by H.B Huntington. / "March 21, 1947." / Bibliography: p. 21. / Army Signal Corps Contract No. W-36-039 sc-32037

Laser ultrasonics has been used to measure the bending stiffness of paper products by measuring the dispersion of ultrasonic plate waves. In laser ultrasonics, ultrasound can be generated by absorption of pulsed laser spot while detection can be carried out by Laser Doppler Interferometry. The research presented in this paper describes a new method to detect ultrasonic plate waves using a recently developed acoustic transducer, more specifically an optical Micro ElectroMechanical System (MEMS) microphone with broadband capability. The MEMS device operates as a non-contact proximity probe placed less than ¼ a millimeter away from the plate. The signals are detected with a capacitive micromachined ultrasonic transducer (cMUT) in which the back electrode of the capacitive transducer on a transparent substrate is shaped as an optical diffraction grating. The displacement of the transducer membrane is determined using an optical interferometer. By applying voltage to deflect the membrane electrostatically, the detection sensitivity is kept at an optimum level. The main purpose of the research presented herein was to test this MEMSs ability to detect ultrasonic waves propagating through paper, to increase the signal-to-noise ratio (SNR), and to calibrate the device in order to quantify the limitations on sensitivity in the context of the detection of ultrasound in paper. Similar tests were conducted for comparison with a modified Mach-Zehnder Interferometer, a more traditional method used for laser ultrasonic detection, and its results are presented in this paper.

No description available.

Abstract The objective of this research is to develop a vibration wave technique for pipeline inspection globally. It is known that the pipeline systems are widely used in chemical industry, petroleum company, or nuclear power plant. In addition, the pipeline systems are also very danger since they usually carry high pressure, high temperature, or even highly corrosive fluids. Therefore, the need for careful nondestructive testing on frequent base to determine the damage of the pipeline and the need for repair arise. The nondestructive testing methods usually used to evaluate the cracks in a pipeline are liquid penetrant method, eddy current testing, ultrasonic testing, acoustic emission method, and radiographic inspection, and etc. Technicians will usually apply one of or the combination of the methods to get the testing job done. However, the above-mentioned techniques (except for acoustic emission) can only inspect a small area or spot of the pipeline, which is very time consuming for evaluating the whole pipeline. The error will also build up easily since the technicians have to perform the measurement repeatedly. To overcome the above-mentioned problems, this research proposes a vibration wave technique to measure the resonant frequency and the vibration mode of the whole or a long pipeline. The experimental results can be used to characterize the damage in the pipeline. The knowledge obtained from the research can also be used to define the criteria of inspection or repair procedures and life cycles of the pipeline.

Thesis (M.S.)--Mechanical Engineering, Georgia Institute of Technology, 2004. / Berthelot, Committee Chair; Lynch, Committee Member; Jacobs, Committee Member. Includes bibliographical references (leaves 111-113).

Thesis (M. Phil.)--University of Hong Kong, 1981.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Ume, I. Charles; Committee Member: Kalaitzidou, Kyriaki; Committee Member: Mayor, J. Rhett. Part of the SMARTech Electronic Thesis and Dissertation Collection.

published_or_final_version / Electrical Engineering / Master / Master of Philosophy

published_or_final_version / Electrical Engineering / Doctoral / Doctor of Philosophy

No description available.