| Train braking is achieved through the friction between the brake pads and brake discs,which consumes kinetic energy through friction.The structural form of the brake pad directly affects the friction braking performance.To optimize the shape and structure of the brake pad friction block,it is necessary to grasp the relationship between the friction block structure,friction braking performance,and the temperature field distribution of the brake disc.Therefore,exploring the influence of the shape and structure of the brake pad friction block on the temperature of the brake disc from the perspective of experiments and simulation calculations is of practical value.This article selects five types of circular composite material brake pads with different hole structures,and uses a combination of experimental and finite element numerical simulation methods to study the influence of the pore structure of the brake pad on the temperature field distribution and friction performance of the brake disc.The following results are obtained:(1)As the diameter of the brake pad increases,the disc surface temperature decreases,increasing from 8mm to 15 mm.Under the operating conditions of 0.50 MPa and 160km/h,simulation calculations show that the peak temperature of the disc surface decreases from294 ℃ to 273 ℃,which is 21 ℃ lower than that of the non perforated brake pad;Under experimental conditions,the surface temperature of the brake pad with no holes was reduced by 17 ℃.The reason is that the position and diameter of the hole reduce the degree of variation of the friction arc length along the friction radius,reducing the effect of the maximum arc length on temperature concentration.(2)Under the conditions of braking pressure of 0.25 MPa and 0.50 MPa,and braking speed of 20～160km/h,compared with the three hole brake pad,simulation calculations show that the disc surface temperatures of the two are close;During the experimental testing,the temperature deviation between the non porous and three porous friction blocks increases with the increase of speed,with the maximum temperature difference between the two at 0.25 MPa and 120km/h.The peak temperature of the three porous brake pad disc surface is 27 ℃ higher than that of the non porous brake pad.Because the position of the three holes is located at a smaller friction arc,the temperature is concentrated in the middle.(3)The diameter of the brake pad increased from 8mm to 15 mm,resulting in a reduction of 17 g in wear.The wear of the three hole brake pad is reduced by 36 g compared to the non hole brake pad.The number and size of holes increase,resulting in an increase in wear resistance.The existence of holes is beneficial for eliminating friction debris,reducing the plowing effect of debris on the friction surface,and playing a role in reducing wear.(4)At a braking pressure of 0.25 MPa and a speed of 20～160km/h,the average friction coefficient of a non perforated brake pad is between 0.511 and 0.565,the average friction coefficient of a single hole brake pad is between 0.525 and 0.578,and the average friction coefficient of a three hole brake pad is between 0.523 and 0.602,indicating that the influence of hole size on the friction coefficient is not significant.The reason is that the friction performance of synthetic materials exhibits significant fluctuations within this range of braking conditions.(5)The hole structure has a significant impact on the duration of the radial high-temperature zone on the disc surface.As the hole size of the brake pad increases,the duration of the high-temperature zone becomes shorter,with the hole size increasing from8 mm to 15 mm.The duration of the high-temperature zone above 200 ℃ on the disc surface decreases from 67 s to 59 s,which is beneficial for improving the wear and tear of the brake friction pair.(6)There is a deviation between the experimental and simulated results,and the peak temperature obtained from the experiment is higher than that from the simulation.The reason is that the simulation calculation is based on the premise of complete contact of the disc,and during the test process,there was local contact on the disc surface,which caused a deviation between the test results and the simulation. |
