Effect Of Braking Condition On The Friction And Wear Properties Of Brake Pad

With the increment of train speed, the brake system supports great burden. In the actual moving, due to the producing error, assemble error, non-uniform wear in the use and the changeable surroundings, it will let the partial contact pressure and temperature higher than that as usual. However, at these adverse friction conditions, the properties that the material shows are always the key factor on the production properties. Therefore, it makes great sense that we research the suitable Cu-based powder metallurgy braking material for high-speed train and analyze the friction and wear properties of that material at the adverse conditions.The friction and wear properties of Cu-based powder metallurgy braking material, fabricated by powder metallurgy, are measured by the constant-speed tester, at the friction speed of 200～3000r/min, the friction pressure of 0.5～1.2MPa and the additive water rate of 5.3ml/min(equal to 25L/h at the area of 200m~2, UIC code). This paper mainly study the friction and wear properties of the material. Accordingly, the result shows that:The friction coefficient increase when the speed is below 1500r/min under the dry friction. As the speed becomes higher, the coefficient maintains an even value. The continuous and compact third body which is formed under the high speed friction can make the friction coefficient stable. The increase of the wear rate under the lower speed friction is more intensively than that in the higher speed friction; under the higher friction speed, the fluctuation of the friction coefficient is not as much as the lower speed condition when friction pressure increase. When pressure is higher enough to break the tough particles of the material, the real contact area increased. As a result of that, the friction coefficient and wear rate increase as well.Because of the lubrication and washing by the water, the coefficient and wear loss of the friction change a lot when friction speed and pressure are lower. The water is evaporated and thrown away from the system when friction speed and pressure are higher. As a result, the fluctuation of the friction coefficient is slightly compared with the dry friction.The friction and wear properties of the brake pad are also influenced by the friction order. Compare two different orders of friction, the fluctuation of the friction coefficient is much greater when the friction order is from low speed to high. The stability of the compact third body that formed in the high speed friction is the reason make that happen.