| Wheel/rail matching equivalent conicity is one of the key parameters for evaluating wheel/rail geometric relationship,which can directly reflect the geometric contact relationship and dynamic performance of wheel/rail.Wheel profile abrasion performance and wheel turning strategy are also the key determinants of wheel operating economy.In order to evaluate the wheel/rail relationship and operation stability of China’s high-speed railway,the field tests research on the emu of China’s backbone lines was carried out.The results show that the wheel/rail relationship in served lines is generally good,but some of the served trains also have abnormal wheel/rail geometric matching relationship,as well as bogie instability alarm and carbody shaking caused by improper wheel/rail matching,which affect the safe and comfortable operation of high-speed railways.In order to study the generation mechanism of these problems and formulate corresponding measures,the paper carried out four research works:(1)Selection of calculation method of wheel/rail equivalent conicity and formulation of standards.The wheel/rail equivalent conicity can represent the high-speed wheel/rail geometric relationship and is the key parameter that can realize the wheel/rail geometric relationship to engineering control,that is,to repair the wheel by running state.There are 5 kinds of wheel tread shapes in served China’s high-speed emu(one of which is being tested),3 kinds of rail profiles,and leading a large number of wheel/rail matches.There are 10 kinds of calculation methods of wheel/rail equivalent conicity.It is necessary to unify the calculation methods of wheel/rail equivalent conicity as the basis of studying wheel/rail geometric relations.By comparing the equivalent conicity algorithm and calculation results,and combining the application status of the wheel/rail relationship in China,this paper determines the wheel/rail equivalent conicity calculation algorithm and formulates the equivalent conicity calculation standard which is suitable for China.At present,this standard has been used as the standard of railway industry.(2)Research on wheel/rail equivalent conicity value based on low-frequency abnormal vibration of emu trains.The bogie instability alarm of major high-speed railway lines,such as wuhan-guangzhou high-speed railway,beijing-shanghai high-speed railway and lanzhou-xinjiang high-speed railway,has occurred one after another,resulting in the slow operation of some EMU trains,even leading a stop on the main line,which has greatly affected the operation order.A special test was carried out in this paper,in which the alarm wheel was made into a force measuring wheel pair.The data of wheel and rail force during the alarm was successfully tested,and the characteristics of wheel and rail force during the alarm were extracted.By tracking the matching data of wheel/rail profile of the same intersect EMU train,it is proved that the overlarge equivalent conicity of wheel/rail contact is the main cause of bogie alarm.By statistical analysis and tracking test,the equivalent conicity interval of actual profile matching of wheel and rail is obtained,and the relation between vibration performance and equivalent conicity is also obtained.The number of bogie alarms is greatly reduced after the railway bureau repairs the wheels according to the equivalent conicity.In order to solve the problem of carbody shaking in the new wheel turning emus,the limit of turning equivalent conicity is put forward by means of the statistics of equivalent conicity,the analysis of the bad shape of treads and the analysis of the working condition of shaking.In this paper,the geometric characteristics of the wheel/rail equivalent conicity curve under different abrasion states are extracted by using the measured wheel/rail matching shape,and the lateral stability and ride comfort under different equivalent conicity curves are studied by using the vehicle dynamic model,so as to put forward the nonlinear parameters of equivalent conicity and the new wheel/rail equivalent conicity index.This index can reflect the characteristics of equivalent conicity curve in 1mm-6mm,and the nonlinear characteristics of equivalent conicity curve.The nonlinear equivalent conicity is more appropriate to reflect the wheel/rail contact relationship under wear condition.(3)Wheel tread optimization design.LMB tread(formerly known as S1002CN or S1002G)is the shape of wheel tread designed for CRH3 emu unit.The line adaptability is not strong,and the large equivalent conicity at the end of the repair cycle can easily trigger the large hunting motion of bogie.The profile of LMB wheel tread under different wear conditions was counted,and the geometric features of the profile in service were extracted to determine the optimization area.Non-uniform b-spline expression profile was adopted,and the shape of the wheel/rail root and the wheel/rail interaction area was optimized by using the genetic algorithm.The objective of optimization was based on the equivalent conicity and vehicle stability:the initial equivalent conicity at the rolling circle was between 0.10 and 0.12,the thickness of the wheel flange was 32mm,and the cycle of wheel repair was not less than LMB tread(more than 250,000 km).The optimization results show that the newly designed tread should be able to inherit the dynamic safety of LMB tread,and generate a large radius difference after the wheelset traverses 6～10mm to ensure the curve passing performance and vehicle stability.The newly designed tread meets the requirements of running stability and stability,and its dynamic performance is better than that of LMB tread.(4)Develop the shape of series of thin wheel flange to solve the problem of body instability after wheel turning.After the wheel turning repair of some emu units in beijing-tianjin inter-city operation,some emu units have the problem of carbody instability,and the wheel and rail geometric matching relation and vibration characteristics of the wheel body instability are obtained through tracking test.Through theoretical analysis and experimental verification,it is determined that the low equivalent conicity of wheel/rail is the main reason for the carbody instability.Finally,through simulation calculation,repair verification and line test,it is concluded that the reason for the low equivalent conicity of wheel and rail after repair is the improper lathe repair strategy.In this paper,the shape of a series of thin wheel flange is designed for the emu and the rotary repair bed in China.The results of line examination show that the emu with thin flange shape restored the operation stability and stability,and the economy of repair was guaranteed,and the first normative document of repair of thin flange was formed.This paper focuse on the problems occurred in the served process of the wheel treads of emu trains in China.From the perspective of wheel/rail matching equivalent conicity,it puts forward the formation mechanism of bogie alarm and carbody shaking,and formulates the limit value of equivalent conicity of in-service wheel/rail and the limit value of equivalent conicity of turning repair to provide support for wheel state repair.LMB tread was optimized to reduce wheel wear and improve bogie stability.The shape of the thin flange was worked out and the turning strategy was optimized.At present,two measures,equivalent conicity limit and thin flange shape,have been widely used.The paper innovatively puts forward the judging index of wheel/rail equivalent conicity curve and corrects the nominal equivalent conicity value.The equivalent conicity calculation method completed by the author has formed a railway industry standard(official edition cloth).At present,interim technical specifications for thin flange appearance of emu are compiled and technical review is organized. |
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