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Articles 1 - 4 of 4
Full-Text Articles in Engineering
Conductivity Of A Periodic Particle Composite With Spheroidal Inclusions, Nicola Harfield
Conductivity Of A Periodic Particle Composite With Spheroidal Inclusions, Nicola Harfield
Nicola Bowler
The effective electrical conductivity of a two-phase material consisting of a lattice of identical spheroidal inclusions in a continuous matrix is determined analytically. The inclusions are located at the node points of a simple-cubic lattice and the axis of rotation of each spheroid coincides with one of the lattice vectors, such that the spheroids are aligned with each other and with the lattice. With an electric field applied in the direction of the rotation axes of the spheroids, the electric potential is found by solving Laplace's equation. The solution is found by analytically continuing the interstitial field into the particle …
Theory Of Thin-Skin Eddy-Current Interaction With Surface Cracks, Nicola Harfield, John R. Bowler
Theory Of Thin-Skin Eddy-Current Interaction With Surface Cracks, Nicola Harfield, John R. Bowler
Nicola Bowler
Eddy-current non-destructive evaluation is commonly performed at relatively high frequencies at which the skin depths are significantly smaller than the dimensions of a typical crack. A thin-skin analysis of eddy currents is presented in which the electromagnetic fields on the crack faces are described in terms of a potential which obeys a two-dimensional Laplace equation. Solutions of this equation for defects in both magnetic and non-magnetic materials are determined by applying thin-skin boundary conditions at the crack perimeter. The impedance change of an eddy-current coil due to the defect is then calculated by numerical evaluation of one-dimensional integrals over the …
Low‐Frequency Perturbation Theory In Eddy‐Current Non‐Destructive Evaluation, Nicola Harfield, Y. Yoshida, John R. Bowler
Low‐Frequency Perturbation Theory In Eddy‐Current Non‐Destructive Evaluation, Nicola Harfield, Y. Yoshida, John R. Bowler
Nicola Bowler
A method is presented by which series solutions for the impedance change in an eddy‐current test probe due to closed cracks in a non‐magnetic, conducting half‐space can be derived at low frequency. The series solution is applicable for flaws whose dimensions are much smaller than the electromagnetic skin‐depth. The problem is formulated using an approach in which the flaw is represented by an equivalent distribution of current dipoles. The electric field scattered by the flaw is then written as an integral, over the flaw, of the product of the dipole density distribution and an appropriate Green’s function. Terms in the …
Analysis Of Eddy‐Current Interaction With A Surface‐Breaking Crack, Nicola Harfield, John R. Bowler
Analysis Of Eddy‐Current Interaction With A Surface‐Breaking Crack, Nicola Harfield, John R. Bowler
Nicola Bowler
The change in electromagnetic impedance of a conductor due to the presence of a long, perpendicular surface‐breaking crack in a normally incident, uniform electric field is calculated in closed form in the high‐frequency limit. At high frequencies, where the skin depth is much smaller than the depth of the crack, the fields near the edge and corners of the crack are effectively decoupled. This means that the solution may be formulated as the sum of contributions from the corners, faces, and edge of the crack. Simple analytical expressions for the electric field are found and used to calculate the impedance …