The Design Of Eddy Current Detection System And Research On Signal Processing Algorithms

Eddy current detection technique that has been developing rapidly in recent years is akind of Non Destructive Testing (NDT) techniques. And Eddy current testing is a kind ofelectromagnetic measurement technologies based on electromagnet induction, it is also a kindof inspection techniques used to test the surface and near surface flaws of conductivecomponent. NDT recently has been widely recognized and applied in the field of NDT, suchas aviation, shipping and so on. Besides, NDT can quickly and accurately find the defects ofmetallic conductor, and make evaluations on electromagnetic properties of materials.This paper makes theoretical research on size detection of crack defect of rod-likematerial and other vital techniques on the basis of in-depth understanding on the developmentof eddy current testing technique at home and abroad. According to electromagnetictheoretical principle, the finite element simulation analysis of impedance characteristic andthe process that laminated coil eddy current sensor induces eddy current are made to supplytheoretical accumulation for the design of eddy current sensor.Detailed introduction of the design of special eddy current probe is made in connectionwith the geometric and physical characteristics of the test piece. This paper analyzes anddesigns every hardware part of eddy current testing system, including the design of incentivesource based on DDS principles, AC self-balancing bridge measurement circuit, dataacquisition circuit and gain control circuit. And graphical visualization software is developedby using LabVIEW software, which will facilitate the realization of system control, datatransmission, defect detection and simplified operation of display. These defects will bedisplayed in the form of a strip chart and impedance plan, and the test results are very clear.Finally, in order to test the reliability and accuracy of the system, this thesis usesdesigned hardware system to make defect detection experiment of various sizes of aluminumrod specimens. The experimental data is processed subsequently to improve the detection accuracy of the system. Then the optimal frequency of pumping signal is determined toprovide reference for other similar detection application through the multi-parameter fitting ofmeasurement data.