On the Question of Inspecting the Plate with a Crack by the Eddy-Current Method

The problem of how one or several rectilinear cracks intersecting at a point affect eddy-currents and electromotive force (e.m.f.) induced in a current loop has been considered. The loop is located above a nonmagnetic infinite plate, orthogonally to the crack lines. Under these conditions, when the plate is geometrically thin and can be replaced with a conductive surface, the problem is solved analytically. The calculation data, which are illustrated by the graphs of how the e.m.f. depends on the proximity to the crack when the current frequency and loop location height are varied, show that crack's contribution to the magnetic reaction virtually fades at distances exceeding the sum of the linear loop length and its height. Results of conducted physical experiments prove the adequacy of the developed mathematical model and its applicability to the solution of such problems.