Research On Propogation Simulation Of Ultrasonic Waves And Flaw Testing Method In Rails

Abstract:As railroad in our country being developed in the direction of high-speed and heavy haul, the quality of rails becomes very important, and much attention has been paid to non-destructive testing flaws in rails. However, there are some disadvantages in traditional flaw testing method in rails, such as testing area could not cover all the rails, and the effective testing area of the transducer was not clear enough. In this thesis, the propagating ultrasound waves in rails are researched, and it will help provide theory and method guidance for nondestructive ultrasonic testing for rails.The multi-Gaussian beam theory is used to model the ultrasonic sound field, and calculate the sound pressure generated by rectangular and circular plane transducers. The characters of reflected and transmitted beams are analyzed which are generated by incident beam strokes interface of different kinds of media in different angles, and it is researched how the curve interfaces affect the propagating beams. Then the multi-Gaussian beam model for multi-layered media is obtained, which could help calculate the sound field in multi-layered media quickly.The propagating ultrasound fields radiated into rails by transducers are researched based on the built multi-Gaussian beam model. In order to test different kinds of flaws in different areas of rails, circular and rectangular plane transducers are selected. The sound fileds changes by the railhead surface can be known through the simulation of radiation beams in rails. And also it can help analyze the blind and effective testing area of transducers when they are placed in different positions. All of these are used to guide to design the testing technology for rails.In order to verify the effectiveness of this method, the rails flaw testing system is designed, including the experiment equipments and the testing software. In equipments, some are designed, such as rail sample, and some are selected, such as transducers and coupling agent. The testing software is designed and finished with VC++and MATLAB hybrid programming method. It contains these basic functions, including ultrasonic data acquisition and display, automatic scan testing for rails, ultrasonic B-imaging and flaw signals analysis, and so on. With this software, the rails can be tested rapidly.At last, the experiments of ultrasonic testing for rails are conducted based on the designed scheme and system. The results show that the flaws within the effective area of the transducers in rail head, rail waist and rail flange can be tested efficiently. What has been done shows it is an effective method to test flaws in rails comprehensively and accurately using simulation of ultrasonic waves propagation in rails to guide flaws testing.