Forward and Inverse Processing in Electromagnetic NDE Using Squids

  • D. McA. McKirdy
  • A. Cochran
  • G. B. Donaldson
  • A. McNab


Electromagnetic NDE has been successfully applied to the detection of surface cracks and is routinely used to locate flaws in airframes, pipelines and in steel offshore oil platforms. However, there are still many problems to be solved, particularly in the aviation industry, which require the detection of deeper flaws such as corrosion in multi-layered structures and cracks around rivet holes which are obscured by the head of the rivet. Most systems use coils as detectors (though Hall probes are occasionally used), which have low sensitivity at low frequencies due to the fact that the induced voltage is proportional to the rate of change of magnetic flux through the coil. Unfortunately it is necessary to use low frequencies to detect deep subsurface flaws on account of the skin-depth effect, otherwise the electromagnetic field cannot propagate down to the depth of the flaw. SQUID (Superconducting Quantum Interference Device) sensors are ideally suited to overcome the deficiencies of coils, because they are primarily detectors of magnetic flux which, together with their high sensitivity, makes the detection of deep flaws more likely. SQUIDs have been successfully used for measuring very low magnetic fields, particularly in the field of biomagnetism, and it is hoped to exploit this sensitivity to detect flaws at large stand-off distances for example in pipelines which are surrounded by thick layers of cladding.


Magnetic Flux Deep Flaw Reciprocity Theorem Magnetic Field Data Transfer Impedance 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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  1. 1.
    A. Cochran, J. C. Macfarlane, L. N. C. Morgan, J. Kuznik, R Weston, L Hao, R. M. Bowman and G. B. Donaldson, IEEE Trans. Appl. Superconductivity, 4, 128 (1994).CrossRefGoogle Scholar
  2. 2.
    A. Cochran, C. Carr, D. McA. McKirdy, M. E. Walker, A. McNab, U.Klein, J. Kuznik, and G. B. Donaldson, in ENDE 95 Workshop Proceedings, ed. R. Collins (IOS Press, Amsterdam, 1995) in press.Google Scholar
  3. 3.
    P. Weidelt, J. Geophys. 41, 85 (1975).Google Scholar
  4. 4.
    A. P. Raiche, Geophys. J. Roy. Astr. Soc. 36, 363 (1974).Google Scholar
  5. 5.
    D. McA. McKirdy, J. Nondestr. Eval. 8, 45 (1989).CrossRefGoogle Scholar
  6. 6.
    J. R. Bowler, J. Appl. Phys. 75, 8128 (1994).CrossRefGoogle Scholar
  7. 7.
    D. H. Michael, A. M. Lewis, M. Mclver and R. Collins, Proc. Roy. Soc. Lond. A 434, 587(1991).CrossRefGoogle Scholar
  8. 8.
    C. V. Dodd and W. E. Deeds, J. Appl. Phys. 39, 2829 (1968).CrossRefGoogle Scholar
  9. 9.
    A. J. M. Zaman, C. G. Gardner and S. A. Long, J. Nondestr. Eval. 3, 37 (1989).CrossRefGoogle Scholar
  10. 10.
    B. A. Auld, J. C. Moulder, S. Jeffries, P. J. Shull, S. Ayter and J. Kenney, Res. Nondestr. Eval. 1, 1(1989).Google Scholar
  11. 11.
    R. E. Beissner and J. A. G. Temple, in Review of Progress in QNDE, Vol. 9, eds. D. O. Thompson and D. E. Chimenti (Plenum, New York, 1990), p. 257.Google Scholar
  12. 12.
    R. E. Beissner and J. S. Graves, in Review of Progress in QNDE, Vol 9, D. O. Thompson and D. E. Chimenti Plenum, New York (1990) p. 885.Google Scholar
  13. 13.
    P. A. Eaton, Geophys. Prosp., 37, 407 (1989).CrossRefGoogle Scholar
  14. 14.
    A. Marcuello-Pascual, P. Kaikonnen and J. Pous, Geophys. J. Int. 110, 297 (1992).CrossRefGoogle Scholar
  15. 15.
    D. Oldenburg, Surveys in Geophys. 11, 231 (1990).CrossRefGoogle Scholar
  16. 16.
    L. R. Lines and S. Treitel, Geophys. Prosp. 32, 159 (1984).CrossRefGoogle Scholar
  17. 17.
    S. J. Norton and J. R. Bowler, J. Appl. Phys. 73, 501 (1993).CrossRefGoogle Scholar

Copyright information

© Plenum Press, New York 1996

Authors and Affiliations

  • D. McA. McKirdy
    • 1
  • A. Cochran
    • 1
  • G. B. Donaldson
    • 1
  • A. McNab
    • 2
  1. 1.Department of Physics and Applied PhysicsUniversity of StrathclydeGlasgowScotland
  2. 2.Department of Electrical and Electronic EngineeringUniversity of StrathclydeGlasgowScotland

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