A Numerical Simulation Of Wheel Polygonization Of High-Speed Trains Based On Friction-Induced Vibration

With increase of the speed of high-speed trains,the dynamic interaction between the vehicle and the track becomes stronger.This strong dynamic interaction will lead to forced vibration of vehicles,and wear of wheels deteriorates accordingly.Wheel polygonalization is a special form of wear damage of wheels.When polygonalization of a wheel is formed,the out-of-round wheel can produce a periodic vertical excitation and lead to forced vibration of vehicles during their operations,which will accelerate the damage of the parts of vehicles,and seriously affect the passengers' comfort.Moreover,the high-frequency vibration may lead to the derailments of vehicles.But there is not a clear and unified view of the formation mechanism of wheel polygonalization.At present,the only effective measure to reduce the damage of wheel polygonalization is machining out-of-round wheels,but this method will increase the maintenance costs and the problem cannot be solved fundamentally.Therefore,understanding the formation mechanism of wheel polygonalization and taking measures to eliminate the production conditions from the source is the best way to solve this problem.Professor Chen from Southwest Jiaotong University provided a viewpoint that the friction-induced vibration of the wheelset-track system may lead to wheel polygonalization.Chen hypothesizes that when a high-speed train is accelerating or braking on a straight track,a wheel may slide on a track at this moment.Meanwhile,the creep force between the wheel and the track becomes saturated,which approximately equals to the friction force.The friction-induced vibration of the wheelset-track system easily occurs under the action of the saturated creep force,which induces the fluctuation of the friction work and bring about the polygonalization of wheel treads.The transient dynamic analysis provided by the finite element software is used to verify that the friction-induced vibration can induce the fluctuation of the friction work based on this viewpoint,which explains how the polygonalization is generated.The influence of the damping and stiffness of the fastener,the friction coefficient and the axle load on the occurrence propensity of the friction-induced vibration is studied by using the complex eigenvalue analysis method provided by the finite element software.Several methods for containing the wheel polygonalization based on the production conditions are proposed.The main research conclusions of this dissertation are presented as follows:(1)The author reviewed wheel polygonalization studies.It is found that domestic and foreign scholars applied simulation and field test methods to study wheel polygonalization.They established coupling models of vehicle-track systems and wheel-tread wear model which considered the initial out of roundness of wheels and conducted the iterative calculation.Their results were compared with the field data at the same time.Researchers applied these models to predict the development of wheel polygonalization and to study the influence of wheel polygonalization on vehicle dynamics.(2)The author studied the dynamic behaviors of wheelset-track system when a high-speed train passes through on a straight track using transient dynamic analysis method provided by ABAQUS.The vertical vibration acceleration signals of the nodes on track surface as well as the signals of the normal contact force between the wheel and the track are analyzed by PSD method,and the obtained dominant frequency is 239.16Hz.The results show that the friction-induced vibration caused by the saturated creep force can induce the fluctuation of the normal contact force,the friction work will also fluctuate at the same frequency.Therefore,the vibration can induce wheel plolygonalization of high-speed trains.(3)The author studied the stability of wheelset-track system using the complex eigenvalue analysis method provided by ABAQUS,which can predict the frequencies of friction-induced vibration and the associated vibration modes.And the vibration dominant frequency obtained by this method is 239.48 Hz.The influence of the damping and stiffness of the fastener,the friction coefficient and the axle load on the occurrence propensity of the friction-induced vibration is also discussed.It is found that increasing the damping of the fastener and increasing the stiffness of the fastener within a certain range or reducing the friction coefficient are feasible measures for suppressing wheel plolygonalization.It is also found that wheel polygonalization canmot be suppressed by changing only the axle load.