Analysis Of Vibration Characteristics Of Wheelset Body System Considering Combined Wheel And Rail Fault Excitation

The vibration characteristics of wheelset vehicle body system are obviously affected by the change of wheel-rail contact state,especially the vibration caused by the fault excitation of track irregularity,wheel tread defects(wheel polygon,wheel flat scar)will be transmitted to the vehicle body through the wheelset,which directly affects the operation safety and service life of rail vehicles.At present,the dynamic modeling of wheelset body system considering axle elasticity is lacking and the vibration transmission mechanism under compound fault excitation is unclear.Therefore,it is necessary to analyze the vibration characteristics of wheelset body system under compound fault excitation.In this paper,the wheelset body system of a railway freight car is taken as the research object,and a dynamic model of the wheelset body system considering axle elasticity is established,and combined wheel-rail fault excitation is introduced.Based on the theory of vehicle system dynamics and power flow method,the vibration response and transmission characteristics of the wheelset body system under the excitation of track irregularity,wheel tread defects and wheel-rail compound faults are analyzed.The main research content includes:(1)The axle model is established based on the finite element method,and the two degrees of freedom model of the vehicle body is integrated to construct the wheelset body system dynamics model considering the axle elasticity.The normal force and creep force of wheel-rail contact are introduced,and the Newmark-β time-domain integral method is used for numerical simulation.The calculated results are compared with model of SIMPACK to verify the correctness and validity of the model.(2)Based on the dynamics model of wheelset body system,track roughness excitation is introduced,and the influence of different speeds and roughness amplitude on the vibration characteristics of wheelset body system is analyzed.The results show that the vibration response of the system increases with the increase of velocity and amplitude,and the amplitude is mainly concentrated in the low frequency range.(3)Aiming at the vibration problem of wheelset body system caused by wheel polygon,the formation mechanism of wheel polygon is analyzed and the polygon excitation is introduced into the dynamics model of wheelset body system.The effects of speeds,polygon amplitude,order and the difference of wheel polygon excitation on the vibration characteristics of wheelset body system are studied.The results show that with the increase of velocity,order and amplitude,the system vibration response and wheel-rail vertical force also increase.In addition,the power flow variation of wheelset body system is most affected under polygon frequency doubling.(4)Aiming at the vibration problem of wheelset body system caused by flat wheel scar,the formation mechanism of flat wheel scar is analyzed,and the flat scar excitation is introduced into the dynamics model of wheelset body system.The effects of different speed and length of flat scar on the vibration characteristics of wheelset body system are studied.The results show that the frequency domain interval corresponding to the vibration response curve under the flat scar excitation is equal to the wheel rotation frequency.The vertical force of wheel and rail decreases first and then increases.(5)The combined wheel-rail fault excitation is introduced into the dynamics model of wheelset body system,including track unevenness and wheel tread defect excitation.The influences of different speeds,polygon amplitude,order and flat scar length on the vibration characteristics of wheelset body system are analyzed.The results show that the curve variation in the frequency domain diagram of vibration response is caused by the combination of wheel tread defects and vertical irregularity.And the suspension system effectively prevents the transmission of medium and high frequency vibration from the wheelset to the body when f > nfr.In this paper,the dynamic model of wheelset body system is constructed,and the vibration response and transmission characteristics of wheelset body system under the combined wheel-rail fault excitation are obtained,which can provide theoretical support for wheelset fault diagnosis and wheel rotation repair limit under wheel polygon and flat scar.