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A SIMPLE DIRECT PROBLEM SOLVER FOR NON-DESTRUCTIVE INSPECTION OF CONDUCTIVE PLATES

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

A SIMPLE DIRECT PROBLEM SOLVER FOR NON-DESTRUCTIVE INSPECTION OF CONDUCTIVE PLATES, Proc Review of Progress in Quantitative Nondestructive Evaluation - QNDE, Burlington, United States, Vol. 00, pp. 140 - 00, July, 2011.

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Abstract
This paper presents a simple algorithm to preview the spatial variation of the voltage detected by an eddy current probe when an metallic plate with machined round hole defects is scanned. The direct 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. The magnetic field perturbation due to the defect subject to an unperturbed field is thus determined. The consideration of the conformal mapping is possible because, in a limited area, the applied magnetic field is considered uniform and the resultant electric field can be considered as the gradient of a scalar potential in that region.
To prove the validity of the model the simulation work was followed by a real experiment. A planar probe with a magnetic sensor based on giant magneto-resistors was implemented to impose an uniform time-variable electric field over a limited region of the plate and to determine the magnetic field at the sample’ surface vicinity. A good agreement was achieved.
Due to its simplicity, the algorithm constitutes a very good tool to test inversion algorithms
Moreover, the achieved results point out a direction to explore for the inversion problem solution.