Journal of Korean Society of Disaster and Security (한국방재안전학회논문집)

Korean Society of Disaster & Security (한국방재안전학회)
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Analysis of Magnetic Flux Leakage based Local Damage Detection Sensitivity According to Thickness of Steel Plate

누설자속 기반 강판 두께별 국부 손상 진단 감도 분석

  • Kim, Ju-Won (Sch. of Architectural Engineering and Landscape Architecture, Sungkyunkwan Univ.) ;
  • Yu, Byoungjoon (Dept. of Convergence of Engineering for Future City, Sungkyunkwan Univ.) ;
  • Park, Sehwan (Dept. of Convergence of Engineering for Future City, Sungkyunkwan Univ.) ;
  • Park, Seunghee (Sch. of Civil. Architectural Engineering and Landscape Architecture, Sungkyunkwan Univ.)
  • 김주원 (성균관대학교 건설환경공학부) ;
  • 유병준 (성균관대학교 미래도시융합공학과) ;
  • 박세환 (성균관대학교 미래도시융합공학과) ;
  • 박승희 (성균관대학교 건설환경공학부)
  • Received : 2018.11.21
  • Accepted : 2018.12.24
  • Published : 2018.12.31
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Abstract

To diagnosis the local damages of the steel plates, magnetic flux leakage (MFL) method that is known as a adaptable non-destructive evaluation (NDE) method for continuum ferromagnetic members was applied in this study. To analysis the sensitivity according to thickness of steel plate in MFL method based damage diagnosis, several steel plate specimens that have different thickness were prepared and three depths of artificial damage were formed to the each specimens. To measured the MFL signals, a MFL sensor head that have a constant magnetization intensity were fabricated using a hall sensor and a magnetization yoke using permanent magnets. The magnetic flux signals obtained by using MFL sensor head were improved through a series of signal processing methods. The capability of local damage detection was verified from the measured MFL signals from each damage points. And, the peak to peak values (P-P value) extracted from the detected MFL signals from each thickness specimen were compared each other to analysis the MFL based local damage detection sensitivity according to the thickness of steel plate.

본 연구에서는 강판에 발생한 국부적인 손상의 진단을 위해 강자성의 연속체 구조물에 적합한 비파괴진단 기법인 누설자속 기법을 적용하였다. 강판시편의 두께 변화에 따른 누설자속 기반 진단 기법의 민감도를 분석하기 위해 각각 다른 두께를 가지는 몇 가지의 강판시편을 준비하였고, 각각의 시편에 3가지 깊이의 인공결함을 가공하였다. 홀센서와 자화요크를 이용하여 일정한 자화밀도를 가지는 누설자속 센서헤드를 제작하여 강판시편으로부터 누설자속 신호를 계측하였다. 센서헤드로부터 수집된 자속신호의 품질향상을 위해 일련의 신호처리 과정을 거쳤으며, 각 손상지점으로부터 계측된 누설자속 신호의 확인을 통해 국부손상 감지의 가능성을 확인하였다. 강판두께에 따른 누설자속 기법의 손상감지 민감도의 분석을 위해 각각 다른 두께의 강판시편으로부터 검출된 MFL 신호에서 P-P value를 정량적으로 추출하였고 그 값을 비교 분석 하였다.

Keywords

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Fig. 1. Principle of magnetic flux leakage method (Kim and Park, 2017)

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Fig. 2. Principle of Hall effect (Lenz, 1990)

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Fig. 3. Magnetic hysteresis curve (B-H curve) (Lacheisserie et al. 2005)

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Fig. 4. Permeability hysteresis curve (Shin, 1995)

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Fig. 5. Magnetic flux distribution according to magnetization level (Boat et al., 2014)

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Fig. 6. Signal processing process for noise reduction

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Fig. 7. Fabricated MFL sensor head

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Fig. 8. Specifications of steel plate specimen

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Fig. 9. Thickness of steel plate specimens

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Fig. 10. MFL signals from 2 mm thickness steel plate

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Fig. 11. P-P value according to damage depth

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Fig. 12. MFL signals from 5 mm thickness steel plate

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Fig. 13. MFL signals from 10 mm thickness steel plate

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Fig. 14. MFL signals from 5 mm thickness steel plate

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Fig. 15. P-P value of MFL signal according to thickness

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