| Rail transit vehicles are subjected to complex loading conditions.In recent years,localized cracking events have continuously occurred in the chassis,bogie frames,antenna beams,obstacle eliminators,and wheelsets.The reason for this is the fatigue strength caused by local resonances.However,under the resonant environment,the service load is not enough for all kinds of loading standards,and there is no complete assessment method for fatigue strength under resonance conditions.The study of fatigue strength under vehicle resonance conditions is one of the topics worthy of in-depth study.In this paper,the antenna beam at the end of the bogie is taken as the research object.Based on the circuit test data and the system dynamics simulation,the resonance fatigue of the structure is studied,and the resonance suppression method and the structural optimization scheme are proposed.Firstly,based on the circuit dynamics test scheme,the dynamic stress and vibration acceleration of the antenna beam are tested.The transmission law of the fatigue strength and vibration characteristics of the antenna beam is analyzed.The modal parameter identification is performed using the PloyMax method to verify the finite element model.Improve the accuracy of simulation calculations.Secondly,a rigid-flexible coupling dynamics model of a metro vehicle is established.By comparing modal parameters and line test data,the model is verified and corrected.The vibration transmission characteristics of the bogie system are studied under consideration of the impact of the wheel bilge and the rail joint.The correlation between the wheel-rail excitation parameters and the structural fatigue life is analyzed.It is proposed that the antenna beam meets the service life requirements under dynamic load.Finally,in order to improve the vibration environment of the antenna beam,considering the addition of a dynamic vibration absorber on the basis of the original structure,the parameters of the vibration absorber are optimized,and the feasibility of the vibration absorber is verified by testing in the vehicle simulation.Through the study of this paper,it is found that the first-order natural frequency of the antenna beam structure is around 45 Hz.Under different vehicle speed conditions,structural resonance will be induced.At this time,the equivalent stress of most measuring points exceeds the fatigue limit and does not meet the fatigue strength design requirements.The impact of the rail seam will excite the resonance of the antenna beam structure.The wavedepth,wavelength and running speed of the vehicle have a great influence on the dynamic stress,and the rail welding state needs to be controlled.The lengths of the old and new wheels have little effect on the vibration of the antenna beam,but the vehicle speed has a great influence.The higher the vehicle speed,the more violent the vibration.The dynamic vibration absorber designed by optimizing the parameters has a significant effect on the vibration of the antenna beam,especially when the first-order resonance,the dynamic stress amplitude is reduced,and the service life is improved to some extent. |
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