Influence Of Different Modelling Approaches Of Wheelset And Track On Dynamic Response Of Metro Vehicles Under Medium-high Frequency Excitation

In modern rail transit engineering,dynamic numerical simulation has become one of the main research methods to study the dynamic performance response of vehicle and track.As vehicles operation,the wheel?rail interaction deteriorates.Short?wave irregularities of wheel and rail,such as wheel flat,rail corrugation and wheel polygonal wear,are common in rail transit system.The short?wave irregularities occurring on the wheel and rail contact surfaces can cause the medium-high frequency vibration response of the wheel?rail system,which puts forward higher requirements on the reliability of the dynamic simulation of railway vehicle.Therefore,it is of great theoretical and practical significance to carry out a indepth study on the dynamic simulation model of railway vehicle.Based on the field test data of a metro line,this thesis carried out a investigation on the influence of different wheelset and track modeling methods on the calculation results and efficiency in the dynamic simulation of metro vehicle.The wheel polygonal wear and P2 resonance problem which are common in metro operation were studied in detail.The main work and conclusions of this thesis are as follows.(1)A field test on a metro line was carried out focusing on wheel out-of-roundness,rail irregularity and vehicle vibration.The dynamic response of the vehicle system under the excitation of abnormal wheel?rail wear was systematically analyzed.The test results showed that the abnormal wear of wheel and rail is serious.The rail weld irregularity is easy to excite the P2 resonance of wheel?rail system.The wheel polygonal wear exacerbates the vibration response of vehicle system and affects the safety and comfort of the vehicle.(2)Using the dynamic analysis software SIMPACK and the finite element analysis software ANSYS,four types of metro vehicle dynamic simulation models were established,including multi?rigid body dynamic model,dynamic model considering wheelset flexibility,dynamic model considering the flexibility of the track structure and dynamic model considering the flexibilities of wheelset and track structure.(3)The differences on wheel-rail dynamic interaction and vehicle system dynamics among four dynamic simulation models under short?wave irregularity excitation of wheel rail were investigated.The accuracy and efficiency of the simulation results for the four models were compared.This provides a reference for the model selection in the dynamic numerical simulation.The results showed that for wheel?rail excitation in the low frequency range of 0?30 Hz,the wheel-rail rigid/flexibility has little effect on the simulation results;however,the calculation efficiency of the rigid?flexible coupling model is low.Thus,it is recommended to use a multi-rigid body model in the simulation for the low frequency range of 0?30 Hz.Under the excitation of medium and high frequency wheel and rail above 30 Hz,considering the elastic deformation dynamic model of the wheelset structure,the calculation result is slightly better than the multi-rigid body model.The dynamic model without considering the elastic deformation of the track structure under medium?high frequency excitation will overestimate the vibration response wheel?rail system,and the calculation results have large errors.The dynamic model considering the flexibilities track structures and the dynamic model considering the flexibilities wheel and track structures can more accurately simulate the inherent modal resonances of wheel?rail system such as P2 resonance,of which the calculation results are more accurate and reliable.In addition,the dynamic model considering the flexibilities wheel and track structures can also better reflect the natural modal frequency of the wheelset.In summary,it is recommended to use a rigid?flexible coupling dynamic model that considers the flexibilities of wheelset and track structures when medium?high frequency wheel?rail excitations are taken into account.(4)The dynamic simualtion model of metro vehicle suitable for medium?high frequency analysis was verified by field test data.Relevant research was carried out on the problems of wheel polygonal wear and P2 resonance.The results indicated that an increase of harmonic wear order and speed can aggravate the vibration of key components of vehicle.When the wheel polygon wear passing frequency is close to the wheel-rail system P2 resonance frequency(64 Hz)and the wheelset bending mode frequency(88 Hz),it will aggravate the dynamic interaction between the wheel and rail,resulting in abnormal vibration of the system;Wheel flat can excite the P2 resonance of the wheel?rail system.The unsprung mass and rail fastener stiffness have a greater influence on the P2 resonance frequency.The P2 resonance frequency increases with an increase of the rail fastener stiffness and a decrease of the unsprung mass.