Time-variant Reliability Analysis Of Motor Hanger For High-speed Train

High-speed train motor hanger is an important bearing component connecting the bogie frame and the traction motor,and its reliability is the basis for ensuring the safe operation of the high-speed train.The leaf springs and bolts are important components connecting the motor hanger and the bogie frame.Their reliability affects the carrying capacity of the motor hanger.As the service time of the train increases and the operating environment continues to deteriorate,the load it bears also changes over time.In view of the influence of the above uncertain factors,the stress and strength of the motor hanger will change with the passage of time,so that its reliability shows a time-variant characteristic.To this end,combined with structural reliability theory,stochastic process theory and time-vaiant reliability theory,with the help of numerical simulation analysis methods,the structural reliability analysis and time-vaiant reliability analysis of the high-speed train motor hanger and its key components are implemented to Its reliability is comprehensively evaluated to ensure the safe and reliable operation of high-speed train.The main research work of this thesis is as follows:In order to solve the problem that the mathematical model of the motor hanger is difficult to obtain in the analysis process,a structural reliability analysis method based on the improved particle swarm optimization support vector regression model(IPSO-SVR)is proposed.Firstly,through the sensitivity analysis of the motor hanger,the random variables that have a greater impact on the target response are selected,and the sample data is obtained using the BoxBehnken design method;secondly,train the sample data and establish an IPSO-SVR-based motor hanger proxy model;finally,combining stress-strength interference theory and Monte Carlo sampling,the reliability of the motor hanger is calculated.The result shows that the reliability of the motor hanger obtained by this method has high accuracy,and at the same time improves the calculation efficiency.In view of the problem that the reliability analysis results of the motor hanger structure fail to reflect the reliability change with time,the time-variant reliability analysis is carried out considering the influence of the load and strength changes with time on the reliability of the motor hanger.Firstly,based on the results of the sensitivity analysis of the motor hanger,combined with the central composite design and finite element method to obtain the experimental design plan,and construct a response surface proxy model of the motor hanger’s size and thickness with respect to the maximum stress.Secondly,according to Brownian motion and Ito’s lemma,the mean and variance of time-variant stress and yield strength degradation are calculated to establish a time-variant reliability model of motor hanger based on the timevaiant stress-strength interference model.Finally,the reliability of the motor hanger has been calculated for 10-year,20-year and 30-year using the checkpoint method.The result shows that the reliability of the motor hanger shows a certain downward trend with the increase of service time.In order to ensure the reliability of the key connecting components of the motor hanger,the time-variant reliability analysis is carried out considering its complex load cases and structural characteristics.In order to reduce the influence of uncertain factors and improve the reliability of connecting bolts,a time-variant reliability analysis method considering the uncertainty of working load is proposed.Considering the uncertainty of design parameters,the probability distribution characteristics of bolt working load are obtained through Monte Carlo simulation;based on the one-dimensional Brownian differential equation and Ito’s lemma,the one-dimensional Brownian differential equation considering the uncertainty of bolt working load is derived,and gives the mean and variance expression of bolt stress under time-variant conditions;based on the time-varying stress-strength interference model,a time-variant reliability model of connecting bolts is established,and the reliability of 30-year is solved by the checkpoint method;Similarly,according to the structural characteristics of the leaf spring and the load conditions,the expressions that characterize its mechanical properties are derived.Based on the Brownian differential equation and Ito’s lemma,the time-variant mechanical properties of the leaf spring are determined,and on this basis,a time-variant reliability model is constructed.Studies have shown that the establishment of a time-variant reliability model of connected components can accurately calculate its reliability.At the same time,the uncertainty of the working load has a great influence on the reliability.In the reliability analysis,the uncertainty of the working load is consistent with the actual operating condition of the structure.