Study On Ultrasonic Testing Based On Virtual Instrument

As a kind of NDT(Non-Destructive Testing), UT(Ultrasonic Testing) is widely used in modern industry, which plays a very important role in improving the quality and the reliability of product. Although along with technical development in electronics, some digital UT instruments have been developed at home, its expandability and the ability of processing data is limited. VI(Virtual Instrument)is a new Instrument structure developed in recent years and is an outcome which combines the computer technique, the communication technique together with the measure technique, which has huge expandability, flexibility and the prosperous vitality. So a method of trying to conjoin the VI and the UT is brought out and a digital UT Device based on A type ultrasonic flaw detector has been made, which will be help to the further research on ultrasonic digital signal processing in future.The theory of ultrasonic and A type ultrasonic flaw detector are firstly introduced on chapter two for directing the design followed. Then a design of A type ultrasonic flaw detector is made. According to characteristics of probe, the request for ultrasonic activation circuit and the main influence factors are analyzed in detail and simulated with circuit emulation software PSpice. Aimed at the characteristics of UT, a receive and adjust circuit is designed, which have character of low noise, wideband, wide dynamic range of input . Taking that the frequency of ultrasonic signalis high into account, a high speed data acquisition circuit controlled by CPLD(EPM7128S) is designed and a new way of improving the frequency of data acquisition is made use of the special character of ultrasonic signal. Matching with MCI of the lingYang company, the interface of serial and network connected with the computer is brought out.The software design of CPLD makes full use of the mean of the Limit State Machine, which improves the reliability of software. The software of interface and the software based on VI are also designed. The VI development tool LabVIEW is introduced. The data process method of mean filter and the autocorrelation works well and the AVG curve fit well.By test, the system works well, showing the good future of combination of the UT and the VI.