C.S. Antonopoulos and E.E. Kriezis
A boundary element technique is applied to an integral formulation of the electromagnetic field quantities, of the electric vector and magnetic scalar potentials for theā¦
Abstract
A boundary element technique is applied to an integral formulation of the electromagnetic field quantities, of the electric vector and magnetic scalar potentials for the evaluation of the propagation phenomenon in stratified media, of planar or cylindrical geometry, due to electric dipole sources. The use of the above described potentials simplify the solution procedure, because of the degrees of freedom, which can de introduced in choosing relations between the field quantities. The main goal of these relations is to make the numerical solution easier, while the Maxwell equations and the boundary conditions remain unaffected. Besides a threeādimensional problem is treated as a two dimensional one. Results and plots of the field, are given for both cases of the geometry. The method can be used for determining the field inside the earth in geological studies, propagation in stratified media, cable technology, shielding problems e.t.c.
T.P. Theodoulidis, C.S. Antonopoulos and E.E. Kriezis
The evaluation of eddy currents in cylindrical geometries is examined analytically by using a method, which utilises the second order magnetic vector potential. As an example theā¦
Abstract
The evaluation of eddy currents in cylindrical geometries is examined analytically by using a method, which utilises the second order magnetic vector potential. As an example the threeādimensional problem of the calculation of eddy currents inside a long conducting cylinder excited by a saddle shaped coil is studied.
C.S. Antonopoulos, T.D. Tsiboukis and E.E. Kriezis
A method, which is using the electric vector potential T and the magnetic scalar potential Ī© is presented for the calculation of the electroāmagnetic field inside conductingā¦
Abstract
A method, which is using the electric vector potential T and the magnetic scalar potential Ī© is presented for the calculation of the electroāmagnetic field inside conducting cylinders of infinite length.The current source is an oscillating current dipole arbitrarilly oriented. The Green's function method is used for the transformation of the Helmholtz's equations for T and Ī© into integral ones. Finally a boundary element technique is used to obtain a system of simultaneous equations. In this system the number of the unknows is greater than the number of the availiable simultaneous equations.Thus some additional conditions between the field quantities, have to be added to the boundary conditions to obtain the final solution of the problem. Problems of electrical machines, electromagnetic shielding or even, problems related to human bodies can be treated with the following analysis.
In eddy current nondestructive testing, a probe with a ferrite core such as an E-core coil is usually used to detect and locate defects such as cracks and corrosion in conductiveā¦
Abstract
Purpose
In eddy current nondestructive testing, a probe with a ferrite core such as an E-core coil is usually used to detect and locate defects such as cracks and corrosion in conductive material. However, the E-core coil has some disadvantages, such as large volume and difficulty in the process of winding the coils. This paper aims to present a novel T-core probe and its analytical model used for evaluating hidden holes in a multi- layer conductor.
Design/methodology/approach
By using a cylindrical coordinate system, the solution domain is truncated in the radial direction. The magnetic vector potential of each region excited by a filamentary coil is derived, and the expansion coefficients of the solutions are obtained by matching the boundary and interface conditions between the regions. By using the truncated region eigenfunction expansion method, the final expression in closed form for the impedance of the multi-turn coil is worked out, and the impedance calculation is performed in Mathematica. For frequencies ranging from 100āHz to 100ākHz, both the impedance changes of the T-core coil above the multi-layer conductor without a hidden hole and in the absence of the layered conductor were calculated, and the influence of a hidden hole in the multi-layer conducting structure on the impedance change was investigated.
Findings
The correctness of the analytical model of the T-core coil was verified by the finite element method and experiments. The proposed T-core coil has higher sensitivity than an air-core coil, and similar sensitivity and smaller size than an E-core coil.
Originality/value
A new T-core coil probe and its accurate theoretical model for defect evaluation of conductor were presented; probe and analytical model can be used in probe design, detection process simulation or can be directly used in defect evaluation of multi-layer conductor.
Details
Keywords
N.A. Golias, C.S. Antonopoulos, T.D. Tsiboukis and E.E. Kriezis
A finite element formulation for the solution of 3D eddy current problems in terms of the electric intensity E is presented. A weak formulation, based on a Galerkin weightedā¦
Abstract
A finite element formulation for the solution of 3D eddy current problems in terms of the electric intensity E is presented. A weak formulation, based on a Galerkin weighted residual procedure, is presented and edge elements, that impose only tangential continuity across element interfaces of the approximated field, are employed for the discretization of the problem with the finite element method. The reliability and validity of the suggested method is verified by its application to the calculation of the 3D eddy current distribution in two conducting systems.
Details
Keywords
N.V. Kantartzis, E.E. Kriezis and T.D. Tsiboukis
The FDTD approach is rapidly becoming one of the most widely used computational methods in electromagnetics. It is a marchingāinātime procedure which simulates the continuousā¦
Abstract
The FDTD approach is rapidly becoming one of the most widely used computational methods in electromagnetics. It is a marchingāinātime procedure which simulates the continuous actual waves by sampled data numerical analogues propagating in a data space stored in a computer. Thus it leads to a complete understanding of near fields and transient effects. In this paper, the study of the propagating modes and the calculation of the energy forced in the interior of a terminated waveguide is performed with an iterative FDTD technique. Results are obtained and compared with the theoretical ones. Their agreement is almost perfect.
A. Karanikolos, P.K. Pantelakis and E.E. Kriezis
The interaction of ELFāLF electric fields with the human body is examined with a method based on surface chargeāintegral equations. The evaluation of the electric field intensityā¦
Abstract
The interaction of ELFāLF electric fields with the human body is examined with a method based on surface chargeāintegral equations. The evaluation of the electric field intensity on the body surface is performed for a realistic model of the human body. Two examples for different postures of the model are given.
C.S. Antonopoulos, Em.E. Kriezis and E.E. Kriezis
The path integral analysis has been used to examine the propagation of a Gaussian beam in two cases. First in free space and second in a space with a nonāpenetrable obstacleā¦
Abstract
The path integral analysis has been used to examine the propagation of a Gaussian beam in two cases. First in free space and second in a space with a nonāpenetrable obstacle, placed parallel to the direction of propagation. Full analytical equations have been given in both cases and results have been taken in the same spatial coordinates in order to facilitate comparisons. No numerical instabilities have been observed and the method seems to be quite tractable and easily extended in spaces with more that one obstacle.
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Keywords
A.G. PAPAGIANNAKIS, T.D. TSIBOUKIS and E.E. KRIEZIS
The dyadic Green's function for a horizontally stratified dielectric medium is computed. The general electric field integral equation describing the scattering from an arbitraryā¦
Abstract
The dyadic Green's function for a horizontally stratified dielectric medium is computed. The general electric field integral equation describing the scattering from an arbitrary dielectric scatterer embedded in one of the layers is formulated using the dyadic Green's function of the respective layer. For the numerical solution of the equation the method of moments is used. Numerical results are given for the case of a cylinder buried in the middle of a fiveālayer space for various cases of plane wave excitation.
In eddy current nondestructive testing, ferrite-cored probes are usually used to detect and locate defects such as cracks and corrosion in conductive materials. However, theā¦
Abstract
Purpose
In eddy current nondestructive testing, ferrite-cored probes are usually used to detect and locate defects such as cracks and corrosion in conductive materials. However, the generic analytical model for evaluating corrosion in layered conductor using ferrite-cored probe has not yet been developed. The purpose of this paper is to propose and verify the analytical model of an E-cored probe for evaluating corrosion in layered conductive materials.
Design/methodology/approach
A cylindrical coordinate system is adopted and the solution domain is truncated in the radial direction. The magnetic vector potential of each region excited by a filamentary coil is derived first, and then the expansion coefficients of the solution are obtained by matching the boundary and interface conditions between the regions and the subregions. Finally the closed-form expression of the impedance of the multi-turn coil is derived by using the truncated region eigenfunction expansion (TREE) method, and the impedance calculation is carried out in Mathematica. In the frequency range of 100āHz to 10ākHz, the impedance changes of the E-cored coil and air-cored coil due to the layered conductor containing corrosion are calculated, respectively, and the influences of corrosion on the coil impedance change are investigated.
Findings
An analytical model for the detection and evaluating of corrosion in layered conductive materials using E-cored probe is proposed. The model can quickly and accurately calculate the impedance change of E-cored coil due to corrosion in layered conductor. The correctness of the analytical model is verified by finite element method and experiments.
Originality/value
An accurate theoretical model of E-cored probe for evaluating corrosion of multilayer conductor is presented. The analytical model can be used to detect the inhomogeneity of layered conductor, design ferrite-cored probe or directly evaluate the corrosion defects of layered conductors.