Eddy current imager for the detection of buried flaws in large metallic structures

The authors present a prototype of an eddy current imager dedicated to the high speed inspection of aeronautic riveted lap joints. The system provides high resolution images of the complex magnetic field distribution at the surface of the inspected structure, and allows thorough defect characterization to be achieved. The system was implemented for the detection of buried notches placed next to the rivets of a laboratory made lap joint mock-up. Associated to a dedicated signal processing method, the system allows 6 mm deep EDM notches (0.2mm'3mm'7mm) to be detected and localized within the depth of the inspected structure, and appears very promising for the characterization of buried defects in actual riveted lap joints.