Abstract
This work proposes a semianalytical technique based on the boundary element method (BEM) to predict the signals due to flaws (cracks) that are typically encountered in eddy current (ECT) nondestructive testing (NDT). Two case studies, for two different narrow opening notches in a finite thickness aluminium plate, were performed by experimental measurements to corroborate the theoretical model. The signal which has been modelled is the perturbation in the magnetic flux density (MFD) components <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B<sub>x</sub></i> , <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B<sub>y</sub></i> , and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B<sub>z</sub></i> due to narrow opening flaws. The proposed analytical model uses the magnetic vector potential (MVP), arising from electric dipole sources, to determine the voltage induced in a hypothetical small circular loop located around the evaluation point. Based on the linear relationship between the voltage induced and the magnetic flux in the surface enclosed by the hypothetical loop, a linearity constant that transforms the induced voltage to the MFD component has been computed. Appropriate vector potential Green’s functions have been used to transform the electric dipole sources to the magnetic vector potential components to determine the voltage induced in the hypothetical loop.
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