Rapid computation of eddy current signals from narrow cracks

An existing boundary element method model for eddy current inspection of ideal or narrow cracks is revised. Using some lately devised concepts on efficiently and rapidly simulating canonical eddy current geometries, we show how this model can be made easier to implement and faster to calculate. The approach is largely based on a novel method for rapidly calculating the Green's function and reducing the matrix fill-time, and also on a similar method for rapidly computing the incident electric field. As a result, the model has been made an order of magnitude faster than the existing one without sacrificing accuracy. We pay attention to numerical analysis details and analyze issues that so far have not been clarified. The validity of our approach is also verified by the experiment. Although we have tested the model against published data, we have also produced our own precision measurements for surface and through-the-thickness slots in plates with the coils performing scans along and across the slots at various frequencies.