Design Of Ultrasonic Guided Wave Excitation Source For Rail Defect Detection

Ultrasonic guided wave detection widely studied by scholars at home and abroad.Compared with the traditional technology,ultrasonic guided wave has the characteristics of long distance and high speed.Also,it has been widely used in the field of rail defect detection.Research on ultrasonic guided wave detection signal of ultrasonic guided wave excitation is an important link in the detection.It is the premise of applying theory to practice.This thesis focuses on the application of ultrasound in rail guided wave detection technology,carried out the research from the theoretical research and practical development of two aspects,and put forward the main research significance of this topic.In theoretical research,we should focus on the basic theory of ultrasonic guided waves.It's including the phase velocity,the propagation characteristics of the guided wave in the wave guide medium rail by numerical finite element analysis method and group velocity dispersion and multi-modal characteristics.In the process of defect detection,the signal period and frequency band width and propagation distance of ultrasonic guided waves are important reference factors.But there are many disadvantages such as the propagation of guided waves is complex and the subsequent analysis is affected by the traditional broadband excitation.So it is very important to select the specific optimal excitation wave formit.Through the window function,the center frequency of the excitation waveform,signal cycle and the research on signal strength proposes a scheme to improve the waveform of the periodic time interval.In the actual development direction,the system development scheme which based on the specific parameters of ultrasonic guided wave excitation source is divided into two aspects: hardware design and software design.The hardware design of the system mainly includes the design of the peripheral circuit of the MCU,the design of the adjustable sine pulse signal,the design of the modulation signal,the design of waveform synthesis,the design of the power amplifier circuit and the design of the key display.From the high reliability and high accuracy and practical economic ideas,each design unit gives a detailed description of performance analysis,component selection,and circuit connection.The system software design mainly includes the main program design,the key processing design as well as the DDS chip programming flow.Software design is in line with the needs of users and has a good user experience.Finally,the use of the ultrasonic guided wave excitation source can be used to illustrate the appearance of the instrument.It is used to test and analyze the output waveform of the excitation source.At the same time,the developed excitation source is used to carry out the experiment.The experimental results show that the output signal has the advantages of high precision,low noise and good stability.