Therefore, the adhesion coefficients should be corrected in actual application.