Research On Wheel-rail Matching Relationship And Rail Profile Asymmetric Optimization Method On Curve Of Metro Under Operation Conditions

As the largest proportion in urban rail transit,metro plays an extremely important role in alleviating urban traffic congestion.With the increase of operation time,a series of problems affecting the wheel-rail matching are gradually exposed,such as the deterioration,damage and wear of wheel and rail materials.Wheel-rail wear will lead to the change of wheel-rail contact geometry,and the wheel-rail dynamic interaction of metro is very sensitive to the change of wheel-rail contact relationship,which has a great impact on operation safety and maintenance.Due to the limitation of geographical conditions,there are usually high proportion of curve lines in metro lines.However,the wheel-rail contact relationship on curve is more complex,and the damage of wheel-rail interface caused by poor wheel-rail matching will be further aggravated.Therefore,it is of great theoretical and practical value to study the wheel-rail matching relationship on curve of metro under the operation conditions.The operation practice shows that when the running speed of metro is increased to more than 80km/h,the vehicle operation performance of some section is obviously reduced,and the abnormal vibration phenomenon is prone to occur,which endangers the operation safety.And the service performance of track structure is deteriorated,which is easy to induce track structure diseases.According to the statistical data,the curve accounts for a large proportion of the subway lines.Regardless of the acceleration and deceleration section around the station,the radius of the curve where the metro vehicles pass at high speed is mostly600-2000 m,and the curve maintenance workload within the radius is usually relatively large.In view of this,combined with the operation practice of Beijing Metro Line 6,taking the common 650 m radius curve with high negotiate speed as the research background,this thesis establishes the dynamic model of metro vehicle and track on curve,and forms the rail profile asymmetric optimization method on curve by combining the rail profile asymmetric optimization model and wear analysis,and analyzes the influence of off-balance superelevation and speed change on rail wear.In order to solve the problem of poor wheel-rail matching,the personalized optimization scheme of rail profile on curve under operation conditions is proposed,which can provide reference for metro maintenance.The main work and achievements of this thesis are as follows:(1)Based on the wheel-rail test profile on curve,the wheel-rail spatial contact geometric characteristics are studiedBased on the statistical analysis of the measured wheel and rail profiles on curve with a radius of 650 m of Beijing Metro Line 6,the worn wheel-rail profiles are determined.And the wear characteristics of worn wheel-rail profiles are studied.The wheel-rail contact model considering the influence of yaw angle is established,and the corresponding calculation program is compiled.The accuracy of the program is verified by comparing with the calculation results of commercial software SIMPACK.Based on the wheel-rail spatial contact model,the influence of yaw angle,rail cant and wheel-rail profile wear on the wheel-rail contact geometric characteristics is analyzed,which lays a foundation for the establishment of vehicle-track dynamic interaction model on curve.(2)The dynamic interaction model of metro vehicle and track on curve is established,and a new two-step numerical integration method is used to solve the dynamic responseOn the basis of fully considering the curve characteristics,the dynamic model of metro vehicle and track is established by using multi rigid body dynamics and structural vibration theory.The dynamic interaction model of vehicle and track on curve is formed by considering the wheel-rail spatial contact model with the influence of yaw angle.A new two-step numerical integration method is used to solve the vehicle-track dynamic interaction model.The numerical integration method can maintain calculation stability and accuracy when using a larger integration step,and significantly improve the calculation efficiency.At the same time,the sliding window method is used to solve the problem of sharp increase of calculation amount due to the long length of curve line.Based on the above vehicle-track dynamic interaction model and solution method,the corresponding calculation program is compiled,and the calculation accuracy of the proposed model is verified by the commercial software SIMPACK,which provides a means for further research on wheel-rail matching relationship and rail profile optimization on curve.(3)The asymmetric design optimization method of rail profile on curve is studiedConsidering the asymmetric wheel-rail contact points distribution of inner and outer rail on curve,an asymmetric design optimization model of rail profile in curve section is established by using multi-point approximate optimization theory with rolling radius difference curve as objective function.In the model,B-spline function is used to construct rail profile,and wheel-rail contact algorithm and regression analysis method are used to iteratively solve the optimized profile,and corresponding calculation program is compiled.By adjusting the optimization scheme,several groups of rail profiles matching the worn wheel profile are obtained,so as to improve the poor wheel-rail matching relationship,and provide the basis for the next step of rail profile comparison.(4)Rail profile optimization based on rail wear analysis on curveWith the dynamic interaction theory of vehicle and track,non-Hertz rolling contact theory based on virtual penetration and Archard wear model,a rail wear prediction model which can calculate the three-dimensional distribution along the longitudinal and lateral direction of rail is established,and the corresponding calculation program is compiled.Based on the wear prediction model,the wear depth distribution of different optimized rail profiles and the influence of wear on the wheel rail matching relationship are analyzed on the curve with a radius of 650 m.According to the analysis results,the optimum rail profiles on the curve are determined,and the rail service status is integrated into the profile optimization.(5)Research on the evolution characteristics of rail wear on curve considering the influence of off-balance superelevation and non-uniform velocity distributionBased on the rail wear prediction model,the wear distribution of different rail cross sections is calculated by using specific sampling-superposition and smooth updating strategies.Based on this method,the optimization effect of the optimum rail profile is verified.At the same time,the wear evolution characteristic of the worn rail profile and the optimum rail profile and its influence on the vehicle-track dynamics are discussed under the condition of off-balance superelevation and non-uniform velocity distribution based on triangular probability density function.The results show that the rail wear light band is basically straight along the longitudinal direction of the track,and the rail wear on the circular curve is greater than that on other positions of the curve;the rail wear is unevenly distributed along the longitudinal direction of the track due to the existence of random irregularity of the track;the state of deficient superelevation is more helpful to reduce rail wear than that of surplus superelevation;compared with the single speed passing,the non-uniform speed passing can significantly improve the rail wear uniformity along the longitudinal direction of the track,and greatly enhance the stability of the vehicle;rail wear has a significant impact on the wheel-rail contact geometry,which aggravates the problem of poor wheel-rail matching on the worn rail profile,while the wheel-rail contact characteristics of the optimum rail profile remain appropriate;with the increase of rail profile updating times,the average contact area and the average maximum contact stress of the optimum rail profiles gradually tend to be stable,which is more conducive to rail health service;In the actual operation of metro,the rail wear rate can be reduced to a certain extent by adopting the high speed dominant non-uniform speed control mode in the peak and low peak periods.