| Accurate prediction of high frequency wheel-rail interactions is not only the basis of wheel-rail relationship research but also the one of the difficult problems in this field.For the high frequency wheel-rail interactions,dynamic method need less computational time but has low accuracy under high frequency dynamic conditions.In addition,the transient finite element model for high-speed wheel-rail rolling contact bases on explicit finite element method develops gradually,this method is suitable for the calculation of high frequency dynamic,but the cost of computation is too high to be used in mass analysis.In this paper,a 3-D transient rolling contact finite element(FE)model which based on the explicit time integration scheme and a wheel-track coupled dynamic model which based on the multi-body dynamics approch is developed,analyzing the wheel-rail contact response results of the two models under high-frequency dynamic conditions,the Hertz spring model is corrected by the results of the finite element model,so as to improve the accuracy of the wheel-track coupling dynamic model.The chapter one introduced the theory of wheel/rail rolling contact and the research progress of wheel/rail contact model,and analyze advantages and disadvantages of the dynamic model and the finite element model.It is necessary to improve the calculation accuracy of the wheel-track coupling dynamics model under the condition of high frequency.Since this paper focuses on the wheel-rail contact model,it simplifies the structure and components irrelevant to contact in the modeling process,as a result,the cost of calculation is reduced and the interference of excessive structural vibration is eliminated.This is beneficial to analyze the influence of the contact model.The three models uses the same material parameters and geometries of the wheelset.For the finite element(FE)model,actual geometries of the wheelset can be included,and arbitrary irregularities is considered in the rail surfaces.Moreover,the important flexibility and continuous vibration at high frequencies is also considered,spin of the rolling contact and gyroscopic effect of the rotating wheelset is automatically taken into account.The finite element(FE)model is more accurate but need higher cost of calculation,as a resule,it is not used in mass analysis.In chapter 3,the amplitude of high-frequency wheel/rail force predicted by three models which inculed rail irregularities(wavelength 20~140 mm,wave depth 0.01~0.20 mm)and the velocity range of 150~500 km/h is compared in detail,it find the wheel/rail force amplitude predicted by wheel-track coupled dynamic model and wheel dynamic model is 46.6% and 76.7% of static load in this paper.It is positive linear relationship between the amplitude of wheel/rail force which predicted by three models and wave depth.Within the velocity range of 150~500 km/h,the amplitude of wheel/rail force predicted by the transient rolling contact model was stable as the velocity increases,and the fluctuation was 5.0 kN(6.4%).The amplitude of wheel/rail force predicted by the wheel-rail coupling dynamics model increases with the velocity,and its maximum value is 46.7kn(59.5%),and then remained stable.The amplitude of wheel/rail force predicted by vehicle dynamics model increased with the velocity.In chapter 4,the relationship between the amplitude of wheel/rail force predicted by the three kinds of model and these factors that included the wave length,wheel rolling speed and excitation frequency is analyzed in detail.Based on the results of the transient rolling contact model,a modified method for the wheel-rail coupling dynamics model is proposed.It find that under the same excitation frequency,the amplitude of wheel/rail force predicted by the wheel-rail coupling dynamics model is the same and despits of the wavelength and velocity.The wavelength and velocity affects the wheel-rail contact response by changing the excitation frequency.The nonlinear Hertz contact stiffness plays a decisive role in the prediction of the wheel-rail contact response.Changing Hertz contact stiffness will change the amplitude-frequency curves of the wheel-rail coupling dynamics model.To modify the Hertz contact stiffness,the correction factor is a seventh-order polynomial function related to the wave length.The error analysis of the modified coupling dynamics model shows that the relative error is less than 15% for the 88% works in this paper,and the maximum elative error is 36%.The variation trend of the relative error was similar to the amplitude-frequency curves of the coupling dynamics model.When the excitation frequency is close to the resonance frequency(601 Hz),the relative error will increase. |
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