Study On Local Fatigue Strength Of Undercarriage Of Emus Under Service Conditions

The load on the high-speed EMU carbody is complicated,and the rigid equipment hanging under the vehicle makes the vehicle body load more severe,which may cause fatigue failure of the local structure.It is becoming more and more important to study the fatigue strength of the local load-bearing structure of the lower suspension of EMU.Based on the analysis system method combining dynamics and fatigue strength,this paper studies the local fatigue strength of the EMU under the service conditions.In this paper,the finite element model of the carbody under the condition of the preparation is established.The model is modified by comparison with the tested mode,and the modes of the structure of the carbody and the local structure of the beam are obtained.Each mode of mode shape.Applying the static load and sweeping load to the relevant load on the vehicle body beam installed on the under-hanging equipment,and performing quasi-static analysis and harmonic response analysis to obtain the quasi-static response function and frequency response function under the corresponding load conditions.Refering to the actual line drawing information of the Beijing-Shanghai line,the whole line is divided into several parts,including straight line,curve,ballast,traction and braking conditions.The rigid-flexible coupling dynamics model is verified based on the measured vibration acceleration data of the line.The time domain load of the suspension position of the suspension body of the vehicle body under each working condition is obtained by simulation,and the load spectrum of the whole line is compiled by linear expansion of the corresponding actual line mileage.The load spectrum can be used as the basis for the study of the local fatigue strength of the undercarriage of the EMU carbody under service conditions.In this paper,quasi-static response function and frequency response function are used as transfer functions,load spectrum is used as input variable,combined with material SN fatigue characteristic curve,and the fatigue strength of hanging part is studied by Miner damage accumulation rule,and the static state is aligned.The results of the method,the modal superposition method and the time-frequency method are compared.Based on the above analysis system combining dynamics and fatigue strength,this paper considers the wheel tread under different wear conditions and the unstable conditions of the EMU,and the local fatigue strength of the suspension under rigid suspension and elastic suspension is carried out.Comparative analysis shows that the rigid suspension is more elastic and will cause more damage to the joint position of the hanging point and the lateral beam.