Research On Vibration Fatigue Performance Of EMU Car Body Excited By Track Spectrum

EMU body structure is the main structure of EMU with the largest weight and the most complex load.It bears various complex dynamic loads in the process of motion,and with the increase of running speed,it will intensify the vibration of the body structure.Under the excitation of track irregularity,the vibration of car body structure belongs to random vibration,and larger random vibration will lead to fatigue damage of car body structure.Therefore,it is necessary to study the anti fatigue performance of EMU body to improve the reliability and safety of vehicle operation.In this paper,the vibration fatigue performance of a EMU under the excitation of track spectrum is studied.The main work is as follows:The finite element mesh model of the EMU car body is established.According to EN12663-2010 standard,the finite element method is used to analyze the strength of the car body under typical working conditions.The results show that the maximum stress of the car body under individual working conditions is 194.1 MPa,which is less than the allowable stress of the material and meets the standard requirements;The modal analysis of the car body under the results shows that the first-order vertical bending mode frequency of the car body structure is11.71 Hz,which is greater than the 10 Hz specified in the standard,and the modal of the car body meets the requirements of the standard.Finite element model of complete body of EMU is established.According to EN12663-2010 standard,strength analysis of body under typical conditions is carried out by means of finite element method.The results show that the maximum stress of body under each condition is 194.1 MPa,which is less than the allowable stress of material and meets the standard requirements.Modal analysis of body under complete condition shows that the first-order vertical bending mode frequency of body structure is 11.71 Hz,which is higher than the 10 Hz specified in the standard.And the modal of the body meets the standard requirements.Based on the modal analysis of the body,the frequency response of the body structure is analyzed by the mode superposition method,and the stress frequency response function of the key positions of the body structure is obtained.The results of frequency response calculation show that the higher frequency of stress in the frequency response curve basically coincides with the natural frequency of the first six modes of the body.According to the topological relationship of EMU body and bogie,and according to the relevant dynamic parameters,the vehicle dynamic model is established in SIMPACKsoftware.Based on the German low interference spectrum,the dynamic simulation of EMU is carried out,and the random load spectrum in three directions of transverse,longitudinal and vertical is obtained.Then,the load spectrum in time domain is transformed into PSD load spectrum in frequency domain by using FFT.The results show that the frequency region with large PSD is concentrated in the low frequency range of 0-15 Hz,which is consistent with the frequency distribution characteristics of the first six modes and the frequency response transfer function of the vehicle body.(4)The vibration fatigue of EMU body is calculated by MSC.Fatigue software.The influence of load correlation and uncorrelation on the vibration fatigue life of EMU body is analyzed.The results show that load correlation and uncorrelation have a great influence on the vibration fatigue life,and the result of load correlation is more reliable.(5)Using Dirlik method and narrow band method,the vibration fatigue life of EMU body is calculated.The results show that the results of the body vibration fatigue life calculated by Dirlik method are smaller,and the minimum vibration fatigue life points calculated by the two methods are located at the check position 4,in the upper left corner of the window.(6)The influence of train speed on vibration fatigue life of EMU body is analyzed.The results show that with the increase of running speed,the vibration fatigue life of the car body presents a downward trend,and when the running speed is 400km/h,the vibration fatigue life of the car body is 47.52 years,which meets the requirements of the EMU train for 30 years.