Numerical and analytical modeling of pulsed eddy currents in a conducting half-space

A weighted-residual-based finite-element model for the computation of transient two-dimensional and axisymmetric magnetic vector potential and eddy-current distributions is formulated. The numerical field predictions are quantitatively tested against two analytical models in the time domain employing inverse Laplace transforms. The basis for the comparison is the determination of the eddy-current distribution in a conducting, nonmagnetic half-space due to either a suspended infinite wire or a suspended current loop. Although the excitation source for both methods is unit step current, the extension to arbitrary transient excitation currents and their corresponding eddy-current responses can be carried out by means of convolution. The resulting numerical temporal and spatial eddy-current distributions at various depths in the half-space are in excellent agreement with analytical distributions, thus quantitatively validating the numerical approach as a viable technique applicable to realistic nondestructive testing situations where field interactions with often arbitrary flaw geometries are of concern