Detection of back-side pit on a ferrous plate by magnetic flux leakage method with analyzing magnetic field vector

Keiji Tsukada, Mitsuteru Yoshioka, Yoshihiko Kawasaki, Toshihiko Kiwa

Research output: Contribution to journalArticle

24 Citations (Scopus)


We have developed a magnetic flux leakage (MFL) system using magnetic resistive (MR) sensors for detecting two dimensional magnetic field components, and an induction coil that generates low magnetic field strengths and extremely low frequencies. The signal at each scanned measurement point (i) was divided by the signal strength Mmes,i and phase αi by a lock-in amplifier. Using the strength Mmes,i and phase αi, we calculated the imaginary part of the signal using the common phase β. By optimization of the common phase β to the imaginary part, the analyzed scanning data curve was shown to be effective in estimating the size (depth and diameter) of back-side pits on a ferrous plate. Comparing the two dimensional magnetic field components of leakage, the imaginary part of the y-component parallel to the induced magnetic field was found to be suitable for detecting the back-side pits.

Original languageEnglish
Pages (from-to)323-328
Number of pages6
JournalNDT and E International
Issue number4
Publication statusPublished - Jun 1 2010



  • Low-frequency magnetic field
  • Magnetic flux leakage
  • Magneto-resistive sensor

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

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