| Disc brake has been widely used in high-speed train brake due to its characteristics of stable braking performance and strong thermal bearing capacity.In the process of disc brake,the friction pair is often in state of high temperature and high stress,which will cause the thermal crack contradiction in the brake disc and affects the driving safety.The braking conditions determine the heat flux density and the braking energy,which is the major factor affecting the temperature field and stress field of the brake disc.Therefore,the study of the braking conditions influence on the temperature field and stress field of the brake disc,analysis and comparison of the temperature field of the train brake disc by infrared thermograph imager,thermocouple and simulated calculation,and discussing the temperature difference between these methods are make great sense to the understand the change law of the temperature field.This article is based on the friction pairs made of brake disc and pad of EMU,using the finite element software ADINA to establish the thermal-mechanical coupling model that including the brake disc and the brake pad.By using the direct coupling algorithm,simulated calculation the change of the temperature field and the stress field of the friction pair under different working conditions,The effect of initial speed of braking and braking pressure on the temperature field and stress field of brake disc are discussed;At the same time,braking experiments are conducted on a 1:1 test bench,The condition of variation of temperature field of brake disc surface is tested,and discussing the errors and reasons between different test methods and the temperature obtained by simulation calculation.The results indicate:(1)The simulation calculation can give the distribution of the temperature field and the stress field of-the brake disc under the condition of uniform contact,the results show that the surface temperature of the brake disc is consistent with the thermal stress,at the peak moment,the radial curve both show "M" font,at the end of braking,the radial curve show "inverted V"font and the location of maximum temperature and stress of the disc surface are occur shifting than the peak moment.The distribution pattern of contact arc length of brake pad and the linear velocity are important factors for affecting the temperature distribution of brake disc.(2)Braking pressure and braking speed are key factors for affecting the peak temperature and temperature gradient,the surface peak temperature and peak stress of the brake disc with the increase of the initial speed of braking shows linearly rising,the speed of braking is 120km/h,and the braking pressure increases from 7KN to 16KN,the peak temperature increases from 215? to 268?,and the peak stress from 281 MPa up to 393MPa;When the speed of braking increases to 200km/h,the peak temperature increases from 360?to 533 ?,and the peak stress from 543MPa up to 863MPa.(3)The braking time obtained by experimental test is greater than the simulation calculation time and the difference between the simulation calculation braking time and the test braking time will increase with the increase of the initial speed of braking,which reasons are that the simulation calculation is based on full contact and the surface of the brake disc will produce the " third body" at high speed and the "third body" has the lubrication effect.(4)The temperature field of the simulation calculation and the experimental test result is a certain deviation,the inhomogeneity of the temperature of the disc surface measured by the infrared thermal imager is greater than the simulated temperature,the maximum deviation temperature appears in the braking early,both the degree of deviation is related to the braking condition,under the braking conditions of 7KN/200km/h and 16KN/250km/h,the maximum temperature deviation of the disc surface at the initial stage of braking respectively are 120 ?and 190?;The temperature deviation of the two methods is smaller in the middle and later stage of braking,causing main reasons for the temperature difference between the test and the numerical simulation are fit degree friction pair and inhomogeneous of pressure distribution.(5)The temperature of thermocouple detection is limited by the quantity,the deviation degree of maximum temperature and the average temperature with the simulation calculation temperature which increase with the increase of the speed of braking.The average temperature detected is below the simulation calculation temperature. |
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