Recent theoretical and experimental studies in a wide range of applications (ultrasonics, underwater acoustics,
seismicoe) have demonstrated that Green's functions (impulse responses) can be extracted from cross-correlation
of diffuse fields using only passive sensors. The technique, whose validity is supported by a physical
argument based on time-reversal invariance, effectively uses a correlation process between the point source and
points located in the focal zone. Indeed, the coherent noise source distributions can be considered as a timereversal
mirror and the cross-correlation operations gives the field measured at one receiver after refocusing
on the other receiver. Passive-only reconstruction of coherent Lamb waves (80-200 kHz) in an aluminum plate
and thickness comparable to aircraft fuselage and wing panels will be presented. In particular, the influence
of the noise source characteristics (location, frequency spectrum) on the signal-to-noise ratio the emerging
coherent waveform will be investigated using a scanning laser Doppler velocimeter. This study suggests the
potential for a structural health monitoring method for aircraft panels based on passive ultrasound imaging
reconstructed from diffuse fields.
| Identifer | oai:union.ndltd.org:GATECH/oai:smartech.gatech.edu:1853/33896 |
| Date | 17 March 2009 |
| Creators | Duroux, Adelaide A. |
| Publisher | Georgia Institute of Technology |
| Source Sets | Georgia Tech Electronic Thesis and Dissertation Archive |
| Detected Language | English |
| Type | Thesis |
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