Experimental Study Of Friction Material On Braking Temperature And Friction Performance

Resin-based synthetic materials,semi-metallic synthetic materials and copper-based powder metallurgy materials are widely used brake friction materials for railway vehicles.The differences in braking temperature and friction performance of the three lead to differences in their application conditions and service environments.Clarifying the differences in the braking temperature and friction performance of different friction materials is helpful for the selection of products in the development stage of brake pads and the selection of friction materials that are more suitable for their service conditions in the actual application stage.Based on the TM-I type reduced-scale braking tester,the paper carried out comparative tests of resin-based synthetic materials,semi-metallic synthetic materials,copper-based powder metallurgy materials with the forged steel brake disc paired under the braking pressure of 0.5MPa and initial braking speed of 50-160km/h.The main conclusions are as follows:(1)The average friction coefficient of the resin-based synthetic material has a significant effect on the peak temperature of the disc surface,but has no obvious effect on the maximum temperature difference of the disc surface.When the initial braking speed is 160km/h,when the distribution range of the average friction coefficient increases from 0.507-0.520 to0.543-0.582,the peak temperature of the disk surface rises from 163～179℃ to 180～197℃,and the maximum temperature difference of the disk surface rises from 78～97℃ to 82～98℃.(2)The sensitivity of the instantaneous friction coefficient to speed and temperature is resin-based synthetic material > semi-metallic synthetic material > copper-based powder metallurgy material.The instantaneous friction coefficient of the resin-based synthetic material presents three changes under three speed conditions;when the speed is 160km/h,the peak temperature of the disk surface of the semi-metallic synthetic material rises sharply to348℃,but the drop in its instantaneous friction coefficient is smaller than that of resin-based synthetic materials;the instantaneous friction coefficient of copper-based powder metallurgy materials maintains a continuous upward trend under three speed conditions.The reason is that the temperature of the disc surface is increased by 100°C,the resin matrix is softened significantly,and the braking performance is reduced,while the performance of the copper matrix remains good at 300°C.(3)The "wave peak" on the radial average temperature curve represents the high temperature area in the radial isotherm diagram,and the number and height of wave peaks represent the activity and duration of the high temperature area.When the braking condition is0.5MPa and 160km/h,the resin-based synthetic material has the lowest radial average temperature,about 120℃,and the distribution uniformity is the best;the semi-metallic synthetic material has the worst radial temperature distribution uniformity.It is in the form of "double peaks" with the maximum temperature difference as high as 205℃;the high temperature zone of the pairing disc of copper-based powder metallurgy material continuously shifts with the passage of braking time,and the radial average temperature curve shows a "multi-peak" shape.