Study On Different Test Methods Of High Friction Synthetic Materials

As the most commonly used brake friction material for freight trains and heavy-duty trains,high-friction composite materials can improve their friction and wear properties to better meet the country’s faster and safer requirements for freight trains.On the one hand,it is very important to correctly select the formula of high-friction synthetic materials and reasonably optimize the formula to achieve the best use effect.On the other hand,due to the limitation of cost and conditions,the reduced-scale disc brake test bench is mostly selected for the formula screening test of high-friction synthetic materials.Although the test results have certain reference,the final brake shoe friction and wear performance test requires.It is carried out on a 1:1 brake test bench.As two common test methods for high-friction synthetic materials,there is less research on the difference between the reduced-scale disc brake and the 1:1 tread brake.The difference research between the two tests will be Provide certain basic data for material development and practical application.In view of the above problems,this paper uses ADINA finite element software,scale brake test bench and 1:1 brake test bench to simulate and test two main test methods of high friction composite materials.The impact of performance was studied and the conclusions are as follows:(1)Under the simulation conditions,when the simulated braking conditions are the same,the peak temperature,braking time and disc surface temperature difference of the 1:1 tread braking simulation are higher than those of the reduced-scale disc braking,increasing the initial braking speed or The brake pressure will increase the difference of the two braking methods,but the increase of the brake pressure will increase the difference to a small extent.Under the braking pressure of 0.52 MPa,when the initial braking speed increased from 40km/h to 105km/h,the peak temperature difference between the two increased from 48.5℃ to 368.3℃,and the braking time difference increased from 4s to 10.5s.At the initial braking speed of 80km/h,when the braking pressure is increased from 0.52 MPa to 0.70 MPa,the peak temperature of 1:1 tread braking increases by 14℃,and the maximum temperature difference increases by 6℃.The peak temperature increased by 8.4℃,and the maximum temperature difference increased by9.8℃.(2)When the simulation conditions are 0.52 MPa braking pressure and 105km/h initial braking speed,with the progress of the braking process,the temperature gradient variation range of 1:1 tread braking simulation is 50-550℃,and the tread temperature is high.The area is large,the maximum temperature difference changes rapidly,the high temperature area is concentrated at 35-55 mm from the inner side of the wheel,and the braking time is 15-30 s.Small,high temperature areas are concentrated in the radius of 120-130 mm,and the braking time is 13-23 s.(3)Under the conditions of the same braking method,there is a certain deviation between the results of the test and the simulation.Under the braking pressure of 0.35-0.70 MPa and the initial braking speed of 40-125km/h,the maximum difference between the scaled disc brake test and the simulated peak temperature is 54.6℃,and the difference between the maximum temperature difference of the disc surface is 57℃;1 :1 The maximum difference of the peak temperature of the tread braking under the braking pressure of 0.35-0.70 MPa and the initial braking speed of 35-95km/h is 70℃,and the difference of the maximum temperature difference of the nodes is 44℃.The simulated peak temperatures are all located at the friction center in the middle of the braking period,while the peak temperatures of the test are located at the end of the braking period,and the peak temperature point is not fixed,which is caused by the uneven contact in the test.(4)Changing the proportion of different components in the material has obvious effects on the average friction coefficient and wear amount.When the content of potassium feldspar in the material is from 16.9% to 19.9%,the average friction coefficient of the friction block is higher,the stability of the instantaneous friction coefficient is good,and the wear resistance is good,but the stability of the average friction coefficient is reduced;when the iron powder content from 19.5% to 22.5%,the average friction coefficient of the friction block is low,but the average friction coefficient is stable and the wear amount is small.