| The rail fastening system connects rail and underneath supporting structure,which is an indispensable critical component of high-speed railway track,as well as a significant guarantee for safe and smooth operations of high-speed trains.However,due to the long term repeated dynamic train loads,fatigue damage phenomenon of rail fastening system,such as rail clip fracture,occur from time to time,which not only increase the running safety risk of high-speed train,but also increase the work burden of routine inspection and maintenance.Nowadays,the high-speed railway development in China has gradually entered the long-term operation,management,and maintenance stage from the previous large-scale construction stage,and maintaining the rail fastening systems in normal service state in a long time period is one of the key tasks of the present stage.By proposing a more efficient dynamic analysis method for rail fastening system,to deepen the understanding of the vibration characteristics of rail clip,and to reveal the mutual influences between the rail fastening system and the wheel/rail dynamic interactions,it will be beneficial to improve the theoretical analysis and maintenance level of rail fastening system.And it is meaningful for guaranteeing the sustained,safe and reliable operation of high-speed railway.This thesis has conducted the following researches aiming at the type WJ-8 rail fastening system which is widely used for non-ballasted track in China’s high-speed railways:1.The vibration characteristics of type W1 rail clip is revealed by adopting the experimental research approach.Among which,the vibration characteristics of rail clip in free state and installation state are revealed by performing modal analyses;the transferring relationship between vertical rail acceleration and vertical rail clip acceleration is revealed by conducting hammer test,and the rail clip acceleration frequency-response function is fitted according to the measured results.2.Based on the principle of modal superposition,a new rail clip dynamics modeling method is proposed.With this method,the rail clip dynamics equations are directly established in modal coordinates with the natural frequencies and mode shape vectors of rail clip exported from the finite element model.This method overcomes the difficulty of rail clip dynamics modeling caused by the complex shape of rail clip.By comparing the calculation results obtained through the proposed method and the Abaqus software,the validity of this method is proved with an example case.Besides,the rail clip dynamics model in installation state is also established according to the proposed method.In this model,the constraint state of the rail clip is simulated by fully considering the vertical,lateral,and longitudinal contact forces between the rail clip and its neighboring parts.3.Based on the vehicle-track coupled dynamics theory,a refined vehicle-track coupled dynamics model involving elaborated rail fastening system model by introducing the rail clip model and the existed nonlinear rail pad model which considering the nonlinear characteristics of visco-elasticity and friction of the rail pad is established,and a dynamics simulation routine is also composed.With the refined model,the influence of wheel/rail dynamic interactions on rail clip dynamic responses can be analyzed directly in the vehicle-track coupled system.Only one simulation is required to obtain dynamic responses of all rail fastening systems in the analyzed track section,which has the advantage of high calculation efficiency.4.A short-wavelength irregularity spectrum of high-speed railway,of which the wavelength ranges from 0.01～1 m,is fitted based on the field measurement data.By superposing the short-and long-wavelength random irregularity samples,an irregularity sample of which the wave-length range is 0.01～200 m is obtained.Dynamics simulations are performed with the refined dynamics model to calculate the dynamic responses of rail fastening systems subjected to the excitation of random track irregularity.The dynamic responses of rail fastening system are statistically analyzed,and the influences of vehicle speed and track irregularity amplitude on rail fastening system are revealed.Besides,the dynamic responses of rail fastening systems which located in the curve section are also analyzed,and the dynamic responses of rail fastening system under excessive superelevation and deficient superelevation conditions are compared.5.Based on the refined dynamics model,the dynamic responses of rail fastening system subjected to the excitation of typical short wavelength irregularities,such as welded rail joint,polygonal wheel,and rail corrugations are analyzed.As for the case of welded rail joint,the differences between excitation at mid-span of adjacent rail seats or above a rail seat,as well as the differences among the excitation of convex A-type,convex B-type,concave type,and double concave type welded rail joint on dynamics responses of rail fastening system are compared,respectively.Besides,the influences of welded rail joint sizes are also analyzed.As for the case of the polygonal wheel,the influence of polygon order and amplitude on rail fastening system are analyzed.And as for the case of rail corrugations,the dynamic responses of all rail fastening systems in the rail corrugation section subjected to the excitation of measured rail corrugation sample are evaluated through simulation,and a method for evaluating the vibration intensity according to the rail clip critical acceleration value is also put forward.6.The influences of installation state and parameter state of rail fastening system on wheel/rail dynamic performance are investigated in depth.As for the installation state of rail fastening system,the influences of rail clip loosening,clamping failure,and rail pad support failure on rail deformation,rail pad force,and wheel/rail dynamic indices,as well as the variation of wheel/rail indices as the number of failed rail fastening system changes,are evaluated in detail.As for the influence of rail fastening system parameter state,the parameters to which wheel/rail dynamic responses are sensitive are selected,and the effects of their randomness on wheel/rail dynamic responses are investigated. |
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