Study On Representative Profile Of Rail Based On Wheel Rail Contact

With the development of railway transportation in China,especially the rapid development of high-speed railway in recent years,rail damage has become a major problem that can not be neglected in railway operation,which seriously affects the safety and stability of train operation.Rail grinding is one of the effective strategies to solve the problem of rail damage,a large number of practical experiences in the United States,Japan,Australia and many other countries prove that rail grinding plays an important role in decreasing rail damage,improving traffic quality,prolonging rail service life,reducing the railway maintenance cost and other aspects.Since the development of rail grinding in China started late,there is still a big gap compared with the developed countries.At present,the grinding equipments used in China mostly depend on imports,and there is no unified mode and standard of rail grinding.Therefore,it is necessary to carry out research on rail grinding technology and promote the development of grinding technology in China.The representative profile is an important research direction in rail grinding,which has high practical value in the optimization of rail profile and the determination of grinding quantity and grinding mode.However,the current research on the representative profile is very scarce.The main goal of this thesis is to explore the calculation method and evaluation standard of the representative profile,to fill the gaps in the research of representative profile and provide a reference for the follow-up studies.This thesis puts forward the research method of representative profile based on wheel rail contact,and the calculation methods and evaluation indexs of representative profile are analyzed.Firstly,in view of the problems of noise interference and position difference in measured rail profile,the pre-processing algorithms such as smoothing filtering and profile alignment methods of the measured data are compared and analyzed,thus the pre-processing scheme of rail profile is determined,that is to use the Savitzky-Golay method to smooth,and use the straight line on the sides of railhead as the alignment reference.Secondly,four representative profile algorithms are designed,such as least square distance method,arithmetic average method,weighted average method and scatter reconstruction method,and according to these algorithms,the representative profiles of two groups of measured profiles on the straight line and curve line are calculated.Then,based on the wheel rail contact geometry and the probability distribution of the contact point,the similarity of the wheel rail contact relation of the representative profiles and the measured profiles is analyzed.Finally,the safety and stability indexes of the vehicle on the straight line and the small radius curve are calculated and compared by using the truck dynamic model based on the representative profiles and measured profiles of the rail.The results show that no matter on a straight line or a curve line,the contact geometry similarity between the measured profile group and the representative profiles of the arithmetic average method and the scatter reconstruction method can mostly reach the medium correlation or strong correlation level,while the similarity between the representative profiles and part of measurement profiles for the least square distance and weighted average method can only reach the weak correlation level.After further comparison,results show that the contact geometry similarity of the arithmetic average method is the highest,followed by the simiarity results of the scatter reconstruction method,while the results of weighted average method and least square distance method are both relatively poor.In addition,by dynamic simulation and analysis,the orbital dynamics performances of the representative profiles obotained by the above four methods,such as the vertical and lateral wheel rail forces,derailment coefficient,wheel unloading ratio and the lateral force of wheelset,are close to the average trend of the corresponding performances of the measured profiles.