Research On Relationship Between Higher-order Modes And Temperature Force Of Continuously Welded Rail

With the increase of train speed,in order to satisfied the requirements of driving safety and operational stability,Continuously Welded Rail is widely used in our country.Since the Continuously Welded Rail is firmly fixed on the track bed by the fasteners,Its cannot expand and contract freely,Temperature force will be generated inside the steel rail.If the temperature is too high,there is a risk of rail breakage or runway.The existing temperature force measurement method cannot accurately measure the absolute value of the rail temperature force in a local section.How to accurately measure the temperature force inside the rail has become a major issue that the railway department urgently needs to solve.This paper studies the mapping relationship between the high-order vibration modes of the rail and the temperature force based on the vibration characteristics of the rail.The main research contents are as follows:(1)The rail-fastener-rail slab finite element model is established and the change rule of rail parameters to the single-order modal of rail is theoretically studied.The influence of different parameters on the single modal of rail is studied.Through theoretical analysis of the relationship between typical frequency and temperature force,fastener spacing,fastener stiffness and elastic modulus.The results show that there is a linear relationship between the rail modal and the temperature force,the temperature increases,the frequency decreases;the fastener spacing,fastener stiffness and rail elastic modulus will all affect the rail modal.The modal frequency change caused by the elastic modulus is the largest,followed by the modal frequency change caused by the fastener spacing,and the modal frequency change caused by the fastener stiffness is the smallest.(2)The relationship between the statistical characteristics of multi-order frequency changes in the range of 500Hz-3000Hz and the track parameters are theoretically studied.Through theoretical analysis of the influence of constant track parameters and normally distributed track parameters on the rail modal,The results show that the statistical characteristics of multi-order frequency changes can significantly reduce the influence of fastener spacing and fastener stiffness on the rail modal.The change of the elastic modulus of the rail will make the statistical mean value of the multi-order frequency change tend to be stable.(3)Derive the mathematical expressions for the confidence interval of the mean value and variance of the track natural frequency based on Bayesian.Assuming that the measured frequency obeys the normal distribution,the frequency variance obeys the inverse gamma distribution,the mean value is the normal distribution with the variance as the conditional probability,The mathematical expressions of the mean value and the variance are derived based on the Bayesian framework.Both simulations and experiments show that the use of the obtained formula can improve the accuracy of parameter estimation and accurately measure natural frequency of the track under the condition of a small sample.(4)The experiment researches the feasibility of the method of measuring the locked rail temperature by using the statistical characteristics of the high-order modal of the rail.By carrying out stretching and sunshine experiments on the rail comprehensive experimental platform,the results show that the statistical characteristics of multi-order frequencies can offset the influence of track parameters on frequency.There is a linear relationship between the multi-order frequency average value and the temperature force,and the linear sensitivity coefficient is 0.7Hz/?.The theories and experiments in this paper prove that the influence of rail parameters on modal changes can be ignored by using the statistical characteristics of high-order modes of rails and the rail lock temperature is measured,The method proposed in this dissertation clarifies the effective technical way to solve the problem of Continuously Welded Rail temperature force measurement,which has great engineering application value.