Improvement of MFL sensing–based damage detection and quantification for steel bar NDE
Ju-Won Kim,Minsu Park,Junkyeong Kim,Seunghee Park
Abstract
A magnetic flux leakage (MFL) method was applied to detect and quantify defects in a steel bar. A multi-channel MFL sensor head was fabricated using Hall sensors and magnetization yokes with permanent magnets. The MFL sensor head scanned a damaged specimen with five levels of defects to measure the magnetic flux density. A series of signal processing procedures, including an enveloping process based on the Hilbert transform, was performed to clarify the flux leakage signal. The objective damage detection of the enveloped signals was then analyzed by comparing them to a threshold value. To quantitatively analyze the MFL signal according to the damage level, five kinds of damage indices based on the relationship between the enveloped MFL signal and the threshold value were applied. Using the proposed damage indices and the general damage index for the MFL method, the detected MFL signals were quantified and analyzed relative to the magnitude of the damage increase.
Key Words
magnetic flux leakage; steel bar inspection; damage quantification; Hilbert transform; generalized extreme value distribution
Address
Ju-Won Kim and Seunghee Park — School of Civil, Architectural Engineering and Landscape Architecture, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 16419, Republic of Korea
Minsu Park and Junkyeong Kim — Department of Civil & Environmental System Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 16419, Republic of Korea
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