Acoustic-Emission Monitoring of Airframe Failure under Cyclic Loading

Abstract

The structural–phenomenological approach used to classify and split acoustic-emission signals into energy clusters, together with the parameters of detection frequency and weight content of location pulses in the clusters, allows real-time monitoring of main trends in damage accumulation at different structural levels and makes it possible to isolate signals generated during the failure of a structural material from accompanying mechanical interference and electromagnetic noise. An example of applying new criterion parameters to determining the moment of delamination of stringer runoffs from the shelves of the MC-21 airframe support strut under conditions of fatigue tests with a symmetric loading cycle is provided. Using the new criterion parameters and developed cluster-analysis techniques, employed, among other things, to discriminate location pulses in the field of spectral characteristics, an interconnection has been established between the process of breaking cohesive and adhesive bonds in the adhesive layer at the boundary between the stringer runoff fastening and the support strut shelves and the generated acoustic signals by their energy, waveform, and spectrum.