Analytical solutions to eddy-current testing problems for a layered medium with varying properties

A one-parameter family of analytical solutions is found for the case where a single-turn coil is located above a two-layer conducting medium. The conductivity /spl sigma/ and the relative magnetic permeability /spl mu/ of the upper conducting layer are constants, while for the lower conducting half-space, these are of the form /spl sigma/(z)=Az/sup b/ and /spl mu/(z)=Bz/sup a/, where A and B are constants and a+b=-2 or a+b=0. The change in impedance is computed, and the results of numerical simulation are presented.