| In many areas of our country,the rails inevitably pass through unattended sandy areas,and the sand covering the rails will cause safety problems such as train derailed.Therefore,the detection of the degree of desertification of the rails has always been a hot issue of railway safety.For the study of this problem,although human inspection,optical or statistical methods of sand volume can be used to detect it,however,human inspection is timeconsuming and laborious,and optical means are difficult to detect around the clock due to factors such as climate,and the method of statistical sand volume cannot accurately reflect the degree of desertification of the rails,so it is necessary to study a desertification detection method that is easy to implement and can work around the clock.This paper studies the scattering characteristics of the rail desertification model in the electromagnetic field through the electromagnetic modeling of the desertification problem.On this basis,it explores the feasibility of detecting the rail desertification by monitoring the electromagnetic wave echo characteristics of the rail.Therefore,the main contents of this paper are as follows:Firstly,the basic knowledge involved in the electromagnetic scattering problem of rail desertification is studied,and the modeling method of random rough surface,the modeling of the dielectric constant of sand dunes and the modeling of the dielectric constant of concrete are systematically discussed.Secondly,the paper analyzes the influence of the degree of desertification on the electromagnetic echo of the rails through the comparison of actual measurement and simulation.Metal plate and sand were placed on the outdoor ground to carry out the simulation measurement experiment of rail desertification.Echo signals of metal plate,part of metal plate covered by sand and all metal plate covered by sand were respectively measured under different polarization modes.It was found that sand had a great influence on the echo of metal plate under vertical polarization,and with the increase of the degree of desertification,the electromagnetic echo of metal plate also increases,and the echo shows a trend of attenuation with the increase of desertification.In the same experiment scene,the echo of electromagnetic wave transmitted by the antenna during the simulation of metal plate desertification also has a attenuation trend.The feasibility of using electromagnetic wave to detect the degree of rail desertification is verified by comparison between actual measurement and simulation.Then,the law of the influence of different degrees of rail desertification on electromagnetic waves is analyzed through simulation experiments.The modeling and electromagnetic scattering characteristics of rails and rail desertification were carried out by using the fullwave simulation software CST Microwave Studio.In the research,when electromagnetic waves of different frequencies are irradiated,the scattering characteristics of the rail itself on electromagnetic waves in different angular domains and the scattering characteristics of the rail under different degrees of desertification are analyzed.The law of the influence of the degree of desertification on the reflection electromagnetic waves is summarized,and the suggestions for the detection of rail desertification are put forward.Finally,the near-field characteristics analysis of rails and sandy rails under electromagnetic wave irradiation is carried out.The color map changes of electric field distribution and power flow distribution of different desertification degrees are analyzed,and the reasons for the changes of far-field electromagnetic scattering characteristics of different desertification degrees are revealed from these phenomena. |
