Magnetic field gradient as the most useful signal for detection of flaws using MFL technique

Zbigniew Usarek 1 , Marek Chmielewski 1 , and Leszek Piotrowski 1
  • 1 Faculty of Applied Physics and Mathematics, Gdansk University of Technology, Gdansk, Poland


The magnetic flux leakage (MFL) technique is extensively used for detection of flaws as well as for evaluation of their dimensions in ferromagnetic materials. However, proper analysis of the MFL signal is hindered by the MFL sensor velocity causing distortions of this signal. Traditionally measured components of the MFL signal are particularly sensitive to the scanning velocity. In this paper, an another signal – the gradient of the normal component of magnetic flux density – was proposed as it is less sensitive to the scanning velocity. Results obtained for scans of the steel plate with artificially manufactured flaws confirm this statement.

If the inline PDF is not rendering correctly, you can download the PDF file here.

  • [1] P. C. Porter, “Use of Magnetic Flux Leakage (MFL) for the Inspection of Pipelines and Storage Tanks”, Proc. SPIE 2454, Non-destructive Evaluation of Aging Utilities (1995), pp. 172–184.

  • [2] Z. Gan and X. Chai, “Numerical Simulation on Magnetic Flux Leakage Testing of the Steel Cable at Different Speed Title”, ICEOE 2011 - International Conference on Electronics and Optoelectronics, Proceedings, 2011, vol. 3, pp. 316–319.

  • [3] L. Zhang, F. Belblidia, I. Cameron, J. Sienz, M. Boat and N. Pearson, “Influence of Specimen Velocity on the Leakage Signal Magnetic Flux Leakage Type Nondestructive Testing”, J. Nondestruct. Eval. vol 34, no 6, 2015.

  • [4] G. S. Park and S. H. Park, “Analysis of the Velocity-Induced Eddy Current MFL Type NDT”, IEEE Trans. Magn., vol. 40, no. 2, pp. 663–666, 2004.

  • [5] L. Lei, C.Wang, F. Ji and Q.Wang, “RBF-Based Compensation of Velocity Effects on MFL Signals”, Insight-Non-Destructive Test. Cond. Monit., vol. 51, no. 9, pp. 508–511, 2009.

  • [6] S. Mandayam, L. Udpa, S. S. Udpa and W. Lord, “Invariance Transformations for Magnetic Flux Leakage Signals”, IEEE Trans. Magn. vol. 32, pp. 1577–1580, 1996.

  • [7] J. B. Nestleroth and R. J. Davis, “The Effects of Magnetizer Velocity on Magnetic Flux Leakage Signals”, Review of Progress Quantitative Nondestructive Evaluation vol. 12A and 12B, D. O. Thompson and D. E. Chimenti (editors), Boston, MA: Springer US, 1993, pp. 1891–1898.

  • [8] G. Katragadda, Y. S. Sun, W. Lord, S. S. Udpa and L. Udpa, “lVelocity Effects and their Minimization MFL Inspection of Pipelines – a Numerical Study”, Review of Progress Quantitative Nondestructive Evaluation, vol. 14, D. O. Thompson and D. E. Chimenti (editors), New York: Plenum Press, 1995, pp. 499–505.


Journal + Issues