Volume 4, Number 3, Summer 1996
A PERTURBATION METHOD FOR FLAW DETECTION
IN EDDY CURRENT TESTING OF CYLINDRICAL TUBES
M.Ya. ANTIMIROV, A.A. KOLYSHKIN AND RÉMI VAILLANCOURT
Abstract. A perturbation method is used to construct
an approximate formula for the change in impedance of a
single-turn coil situated coaxially inside a cylindrical tube
with a flaw in the tube wall. It is assumed that the electric
conductivities of the flaw and the tube are nearly the same.
It is found that, in order to obtain the change in the coil
impedance due to the flaw, it is sufficient to know only the
azimuthal component of the vector potential. Numerical
results are given for different positions of the flaw with respect
to the coil.