Vibration Fatigue Analysis And Optimization Of Straddle-type Monorail Vehicle Body

Chongqing Rail Transit Line 3 is the first independently developed and operated straddle type monorail line in China.As the main bearing component and installation carrier,the vehicle body needs to have sufficient structural strength and fatigue reliability to ensure the safety of train operation.However,during routine maintenance and weld flaw detection,it was found that there was a problem of weld fatigue damage at the underframe of the vehicle body.In order to deeply study the fatigue failure mechanism of the vehicle body structure of straddle type monorail vehicles,this thesis combines two vibration fatigue analysis methods in time domain and frequency domain,based on the rigid flexible coupling dynamic model of a single section and the dynamic model of a multi marshalling train,obtains the modal displacement and corresponding external load power spectral density of the vehicle body,conducts vibration fatigue analysis on the vehicle body of straddle type monorail vehicles,and optimizes the fatigue failure location based on the analysis results.The main research work is as follows:(1)Dynamic characteristics analysis of the body structure of straddle type monorail vehicles.Based on the analysis of vehicle body structure,a finite element model of the vehicle body structure of straddle type monorail vehicles is established.Conduct modal analysis and frequency response analysis based on the finite element model,explore the dynamic characteristics of the vehicle body structure,and obtain the flexible vehicle body model,frequency response analysis result file,and modal stress result file required for subsequent fatigue research.(2)Fatigue analysis of vehicle body based on modal stress recovery method.Based on the analysis of the structure of each subassembly of a straddle type monorail vehicle and the study of the vehicle topology,a rigid flexible coupling dynamic model of a single section vehicle is established.Through modal displacement analysis,the influence of various modal displacements of the vehicle body on the vibration deformation of the vehicle body is explored.Based on the modal stress recovery method,the stress spectra of three typical working conditions are obtained,and the nominal stress method is used to analyze the fatigue strength of the vehicle body.(3)Fatigue life analysis of vehicle body random vibration based on frequency method.Based on the plane design drawing and coupler numerical simulation parameters of Chongqing Line 3 Phase I Project,a multi formation train dynamics simulation model from Tongyuan Bureau to Liangkou intersection is established.Obtain the power spectral density of the corresponding external loads of the air spring,center pin,and coupler after Fourier transform.The Dirlik frequency domain method is used to analyze the random vibration fatigue life of the vehicle body with welds.(4)Study on fatigue optimization of vehicle body welds.Combining the results of two types of vibration fatigue analysis,based on the influence of various modes of the vehicle body on the vibration deformation of the vehicle body and the research on the excitation frequency of the external load of the coupler,an optimization scheme for the fatigue crack location is designed.A multi-objective optimization study was conducted to maximize the natural frequencies of the first two modes of the vehicle body and minimize the stress at the crack to improve the fatigue performance of the weld crack.The research work in this thesis provides good engineering guidance and practical reference value for the future dynamic fatigue research and structural optimization design of vehicle bodies.