Transient Eddy-Current NDE for Hidden Corrosion in Multilayer Structures

摘要

The development of reliable nondestructive evaluation (NDE) techniques to detect and characterise hidden corrosion in aircraft structures is one of the key problems in maintaining aging military aircraft. Previous work [1–3] has demonstrated that transient eddy-current techniques have significant advantages for the detection of hidden corrosion in multilayer structures compared with conventional eddy-current NDE. The use of a pulsed rather than single-frequency excitation, combined with time-domain measurements, allows the response over a wide range of frequencies to be captured in a single measurement, giving a very significant performance advantage over multi- or swept-frequency methods. Furthermore, by detecting the transient magnetic field using a Hall-effect device rather than detecting the voltage developed in a pickup coil, transient eddy-current NDE can probe more deeply into a multilayer structure than conventional eddy-current NDE, providing greater sensitivity to deeply hidden corrosion.