Abstract
A theoretical model is derived for the prediction of eddy-current probe impedance changes caused by three-dimensional, surface-breaking flaws. Magnetic scalar potential theory and the surface impedance approximation are used to calculate fields on the flaw surface for arbitrary probe position and flaw geometry. Impedance changes are determined by a first-order perturbation calculation, with skin depth being the perturbation parameter. The end result is a relatively simple, three-dimensional model for simulating an eddy-current inspection. Numerical results for rectangular slots include maps of the impedance signals obtained in raster scan patterns and studies of skin-depth effects as a function of probe size, lift-off, and flaw dimensions.
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Beissner, R.E. Approximate model of eddy-current probe impedance for surface-breaking flaws. J Nondestruct Eval 7, 25–34 (1988). https://doi.org/10.1007/BF00565774
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DOI: https://doi.org/10.1007/BF00565774