Analysis And Parameter Optimization Of Multiple Braking Friction Characteristics Of Train Brake Discs

As an important part of the braking system,the brake disc is an important component to ensure the safe and smooth operation of the train.During the braking process,the topography of the brake disc surface changes and affects the subsequent braking.Therefore,it is very important to study the surface change of the surface topography of the brake disc under multiple braking actions and to analyze its thermal-mechanical coupling.In this paper,the variation law of the friction coefficient of the brake disc surface during the multiple braking process is obtained by using the brake disc friction test,and the finite element simulation method is used to establish the finite element simulation model of the variable friction coefficient of the brake disc under the action of multiple braking.The temperature and thermal stress variation laws of the brake disc were analyzed,and the braking parameters were optimized based on the optimization method using the response surface.The main research contents and results are as follows:(1)Analyze the change of the brake disc surface under five consecutive braking actions.Using the brake disc friction tester to study the change of the surface of the brake disc during the five braking processes.At the same time,The surface topography data of multiple braking is obtained by using the topograph,and the change of surface roughness during the five braking process is analyzed.The surface roughness changes gradually with the increase of braking times,and the surface roughness changes greatly during the first three brakings.According to the three-dimensional fractal theory,the rough surface model of brake disc and brake pad is established.Through the finite element simulation software,the variation law of the friction factor of the brake disc during the multiple braking process is analyzed.The friction coefficient changes greatly during the first three brakings,and the friction coefficient gradually tends to0.31 with the increase of braking times.(2)Thermal-mechanical coupling analysis of the brake disc under five continuous braking conditions.According to the operating conditions of a certain train,considering the influence of temperature on the material parameters of the brake disc,establishment of a thermomechanical coupling simulation model of brake disc variable friction coefficient under five continuous braking actions,and the distribution and change of the temperature and thermal stress of the brake disc during five consecutive brakings are obtained The distribution and change of the temperature and thermal stress of the brake disc are obtained by analysis.The results show that: in the process of five braking,the maximum thermal stress and maximum temperature of the brake disc change sharply in the first three brakings,and the thermal stress and temperature change smoothly in the last two brakings.With the increase of braking times,the maximum stress gradually tends to 300 MPa,and the maximum temperature gradually tends to 390℃.(3)Analyzing the influencing factors of thermal coupling under multiple braking conditions,and optimizing the parameters of the braking process with the goal of minimizing the maximum temperature difference of the brake disc.Based on the thermal-mechanical coupling simulation model of the variable friction coefficient of the brake disc under multiple braking actions,the effects of the braking time interval,the thickness of the brake disc and the number of heat dissipation ribs of the brake disc on the temperature and thermal stress during the multiple braking process are analyzed.Taking the braking time interval,the thickness of the brake disc and the number of heat dissipation ribs of the brake disc as variables,the difference between the maximum temperatures of the two adjacent braking is the response,and the response surface of the maximum temperature difference is established for fitting evaluation and obtain the minimum maximum temperature difference.The results show that when the time interval is 115 s,the number of radiating ribs of the brake disc is 24,and the thickness of the brake disc is 27 mm,the maximum temperature difference is the smallest during the multiple braking process.The above research work has important theoretical and practical significance for the design of the brake disc.