Effect of Crack Presence on In-Flight Airframe Noises in a Wing Attachment Component

Abstract

The relation of the occurrence of airframe acoustic emissions to aircraft manoeuvre are reported for Avro CF-IOO upper forward wing trunnions. Periods of excessive noise are found when the airframe load is changing during entry to and exit from sustained-G manoeuvres. During constant-G periods, the airframe noise level is reduced by a factor of more than one hundred. These quiet periods provide a suitable signal-to-noise level for the in-flight detection and monitoring of slow, stable crack growth in cornmon airframe materials, even in a noisy load transfer component such as the wing trunnion studied here. Simultaneous in-flight acoustic emission measurements in symmetrically-located airframe components are also reported. The ratio of the number of recorded event counts in a cracked component to that in an uncracked component during the same flight is found to increase linearly with the crack face area for through crack lengths in the range 0-5 rnm.

Acoustic Emission Detection of Crack Presence and Crack Advance During Flight

“…The design is based on criterta dertved from the RMC work of almost a decade in the area of acoustic emissionmonitaring durtng flight (3,4,5). These studies established the importance of the difference in arrtval time of an event at different locations, signal rtsetime, and t.he magnitude and vartation of the applied stress at the time of occurrence of the event.…”

Acoustic Emission Detection of Crack Presence and Crack Advance During Flight

“…The dual-channel, digital data acquisition system used here was designed and constructed specifically for the recording and interpreting of acoustic emission data durtng flight. The design is based on criterta dertved from the RMC work of almost a decade in the area of acoustic emissionmonitaring durtng flight (3,4,5). These studies established the importance of the difference in arrtval time of an event at different locations, signal rtsetime, and t.he magnitude and vartation of the applied stress at the time of occurrence of the event.…”