Fatigue Reliability Analysis Of Transmission Gear Based On Multiple Failure Modes

The rapid development of high-speed railway puts forward higher requirements on reliability of vehicle parts.Transmission gear,as the most important part of EMU transmission mechanism,plays a vital role in the safety of passengers and trains.The strength and stress of transmission gear are time varying.This results in a fluctuating decline in reliability over time.In addition,the joint action of multiple failure modes is not considered in traditional reliability calculation methods.Therefore,it is of great significance to calculate the reliability of EMU transmission gear considering the influence of correlation and strength degradation simultaneously.Based on the stress-strength interference model and using time-varying mixed Copula function and nonlinear Gamma function,a transmission gear reliability model is established considering the multi-failure mode dependence and time-varying interaction.Calculate the time-varying reliability.To ensure the safe operation of EMU.The main research work of this paper is as follows:Firstly,the static fatigue reliability of EMU transmission gear is calculated considering multi-level failure correlation.To solve the problem that the traditional reliability calculation method assumes that elements at all levels are independent from each other,which is inconsistent with the actual situation,a reliability analysis method is proposed considering the correlation of random variables,stress-strength correlation and the correlation of failure modes.Firstly,a correlation model of transmission gear random variables based on correlation matrix is established.Monte Carlo sampling method is used to obtain random variable sampling data considering correlation.Secondly,a stress-strength correlation model based on improved correlation Angle is established.The stress-strength data of each failure mode considering correlation are obtained.Finally,a multi-failure mode correlation model based on mixed Copula function is established.The maximum likelihood estimation method is used to calculate the parameters of mixed Copula function.The static reliability model of EMU transmission gear is established.The fatigue reliability of transmission gear based on multistage correlation is calculated.Secondly,the dynamic fatigue reliability of EMU transmission gear is calculated by considering strength degradation.A time-varying reliability calculation method based on P-S-N curve and nonlinear Gamma degradation process is proposed to solve the problem that the strength degrades with time due to the constant change of random parameters at any time or the number of loads.The characteristic parameters of the nonlinear Gamma function are derived from the P-S-N curve of the material.The characteristic parameters of intensity degradation are obtained by Gamma function.A time-varying stress-strength interference model for tooth surface contact fatigue and tooth root bending fatigue failure modes is established considering strength degradation and stress randomness.The model is used to sample the parameters.Determine stress and strength probability distributions.The time-varying reliability model of EMU transmission gear is established.The time-varying fatigue reliability of transmission gear under multiple failure modes is calculated.Finally,the dynamic fatigue reliability of EMU transmission gear is calculated by considering the correlation of multiple failure modes and the influence of time on the reliability.In order to solve the problem of multi-failure mode correlation of transmission gear,a time-varying hybrid Copula function sensitive to the correlation of upper tail and lower tail is proposed.The sample of time-varying mixed Copula function is extended by random sample expansion method and random sample combination.The improved coefficient calculation formula of Copula function is obtained.The weight and parameter matrix of time-varying mixed Copula function are calculated based on ARMA procedure.The time-varying mixed Copula functions that meet the requirements are screened by the red pool information criterion.Combined with this function,the time-varying reliability model of EMU transmission gear is established.The time-varying fatigue reliability of transmission gear considering both correlation and strength degradation is calculated.