2005 Volume 5 Issue 2 Pages 105-108
We calculated the eddy current distribution in an aluminum plate, excited perpendicularly by a small ring coil for quantitative understanding of the interaction of the eddy currents with a flaw in the plate. The calculation is based on the equations developed by Dodd and Deeds for axis-symmetric problems. After confirming the accuracy of the calculated results by comparing them with the measured data, we characterized the profiles of amplitudeand phase of eddy currents in the aluminum plate. We confirmed that the phase of the eddy currents depends linearly on the distance between the source point and the observation point, as found in an ideal one- dimensionalcase, when the angle between the vertical line and the line connecting the source point to the observation point is less than 60 degrees. We extended the equation to express the magnetic field that may be produced out of the aluminumplate by the interaction between injected eddy currents and a small flaw in the sample. On the basis of theequation, we also show how to evaluate the magnetic fieldfrom a flaw.
