Design And Research Of Ultrasonic Flaw Detection-Hardware Designing And Echo Processing

Recently, with the improvement of train speed and trainload, traffic safety on railway becomes more and more important. Accordingly, the demand of Non-Destructive Testing (NDT) is growing higher. In order to solve the problem of traditional inspection instruments which have low real-time processing capability and less intelligence, and meet modern industrial development on the requirements of inspection instruments which have high efficiency and real-time processing capability, an ultrasonic flaw detecting scheme and implementation method based on high-speed signal processing and intelligent controlling are proposed.The ultrasonic flaw detecting scheme proposed by this paper contains three modules: Ultrasonic receiving and sending circuit module, high-speed signal processing and intelligent controlling module, and keyboard controlling module. The second module is the most important part of the scheme, and it is divided into echo processing block and intelligent controlling block. After studying of the characteristics of ultrasonic echo, the echo processing block is designed based on Field-Programmable Gate Array (FPGA) and it contains digital filter and extreme value finding in cluster. Future more, the intelligent controlling block based on ARM microprocessor is proposed and it could meet the following requirements:Split-screen displaying, intelligent flaw detecting, automatic alarming, etc.The ultrasonic flaw detection scheme based on high-speed signal processing FPGA and core controlling ARM owns the following characteristics:Real-time signal processing, intelligent signal processing and terminal graphic displaying. Real-time signal processing is realized by using the processor whose frequency is higher than 100MHz and processing different channel data by time dividing, thus the processor could deal with the data of the latest channel completely before the new channel is selected. Intelligent signal processing can identify the following information by using signal-channel curve fitting:Screw, wire through hole, and section of the rail, etc. Terminal graphic display window is created by using QT, so users can get the results of A-type and B-type display at the same time. Experiments and statistical show that maximum horizontal linear error and vertical linear error are less than 0.97% and 4.9% respectively, the total attenuation of system is more than 80dB, the blocking range of the sensor is less than 15mm, while the restrain is minimum, the dynamic range of the system is not less than 20dB. When the standard testing block is used, the failure detection rate does not exceed 12.5%. System has the strong real-time processing capability and high reliability.