Eddy Currents Testing of Long Cylindrical Products with Long Solenoids

Abstract

The scientific interpretation of the results obtained by eddy currents testing long cylindrical products is much easier when using long rather than short solenoids. The long product is then in an uniform state of magnetic induction. A simple model is developped to size long axial emerging rectangular defects of various widths and depths.

For non-ferromagnetic materials, at relatively high frequency, the inductance L varies linearly with the cross-section of the defect and the resistance R varies also linearly with the depth of the defect. The model allows to calculate the linear coefficients of influence. Experimental tests carried on copper and aluminium rods have fully validated the theoretical model.

For ferromagnetic materials, the model is modified in order to take the magnetization into account. Experimental tests are in progress and results will be presented elsewhere.