The Effect Of Braking Conditions On The Temperature Of The Braking Friction Pairs On The Treads Of Railway Freight Vehicles

With the rapid development of my country’s railway freight industry,the performance of railway freight cars is constantly improving.As the core component of the railway freight car,the braking performance of the brake system is related to the safe operation of the freight car.At present,tread braking is still the main braking method for railway freight cars.Tread braking is to convert the kinetic energy of the truck into heat energy to achieve the braking effect through the friction of the friction pair of the brake shoe and the wheel.In the actual braking process,the strong friction between the brake shoe and the wheel pedal will put it in a high temperature environment and affect the braking performance.In this paper,based on the ADINA finite element analysis software,a thermal mechanical coupling model including brake shoes and wheels is established for the tread brake friction pair,and the direct coupling method is used to simulate and calculate the temperature of the tread brake friction pair under different braking conditions.Field changes.The effects of initial braking speed,braking pressure and load application method on the temperature field of friction pairs are analyzed and discussed.At the same time,a brake test was carried out on a 1:1 train brake test bench,and the temperature field of the wheel tread was collected through an infrared thermal imager and a thermocouple.By comparing the simulation results with the test results,the following conclusions are drawn:(1)Braking pressure and initial braking speed are important factors that affect the peak temperature and temperature gradient of the tread.The initial braking speed is 35km/h.When the braking pressure increases from 10 k N to 20 k N,the peak wheel tread temperature increases from 87℃ to 107℃,and the temperature difference between the wheel tread and the radial depth 20 mm increases from 27℃ to 48℃.When the initial braking speed increases to95km/h,as the braking pressure increases from 10 k N to 20 k N,the peak wheel tread temperature increases from 241°C to 291°C,and the radial temperature difference increases from 110°C to 160°C.(2)The change of the applied angle of the brake pressure load has an important influence on the change of the actual contact pressure distribution of the friction pair.In the simulation calculation,the inclined pressure load along the axis of the wheel will cause the contact pressure concentration point of the friction pair and the position of the high temperature zone to shift by about 30 mm.The uneven distribution of the actual contact pressure will cause the uneven distribution of the temperature field.(3)The brake pressure and the temperature of the friction surface will affect the contact state of the friction pair.When the temperature of the wheel tread is lower than 160℃,the brake shoe is in contact with the wheel tread on one side,and the width of the high temperature belt is about 15 mm.When the temperature of the wheel tread is higher than160℃,the brake shoe and the wheel tread have a higher degree of adhesion,the actual contact area is larger,and the high temperature belt width exceeds 30 mm.(4)The friction speed and the temperature of the friction surface have an important influence on the fluctuation of the instantaneous friction coefficient of the friction pair.At the initial braking speed,the impact load and high temperature softening of the wear particles on the friction surface of the brake shoe cause the fluctuation of the instantaneous friction coefficient.The fluctuation of the friction coefficient has a certain influence on the difference between the test and the simulated temperature.