Journal of Nondestructive Evaluation

, Volume 12, Issue 4, pp 199–207 | Cite as

Crack detection in conducting materials using SQUID magnetometry

  • Ronald R. Gans
  • R. M. Rose
Article

Abstract

A highly sensitive multichannel SQUID gradiometer, optimized uniquely for spatial resolution, was used to map in two dimensions the magnetic field perturbations from circular holes and thin slots in conducting plates and strips, respectively. Holes as small as 0.75 mm radius in electrically conducting plates were measured directly using a single channel. Edge slots as short as 0.5 mm long in conducting strips were detected, using a multiple-channel measurement method which eliminated the effects from the edge of the strip and the current leads. Clear magnetic signatures from these simulated cracks were measured using low current densities. Numerical computations of the theoretical field distributions are presented which confirm the experimental results. Calculations indicate that much smaller defects should be detectable with an optimization of test parameters.

Key words

Crack detection NDE SQUID magnetometry magnetic methods current perturbation 

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References

  1. 1.
    Robert C. McMaster, Paul McIntire, and Michael L. Mester, eds.,Nondestructive Testing Handbook, 2nd ed. (American Society for Nondestructive Testing, 1986).Google Scholar
  2. 2.
    A. P. Rogel and J. J. Scalese, Automatic eddy current bolt-hole scanning system,Mater. Eval.,41 (7):839–843 (1983).Google Scholar
  3. 3.
    R. E. Beissner, C. M. Teller, G. L. Burkhardt, R. T. Smith, and J. R. Barton, Detection and analysis of electric-current perturbation caused by defects, inEddy-Current Characterization of Materials and Structures, ASTM STP 722, G. Birnbaum and G. Free, eds. (American Society for Testing and Materials, 1981), pp. 428–446.Google Scholar
  4. 4.
    G. L. Burkhardt, F. N. Kusenberger, and R. E. Beissner, Electric current perturbation inspection of selected retirement-for-cause turbine engine components, inReview of Progress in Quantitative Nondestructive Evaluation, Vol. 3B, D. O. Thompson and D. E. Chimenti, eds. (1983), pp. 1377–1387.Google Scholar
  5. 5.
    H. Weinstock and M. Nisenoff, Nondestructive evaluation of metallic structures using a SQUID magnetometer, inSQUID '85, H. D. Hahlbohm and H. Lubbig, eds. (de Gruyter, Berlin, 1985), pp. 853–858.Google Scholar
  6. 6.
    B. J. Roth, N. G. Sepulveda, and J. P. Wikswo, Jr., Using a magnetometer to image a two-dimensional current distribution,J. Appl. Phys.,65:361–372 (1989).Google Scholar
  7. 7.
    Y. P. Ma and J. P. Wikswo, Jr., Detection of a deep flaw inside a conductor using a SQUID magnetometer,Rev. Prog. Quant. Nondestr. Eval.,11A:1153–1159 (1992).Google Scholar
  8. 8.
    J. P. Wikswo, Jr., J. van Egeraat, Y. P. Ma, N. G. Sepulveda, D. J. Staton, S. Tan, and R. S. Wijesinghe, Instrumentation and techniques for high-resolution magnetic imaging. inDigital Image Synthesis and Inverse Optics, Vol. 1351, A. F. Gmitro, P. S. Idell, and I. J. LaHaie, eds., (1990), pp. 438–470.Google Scholar
  9. 9.
    J. P. Wikswo, Jr., N. G. Sepulveda, Y. P. Ma, W. P. Henry, D. J. Staton, and D. Crum, An improved method for magnetic identification and localization of cracks in conductors,J. Nondestr. Eval.,12:109–120 (1993).Google Scholar
  10. 10.
    A. D. Hibbs and T. Altshuler, Final Report: Ultra-Sensitive Magnetic Measurement System To Evaluation Corrosion, presented to Naval Surface Warfare Center, Contract N60921-89-C-0028.Google Scholar
  11. 11.
    N. G. Sepulveda, D. J. Staton, and J. P. Wikswo, Jr., A mathematical analysis of the magnetic field produced by flaws in two-dimensional current-carrying conductors,J. Nondestr. Eval.,11:89–101 (1992).Google Scholar

Copyright information

© Plenum Publishing Corporation 1993

Authors and Affiliations

  • Ronald R. Gans
    • 1
  • R. M. Rose
    • 2
  1. 1.Massachusetts Institute of TechnologyCambridge
  2. 2.Materials Science and EngineeringMassachusetts Institute of TechnologyCambridge

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