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Ultrasonic measurement of thin condensing fluid filmsShear, Michael A. January 2002 (has links)
Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: microgravity; condensation; ultrasound. Includes bibliographical references (p. 138).
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Characterization of air voids in fresh cement paste through ultrasonic nondestructive testingKmack, Richard Matthew. January 2008 (has links)
Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Jacobs, Laurence; Committee Co-Chair: Kurtis, Kimberly; Committee Member: DesRoches, Reginald.
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Characterization of nonlinearity parameters in an elastic material with quadratic nonlinearity with a complex wave fieldBraun, Michael Rainer. January 2008 (has links)
Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Jacobs, Laurence; Committee Co-Chair: Qu, Jianmin; Committee Member: DesRoches, Reginald. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Analytical investigation of internally resonant second harmonic lamb waves in nonlinear elastic isotropic platesMueller, Martin Fritz. January 2009 (has links)
Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Laurence J. Jacobs; Committee Member: Jianmin Qu; Committee Member: Jin-Yeon Kim. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Analysis and modeling of diffuse ultrasonic signals for structural health monitoringLu, Yinghui. January 2007 (has links)
Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008. / Durgin, Gregory, Committee Member ; Vachtsevanos, George, Committee Member ; Michaels, Thomas, Committee Member ; Michaels, Jennifer, Committee Chair ; Jacobs, Laurence, Committee Member.
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EMBEDDED SPECKLE BONDLINE DEFECT DETECTION USING ULTRASONIC DIGITAL IMAGE CORRELATION (UT-DIC)Lim, WeiChiang Eric 01 August 2018 (has links)
The primary objective of this research is to conduct further evaluation of ultrasonic digital image correlation (UT-DIC) on strain map analysis and defect detection of adhesive joints with embedded speckle pattern. UT-DIC is a non-destructive evaluation method that utilized ultrasonic C-scan images for whole field strain and displacement analysis. Acrylic glass, epoxy resin system and metal shavings with high acoustic impedance of a specific weight were used to create the samples which were loaded under tension. Defects with varying shapes and sizes were implemented by surface preparation to understand the limits of this approach. UT-DIC and optical DIC strain map results were compared, and it was found that each approach detected certain shapes of defect better than the other.
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Ultrasonic measurement of membrane fouling during microfiltration of natural brown waterMbanjwa, Mesuli Bonani January 2007 (has links)
Thesis (MTech (Engineering))--Cape Peninsula University of Technology, 2007 / The removal of the colour-eausing natural organic matter (NOM) from natural
brown water (NSW) to be used for drinking purposes is of paramount
importance. One of the methods available to remove NOM from NSW is the use
of pressure-driven membrane separation systems. One of the limitations in
efficiently applying membrane filtration in the treatment of NOM-eontaining
water is membrane fouling that is caused by foulants, such as NOM, that
accumulate on the membrane surface and in the membrane pores.
Microfiltration (MF), as a membrane separation system, is susceptible to severe
membrane fouling during membrane filtration of NSW. Fouling is characterized
by a rapid decline in permeate flux and loss of productivity.
Progress in developing more effective control and prevention of fouling is
impeded by the absence of suitable fouling measurement and characterization
techniques. An in situ method for measuring membrane fouling is necessary for
detection of membrane fouling during MF of NSW at the eartiest stages so that
the corrective actions can be taken before fouling is permanently adsorbed onto
the membrane surface.
In this study, an ultrasonic-based method was effectively used to detect and
measure the growth of membrane fouling dUring MF of NSW, in situ. Fouling
exp~riments results showed the formation of a new peak on the ultrasonic
response echo signal due to the presence of a fouling layer on the surface of
the membrane. The ultrasonic signals acquired during the in-situ detection of
membrane fouling were analysed using wavelet transforms (WTs). Wavelet
analysis was applied to differential signals to obtain additional information about
fouling. Differential signals were calculated by subtracting the baseline
measurement signals from the test signals. The presence of the fouling layer on
membranes was verified by atomic force microscopy (AFM) and scanning
electron microscopy (SEM) analyses of the fouled membranes.
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Acousto-ultrasonics for defect assessment of composite materialsDugmore, Kevin M. January 2002 (has links)
A thesis submitted in compliance with the requirements for the Masters Degree in Technology: Mechanical Engineering at Technikon Natal, 2002. / The experiments and their results contained herein will form the basis for the development of a portable non-destructive testing device for composite structures. This device is to be capable of detecting any of a variety of defects and assessing their severity within a short time / M
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Advanced ultrasonic digital imaging and signal processing for applications in the field of non-destructive testingWeston, Miles January 2012 (has links)
Non-destructive testing (NDT) is the process of non-invasive material examination. Within this field, ultrasonic inspection is one method of examination used to detect flaws in structural and functional industrial components, to assess their structural integrity and fitness for service. Conventional NDT ultrasonic array techniques transmit on multiple elements in parallel, according to a focal law, which facilitates beam steering, focussing and scanning within the test component. Received signals are then 'stacked' to generate images of the test component. With the advent of affordable high speed computing, novel data acquisition techniques based on sequential transmission are now able to be developed, which allow images to be generated using advanced signal processing and image reconstruction algorithms. One such data acquisition technique known as Full Matrix Capture (FMC), has received considerable research attention in recent years, largely because it allows fully focused images of test components to be generated. This project provides an improved understanding of the FMC technique and associated signal processing algorithms. It achieves this through the development of novel inspection techniques and signal processing algorithms. Collectively algorithms developed within this work were termed Sequential Phased Array (SPA). Initially comparisons were made between conventional ultrasonic techniques and the SPA algorithms in terms of image quality and speed of inspection. A novel approach was then suggested to facilitate inspection through dual-layered media, separated by a refractive interface using the SPA algorithms. The use of sparse arrays to enhance the speed of inspection using the SPA algorithms was also investigated, and the trade-off between speed of inspection against image degradation was addressed. Finally a novel approach to calibration of a FMC based system was developed, in order to provide uniform image sensitivity during inspection.
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Suppression of Higher Acoustic Harmonics by Application of Solid-Solid Periodic Layered Structure in Nonlinear Ultrasonics Nondestructive Evaluation FieldKang, Jinho 05 1900 (has links)
Nondestructive testing (NDT) using ultrasound band 1-5 MHz, has been widely used for the early-stage detection of structural failure; however, it fails to detectf material degradation, fatigue, and microcracks. NDT with nonlinear ultrasound (NLU) can detect a microscopic discontinuity or imperfection that may be a source of the second harmonic in the reflected signal. In this research, we focus on creating a metamaterial band filter that filters out nonlinearities induced by the instrument itself. A 1D elastic superlattice (SL) acoustic filter is designed with a bandgap in its frequency spectrum that covers the frequency range of second harmonic. The SL is made of periodically alternating Cu and Sn-Pb solder layers. We conducted analytical and numerical calculations to obtain the appropriate thickness of each layer. The metamaterial in this study has the pass band for the fundamental frequency of 5 MHz and the first stop band centered near the frequency of 10 MHz; 5 MHz was chosen because the second harmonic at 10 MHz can detect 200μm micro-scale damage. Experiments with aluminum as the reference specimen and with SL filter were conducted. A function-generator generates 3 pulses sine signal, within the frequency range from 2.5 MHz to 20MHz. Spectral analysis of the signal through the SL filter shows 100 times voltage suppression of the second harmonic as compared to the signal transmitted through the Al specimen. By filtering out the device's inherent nonlinearity with the SL ultrasonic filter, one can detect microcracks, fatigue and material degradation with much higher accuracy.
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