| As one of new dynamic Nondestructive Testing methods, Acoustic Emission (AE for short) technique has been used widely in petroleum and chemical industry, electric power industry, material examination, civilian engineering, spaceflight and aeronautic industry, metallic machining and transportation industry etc. AE instruments have developed from early Parameter type to current Full Wave-form type. For the moment, the manufactures of AE instruments in our country mostly are Parameter type, and Digital AE instruments take up a fat lot. Yet in the overseas, AE instruments have developed the advance level of extremely high speed, full digital, full waveform, multi-passages and strong anti-interference. But these superior instruments are difficulty to popularize and use widely in our country because of their expensive prices, discommodious operation and maintain, untimely after service. Therefore, the application of AE technique is limited greatly.This thesis introduces firstly the present development situation of AE instrument, the analysis methods of AE signal, the signal characteristics of rock AE, and aiming at the low frequency of rock AE, a kind of scheme of signal sampling and process base on the sound card of multi-media computer is put forward; In succession, the thesis shows the development course of AE technique, the application scope of rock AE and testing process of AE, explains the conception and characteristics of virtual instrument(VI for short), analyzes the feasibilities of sound card substitute for data sampling card and constructs the system structure of virtual instrument of AE. Afterwards this paper introduces the general software structure and the process of design and implement of performance modules of virtual instrument from the degree of programming; At last it discusses the principle of AE source location and constructs the hardware structure of locating via multi-passages switch and parallel port of computer.Base on the platform of Visual C++, author develops the virtual instrument of full wave-form digital AE, carries out the modules of signal sampling, wave-form display of real-time sampling and wave file, management of data, alarm beyond limit, and the settings of parameters etc, realizes the extraction of characteristic parameters from data flow and the measurement of speed between two points. Consequently, theVI is provided with the functions of monitoring and analysis of AE source,simultaneity the function of assistant AE source locating .The VI system takes on thecharacteristics of low price, convenient operation, good compatibility and strongexpansibility, so it is applicable in any computer with sound card and reliable inperformances. |
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