Research On Eddy Current Detection System And Defect Signal Processing

Eddy current nondestructive testing is widely used in modern industry, it can detect the surface and near surface defects. In practical application of eddy current detection, it mainly relies on the human judgment of eddy current impedance signals, lacking of intelligence and automation in testing. To improve the accuracy of eddy current testing and automation level is great significant for defect depth localization and classification of the eddy current testing.In order to improve the signal-noise-ratio of the eddy current signal, it makes comparative of the wavelet denoising and wavelet packet denoising, and it is concluded that wavelet packet is better for denoising. Aim at the defect depth localization and classification problems, one dimensional amplitude method for the impedance signal was proposed, which extracts two characteristics of peak and peak time on this basis, this method improve the reliability of defect depth localization and classification. By extracting the characteristics of multiple sets of experimental data, the matching curves is gotten, and the defect depth calibration function can realize the defect depth location problem. It can classify defects by comparing the characteristic method, the principal component analysis method and based on principal component analysis of the characteristics, through the analysis and calculation, the characteristic method based on the characteristics of the principal components can better realize the classification of defects.Based on SMATR-2005 eddy current testing instrument produced by Xiamen EDDYSUN Electronics Company, taking computer as the core, with the aid of LABVIEW and MATLAB software, eddy current detection system was developed, which main functions include signal collection and display, signal denoising, feature extraction, defect classification and depth positioning, etc.Aluminum alloy samples with artificial defects were made for verifying denoising,positioning and quantitative function of the, developed eddy current testing system, the results showing that validity, adaptability and reliability of the system.