Research Of Crack Detection System Based On Acoustic Emission

Pump head body, as the core component of oil exploitation equipment, is not only working under an alternating high voltage loads, but also withstanding the erosion of the working medium. What's more, in order to work in conjunction with fracturing pump truck, its size and weight are limited. So the pump head body is prone to early failure.While there is no room for improvement in the size and the structure design, so choosing better materials seems to be the key means to solve the problem of early failure of the pump head body.The aim of the research was to provide more effective basis for material selection to solve the problem of early failure of the pump head body.The acoustic emission crack detection system was designed based on the acoustic emission technology. Acoustic emission testing technology has high sensitivity to early cracks,and it is able to detect the AE signals of the inside early failure of the material.In addition,by using this testing technology,continuous monitoring can be realized during the entire process, which is very suitable for the research of material failure of the whole process.This paper introduced the basic theory of acoustic emission testing technology, and emphatically introduced the self-designed acoustic emission detection system and the research results.In terms of hardware,the acoustic emission detection system was based on high-speed data acquisition card to realize continuous AE signals acquisition. In terms of software, with the mixed programming of VB and MATLAB, the system realized the function of basic operation controlling and data processing. From several experiments, the acoustic emission detection system collected the AE signals of actual pump head material under the high pressure. After the analysis of AE signals, some important conclusions were found.Results have shown that: the self-designed acoustic emission crack detection system can effectively identify and extract AE characteristics of the pump head materials from the fatigue crack initiation period to the whole propagation process. After signals processing and analysis by fast Fourier transform and wavelet transform,it proved that the frequency of fatigue cracks was in the high frequency band,almost above 200 k Hz. By wavelet decomposition and restructuring,the variation law of energy coefficients of different layers could reflect the characteristics of fatigue cracks during the whole experiment. In conclusion,with the acoustic emission detection system,it was effective to get the law of material failure and provide reliable experimental basis for the material selection.