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Electromagnetics and Photonics Commons™
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- Keyword
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- Eddy current (4)
- Eddy Current Crack Response (3)
- Capacitance Sensors (2)
- Crack (2)
- Eddy Current Probes (2)
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- Analytical model (1)
- Arc electrode (1)
- Bessel functions (1)
- Borehole (1)
- Boundary elements (1)
- Capacitance (1)
- Coil impedance (1)
- Cracks (1)
- Eddy Current Edge Effects (1)
- Eddy currents (1)
- Edge effect (1)
- Ferrite core (1)
- Four Point Probe Potential Drop (1)
- Four point probe (1)
- Impedance (1)
- Integral equation (1)
- Inversion (1)
- Nondestructive evaluation (1)
- Permittivity measurement (1)
- Potential drop (1)
- Probe (1)
- Transient field (1)
- Wedge (1)
Articles 1 - 7 of 7
Full-Text Articles in Electromagnetics and Photonics
An Analytical Model Of A Ferrite-Cored Inductor Used As An Eddy Current Probe, John R. Bowler, Yi Lu, Theodoros P. Theodoulidis
An Analytical Model Of A Ferrite-Cored Inductor Used As An Eddy Current Probe, John R. Bowler, Yi Lu, Theodoros P. Theodoulidis
John R. Bowler
An analytical model of an axisymmetric eddy current ferrite-cored probe above a multi-layered conducting half-space has been developed using a procedure in which the domain of the problem is truncated radially. This means that solutions can be expressed in the form of generalized Fourier-Bessel series. The expansion coefficients are found by matching the field across the interfaces between the subregions of the problem. Initially, the magnetic vector potential of a simple circular current filament is expanded in a series form. The solution is then modified to accommodate an infinitely long coaxial ferrite core, and the principle of superposition is invoked …
Evaluation Of Eddy-Current Probe Signals Due To Cracks In Fastener Holes, John R. Bowler, Theodoros P. Theodoulidis, Hui Xie, Yuan Ji
Evaluation Of Eddy-Current Probe Signals Due To Cracks In Fastener Holes, John R. Bowler, Theodoros P. Theodoulidis, Hui Xie, Yuan Ji
John R. Bowler
Cracks in conductors are detected through changes in the impedance of a coil that induces current in the material. In order to gain insight into the physics of the inspection, we have developed a theoretical and computational model that predicts the signals due to cracks in circular cylindrical holes using a boundary element calculation. In formulating the problem, the electromagnetic field is decomposed into transverse electric and transverse magnetic scalar modes. The effect of a planar crack in an electromagnetic field is represented by an electric current dipole layer orientated normal to the crack surface. The dipole density is determined …
Analysis Of Arc-Electrode Capacitive Sensors For Characterization Of Dielectric Cylindrical Rods, Tianming Chen, Nicola Bowler, John R. Bowler
Analysis Of Arc-Electrode Capacitive Sensors For Characterization Of Dielectric Cylindrical Rods, Tianming Chen, Nicola Bowler, John R. Bowler
John R. Bowler
An arc-electrode capacitive sensor has been developed for quantitative characterization of permittivity of cylindrical dielectric rods. The material property of the cylindrical test piece can be inversely determined from the sensor output capacitance based on a theoretical model. For the modeling process, the electrostatic Green’s function due to a point source exterior to a dielectric rod is derived. The sensor output capacitance is numerically calculated using the method of moments (MoM), in which the integral equation is set up based on the electrostatic Green’s function. Numerical calculations on sensor configuration optimization are performed. Calculations also demonstrate the quantitative relationship between …
Evaluation Of The Transient Potential Drop Of A Four-Point Probe, John R. Bowler
Evaluation Of The Transient Potential Drop Of A Four-Point Probe, John R. Bowler
John R. Bowler
The time-dependent voltage across the pick-up electrodes of a four point probe has been determined analytically for a transient current pulse injected into a thick conductive plate modeled as a half-space. This is a step towards analyzing more complex transient four point probe signals from measurements on inhomogeneous conductors. Potential applications include the evaluation of depth-dependent conductivity profiles in metals and semiconductors. The analysis of homogeneous conductors shows how the signals are characterized by a time constant of the drive current and additional time constants dependent on the electromagnetic material properties and electrode spacings
On The Interaction Of An Eddy Current Coil With A Right-Angled Conductive Wedge, John R. Bowler, Theodoros Theodoulidis
On The Interaction Of An Eddy Current Coil With A Right-Angled Conductive Wedge, John R. Bowler, Theodoros Theodoulidis
John R. Bowler
A fundamental problem in eddy-current nondestructive evaluation is one of finding the quasi-static electromagnetic field of a cylindrical coil in the vicinity of the edge of a metal block. Although the field can be calculated numerically, an effective analytical approach can potentially provide a better understanding of the edge fields and form the basis of a procedure for solving a whole class of related edge problems including edge structures that contain corner cracks. One can represent the metal block as a conductive quarter space in an unbounded region. However, it has been found that the analysis is more straightforward if …
Eddy Current Interaction With An Ideal Crack, Part I: The Forward Problem, John R. Bowler
Eddy Current Interaction With An Ideal Crack, Part I: The Forward Problem, John R. Bowler
John R. Bowler
The impedance of an eddy-current probe changes when the current it induces in an electrical conductor is perturbed by a flaw such as a crack. In predicting the probe signals, it is expedient to introduce idealizations about the nature of the flaw. Eddy-current interaction is considered with an ideal crack having a negligible opening and acting as a impenetrable barrier to electric current. The barrier gives rise to a discontinuity in the electromagnetic field that has been calculated by finding an equivalent electrical source distribution that produces the same effect. The choice of source is between a current dipole layer …
Eddy-Current Interaction With An Ideal Crack. Ii. The Inverse Problem, John R. Bowler, David Harrison, Steve Norton
Eddy-Current Interaction With An Ideal Crack. Ii. The Inverse Problem, John R. Bowler, David Harrison, Steve Norton
John R. Bowler
Eddy-current inversion is the process whereby the geometry of a flaw in a metal is derived from electromagnetic probe measurements. An inversion scheme is described for finding the shape and size of cracks from eddy-current probe impedance measurements. The approach is based on an optimization scheme that seeks to minimize a global error function quantifying the difference between predicted and observed probe impedances. The error minimum is sought using a standard descent algorithm that requires a knowledge of the gradient of the error with respect to a variation of the flaw geometry. Computation of the gradient is based on a …