A Multiscale Algorithm for Eddy-Current Nondestructive Evaluation Based On Volume-Integral Equations: Initial Concepts

Abstract

The use of coupled integral equations and anomalous currents allows us to efficiently remove ‘background effects’ in either forward or inverse modeling. This is especially true when computing the change in impedance due to a small flaw in the presence of a larger background anomaly. It is more accurate than simply computing the response with and without the flaw and then subtracting the two nearly equal values to obtain the small difference due to the flaw. In this paper, we compute the change in impedance of a probe due to a flaw in the presence of a much larger background anomaly, when the probe, which consists of a coil with a ferrite core, lies within the host region, and then apply the model and algorithm to the problem of inspecting a bolt hole in a plate or other layered medium with a ‘SplitD’ eddy-current probe.