Novel Low Frequency Eddy Current Detection of Interior Cracks in Multi-Layer Metallic Airframe Structures

The detection of small cracks and corrosion deep within a metal structure is a crucial unsolved problem for aircraft NDE. Examples include cracks and voids in thick structural members, interfacial corrosion in layered structures and cracks radiating from the fastener hole on interior layers of a lap joint. We propose the development of a novel eddy current system to detect these defects. To achieve this improved performance without cryogens or other bulky apparatus, we combine a new sensor technology with sensitivity-improving techniques that were originally developed for SQUID applications and could not work with previous sensors. The resulting instrument is intrinsically insensitive to lift-off and can self-calibrate. Quantum Magnetics is uniquely qualified for this work because of its expertise in NDE, in magnetic detection and in noise rejection strategies.