Study On Wheel-rail Contact Relationship Of High Speed Railway Turnout

The direct factor affecting driving safety and stability is the wheel-rail contact geometry relationship while the key factor affecting the relationship is the wheel-rail profile.High-speed turnouts' complex structural characteristics compared with the section lines and the difficult technical performance requirements compared with the general-speed turnouts make the wheel-rail relationship in high-speed areas complex and demanding.On the basis of relevant research in domestic and at aboard,the author explores the wheel-rail contact geometry relationship of high-speed turnouts in depth.The main research content is as follows:1.The research on the wheel-rail contact geometry relationship of turnouts.The author puts forward an algorithm for wheel-rail contact geometry concerning about variable cross-section characteristics of rail in turnout areas--normal cutting method based on moving window.The normal cutting method is assessed by comparative analysis of wheel-rail geometry contact points calculated by section profile method and normal cutting method in interval lines.Under shaking condition,a comparative analysis is conducted to calculate the differences of wheel-rail contact points in turnout areas with the two algorithms which indicates the necessity of calculating wheel-rail contact points by normal cutting method considering variable cross-section characteristics of rail in turnout areas.The author uses normal cutting method to analyze the influence of different track design parameters on wheel-rail contact points and wheel-rail contact geometric parameters which provides a reference for the design of rail gauge and the safety range of changing semidiameter on left and right wheels.2.The vehicle-track coupling dynamics in turnouts.On the premise of normal cutting method considering variable cross-section characteristics of turnouts and the basis of vehicle dynamics theory and turnout dynamics theory,a vehicle-track coupling dynamics model is established to sort out the distribution regularities of wheel-set transverse movement.It can not only provide a reference for determining evaluation methodology of wheel-rail contact in high-speed turnouts,but also analyze the influence of wheel profile evolution on dynamic performance in high-speed turnouts.In coupling model,the vehicle sub-model consists of one body,two frames and four wheel-sets with a total of seven rigid bodies,first and second system suspension device.There are 31 degrees of freedom,among them,four degrees of freedom for wheel-sets are considerd for side-rolling,transverse movement,ups and downs and shaking while five degrees of freedom for bodies and frames are considered for side-rolling,transverse movement,ups and downs,shaking and nodding.On the basis of including the switch,connection and frog,the turnout sub-model involves the influence of various parts such as limit device,interval iron and top iron on the vibration.It also involves the variable cross-section characteristics of switch rail and point rail as well as the non-linear support of sliding plate.In wheel-rail contact model,the author uses the normal method in Chapter Two to realize the dynamic calculation of geometric relations of variable section rails in turnouts and establish coupling vibration equation based on Hamilton Principle.3.The evaluation methodology of wheel-rail contact in high-speed turnoutsThe irregularity specimen generated by the equivalent algorithm of frequency domain power spectrum and irregularity spectrum of ballastless track in China high-speed railway is set as system incentive.The author analyzes the influence of different turning-in postures on the wheel-set transverse movement with vehicle high-speed turnout vibration equation and illustrates dynamic regularities of wheel-set transverse movement with hypothesis test theory.According to the wavelength formula of serpentine movement,the author deduces the equivalent wheel-set conicity matching with asymmetric rail profile section.Besides,the equivalent conicity under special condition is solved according to the least principle of gravitational rigidity.The equivalent conicity of transverse movement based on maximum wheel probability is defined as nominal equivalent conicity which reflects the different semidiameter between right and left wheels under different transverse movement from the perspective of wheel radial and represents the stability of vehicle operation.The author uses the structural irregularity based on maximum probability wheel-set transverse movement to reflect the change rules of wheel-rail contact points along the longitudinal direction of the track in transverse and vertical directions caused by the structural characteristics of turnouts.The contact band width is used to reflect the wheel-rail contact horizontally on the track coordinate system to indicate the abrasion of wheel-rail surface.4.The influence of wheel contour evolution on wheel-rail match in turnouts.Using the wheel-rail contact geometry algorithm program,dynamic numerical simulation program and CONTAT software in this paper to analyze the distribution of wheel-rail contact points,the evaluation index of wheel-rail contact geometry,contact stress and the safety,comfort of vehicle operation and comfort index when when the tested wheel contour matches the switch of No.18 high-speed turnout at 350 km/h under different operating mileage which can illustrate the tremendous influence of wheel contour evolution on wheel-rail contact geometric relation.Under certain conditions,the initial wear of wheel can increase the “conformity” of rail and wheel profile which can reduces the contact stress to a certain extent.With the deepening abrasion,the conformity decreases.But because of the changing wheel-rail contact points and wheel curvature,the contact stress decreases first and then increases.The wheel contour evolution reduces the comfort of train operation,but has little effect on the safety of train operation.5.The optimal design for wheel-rail relation in high-speed turnout areasThe influence of Kalker's weight coefficient and friction coefficient on the wheel-rail relationship in the reverse operation of Chinese high-speed railway turnout zone is analyzed from dynamic behavior and wheel-rail damage performance under ideal condition that the dynamic parameters of vehicles and the profile of wheel and rail remain unchanged.Due to different Kalker's weight coefficients and friction coefficients,the vehicle's dynamic behaviors during the switch panel,crossing area and the closure panel totally differs each other.In order to improve the stationarity of trains in turnouts,the author sets equivalent coincity as optimization goal and uses the relation of equivalent coincity-RRD curve-rail profile slope to put forward a reverse design method aiming at guiding the burnish of point rail in service.