Friction Performance And Life Prediction Of Copper-based Powder Metallurgical Brake Pads For Railway Coaches

As an important component of the braking system,copper-based powder metallurgy brake pad play a key role in the braking of trains.In China’s"Fourteenth Five-Year Plan"for railway development,further plans have been made to increase the speed of high-speed trains,which places increasingly high demands on train braking systems.However,the research on copper-based powder metallurgy brake pad has not been adequately studied in terms of friction performance,wear rate and service life prediction.To address these problems,a multi-factor coupled braking test was carried out on a copper-based powder metallurgy brake pad using a 1:1 braking test bench,and its friction properties and wear surface were investigated in conjunction with a scanning electron microscope energy spectrometer;the ASO-BP algorithm was proposed to predict the wear rate of the brake pad;the SMOTE algorithm was used to expand the pads wear rate data and predict the brake pad life by Weibull distribution.Details are as follows:(1)Aiming at the problems of complex and changeable working environment and insufficient research on friction performance changes of copper-based powder metallurgy brake pad for high-speed trains,the trend of friction performance of brake pad under multi-factor coupling was studied.In this paper,the friction coefficient,friction temperature,braking distance and wear rate under multi-factor coupled braking conditions are investigated with copper-based powder metallurgy brake pad,and the surface change mechanism is analysed using electron microscopy scanning energy spectrometry.The results show that:braking speed and braking pressure are the main factors affecting the braking performance of copper-based powder metallurgy brake pad,the average friction coefficient of copper-based powder metallurgy brake pad under different braking conditions varies between 0.35 and 0.45,and the maximum temperature,braking distance,braking time and wear rate of the pads are 473°C,3506m,138s and 0.14cm~3/MJ respectively.(2)Aiming at the difficulty in obtaining the surface temperature of copper-based brake pad during train braking,the friction heat of copper-based powder metallurgy brake pad was analyzed based on the finite element method.The copper-based powder metallurgy brake pad and discs were modelled using 3D modelling software,and the models were imported into finite element software for meshing and load application,followed by numerical analysis to obtain their frictional thermal clouds.The analysis found that the surface temperature of the copper-based powder metallurgy brake pad,with time first increase and then decrease;copper-based powder metallurgy brake pad friction block of the radial temperature conduction uniformly decreases;copper-based brake pad surface high temperature reached in 34s;compared to the brake test,its surface temperature change trend is the same,but the maximum temperature value has a certain difference.(3)Aiming at the problem that the wear rate of copper-based powder metallurgy brake pad is difficult to predict,a wear rate prediction method of copper-based powder metallurgy brake pad based on ASO-BP neural network is proposed.The basic principle of predicting the wear rate of copper-based powder metallurgy brake pad by ASO-BP is to use the atomic search algorithm to optimize the weights and thresholds of the BP neural network,and then predict the wear rate.The results show that the wear rate prediction accuracy of copper-based powder metallurgy brake pad based on ASO-BP neural network can reach 97.3%.(4)Aiming at the small sample of copper-based brake pad wear data and the difficulty in predicting the service life during service,the service life of the brake pad is predicted by combining the SMOTE algorithm and the three-parameter Weibull distribution.Firstly,the SMOTE algorithm is used to expand the data samples obtained from the braking test.Secondly,the parameters of the service life model of copper-based powder metallurgy brake pad based on three-parameter Weibull distribution are calculated.Finally,the service life of copper-based powder metallurgy brake pad is predicted,which can provide reference for the replacement cycle of train copper-based brake pad.