Fatigue Evaluation Of Welded Frame Of High-Speed EMU Bogie

With the rapid development of China High-Speed Railway,the train running speed is also constantly increasing,which has higher requirements for the safety and reliability of vehicles.The high-speed operation of the EMU has caused great changes in the vibration characteristics and service environment of the key components of the bogie under the action of the track disturbance.The welded frame acts as an important structure for the bogie to support the car body and connect the components.Its safety and reliability directly affect the safety of the vehicle system.To this end,this thesis takes the CRH 380B EMU bogie welded frame as the research object,and studies the static strength,fatigue strength,dynamic characteristics and load time history.With reference to UIC 615-4 and EN 13749 standards,the finite element method is used to calculate the abnormal load conditions and the simulated operating conditions.Under the extraordinary load conditions,the maximum stress is 329 MPa,which is located at the root of the arc of the vertical plate of the positioning seat.Exceeding the yield limit of the material,the maximum stress under simulated operating conditions is 229 MPa,which is located at the joint between the vertical plate of the positioning seat and the lower cover of the side beam,and does not exceed the allowable stress of the material,and the frame satisfies the static strength requirement.According to the calculation results of the simulated operating conditions,the Goodman fatigue limit diagram was selected to evaluate the uniaxial fatigue strength of the key parts of the welded frame.The evaluation points are all located in the envelope and the uniaxial fatigue strength meets the requirements.The maximum principal stress method is used to transform the multiaxial stress state into the uniaxial stress state,and the Goodman limit diagram is used to evaluate the fatigue strength.The joint location of the arm locating weld seam adopts Crossland and Papadopoulos multi-axis fatigue assessment criteria,and the safety margin concept is introduced to evaluate the fatigue strength.The safety factor calculation results are all greater than 1,meeting the fatigue strength requirements.The multi-body dynamics model of CRH 380B is established.The spectrum analysis of the vehicle body,frame and wheelset under the condition of straight line running and curve passing can be obtained.The vibration frequency and vibration energy of the vehicle system are mainly distributed in the low frequency range,and the simulation data and The comparative analysis of the reference literature shows that the vibration characteristics of the time domain and the frequency domain are in good agreement with the referenced literature values,which verifies the correctness of the established model.The load time history of the boom positioning seat in the fatigue zone was extracted,and the 16-stage load spectrum was compiled by the rain flow counting method.In order to obtain a more accurate equivalent stress to solve the conversion coefficient,the sub-model method is used to calculate the finite element of the arm positioning seat.The final equivalent stress value is less than the allowable stress of the weld material of 70 MPa,which meets the requirements of more than 12 million kilometers of safe operating mileage,and the results meet the design requirements.