Articolele autorului Gabriel Preda
Link la profilul stiintific al lui Gabriel Preda

Polarization Method for Static Fields

An overview of the polarization method is presented. The method can by applied for different regimes of the electromagnetic field as well as for electric circuits. Criteria for the choice of the permeability are proposed, so that the iterative scheme leads to a Picard–Banach fixed point procedure. The errors are evaluated. An efficient overelaxation method is presented. The modality of using FEM numerical method is analyzed in order to ensure the

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Reconstruction of Crack Shapes From the MFLT Signals by Using a Rapid Forward Solver and an Optimization Approach

In this paper, the reconstruction of crack shapes from the magnetic flux leakage testing (MFLT) signals is realized by introducing a rapid forward simulator and applying a deterministic optimization approach. The MFLT signals due to cracks of different shape are calculated with an FEM-BEM code employing method and polarization algorithm, which is accelerated by the new rapid forward scheme. For reconstructing the crack shape, the conjugate gradient

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Neural network for inverse mapping in eddy current testing

A neural network mapping approach has been proposed for the inversion problem in eddy-current testing (ECT). The use of a Principal Component Analysis (PCA) data transformation step, a data fragmentation technique, jittering, and of a data fusion approach proved to be instrumental auxiliary tools that support the basic training algorithm in coping with the strong ill-posedness of the inversion problem. The present paper reports on the further improvements

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Direct computation of static difference magnetic field in nonlinear magnetic materials and application to shape reconstruction of damaged areas in aging materials

In order to accurately compute the magnetic field variation due to changes in material properties (e.g. material aging) we propose a technique that computes directly the difference magnetic field. Nonlinear materials are analyzed by means of the polarization technique. The linear field problem is solved using a fast Green function approach. A 2D formulation is validated upon comparison with measurement data. Then it is used as fast forward solver

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Nonlinear FEM-BEM formulation and model-free inversion procedure for reconstruction of cracks using pulse eddy currents

Pulse eddy currents are proposed as a nondestructive testing (NDT) technique to detect flaws in conductive structures with large thickness. The harmonic component of a pulse is rich, so that the pick-up signal containing the amount of information corresponds to a multifrequency analysis. Due to the short time length of the pulse, the amplitude of the excitation increases up to 100 times of the amplitude for an AC signal. Both direct simulation of

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A nonlinear eddy-current integral formulation for moving bodies

This paper presents an integral formulation for the calculation of the eddy-current problems in moving conductors in the presence of magnetic media. The quasistationary Maxwell equations are written in local reference frames associated with moving bodies. Only the conducting and ferromagnetic domains are discretized. The eddy current is described in terms of a two component electric vector potential for which edge elements are used along with the

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