Analysis On The Gradual Reliability Of The Drum Brake Of Freight Cars

This paper selects a truck’s rear wheel drum brake as the key part of the analysis.Through multi-physics simulation analysis,the brake temperature and stress of the drum brake under emergency braking conditions are obtained.For the weak parts of the brake drum,the gradual reliability analysis is carried out considering the structural strength degradation with the number of braking and the correlation of random variables.The thermal-structure coupling simulation,reliability design experiment,correlation coefficient and reliability theory are used to comprehensively consider the influence of structure,material and other parameter variables on the gradual reliability of the brake drum.The main research contents of this paper are as follows:(1)The affine response surface method is used to analyze the braking torque interval,and the variation range of the output maximum braking torque under emergency braking conditions is obtained.Ignore the influence of friction resistance to conduct mechanical analysis of the brake system,Construct the braking force and braking torque expressions related to random variables,and use the IARSM affine algorithm of non-probabilistic reliability interval analysis to solve it.The interval Monte Carlo algorithm is used to test the solution results,and the data comparison shows that the affine response surface method can suppress the interval expansion problem better.The expression of the braking force output by the braking system is obtained,which lays the foundation for the following simulation analysis.(2)Through simulation analysis,the main failure modes of the brake drum are revealed,and the functional relationship between the random maximum load and the parameter variables is constructed.Parameterized modeling of the drum brake,transient simulation and coupling simulation analysis of the structure under emergency braking,and the main failure parts of the structure are the flange root of the brake drum and the inner surface of the brake drum.The flange root is less affected by the thermal stress,so the function relationship between the random load and the variable is obtained through experimental fitting in the transient analysis,and the maximum stress and related variables at the inner surface of the brake drum are obtained in the thermal-structure coupling analysis The mathematical relationship of,pave the way for the following gradual reliability analysis.(3)The limit state equations of the two dangerous parts of the brake drum are constructed and the gradual reliability analysis is carried out,which reveals the influence of random variables on the reliability of drum brakes.Calculate the emergency braking times when the dangerous part of the brake drum is damaged,use the Gamma function to simulate the strength random degradation process,establish the limit state equation according to the stress intensity interference model,and obtain the reliability and reliability of the flange root of the brake drum.Sensitivity change curve.For the gradual reliability analysis on the inner surface of the brake drum,the nCode Dsignlife software was used to obtain the fatigue damage of the brake drum during an emergency braking process,and combined with the residual strength theory to construct the critical state expression,using the fourth-order reliability analysis The moment method is used to obtain the influence of structural reliability changes and random variables on the reliability of brake drums.(4)In the gradual reliability analysis of the two dangerous parts of the drum brake,the influence of the correlation of random variables on the reliability index and the gradual reliability are respectively considered.Studies have shown that the correlation between the material properties of the brake drum has a greater impact on the reliability index.The structural parameters of the brake drum and the correlation coefficient between the applied load have little effect on it.The correlation theory is introduced in the gradual reliability analysis,and its influence on the reliability of the brake drum is within the allowable range.(5)According to the researched drum brake,build a test bench for stress measurement,analyze the change in radial stress of the friction lining during the braking process when emergency braking is performed at different initial speeds.According to the measured brake size and the collected experiments The relevant data is simulated and analyzed,and the comparison between the experimental results and the simulation results shows that the braking stress obtained by the simulation is more consistent with the experimental data.Therefore,the gradual reliability analysis of the brake drum based on the finite element simulation results is of guiding significance for the actual engineering.