Study On Vibration Fatigue Of Bogie Frame Based On Metro Vehicle Structural Dynamics

In recent years,with the increase of the traffic density and the volume of metro vehicles,overload operation has become the norm,and wheel/rail short wave irregularities such as rail corrugation and wheel polygonal wear are more likely to occur,which leads to high-frequency excitation,which is easier to cause rail corrugation and wheel polygonal wear.The wheel/rail high frequency excitation caused by the wheel/rail short wave irregularity is easily leads to the resonance fatigue problem of the bogie system.Aiming at the failure cases of subway frame and its accessory parts,this thesis studies the vibration fatigue of the bogie frame based on the structural dynamics of metro vehicles,which has a certain design guiding significance and engineering application value.The main works are as follows:(1)The differences between the design standard load of metro bogie and the service load of vehicle are discussed in detail.The results show that the definitions of bogie frame load in existing standards are from top to bottom,ignoring the influence of wheel/rail high frequency load and structural resonance frequency;the coupled wheel/rail vibration frequency is complex and abundant,but mostly locates at 30～80 Hz medium and low frequency band and180～600 Hz high frequency band;The passing frequencies of rail corrugation are mainly located at 53～167 Hz,167～265 Hz and 333～538 Hz.Finally,a dynamic design process of bogie vibration fatigue is proposed.(2)Considering different track types and rail corrugation characteristics,the static modal matching of bogie frame is studied.The results show that the corrugation frequency and coupled wheel/rail vibration frequency are easy to couple with the bending mode of side beam and deformation mode of frame end.The dynamic modal matching of bogie frame in service is studied by frequency sweep method,the results show that the increase of damping ratio has a certain attenuation effect on the vibration transmission of bogie frame,and the influence on the vibration transmission at the end of bogie frame is the greatest;The primary vertical stiffness has little effect on the vibration transmission of the bogie.(3)The weak position of the frame is identified in terms of the static and dynamic method,and the dynamic stress of the weak position is analyzed by time-frequency method.The results suggest that these weak positions are more sensitive to the lateral bending mode of side beam at 70～100 Hz,the vertical bending mode of side beam at 100～200 Hz and the end deformation mode at 200～240 Hz;Based on the measured power spectrum of axle box acceleration,the stress spectrum of the weak position of the frame can be obtained.The results indicate that The stress spectrum of weak position can reflect the main frequency of axle box vibration power spectrum better,and the high-frequency excitation caused by rail corrugation in service can be transmitted to the frame.(4)The characteristic stress spectrum of the weak position of the frame is studied.The results show that: as the increase of vehicle speed,the amplitude and total cumulative frequency of dynamic stress at the weak position increase;as the increase of superelevation of the curve,the dynamic stress response at the weak position becomes stronger and the amplitude and total cumulative frequency of dynamic stress slightly increase;as the increase of curve radius,the dynamic stress response curve at the weak position becomes weaker and the amplitude and total cumulative frequency of dynamic stress decrease.(5)The fatigue life of the weak position of the frame is predicted.The results show that:the curve radius has a certain influence on the damage of the weak position of the frame,but there is no obvious law;the rail corrugation of different wavelengths has a certain influence on the fatigue life of the weak position of the frame,and the rail corrugation with median wavelength of 60～100 mm has the greatest impact on the end weld of the bogie frame;The predicted service life of frame end is 1.587 million km,which is close to the actual service life of metro vehicle frame end,and does not meet the service life requirement of bogie frame of3.5 million km.The other three weak positions all meet the service life requirement of 3.5million km.