Research On Service Safety Of Bogie Spring Of Heavy-haul Freight Wagon

As an important component of freight wagon bogies,bolster spring plays an important role in achieving uniform load bearing and mitigating vibration and impact caused by track irregularity.With the increase of axle load and vehicle turnover times of heavy-haul freight wagon in China,the frequency and amplitude of vertical dynamic load of bolster spring increase greatly,which worsens the operating conditions of spring and reduces the service life of spring,thus affecting the operation safety of heavy-haul freight wagon.Secondly,the service life of bolster spring is also affected by the uncertainty of geometric size,material mechanical properties and load characteristics,The influence of certain factors is random.If the deterministic method is used for analysis,it will be inconsistent with the actual results.Therefore,this paper takes the bolster spring of K6 bogie as the research object,carries out the spring robustness design,dynamic reliability analysis and spring system reliability analysis,so as to provide reference for the spring design and spring system maintenance strategy formulation.The main contents of this paper are as follows.(1)The bolster spring is designed for robustness.Taking spring stiffness and fatigue strength as performance indexes,a single performance index robustness model is established,and the weight coefficient is introduced to establish a comprehensive performance robustness model.The optimal Latin hypercube sampling design method is used to analyze,and the influence of spring design variables on spring performance is obtained,and it is determined that under different weight coefficients,it is necessary to make spring comprehensive performance more robust,The range of variation coefficient of strip diameter.(2)The strength degradation model of bolster spring is established.The P-S-N curve of60Si2 Cr VAT spring steel was obtained by lifting method and group method,and the P-S-N curve of spring was obtained by correction.The strength degradation model of bolster spring is established based on gamma random process,and the characteristic parameters of the random process are estimated by P-S-N curve of spring steel material.(3)Dynamic reliability sensitivity analysis of bolster spring.Considering the degradation of spring strength,the dynamic reliability model of spring is established based on the stress strength interference model.The dynamic reliability and reliability sensitivity of spring are calculated by perturbation method and fourth-order moment method based on the measured load spectrum and AAR load spectrum.The mean value and variance sensitivity of random variables are analyzed,and the dynamic reliability model of spring is simplified.(4)Reliability analysis of bolster spring system.By comparing with several commonly used system reliability models,this paper analyzes the reliability properties of bolster spring system,studies the influence of several spring failures on the fatigue reliability of residual spring,and obtains that the failure of external spring of spring system has a great influence on the reliability of residual spring.Combined with the analysis results,this paper gives some suggestions on the maintenance of spring system.