Linear Magnetic Modeling for NDE
This talk covers two topics in which linear models are used to predict and interpret
electromagnetic measurements in NDE. The first of these is the problem of finding the case
depth of case hardened steels using alternating current potential drop (ACPD) and eddy
current data. The second is the task of predicting the electromagnetic field in the presence
of a crack in a ferromagnetic part. Now it may be thought that by treating a ferromagnetic
component as linear, isotropic and piecewise homogeneous, one ignores all the really
interesting material properties and I would have to agree. But you may also get a thrill from
using a theory to estimate a useful parameter in a controlled experiment, in which case you
may be content with a linear model. Especially as realistic models are often difficult to
develop. Even something as simple as ACPD can turn out to have hidden problems that you
never knew existed.