A Study On Relationship Of The Pattern Of Friction Pair And Braking Performance

The stability of the braking performance is an important factor to ensure the safe operation of the train. Various factors, such as material property, braking condition, friction pair structure, etc., can affect the braking performance. The form of friction pair is one of the important factors in the braking performance. The braking performance of friction pair is tested on the test-bench.1:1test bench of braking dynamic can imitate the braking condition of the real operation of train to test the performance of friction pair. However, it has complex structure, with high cost and long time cycle of test, etc. It is rarely used in the process of research and development of braking material. The scaled inertia brake test bench can not only imitate the real braking condition, but also save space, reduce the cost of research and development, and speed up the research and development. So it can be used in the test of braking performance of friction pair.This paper made3kinds of friction block from copper-based powder metallurgical material:Circular friction block A (1256mm2), Triangular friction block B(2930mm2); Circular friction block C (3317mm2), they are connected with H13alloy steel to make3kinds of friction pair. Emergency braking, conventional braking and preliminary braking experiments were conducted on an inertia test bench under the conditions of46kg.m2rotational moment of inertia, and50～300km/h initial velocities. The experiment result indicates:(1) Under the same braking condition, the friction coefficient and temperature of friction pair A fluctuate the most. When the temperature of friction pair is the highest, the average friction coefficient is the lowest, the braking time and braking distance is the longest. Apply the brake under the condition of300km/h initial velocity. When the speed downs to around50km/h, the coefficient of friction appears obvious heat fading. During emergency braking, the highest temperature of friction pair A is over900℃. The friction coefficient and temperature of friction pair B fluctuate the least, without obvious heat fading during braking process. Temperature on friction pair was slightly higher than the friction pair C, the average friction coefficient is the highest, the time and distance of braking is the shortest.(2) The distribution characteristics of friction power is related to the structure of friction pair. Comparing the power generated at point of radius r, to the total power, this ratio is defined as power density factors, defined as: ε=(?).The ratio can represent the distribution of frictional power on the frictional pair. (3) Braking performance of friction pair is closely related to the power density factor. The greatest the peak value of the power density factor on friction pair A, the more concentration of the friction work distribution, and the highest the temperature of the friction surface. The high temperature lowers the strength of the friction material, causing reduced engaging force between the friction surfaces, and leading to lower friction coefficient, resulting in longer braking time and distance. The distribution pattern of the power density factor also affects the braking performance. The peak power density factor locates towards the region with a large friction radius on friction pair B, so does the friction concentration.Thus it can be seen, The calculation of power density of the friction factor method can compare and evaluate the influence to braking performance of the friction pair.