SOME CHARACTERISTICS OF THE PULSED EDDY-CURRENT METHOD FOR NON-DESTRUCTIVE EVALUATION

Abstract This contribution investigates the use of the pulsed eddy-current procedure to determine the presence of back wall defects, particularly in double skinned structures of the kind commonly found in aircraft frames. A novel arrangement of inspection coil is proposed, and the interpretation of the response of the structure is shown to be best achieved by consideration of the parameters of the received pulse, rather than by trying to determine changes in probe impedance in the presence of defects. It is shown analytically that the pulsed approach offers a deeper field penetration, and consequently greater utility, than the conventional sinusiodally excited method.