Abstract
We examine the magnetic field produced by small flaws in a two-dimensional, conducting plate carrying an otherwise-uniform current. We use a conjugate function approach to calculate the current and voltage distributions about the circular and elliptical flaws in the conducting plate, and examine the dependence of the normal component of the magnetic field upon distance, hole size, elliptical eccentricity, and elliptical orientation. We show that when the field is calculated, far from the hole, the field falls off as 1/z 3, wherez is the distance above the plate, and as 1/r 2, wherer is the distance from the center of the hole to the observation point. We also show that for circular and elliptical flaws, the normal component of the magnetic field in the far-field region is linearly related to the area of the flaw.
Similar content being viewed by others
References
H. Weinstock and M. Nisenoff, Nondestructive evaluation of metallic structures using a SQUID gradiometer, inSQUID '85, H. D. Hahlbohm and H. Lubbig, eds. (De Gruyter, Berlin, 1985), pp. 843–847.
J. P. Wikswo, Jr., J. M. 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. (SPIE Proceedings, 1990) pp. 438–470.
J. P. Wikswo, Jr., N. G. Sepulveda, Y. P. Ma, D. J. Staton, W. P. Henry, and D. Crum. An improved method for magnetic identification and localization of cracks in conductors.J. Nondestr. Eval. 12 (in press).
D. H. Michael, P. G. Williams, F. Toufic, and R. Collins. Surface distributions for eddy current problems,Rev. Prog. QNDE 5A:259–269 (1986).
M. R. Spiegel,Theory and Problems of Complex Variables, with an Introduction to Conformal Mapping and Its Applications (Schaum Publishing Co., New York, 1964).
L. V. Bewley,Two-Dimensional Fields in Electrical Engineering (Dover Publications, New York, 1963).
J. P. Wikswo, Jr., The calculation of the magnetic field from a current distribution: Application to finite element techniques,IEEE Trans. Magnet. MAG-14:1076–1077 (1978).
J. D. Jackson,Classical Electrodynamics (John Wiley & Sons, New York, 1975).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Sepulveda, N.G., Staton, D.J. & Wikswo, J.P. A mathematical analysis of the magnetic field produced by flaws in two-dimensional current-carrying conductors. J Nondestruct Eval 11, 89–101 (1992). https://doi.org/10.1007/BF00568292
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF00568292