Title :
Removal of Probe Liftoff Effects on Crack Detection and Sizing in Metals by the AC Field Measurement Technique
Author :
Amineh, Reza K. ; Ravan, Maryam ; Sadeghi, S. H Hesamedin ; Moini, Rouzbeh
Author_Institution :
1 Dept. of Electr. & Comput. Eng., McMaster Univ., Hamilton, ON
Abstract :
In the alternative current field measurement (ACFM) technique, the nonzero value of liftoff distance for the magnetic sensor acts as a low-pass filter on surface crack signals, causing errors in crack detection and sizing. We present a blind deconvolution algorithm for liftoff evaluation and surface crack signal restoration. The algorithm employs the available closed-form expressions for the distribution of electromagnetic fields at the metal surface in the vicinity of a crack. To examine the accuracy of the algorithm, we use the original and the restored signals for crack sizing by a wavelet network inversion method. We present simulated and experimental results to demonstrate the role of the proposed algorithm in improving the inversion process.
Keywords :
electric field measurement; low-pass filters; magnetic sensors; nondestructive testing; surface cracks; ACFM; alternative current field measurement technique; blind deconvolution algorithm; crack detection; electromagnetic fields; inversion process; low-pass filter; magnetic sensor; metals; nondestructive evaluation; probe liftoff effects; surface crack signal restoration; AC field measurement; crack sizing; deconvolution; liftoff; nondestructive evaluation;
Journal_Title :
Magnetics, IEEE Transactions on
DOI :
10.1109/TMAG.2008.923393