Non-destructive test procedure for riveted joints in fuselage layer of aircraft - involving use of Foucault probe for testing joint by analysis of signal as probe is drawn along joint

摘要

The process involves using a probe sensitive to Foucault currents, which is drawn along the line of the joint following a series of rivets. The probe produces a signal of characteristic shape corresponding to the passage of each rivet in front of the sensitive element. The probe is used with a network of neurones in order to study the signal relating to three-quarters of the inter-rivet space, before and after each rivet. Analysis includes use of a function which describes the angle of the tangent to the curve of the cyclical signal, considering each quarter inter-rivet space in turn. ADVANTAGE - Allows production of three invariant curve descriptors.