The use of Rayleigh-like waves for crack growth monitoring at fastener holes has been studied. The excitation distance was selected such that the main part of the energy is concentrated on the back side of the specimen at the hole, where a starter notch was made. The development of fatigue cracks at fastener holes is a common problem in aircraft maintenance. This contribution investigates the use of Rayleigh-like waves for the in-situ monitoring of fatigue crack growth in tensile, aluminum specimens. Experimentally the Rayleigh-like wave is excited using standard angle beam transducers and measured using either standard pulse-echo equipment or laser interferometry. The influence of a fatigue crack on the scattered field at the hole was investigated by means of three-dimensional finite-difference calculations. Comparison of the predicted scattered field with laser interferometer measurements showed good agreement, validating the FD code. The modifications of the measured pulse-echo signals due to a crack were evaluated using the reflected energy ratio for a windowed portion of the signal. Good sensitivity was found using the complete reflected waveform, where the detection limit was below 1 mm. A reduction of the time window allowed for an improvement of the measurement repeatability, showing potential for crack sizing.
In-situ monitoring of fatigue crack growth at fastener holes using Rayleigh-like waves
In-Situ Überwachung des Wachstums von Ermüdungsrissen an Befestigungslöchern mittels Rayleigh ähnlichen Wellen
2008
8 Seiten, 7 Bilder, 12 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
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