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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 …