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In this work, a parametric study is carried out on carbon fiber-reinforced plastic (CFRP) materials to investigate how the spatially varying fiber distribution influences the measured signal in an eddy current testing (ECT) configuration. The measurement setup was modeled using finite element method, while the fiber distribution is taken into account by an inhomogeneous anisotropic conductivity tensor. The study revealed a trade-off relation between the size of the ECT coil and the maximal dynamic range of the ECT signal, which contributes to the understanding of the connection between the fiber arrangement and the ECT signal and provides an opportunity for optimal ECT coil design. [ABSTRACT FROM AUTHOR]

Litz wires consist of many individual, isolated conductor strands. Certain litz wires are fabricated by simply twisting the bundle of strands, hence a wire pitch is realized. In this paper, the ac resistance of coils made of such twisted litz wire are calculated by combining two-dimensional finite element simulation and circuit laws. In so doing, the inherently three-dimensional problem can be solved at much lower computational cost. Results are presented for the current distribution, and for the alternating current resistance of coils, validated against measured data. [ABSTRACT FROM AUTHOR]

Magnetic flux simulations were utilized in a novel magnetic measurement method performed for the detection of local thinning of ferromagnetic plates. It was shown by numerical simulation, how parameters affect detectability of the defects. Linear relationship was found between the evaluated parameters and size of the artificial slot. Good correlation was found between theoretical and experimental results. [ABSTRACT FROM AUTHOR]

Scattering from propellers is investigated using the 3D Finite Element Method (FEM), alongside a simpler integral equation (IE) method using 1D discretization. It is shown that under certain conditions and near the propellers' resonant frequency, results using the two methods are in agreement, justifying the use of the IE method; this is advantageous because of smaller computation times, and for providing a physical insight to the scattering phenomena at hand. Anechoic chamber measurements are performed to validate the numerical results. [ABSTRACT FROM AUTHOR]

A nonlocal generalization of the IBC (impedance boundary condition) concept is introduced in this work for modeling the coil wires in resonant WPT (wireless power transfer) links. Such NLIBCs (nonlocal IBCs) can accurately account for the skin and proximity effects in the wires for all frequencies relevant to resonant WPT systems and can be utilized in both finite-element and surface-integral-equation numerical frameworks. The NLIBCs have run-time performance close to that of the IBC because the NLIBCs take advantage of the quasi-2D nature of the electromagnetic field inside the wires. The results for a typical WPT configuration illustrate the performance. [ABSTRACT FROM AUTHOR]

Fluxset magnetic sensor based probes with a double exciting coil system have been developed for detecting weakly interacting, low mass and small size magnetic particles for biomedical application. The probe measures the magnetic response of particles to an AC excitation. Measurements were carried out on samples containing 20, 30 and 40 nm size nanoparticles, which were embedded in a cylinder containing aguar-aguar. It was shown that the probe can detect nanoparticles of 20 nm size if their concentration is at least 0.06 mg/mm3 from a distance of 1 mm with reliable signal to noise ratio. The probe detection was found to be improved after magnetization of particles. [ABSTRACT FROM AUTHOR]

Fluxset magnetic sensor based probes with single and double exciting coils have been developed for detecting weakly interacting, low mass and small size magnetic particles. Test measurements were performed on capsules containing 0.15-13.53 mg magnetic iron oxide particles. It was shown that even 0.7 mg of magnetic nanoparticle of size 30 nm could be detected from a distance of 3.5 mm with reliable signal to noise ratio. [ABSTRACT FROM AUTHOR]

Accurate numerical simulation of Eddy-Current Testing (ECT) experiments usually requires large computational efforts. So, a natural idea is to build a cheap approximation of the expensive-to-run simulator. This paper presents an approximation method based on functional kriging. Kriging is widely used in other domains, but is still unused in the ECT community. Its main idea is to build a random process model of the simulator. The extension of kriging to the case of functional output data (which is the typical case in ECT) is a recent development of mathematics. The paper introduces functional kriging and illustrates its performance via numerical examples using an ECT simulator based on a surface integral method. A comparison with other classical data interpolation methods is also carried out. [ABSTRACT FROM AUTHOR]

An adaptive sampling method based on simplex-mesh refinement is proposed for creating a database that facilitates the inverse problem solution in NDT. The resulting database is used as a generic interpolator of the forward problem. In order to obtain optimal sampling for the purpose of interpolation, physically based mesh generation technique relying on spring analogy is utilized. The method is tested with a four-parameter crack reconstruction problem. It is demonstrated that the optimized database provides high interpolation quality comparing to regular grid databases. [ABSTRACT FROM AUTHOR]

Practical quantities have been introduced by the authors to characterize the interaction among multiple defects located in a specimen under eddy-current testing (ECT). If these quantities indicate that the interaction between the pairs of defects is negligible, the signal of an ECT probe for multiple defects can be calculated as the superposition of those signals, which are obtained for each defect as if it would be a single one. Conversely, if the criteria holds, the measured ECT signal can be decomposed into signals associated with the individual defects, which essentially simplifies the solution of the inverse problem of defect reconstruction. As an application of the criteria, the design of a novel barcoding system is presented, which is developed for marking metallic parts by laser treating, and where the applicability of linear signal processing methods for the reading out of the barcode is a requirement. [ABSTRACT FROM AUTHOR]

The accuracy of the calculation of the signal due to the interaction of an eddy current testing (ECT) probe and a thin crack in a plate is basically depending on the discretization of the boundary integral equation which is modelling the actual physical arrangement. In this paper a solution method is introduced, where global approximation functions are used for proper discretization of the equivalent dipole density on the thin crack surface in that integral framework. Among other items, emphasis is put on the evaluation and control of the resulting numerical error. Using such results the automated discretization of rectangularly-shaped thin cracks analysed by an ECT signal prediction software will be shown to become feasible. [ABSTRACT FROM AUTHOR]

Neural network is applied for the non-destructive evaluation of in-material defects based on the measured or simulated data of an eddy-current testing experiment. The network is trained with the data measured for suitably selected defect prototypes, so that this selection constitute a consistent representation of the forward problem. This network performs in defect reconstruction better, than those networks trained with randomly or regularly selected defect prototypes of about the same number. [ABSTRACT FROM AUTHOR]

Global approximating function sets applicable to the solution of the integral equation used to calculate an eddy current testing probe signal are proposed. Rectangularly-shaped cracks normal to the surface of plate specimens are considered. The approximating functions are orthogonal harmonic functions satisfying the boundary conditions at the edges of the crack. The calculations using the proposed approximating functions are fast, numerically stable and provide a robust alternative to other methods used in the literature. A number of numerical examples are shown for illustration and discussed. [ABSTRACT FROM AUTHOR]

Eddy current testing (ECT) probe signal due to cracks can be predicted by separating the calculation steps to the evaluation of the incident field and the reaction of the crack. Finite element (FEM) and boundary integral (ElM) methods can be, for example, advantageously applied for the calculation of the incident and reaction fields, respectively. The computational environment presented in this paper allows the blending of the different calculation methods for the purpose of ECT probe signal calculation. As a result, a fast and versatile tool is obtained to calculate the signal of complicated ECT probes due to cracks. The developed approach is validated through comparisons with experimental data. [ABSTRACT FROM AUTHOR]

The reconstruction problem of porous silicon (PS) structures is investigated by means of a specific optimized inversion database. The database is supported by a generic n-dimensional adaptive anisotropic simplex mesh. The proposed mesh database carries additional information on the inverse problem: the number of database nodes indicates the relevance of the model used for the reconstruction, while the mesh structure reflects the capabilities of the inversion as well as the role of the chosen model parameters. Based on this information one is able to propose an optimal model for the given inverse problem. [ABSTRACT FROM AUTHOR]

Focuses on a study which calculated the time-dependent response of the interaction of a stratified plate specimen of linear conductor with a planar flaw and an eddy-current induction coil fed by a current pulse. Discussion on pulsed eddy-current testing methods; Calculation of the time-harmonic electromagnetic field; Computation of the time-dependent field; Examples of application.

The scanning of parts in eddy current testing can lead to a large amount of measurement data (predictors). Partial least square (PLS) regression is a mean to reduce the dimensionality of the subsequent inverse problem by projecting the predictors in a latent subspace of reduced dimension maximizing the covariance between the projection and the responses which have to be estimated. In a second step, a regression model is elaborated linking the responses to the latent variables. PLS was originally developed in the field of chemical analysis. In this paper, the PLS method is applied in the field of eddy current testing for the characterization of minute cracks. It is tested firstly on simulated data and then on experimental data. It is found that the reconstruction of the area of minute cracks is made possible by PLS. [ABSTRACT FROM AUTHOR]