Research On The Key Technique Of Dynamic Detection Of Rail Based On Ultrasonic Guided Waves

With the development of society and the improvement of living standard,train,bullet train and high-speed railways are becoming the first choice for travel.Rail transport is widely used because of its cheap,efficient and other advantages.The important part of the railway transport system is steel rail,which performance determines the traffic efficiency,stability and safety of the train.Steel rail is composed of the rail head,rail web and rail bottom,and all parts may be damaged.Once failed to detect and deal with the damage in time,there will be disastrous consequences.Now,the existing detection techniques have their limitations,especially on the detection of rail web and rail bottom,which is difficult to find the damage.Thus,based on the above background,this paper presents the research on the key technique of dynamic testing of rail based on ultrasonic guided waves.In this dissertation,semi-analytical finite element method is applied to select suitable guided wave mode for railhead,rail web and rail bottom detection.By designing the methods of excitation and reception of each mode guided waves at orbital head to simulate and experiment the mechanism of the mode guided waves and the defect in rail head,rail web and rail bottom,we propose a method for steel rail detection with multi-mode guided waves.Besides,based on the new dynamic detection program of the rail guided wave,we also design and develop a set of rail track dynamic detection system which includes the hardware system,the software system,the special transducer and the mechanical structure,and so on.We use system prototype to detect the rail in the laboratory,realize the detection of defects in all parts of the rail and lay the technical foundation for the dynamic detection of rail ultrasonic guided waves.The main research contents are as follows:Chapter 1,the background and significance of the research is introduced.The significance of applying NDT technology or ultrasonic guided wave in rail is analyzed for the latest research and developing orientation.In the end,the rail defect detection with ultrasonic guided waves is raised.Moreover,the chapters of the dissertation are arranged.Chapter 2,the propagation characteristics of the guided wave are described in detail.The dispersion curve of the ultrasonic guided wave in the rail is obtained based on the semi-analytical finite element method.The wave structure of the ultrasonic guided wave in the rail is analyzed.And the guided wave modes that are suitable for the defects detection of the rail head,the rail waist and the rail bottom have been determined.The defect-free model of rail and the defect model in different places are established in ABAQUS software to analyze the feasibility of ultrasonic guided wave detection in rail head,rail waist and rail bottom.Chapter 3,a dynamic detection system of rail ultrasonic guided wave is established.This system includes four modules' design,,namely transducer design,hardware design,software design and vehicle body mechanical structure design.Chapter 4,we carry out the experimental research on the dynamic detection system of the rail ultrasonic guided wave,and analyze the detection ability of the ultrasonic guided wave on the real rail head,rail waist and rail bottom defects as well as the different types of defects.The detection sensitivity of the detection system developed in this paper is 3%,5%and 8%respectively for rail head,rail waist and rail bottom defects.It proves the feasibility and effectiveness of dynamic detection of rail guided wave.Chapter 5,the main work and conclusion were summarized and the prospect for future research was put forward.