Eddy Current Imaging Reconstruction And Parameters Estimation Of Defect

Eddy current defect imaging technology can obtain the information of defect profile and shape intuitively.It has an advantage of good visibilty.Also it can describe defect better quantitatively.Imaging technology become an important development trend of eddy current nondestructive testing(NDT).In this paper,fundamental questions of defect information extraction,defect imaging method based on C scan,defect imaging method based on non-scan array GMR and defect parameters estimation are studied.The main contents are follows:The fundamental questions of defect information extraction are studied.The theoretical analysis and simulation results show that the signal detected along the direction perpendicular to the surface of tested specimen can reflect the defect edge more accurately.The signal fusion method based on orthogonal excitation is studied.The complete profile of defect is obtain using larger value fusion method.The rectangle excitation coil for C scan is optimization by simulation.Then probe is designed through sloving the parameter optimization formula.The defect image of C scan is obtained by experiment using eddy current testing(ECT)platform based on GMR sensor.In this study,a defect parameter estimation method combining image processing is proposed.The processed image can show the size and shape of defect more intuitively.The quantitative description is more accurate.For defects long-term monitoring,a non-scan probe based on GMR array and orthogonal excitation is designed.The image super-resolution reconstruction technique is introduced to extend the detected data.Meanwhile,error of expansion data is studied.The experimental results show that reconstructed data is more intuitive and more conducive to quantitative description.The defect depth information estimation method is studied in this paper.The magnetic field direct problem of ideal defect in rectangular coil excitation and phase of defect signal is derived.For surface defect and subsurface defect,magnetic field information on conductor surface and phase information of defect signal is calculated through iteratively solving inverse problem to estimate the depth information of defect.The calculation step is given.