This thesis presents a multi-purpose sensor concept viable for the simultaneous
measurement of pressure, temperature and thickness of plate structures. It also
establishes the knowledge base necessary for future sensor design. Thermal-Acousto
Photonic Non-Destructive Evaluation (TAP-NDE) is employed to remotely initiate and
acquire interrogating ultrasonic waves. Parameters including pressure, temperature and
plate thickness are determined through exploring the dispersion features of the
interrogating waves. A theoretical study is performed, through which a modified wave
propagation theory applicable to homogeneous, isotropic, linear elastic materials is
formulated along with an associated numerical model. A numerical scheme for solving
the model is also developed using FEMLAB, a finite element based PDE solver. Gabor
Wavelet Transform (GWT) is employed to map numerical time waveforms into the joint
time-frequency domain. Wave time-frequency information enables dispersion curves to
be extracted and material pressure, temperature and thickness to be determined. A sensor
configuration design integrating the wave generation and sensing components of the
proven TAP-NDE technology is also developed.
Conclusions of the research are drawn from wave dispersion obtained corresponding
to the following ranges of parameters: 300-500kHz for frequency, 25-300oC for
temperature, 1-3mm for plate thickness, and 6 10 1?? - 7 1 10 ?? N/m for pressure. Each of
the three parameters considered in the study has a different level of impact on plate wave
dispersion. Plate thickness is found to have the most impact on wave dispersion,
followed by temperature of the plate. The effect attributable to pressure is the least
prominent among the three parameters considered. Plate thickness and temperature can
be readily measured while simultaneously resolved using dispersion curves. However,
pressure variation can only be differentiated when the plate is smaller than 1mm in thickness. It is observed that the thicker the plate, the faster the frequency group velocity.
Also, the group velocities of all frequency components considered are seen to increase
with increasing temperature, but decrease with increasing pressure.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/2598 |
| Date | 01 November 2005 |
| Creators | Lo, Tzu-Wei |
| Contributors | Suh, Chii-Der S. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 3418956 bytes, electronic, application/pdf, born digital |
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