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MODELING EDDY CURRENT INSPECTION OF A METALLIC SAMPLE WITH ROUND HOLE DEFECTS

Ramos, H. ; Ribeiro, A. L. ; Pasadas, D. ; Rocha, T.

MODELING EDDY CURRENT INSPECTION OF A METALLIC SAMPLE WITH ROUND HOLE DEFECTS, Proc IMEKO 17th Symp. IMEKO TC 4 - Measurement of Electrical Quantities, 15th International Workshop on ADC Modelling and Testing, 3rd Symp. IMEKO TC 19 - Environmental Measurements, Natal, Brazil, Vol. 00, pp. 00 - 00, September, 2011.

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Abstract
This paper presents a simple algorithm to model eddy current inspection when an uniform time-variable electric field in imposed in a region of a metallic plate sample with machined hole defects. The magnetic field perturbation due to a round hole defect subject to an unperturbed field is determined. The problem is formulated in terms of complex potentials and the method of conformal mapping is used to transform the domain with a round hole into a simpler domain in which the solution can be computed. To check the validity of this method the acquired voltage signals previewed with the algorithm are compared with data values measured using an experimental eddy current testing setup.
In addition to its great value in the design of non destructive testing instrumentation, optimum operating conditions and calibration methods, the algorithm described in this paper can constitute an important contribution to solve the inverse problem. The purpose of the inverse problem is to estimate the defect in the plate from measured data values. The measured data values include unknown measured noise that the inversion solution method amplifies and which can completely hide the physical solution corresponding to the noise free data. Thus an approach for the inverse problem solution from the accurate output results obtained with the purposed forward problem solver can be essential to the problem clarification.