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1
Empie, Laurel E. "Measuring and interpreting civil engineering vibrations." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/21430.
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2
Kang, Ma Ru. "Measurement of Vibrations of Gears Supported by Compliant Shafts." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1253021230.
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3
Lin, Shawn Hsien Fan. "A laser interferometer for measurement of surface vibrations and ultrasound." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/15985.
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4
Pugh, Alan James. "An optical displacement monitor for the measurement of low frequency vibrations." Thesis, University of Exeter, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335511.
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5
McMahon, Kim J. "Whole-body vibration comfort measurement aboard the S. A. Agulhas II and just noticeable difference threshold testing in the laboratory." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95938.
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Thesis (MEng) -- Stellenbosch University, 2014.<br>ENGLISH ABSTRACT: A continuous comfort analysis of the whole-body vibration level aboard the
S.A. Agulhas II during the 2013-2014 Antarctic voyage was conducted ac-
cording BS ISO 2631-1:1997, assuming a standing posture. Just noticeable
difference in magnitude testing was conducted on nine subject in the standing
posture on a man-rated shaker in the laboratory environment. Two stimuli,
a 5 Hz sinusoidal stimulus with a magnitude of 0,5 m.s-2 and a slamming
event recoded during the voyage with a magnitude of 0,2 m.s-2 where selected
as the stimuli on which to investigate the just noticeable difference thresh-old. The study shows that the vibration level for the duration of the voyage
can be considered to be not uncomfortable. The results of the just notice-able difference threshold obtained for the sinusoidal stimulus concur with that
found in literature for seated subjects. The just noticeable difference threshold
obtained for the ship stimulus does not correlate with the results for the sinu-soidal vibration, implying that there may be an error in the vertical weighting filter provided by the standard or that Webers law does not hold for the just
noticeable difference threshold of standing subjects.<br>AFRIKAANSE OPSOMMING: 'n Deurloopnede gemakanalise van volliggaam vibrasievlakke aanboord die
S.A. Agulhas II is uitgevoer. Die analise tydens die 2013-2014 Antarktiese
reis is gedoen volgens BS ISO 2631-1 : 1997 vir 'n staande postuur. 'n Net-opmerkbare-verskildrempel toets is uitgevoer op nege vrywillers in 'n staande postuur deur vibrasieherkonstruksie op 'n platform in die laboratorium. Twee stumuli, 'n 5 Hz sinusvorminge stimulus (0,5 m.s-2 r.m.s.) en 'n branderim-pak stimulus (wat tydens die reis opgeneem is, 0,2 m.s-2 r.m.s. is gebruik)
om die net-opmerkbare-verskildrempel to ondersoek. Die studie toon dat die
vibrasievlakke gedeurende die reis as `nie ongemaklik' geklassifiseer kan word.
Die resulte van die net-opmerkbare-verskildrempel verkry vir die sinusvormige
stimulus stem saam met bevindinge vir sittende vrywilligers uit die literatuur.
Die net-opmerkbare-verskildrempel verkry vir die skip stimulus stem egter nie
'n moonlike onakkuraatheid weegfunksie is wat deur die standard is aanbeveel
word of datWeber se wet nie toepaslik is vir die net-opmerkbare-verskildrempel van staande vreywilligers nie.
6
Carson, Gillian. "Particle sizing using hertz-zener theory and ultrasonic measurement of impact vibrations." Thesis, University of Strathclyde, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488858.
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In this thesis a theoretical model that describes particles impacting with a circular plate, the resulting flexural vibrations of the plate, and its detection by an ultrasonic transducer, is described. Using a variety of approximations, an analytic expression for the plate vibrations is derived. This is then expressed as a Fourier series and an analytic expression for the frequency of the first main peak of the spectrum is obtained.
7
Yang, Ming. "Development and analysis of a multiple beam laser system for measurement of surface vibrations." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/17685.
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8
Monnot, Olivier. "Recalage de modèles dynamiques à partir de la réponse en fréquence : application au recalage des modèles du lanceur Ariane 5." Châtenay-Malabry, Ecole centrale de Paris, 1995. http://www.theses.fr/1995ECAP0407.
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Le contexte général du recalage de modèle à partir d'essais vibratoires est présenté dans le premier chapitre. En particulier, les critères usuels pour confronter modes calcules et modes mesures sont décrits. Dans une seconde partie, un recensement des méthodes de recalage déjà existantes est effectué. On distingue ainsi les méthodes de correction globale de celles basées sur le contrôle paramétrique du modèle. Ces dernières reposent sur trois idées différentes : les techniques de sensibilité, l'évaluation des forces résiduelles dans les équations d'équilibre, l'analyse des erreurs en relation de comportement. La démarche adopté par l'auteur est développée dans le troisième chapitre. Elle est composée de trois étapes : l'expansion des données expérimentales, étape la plus critique, la localisation des erreurs par l'analyse des forces résiduelles, la correction paramétrique des zones localisées par minimisation sous contraintes d'une fonctionnelle énergétique. Une méthode d'optimisation de l'emplacement des capteurs basée sur la maximisation de la matrice d'information de Fisher est également présentée. Dans la dernière partie, la méthode a été appliquée sur un cas test garteur, et également pour le recalage des modèles du lanceur Ariane 5. De nombreuses références bibliographiques sont fournies
9
Liu, Zhao. "Modeling and measurement of the effects of atmospheric turbulence and platform vibrations on laser communication." Diss., Online access via UMI:, 2009.
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Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Electrical and Computer Engineering, 2009.<br>Includes bibliographical references.
10
Soal, Keith Ian. "Vibration response of the polar supply and research vessel the S. A. Agulhas II in Antarctica and the Southern ocean." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/96058.
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Thesis (MEng) -- Stellenbosch University, 2014.<br>ENGLISH ABSTRACT: Full scale measurements were conducted on the polar supply and research vessel
the S.A. Agulhas II during a 78 day voyage from Cape Town to Antarctica in
2013/2014. Investigations were conducted into the effect of vibration on human
comfort and the structural dynamic response of the vessel. Vibration measured
in the bridge of the vessel is found to have little effect on human comfort for a
standing person and is classified as not uncomfortable according to BS ISO 2631-1.
Structural fatigue as a result of vibration is found to reach levels where damage
is possible in the stern and where damage is probable in the bow during open
water navigation, according to ship vibration guidelines by Germanischer Lloyd.
Multivariate statistical analyses are performed to investigate the relationships between
multiple predictor variables and vibration response. Factor analysis revealed
data structure from which specific physical phenomena could be identified. Multivariable
linear regression models are developed to predict vibration response and
are found to provide more accurate predictions in open water than in ice. The
2-node, 3-node and 4-node normal bending modes of the structure are identified
using operational modal analysis while the vessel was moored in the harbour. The
natural frequencies, damping ratios and mode shapes are estimated and compared
using LMS Operational PolyMAX and ARTeMIS CCSSI. A comparison of operational
modal analysis results to the STX Finland finite element model show that
the vessel’s modes occur at lower frequencies than numerically predicted. Clear
potential is identified to further investigate structural vibration and operational
modal analysis algorithm development in future research.<br>AFRIKAANSE OPSOMMING: Volskaal metings was op die poolvoorsienings en navorsingskip die S.A. Agulhas
II uitgevoer tydens ’n 78 dae reis van Kaapstad tot Antarktika in 2013/2014.
Ondersoeke is uitgevoer met betrekking tot die effek van vibrasie op menslike gemak
en die strukturele dinamiese reaksie van die vaartuig. Vibrasie wat in die brug
van die skip gemeet is, het min invloed op menslike gemak vir ’n staande persoon
en word geklassifiseer as nie ongemaklik volgens BS ISO 2631-1. Strukturele vermoeidheid
as gevolg van vibrasie bereik vlakke waar skade moontlik is in die spieël
en waar skade waarskynlik is in die boog tydens navigasie in oop water, volgens
skip vibrasie riglyne deur Germanischer Lloyd. Meerveranderlike statistiese ontledings
is uitgevoer om die verhoudings tussen verskeie voorspellerveranderlikes
en vibrasieterugvoer te ondersoek. Faktorontleding het data struktuur openbaar
waaruit spesifieke fisiese verskynsels geïdentifiseer kan word. Multi-veranderlike lineêre
regressiemodelle was ontwikkel om vibrasie reaksie te voorspel en lewer meer
akkurate voorspellings in oop water as in ys. Die 2-nodus, 3-nodus en 4-nodus normale
buig modes van die struktuur is geïdentifiseer met behulp van operasionele
modale analise terwyl die skip vasgemeer in die hawe is. Die natuurlike frekwensie,
demping verhoudings en mode vorms is beraam en vergelyk met behulp van
LMS operasionele Polymax en ARTeMIS CCSSI. ’n vergelyking van operasionele
modale analise resultate en ’n STX Finland eindige element model toon dat die
vaartuig se modusse voorkom by laer frekwensies as wat numeries voorspel word.
Duidelike potensiaal is geïdentifiseer om strukturele vibrasie en die ontwikkeling
van operasionele modale analise algoritmes te ondersoek in toekomstige navorsing.
11
Sica, G. "Groundborne vibrations caused by railway construction and operation in buildings : design, implementation and analysis of measurement for assessment of human exposure." Thesis, University of Salford, 2014. http://usir.salford.ac.uk/32832/.
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Environmental issues surrounding railway operation and construction have become more prominent in recent years, increasing the need for administrators and researchers to understand how residents living around railways respond to the noise and vibration generated by them. Within this context, the University of Salford, within the project funded by Defra “Human response to vibration in residential environments” (NANR209), has derived exposure response relationships for railway traffic and construction for a population sample of 1281 people: 931 for railway traffic and 350 for railway construction. Vibration measurements within residences have been used for assessing human exposure to vibration alongside a social study questionnaire based on face-to-face interviews for quantifying the human response. The first part of this work is concerned with the exposure side of NANR209. The design and implementation of measurement methodologies are presented and discussed, which provide exposure data suitable for building an exposure response relationship for vibration caused by the sources mentioned above. In light of the large amount of vibration data gathered during the project, the analysis of vibration signals is considered in the second part of the dissertation. Two aspects connected with the assessment of the human exposure to vibration are investigated: wave field assessment and ground to building transmissibility analysis.
12
Fučík, Ondřej. "Návrh opatření pro snížení hluku Rootsova dmychadla." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443883.
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The Master‘s thesis deals with issues of noise and vibrations of Roots blowers. In the theoretical part, potential sources of noise and vibrations are described. Detailed knowledge of basic types of mufflers is summarized, and their suitability for the corresponding application is evaluated. The practical part is focused on performing experimental measurements of the Roots blower’s noise and vibrations and the main sources of noise are determined. Subsequently, the existing anti-noise measures are analyzed and the proposal for adjusting the current measures for further noise reduction is presented.
13
Moine, Pascal. "Recalage de modèles éléments finis avec amortissement." Châtenay-Malabry, Ecole centrale de Paris, 1997. http://www.theses.fr/1997ECAP0537.
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Cette thèse est consacrée au recalage de modèles éléments finis avec amortissement visqueux non proportionnel sur les caractéristiques modales des structures modélisées. Le document est scindé en trois parties. - la première partie consiste en un rappel succinct des différents types d'amortissement couramment utilisés, un exposé de la problématique du recalage et une présentation des méthodes de recalage disponibles. - la seconde partie rassemble les nouveaux développements réalisés par l'auteur. Trois méthodes de recalage de modèles sur les caractéristiques modales des structures correspondantes sont présentées : la méthode de sensibilité inverse des valeurs et vecteurs propres, la méthode d'erreur en valeurs et vecteurs propres et la méthode d'erreur en loi de raideur. Deux méthodes de localisation des erreurs de modélisations sont proposées : la méthode d'erreur en loi de raideur et la méthode d'erreur en loi d'inertie. - la troisième et dernière partie est consacrée à l'utilisation des méthodes figurant dans la seconde partie du document pour le recalage de modèles industriels sur des données issues de mesures. Trois modèles sont recalés : le modèle de la maquette du bâtiment réacteur Hualien, le modèle d'une tuyauterie sur appuis en caoutchouc et le modèle d'une machine tournante.
14
Weiss, Lukáš. "Návrh ovládacího zařízení pro vibrografické měření." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-221087.
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This diploma thesis deals with designing of the control device for vibrographic measurement. The device is primary used in cooperation with MERCURY Real Time Tracking System. The main task of the device is time-controlled triggering of camera system. In the first step, the summary of basic information about technical diagnostic and vibrodiagnostic is reported. The second part describes vibrodiagnostic measurements with MERCURY system. The third part describes a hardware design of the device and functional blocks and its parameters. Next part provides a simple algorithm of the device operation and a communication protocol. Last part contains measured data of the realized device and vibrographic measurement with laboratory sample.
15
Meruani, Azeem. "Tweel (TM) technology tires for wheelchairs and instrumentation for measuring everyday wheeled mobility." Thesis, Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-04032007-174305/.
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Vukušičová, Daniela. "Analýza dynamických účinků působících na železniční výhybky." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265636.
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This thesis is focused on measurement and analysis of dynamic effects on railway turnouts. Two same-type turnouts with different fastening elasticity were chosen. My attention was focused mainly on the crossing part of the turnout, where the highest dynamic impacts occur. The point of the thesis is comparison of the crossing part of turnouts in term of dynamic behaviour and assessment of influence of soft rail pads on spread of dynamic energy through the construction. A part of the thesis is choice of methodology of the measurement and proposal of convenient mathematical apparatus for analysing of the dynamic effects on crossings.
17
Maigrot, Philéas. "Compréhension des mécanismes perceptifs associés à la gêne due aux bruit et vibrations du trafic ferroviaire en zone urbaine." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI051.
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La co-exposition au bruit et aux vibrations est source de gêne pour les riverains et peut engendrer des troubles de la santé. L’objectif de la thèse est d’apporter des éléments de compréhension au regard des phénomènes perceptifs mis en jeux lors de l’exposition combinée au bruit et aux vibrations ferroviaires. Des expériences sont menées dans ce but, en conditions contrôlées et à l'aide d'enregistrements acoustiques et vibratoires réalisés à proximité d'une voie ferrée, à l'intérieur d'un logement. Une première étude a été réalisée afin de valider un protocole expérimental permettant de recueillir en laboratoire des réponses de gêne. Pour plusieurs combinaisons d'enregistrements de bruit et de vibrations ferroviaires présentés à différents niveaux, la gêne 1) partielle due au bruit, 2) partielle due aux vibrations et 3) totale due à la co-exposition au bruit et aux vibrations étaient recueillies. Les résultats de cette première étude ont été utilisés afin d'adopter un même protocole expérimental tout au long de ces travaux de thèse. Les études traitant de la gêne due aux bruit et vibrations ferroviaires sont majoritairement basées sur des indices ne reflétant que la quantité d’énergie liée à chaque exposition et leurs résultats peuvent être contradictoires. Une seconde étude a été menée en laboratoire dans le but d'évaluer l’influence de l’intensité (sonore, vibratoire) sur la gêne et afin de déterminer l'origine des différences de résultats dans la littérature. Les hypothèses testées étaient que ces différences pourraient être dues aux différentes plages de niveaux sonores et vibratoires étudiées, ou à des différences de contenus fréquentiels au sein des stimuli utilisés dans les différentes expériences. Dans la littérature, un besoin d’autres études en laboratoire est souligné afin de mieux comprendre l’influence des paramètres autres que le niveau global vibratoire (p. ex. contenu spectral, modulation) sur la gêne due aux vibrations ferroviaires. Un travail a été réalisé afin de mieux comprendre le rôle du contenu spectral vibratoire dans la gêne spécifique due aux vibrations, en l'absence de bruit. Une expérience a été conduite en utilisant des stimuli vibratoires artificiels, créés à partir des spectres d'enregistrements de vibrations ferroviaires. L'importance des paramètres autres que les niveaux de bruit et de vibrations globaux sur les variations de la gêne due à la co-exposition aux bruit et vibrations ferroviaires a fait l'objet d'une dernière étude. Les stimuli utilisés étaient obtenus à partir de 19 enregistrements sonores et vibratoires réalisés chez un riverain d'une voie ferrée, en les ramenant à une durée de 10s et en contrôlant les variations de niveau de bruit et de vibrations. Cette étude a montré que l'importance relative des paramètres temporels et fréquentiels de la co-exposition au bruit et aux vibrations était faible au regard de celle des paramètres énergétiques<br>Vibrations due to railway traffic propagate from the tracks to inside neighbour houses. Residents who are exposed to vibrations are also exposed to railway noise. This combined exposure to noise and vibration leads to annoyance, as well as to some health issues. Few studies have been conducted to investigate this combined exposure in terms of annoyance. The goal of the thesis is to improve the knowledge concerning the perceptual phenomena involved when both railway noise and railway vibration occur at the same time. Experiments are carried out in controlled conditions for that purpose, using acoustic and vibratory recordings obtained in the vicinity of a railway track, inside a dwelling. A first study was conducted in order to test the validity of an experimental procedure allowing to collect annoyance responses in laboratory conditions. For several combinations of noise and vibration at different noise and vibration levels, annoyance responses were collected: 1) partial annoyance due to noise, 2) partial annoyance due to vibration and 3) total annoyance due to combined noise and vibration. Results of this first study led to a common procedure used for the rest of the experiments carried out during this thesis work. Studies about annoyance due to combined railway noise and vibration often use indices which only describe an amount of energy for each single exposure. Results can be contradictory. A second study was conducted in the laboratory in order to evaluate the influence of (noise and vibration) intensity on annoyance and to determine the reason of the contradictory results observed in the literature. The initial hypotheses made in the current work were that those could be due to the different ranges of variation of noise and vibratory levels, or to the different spectral contents of the stimuli used in the studies of interest. In the literature, there is a reported need of further investigations about the influence of parameters not related to vibration level (\textit{e.g.} frequency content, modulation) on railway vibration annoyance. During this thesis, work was done in the aim of a better understanding of the role of vibratory spectral content in specific annoyance due to vibration in the absence of noise. An experiment was conducted using artificial vibration stimuli based on the railway vibration recording spectra. The importance of parameters other than overall noise or vibration levels on variations of the annoyance due to combined railway noise and vibration was investigated during a last study. The stimuli were based on 19 noise and vibration recordings obtained inside a dwelling, after having reduced their duration to 10s and with controlled variations of noise and vibration levels. The results showed that the relative importance of temporal and spectral parameters of the combined exposure to noise and vibration was low as compared to that of energetic parameters
18
Janoušek, Michal. "Virtuální prototypy hnacích ústrojí." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-263346.
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The thesis deals with computational modelling of heavy duty off-road vehicle driveline components. The thesis is divided to two main parts. The first part deals about modal analysis of selected driveline components. MBS computational study was performed based on modal analysis results. The second part of thesis deals with experimental verification of computational model. Pass-by noise and vibration measurement was performed. Measured signals were processed in frequency domain to find noise and vibration sources.
19
Xiao, Xinghua. "Vibration measurement using videogrammetric method /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202009%20XIAO.
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20
Rozsypal, Filip. "Senzor na bázi optovláknového interferometru." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2019. http://www.nusl.cz/ntk/nusl-400895.
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This diploma thesis deals with comparsion of 2x2 and 3x3 couplers. There is also description of issue of the Michelson interferometer and its use as a sensor. This sensor is very good at detecting vibrations. Part of the work is description of simulation of Michelson interferometer with 3x3 coupler as vibration sensor and localization of vibration on optical fiber by Michelson and Mach-Zehnder interferometer.
21
Cinarel, Dilara. "Vibration Isolation Of Inertial Measurement Unit." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614069/index.pdf.
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Sensitive devices are affected by extreme vibration excitations during operation so require isolation from high levels of vibration excitations. When these excitation characteristics of the devices are well known, the vibration isolation can be achieved accurately. However, it is possible to have expected profile information of the excitations with respect to frequency. Therefore, it is practical and useful to implement this information in the design process for vibration isolation.
In this thesis, passive vibration isolation technique is examined and a computer code is developed which would assist the isolator selection process. Several sample cases in six degree of freedom are designed for a sample excitation and for sample assumptions defined for an inertial measurement unit. Different optimization methods for design optimizations are initially compared and then different designs are arranged according to the optimization results using isolators from catalogues for these sample cases.
In the next step, the probable designs are compared according to their isolator characteristics. Finally, one of these designs are selected for each case, taking into account both the probable location deviations and property deviations of isolators.
22
Donarski, Robert J. "Bone fracture measurement using mechanical vibration." Thesis, University of Kent, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.256998.
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23
Lam, Frank C. F. "Analytical and experimental studies of the behaviour of equipment vibration isolators under seismic conditions." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25110.
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Analytical and experimental studies of the behaviour of equipment vibration isolators under seismic conditions are presented. A preliminary parametric study of the effect of equipment-structure interaction on the ultimate equipment response of general equipment-structure systems is considered first. The results of this study indicate the conditions under which a non-interactive approach can yield adequate ultimate equipment response estimates.
A model of a prototype air handling unit mounted on vibration isolators was constructed for use in the experimental studies. Two types of vibration isolators -elastomeric isolators and open spring isolators with uni-directional restraint - were tested under static and dynamic conditions. The frequency and seismic response characteristics of these vibration isolated systems were obtained. The experimental results indicate that the vibration isolators have nonlinear stiffness characteristics and high damping values. The results also show that the elastomeric isolators can survive a substantially higher level of base excitation than the open spring isolators with uni-directional restraint
Analytical models of the vibration isolated systems, based on the model identification test results, have been formulated. A numerical procedure, utilizing time series analysis, was used to solve the equations of motion of the systems. Good agreement between the experimental results and the analytical results was observed. This study indicates that the analytical procedure can be used to accurately predict the response characteristics of vibration isolated equipment systems subjected to known base excitation inputs.<br>Applied Science, Faculty of<br>Civil Engineering, Department of<br>Graduate
24
Mignosi, Christine. "Non-contact optical sensing for vibration measurement." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341505.
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Chen, Justin Gejune. "Video camera-based vibration measurement of infrastructure." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104119.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2016.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (pages 257-266).<br>Functional infrastructure-including transportation, energy, and buildings and other facilities - is key to the economic production of a country and the daily lives of its people. Due to deterioration and potential damage, timely inspections and repairs are necessary to keep infrastructure functioning at full capacity. Visual testing is one of the oldest and most widely used methods for condition assessment; however, this technique is limited since it is based on an inspector's subjective rating rather than on an objective quantitative measure of structural condition. Quantitative alternatives to visual testing have emerged over time. These include vibration analysis, in which a structure's operational resonant frequencies and mode shapes are measured and compared against a healthy baseline to detect changes. Typically, contact sensors such as accelerometers have been used to measure vibrations. When physical access to a structure is limited or the placement of contact sensors is too time-consuming, new technologies that allow for non-contact measurements can be used. Video cameras, where each pixel is effectively a sensor, can remotely collect a large amount of data from a structure. The challenge is then to interpret these videos into quantitative vibration data. In this research, newly developed computer vision techniques for analyzing small motions in videos and their application to the vibration measurement and condition assessment of infrastructure are presented. These techniques allow for qualitative visualizations of normally imperceptible motions as a form of enhanced visual testing, and quantitative measurements of the displacements and vibrations of structures as a basis for condition assessment. Computer vision algorithms for processing video are described and the technique is experimentally validated against traditional sensors. The methodology is demonstrated with a series of laboratory measurements of simple representative structures and field measurements of civil infrastructure, including the WWI Memorial Bridge in Portsmouth, New Hampshire.<br>by Justin Gejune Chen.<br>Ph. D.
26
Perez, Hugo. "New Measurement Methods For Ground Vibration Test." Thesis, KTH, Flygdynamik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-276465.
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Flight-testing represents an important step of an airplane development. Every new or modified aircraft configuration is tested. Through set of tests, the quality and reliability of aircrafts are guaranteed. At Dassault Aviation, the flight test Directorate responsible for carrying out flight tests is located at Istres, in South of France. One major test before flying is the Ground Vibration Test (GVT). The aim of this test is to measure Eigen frequencies and mode shapes of the structure. Those results are after compared to the ones given by the finite element model in order to verify it or update it. Determining the structural behavior has a significant importance for aircraft safety, for instance, it helps to determine the aircraft’s flutter boundary. Under unsteady aerodynamic loads, the aircraft structure can be dynamically unstable, meaning that the amplitude of oscillations increases with time. This phenomenon called flutter can highly damage the airplane or can even lead to the complete destruction of its structure. GVTs are performed by exciting the aircraft with oscillatory forces on designated parts. Then, hundreds of accelerometers are used to measure the vibrations. Knowing exactly the input excitation and how the structure answers, it is possible to calculate the relations (so-called transfer functions) between the applied oscillatory forces and the acceleration measurements. This measurement method based on accelerometers is highly accurate; however, one accelerometer only provides one punctual measurement. In order to have an infinite number of measurement points and thus, a better understanding of the mode shapes, new measurement methods should be investigated. As part of Ground Vibration Testing, this paper presents an investigation on new innovative measurement methods that could improve and complement the current methods based on accelerometers. This report is structured in three parts; the first part gathers and presents some innovative measurement methods and the two following parts focus on experimentations of two measurement methods using rapids cameras and 3D laser scanners.<br>Flygtestning är ett viktigt steg av att utveckla ett flygplan. Genom en uppsättning tester blir varje ny eller modifierad flygkonfiguration certifierad. Certifiering garanterar säkerhet, kvalitet och pålitlighet. Avdelningen för flygtestning på Dassault Aviation är ansvarig för genomförandet av flygtester I Istres, södra Frankrike. Ett viktigt test före flygning är Ground Vibration Test (GVT). Målet med detta test är att mäta strukturens egenfrekvenser och lägesformer. Resultaten jämförs sedan med dem som ges av den finita elementmodellen för att kunna verifiera eller uppdatera dem. Att fastställa det strukturella beteendet är av stor vikt för flygplanets säkerhet; till exempel hjälper det att stipulera planets flygstabilitet och fladdergränsen. Under ostadiga aerodynamiska belastningar kan flygplanets struktur vara dynamiskt instabil, vilket innebär att svängningens amplitude ökar med med tiden. Resonansfenomenet som kallas för fladder kan allvarligt skada eller till och med leda till total förstörelse av flygplanets struktur. GVT: er utförs genom att utsätta flygplanet för svängande krafter på utsedda delar av planet. Sedan används hundratals accelerometrar för att mäta deformationerna. Genom att veta exakt inmatningsexitering och hur strukturen svarar, är det möjligt att beräkna förhållandena (de så kallade överföringsfunktioner) mellan de applicerade oscillerande krafterna och accelerationsåtgärderna. Denna mätmetod baserad på accelerometrar är mycket exakt; installationen tar emellertid mycket tid och skapar en viktig överbelastning på grund av ett stort antal accelerometrar och kablar som används. Som en del av markvibrationstest presenterar detta dokument en utredning om nya innovativa mätmetoder som kan förbättra, komplettera eller till och med ersätta de nuvarande metoderna baserade på accelerometrar. Denna rapport är strukturerad i tre delar; en kort konstnärligt samling där det presenteras några innovativa mätmetoder och sedan två delar med fokus på experiment av två mätmetoder med hjälp av rapids kameror och 3D-laser. Arbetet är ett första steg i en lång forskning som säkert på några år kommer att avföra accelerometrar och ersätta dem med nya metoder som är mycket bekvämare.
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Kaplan, Shaun. "A wireless sensor network for vibration measurement." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/11424.
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Wireless sensor networks (sensornets) enable distributed sensing, opening up sensing possibilities not previously available. One application of sensornets is online, non-intrusive power transformer monitoring.
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Cunha, Irlon de Ângelo da. "Exposição ocupacional à vibração em mãos e braços em marmorarias no município de São Paulo: proposição de procedimento alternativo de medição." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3134/tde-10042007-000855/.
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No Brasil, como em outros países, podem ser encontrados milhões de trabalhadores com distúrbios e problemas resultantes da exposição ocupacional a vibrações mecânicas. No entanto, são escassos, os estudos e as pesquisas voltados a esse agente, seja com relação ao seu reconhecimento, à sua avaliação ou ao seu controle. Neste trabalho estimou-se a exposição ocupacional a vibrações em mãos e braços dos trabalhadores que atuam nas atividades de acabamento, em marmorarias no município de São Paulo. Os principais critérios técnicos internacionais relacionados ao agente, sua aplicação e interpretação são discutidos frente à legislação nacional. Para a obtenção de um sinal de vibração representativo da exposição dos trabalhadores, utilizou-se um procedimento alternativo de medição, mediante uso de um mini-acelerômetro triaxial e um adaptador de palma fixado diretamente nas mãos dos operadores. Dessa forma, procurou-se contabilizar de modo mais representativo as diversas posturas, forças e posições aplicadas durante a execução das atividades. Foram avaliados os processos de acabamento a seco e a úmido em treze marmorarias do município de São Paulo de um total de vinte e cinco empresas visitadas. Os resultados indicam que há uma predominância das exposições acima do nível de ação (A(8)=2,5 m/s2) em vigor na Comunidade Européia a partir de 2005, sendo importante a adoção de medidas preventivas e de vigilância à saúde dos operadores. Em contrapartida, os Programas de Prevenção de Riscos Ambientais (PPRAs) presentes em parte das empresas abordadas, não fazem menção ao agente, apesar da obrigatoriedade legal. São sugeridas estratégias voltadas à prevenção e ao controle, com base nas observações de campo e nos estudos efetuados junto à bibliografia especializada.<br>In Brazil, such as in others countries, millions of workers have problems and disturbs related with human exposure to vibration. In spite of that, exist few studies and researches related to recognition, evaluation and control of this agent. In this study it was estimated the occupational exposure to hand-arm vibration of workers involved in ornamental stone enterprises in São Paulo city. The main International technical standards related to this agent, it\'s application and interpretation are discussed facing Brazilian\'s regulations. In order to obtain a representative information of worker\'s exposure to vibration, it was used an alternative procedure based on a palm adapter and a mini accelerometer. Both were fixed on the worker\'s palm and aimed to take into account the different postures, forces and positions applied by operators during their activities. The evaluation\'s process and vibration measurements included dry and wet cutting, grinding and polishing of granite and marble in thirteen enterprises in São Paulo city of a total of twenty five enterprises visited. The results indicated that there is a predominance of worker\'s exposure above the action level (A(8) = 2,5m/s2) in force by European Community since 2005, implying the application of preventive measures and worker\'s health surveillance. On the other hand, the Preventive Programs for Environmental Risks presented by the enterprises visited, did not mention anything about the agent, in spite of legal obligation set out by Brazilian\'s regulations. Suggestions related to control and prevention strategies are set out based on field\'s observation and literature revision.
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Engelbrecht, André. "Structural integrity monitoring using vibration measurements." Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-07032006-122342/.
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Clement, Pierre. "Solutions aux limites des interrogateurs B-OTDR pour la surveillance d'infrastructures : augmentation de la portée de mesure et décorrélation des paramètres de température et de déformation." Electronic Thesis or Diss., Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAT042.
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Cette thèse porte sur l’étude des systèmes de mesure répartie de la rétrodiffusion Brillouin dans une fibre optique, que l’on nomme B-OTDR et qui sont sensibles à la température et à la déformation de la fibre. Les solutions d'interrogateurs actuelles permettent l'instrumentation de grandes infrastructures. Cependant, il existe des limites, inhérentes au phénomène physique utilisé, qui ne permettent pas d'adresser certaines applications spécifiques. Ces limites portent sur la distance de mesure maximale accessible par ces interrogateurs mais également sur la décorrélation de la mesure des paramètres de température et de déformation. Nous avons donc cherché, au cours de cette thèse, à adresser des solutions à ces problématiques. Un nouveau système de ré-amplification optique, basé sur les technologies EDFA, a été mis au point. Associé à un système B-OTDR, cette solution nous a permis de réaliser une mesure distribuée de température sur 150 km de fibre avec une répétabilité de 1,5 °C. Cette avancée propose, à notre connaissance, les meilleurs résultats obtenus avec un tel système et nous permet d’envisager son déploiement pour la surveillance d’infrastructures du transport de l’énergie sur de longues distances. Nous avons dans un second temps conçu un nouvel interrogateur, utilisant la rétrodiffusion Brillouin, et permettant la décorrélation des mesures de température et de déformation sur une seule et unique fibre optique. Ce nouvel interrogateur, caractérisé et breveté durant cette thèse, a permis de réaliser une mesure indépendante de température et de déformation sur un câble spécifique inséré dans un puits de forage. Les résultats de ces mesures ont montré à la fois des variations de température et de déformation sur le câble, donnant des informations précieuses à l’opérateur du puits. Le nouvel interrogateur mis au point, permet une séparation de ces deux paramètres avec une répétabilité inférieure à 1 °C et 20 μm/m pour une distance de l’ordre du kilomètre. Pour des distances de l’ordre de la dizaine de kilomètres, la répétabilité de mesure est de 3 °C et 75 μm/m. Ce résultat fait l'état de l'art dans la séparation température/déformation par B-OTDR. Enfin, les différents travaux réalisés pour répondre à ces deux problématiques ont abouti au développement d’un prototype d’interrogateur qui laisse envisager une mesure simultanée de la température, de la déformation, des vibrations acoustiques et de la pression hydrostatique. Ce prototype conduit à des perspectives intéressantes pour une solution complète de surveillance d’infrastructures<br>This thesis deals with distributed optical fiber sensors, especially Brillouin sensors called B-OTDR that are sensitive both to temperature and strain. Some actual limitations due to the scattering phenomenon avoid deployment of this technology for some specific applications. These limitations are about the maximum length measured by the sensor but also the double sensitivity to strain and temperature. From our current B-OTDR sensor, we propose solutions to address these issues.A new re-amplification module using EDFA has been developed and characterized associated to a B-OTDR system. A 150 km distributed temperature measurement with 1,5 °C repeatability has been reached. This record performance let us consider a deployment for very long infrastructure monitoring for the energy transport. In another hand, we developed a new sensing device using Brillouin scattering and able to separate temperature and strain. This patented device has been characterized and used on a specific cable inserted in a well drilling. Results have shown a combination of strain and temperature variations on the cable that give very useful information to the well operator. We have reached a temperature repeatability of 1 °C and a strain repeatability of 20 μm/m for 1 km fiber. At 10 km, temperature repeatability has been evaluated to be 3 °C and strain to 75 μm/m. These results are to the state of art for temperature/strain separation using B-OTDR.These works have led to a new distributed measurement prototype that could address simultaneously temperature, strain, acoustic vibrations, and pressure sensing. Some interesting perspectives could result from these works to address a complete infrastructure monitoring using fiber optic sensing
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沖津, 昭慶, Akiyoshi Okitsu, 秀幸 畔上 та ін. "振動インテンシティ計測法の基礎的検討". 日本機械学会, 1990. http://hdl.handle.net/2237/7230.
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Jones, Janeen Ayana. "Modal analysis on a stiffened panel : an application of laser vibrometry." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/16397.
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Jamasbi, Nooshin. "Detection of the Resonant Vibration of the Cellular Membrane Using Femtosecond Laser Pulses." Thesis, University of North Texas, 1989. https://digital.library.unt.edu/ark:/67531/metadc331235/.
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An optical detection technique is developed to detect and measure the resonant vibration of the cellular membrane. Biological membranes are active components of living cells and play a complex and dynamic role in life processes. They are believed to have oscillation modes of frequencies in the range of 1 to 1000 GHz. To measure such a high-frequency vibration, a linear laser cavity is designed to produce a train of femtosecond pulses of adjustable repetition rate. The method is then directly applied to liposomes, "artificial membrane", stained with a liphophilic potential sensitive dye. The spectral behavior of a selection of potential sensitive dyes in the membrane is also studied.
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Birch, David James. "Impulsive vibration measurement for rolling bearing condition assessment." Thesis, University of Manchester, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635645.
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Rolling element bearings, an essential part of virtually all rotating machinery, fail unpredictably. Systems to measure bearing condition are therefore essential to avoid the financial and human consequences of bearing failure. An impulsive vibration condition monitoring technique known as shock pulse measurement has been used commercially for over thirty years. Its success is well documented yet it is based purely on empirical evidence. No attempt to understand the theory behind it was academically published until the work of Ho (1998). This research extends Ho's work to better understand the determination of rolling element bearing condition from the measurement of impulsive vibration. A rolling element bearing continually produces small impulsive shocks due to the interaction of roughness asperities on the rolling surfaces. A theoretical, stochastic model has been developed that accurately predicts the pattern of such pulses. It predicts patterns produced by various lubricant film thickness in good condition bearings, and those that will be produced by bearings with damage. It can consequently predict the deterioration of a bearing as film thickness decreases through to the onset of damage. A major contribution to the understanding of shock pulse measurement has been made in recognising that the asperity shock pulse patterns are different to the pattern of enveloped pulses produced by the resonant transducers and instrumentation typically used to measure them. Theory has been developed to successfully explain this difference in terms of asperity pulse shape. Appropriate compensation has been included in the model to adjust its output for the various shapes of pulse produced by different asperity interactions. Experiments covering a practical range of bearing sizes and operating conditions, for both bearings in good condition and bearings with damage, have been conducted to validate the model. Low cost, portable instrumentation and resonant transducers have been designed and manufactured to obtain the shock measurements. These devices are capable of being developed into cost effective commercial products with a minimum of additional effort. A better understanding has been gained of the characteristics of piezoelectric transducers when used for shock pulse measurement. This understanding allows transducers to be optimally designed for a given application. A rig and procedure have been developed to obtain the calibration values for resonant transducers used for impulsive vibration measurement. This calibration technique takes into account the pulse shape theory and can be developed into a commercial calibration process with a minimum of effort. Collaboration with a world leading manufacturer of tapered roller bearings, including full access to their existing resources, was a major contribution to the success of this research.
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Rothberg, Steven Joseph. "Laser speckle studies for vibration and torque measurement." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241481.
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Hunt, Hugh Edmund Murray. "Measurement and modelling of traffic-induced ground vibration." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292999.
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Braun, Jeremy Thomas 1980. "A distributed data acquisition network for vibration measurement." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/87382.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.<br>Includes bibliographical references (leaves 107-108).<br>by Jeremy Thomas Braun.<br>M.Eng.
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Yang, Jiansheng. "Vision-based measurement for combustion and vibration studies." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/11650/.
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Vision-based measurement as a useful tool has been applied successfully in many applications. The aim of this thesis is to apply vision-based measurement in both combustion and vibration studies. The purpose is to process and analyse the recorded light information for understanding combustion and vibration conditions. The chemiluminescence emission from a flame contains fundamental information on combustion, and the reflected light from an object’s surface can also provide information on the condition of the measured object. These types of information can be recorded quantitatively into images through a camera. Further processing and analysis of the image data can explore useful information. In this work, a high-speed stereo colour imaging system is employed for both combustion and vibration studies. In each study, a suitable methodology is developed. In a premixed hydrocarbon flame, the blue-green flame colour is mostly attributed to the presence and mixture of chemiluminescence emissions of CH* and C2*. The modern colour camera with the colour filter array (CFA) scheme inherently encodes with red, green, and blue wide-band wavelength filters. According to the aforementioned principles, a flexible image colour model is proposed to detect flame chemiluminescence emissions of CH* and C2*. A sensor calibration process is employed to refine the CH* and C2* concentration expressions based on different camera sensor spectral sensitivities. The detected CH*/C2* ratio is utilised to analogue the fuel/air ratio for combustion diagnostics. Two cases of flame propagation in tubes and flame ignition to impinging are studied using this proposed image colour-based flame chemiluminescence measurement. Combined with stereo imaging and high-speed imaging, the ability of the proposed method to perform multi-dimensional measurement is demonstrated. The reflected light from the measured object is the result of the interaction between the incident light and the object’s surface. A camera captures the illumination of the reflected light as intensity in an image. When the positions of the light source and camera are fixed, any image intensity variation from the reflected light could indicate the object’s movement. Hence, the measured images of a vibrating object would show intensity fluctuations. Based on this, an image intensity fluctuation-based vibration measurement is proposed. Two cases, wind turbine blade vibration monitoring and industrial coupling rotation-vibration testing, are studied using the proposed method. The ability of the image intensity fluctuation-based vibration measurement to perform one-dimensional and two-dimensional measurements is demonstrated successfully.
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Langston, Paul Wesley. "Implementation and evaluation of a two-dimensional laser doppler vibrometer system for non-contact monitoring of external stress loading of aluminum samples." Thesis, Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/33808.
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This thesis details the development and validation of a laser Doppler vibrometer-based measurement system that is capable of quantifying not only the normal vibration of a solid body but also the component of vibration that is parallel to the plane containing the surface of interest. LDV manufacturers produce various devices that capture 3D measurements in a beam configuration that can be used to decompose the measured signals into not only the normal velocity of the surface of an object but also two orthogonal in-plane components of the vibration. It was a slightly simplified two-dimensional version of this approach that was chosen for implementation in the Wave Physics Lab using individual components to create a cheaper, more flexible system than those produced by companies such as Polytec. The goal of this system is to facilitate the exploration and discovery of areas and applications where 2D measurement may provide a more complete and precise view of the physics of different phenomena. Upon completion of the system development and validation, a study was done that sought to measure the acoustoelastic effect in an Aluminum plate by measuring how increasing loads alter both the normal and in-plane components of Lamb wave propagation in the plate. The acoustoelastic effect is the effect of stress on wave speed caused by non-linearity in the propagation medium.
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Aydogan, Mustafa Ozgur. "Damage Detection In Structures Using Vibration Measurements." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1058809/index.pdf.
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Cracks often exist in structural members that are exposed to repeated loading, which will certainly lower the structural integrity. A crack on a structural member introduces a local flexibility which is a function of the crack depth and location. This may cause nonlinear dynamic response of the structure.
In this thesis, a new method is suggested to detect and locate a crack in a structural component. The method is based on the fact that nonlinear response of a structure with a crack will be a function of the crack location and crack magnitude. The method suggested is the extension of a recently developed technique for identification of non-linearity in vibrating multi degree of freedom
system. In this method, experimentally measured receptances at different forcing levels are used as input, and the existence and location of a nonlinearity are sought.
In order to validate the method, simulated experimental data is used. Characteristics of a cracked beam are simulated by using experimentally obtained analytical expressions, given in the literature. The structure itself is modelled by using finite element method. Several case studies are performed to test and demonstrate the applicability, efficiency and sensitivity of the method suggested. The effect of crack depth on nonlinear system response is also studied in numerical examples.
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Granberg, Alexandra, and Häggstam Manfred. "FE-modellering av håldäcksbjälklag för dynamisk analys : Jämförelse med fältmätningar." Thesis, KTH, Bro- och stålbyggnad, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-148017.
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Det byggs mer och mer med prefabricerade håldäcksbjälklag vilka har stora dimensionerings och produktionsfördelar. Långa spännvidder och lätta bjälklag gör denna typ av konstruktion känslig för vibrationer och därför ställs konstruktörer idag inför en problematik som inte tidigare vanligtvis varit en dimensionerande faktor. Som en naturlig följd av detta är kunskapen inom området begränsad och förståelsen för denna typ av konstruktion vid dynamiska problem eftersatt. Hur håldäcksbjälklag beter sig vid små dynamiska laster, från mänsklig aktivitet på bjälklaget, och hur denna typ av problematik ska hanteras beräkningsmässigt behöver studeras. Vid statiska beräkningar antas bjälklaget vara enkelspänt men vid dynamiska beräkningar kan bland annat inte detta antagande göras då effekten från elementens sammankopplingar och eventuella pågjutningar påverkar bjälklagets styvheter och därmed dess dynamiska beteende. Dynamikproblem kan inte behandlas genom att studera enskilda element då bjälkaget måste hanteras som en sammanhängande enhet där kringliggande struktur påverkar hela bjälklagets dynamiska beteende. I detta arbete har fältmätningar i en befintlig byggnad, med excitering av en mänsklig analyser för att studera hur bjälklaget kan hanteras och dynamiska responsberäkningar. Fältmätningar har genomförts på tre olika bjälklagstyper där accelerationer har studerats i en mängd olika punkter. Accelerationer i fältmitt, intill upplagsväggar, parallella väggar och balkar har studerats för att leda till slutsatser kring hur bjälklagets styvheter påverkar dess dynamiska beteende. Dessa slutsatser kring uppmätta accelerationer har sedan legat till grund modeller kan representera verkligheten på ett godtagbart sätt beträffande dynamiska problem. Finita element-beräkningar för de tre olika bjälklagen har genomförts med varierande resultat, där det kunnat konstateras att komplicerade bjälklagsgeometrier med inslag av pelare, balkar och flera fack håldäckselement är svårt att beräkningsmässigt representera på ett bra sätt. Däremot har det visat sig att enkla bjälklagsgeometrier med endast ett fack håldäckselement upplagt på betongväggar kan representeras relativt väl. Parallella väggar har kunnat konstateras fungera som upplag med accelerationer av samma storleksordning som intill upplagsväggar. Dessutom har det visat sig genom mätningar och beräkningar att en pågjutning rimligen kan antas ha en uppstyvande effekt för bjälklaget. Däremot hur stor denna uppstyvande effekt är har inte kunnat konstateras, då detta skulle kräva andra typer av mätningar.
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Rubenstein, Stephen P. "An experiment in state-space vibration control of steady disturbances on a simply-supported plate." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-03172010-020629/.
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Bell, John R. "Application of laser doppler velocimetry to rotor vibration measurement." Thesis, Loughborough University, 2001. https://dspace.lboro.ac.uk/2134/7563.
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Vibration measurement is of fundamental importance in many machinery applications including for the development and monitoring of rotating machinery. In such applications, measurement of the vibration transmitted from the rotor into a non-rotating part of the structure is the most common arrangement but this cannot always be relied upon because vibration transmission may be low. In such cases, the use of a non-contacting vibration transducer capable of measuring vibration directly from the rotor itself is desirable. Laser Doppler Velocimetry (LDV) is a non-contacting vibration technique capable of such measurements but vibration measurements on rotating structures using LDV have been shown to be ambiguous. The sensitivity of the measured velocity to other rotor vibration components can be significant enough to mask the intended vibration measurement entirely. This thesis examines the use of LDV for vibration measurements on rotating structures more comprehensively than in any previous study. A new and completely general theory is developed to allow the velocity sensitivity of LDV measurements taken from rotating structures to be described for laser beam incidence in an arbitrary direction on a target element requiring 6 degrees of freedom to define its vibratory motion fully. Extension of the' theory to optical configurations incorporating multiple laser beams is also included with a number of useful instrument configurations established. The theory enables some fundamental questions regarding the use of LDV on rotating structures to be answered. Of particular importance is the confirmation that direct measurement of radial or pitch and yaw vibration is not possible because the measurements will always be unavoidably cross-sensitive to other motion components. Resolution of these components is possible, however and a new method of resolving steady state, non-synchronous radial, pitch and yaw vibrations is presented enabling a range of measurements to be made for the first time using LDV. Several of these measurements were made on a running IC engine and of special note are the angular vibration measurements made using a novel instrument incorporating 3 beams, the laser angular vibrometer, designed specifically for the task. Errors within the resolution technique are considered in detail and, looking forward, a number of promising means by which to reduce error magnitudes are introduced and recommended for further investigation. LDV has great potential for rotating machinery diagnostics and such developments are key to achieving this potential.
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Lo, Kam Tong. "Measurement and modelling of vibration transmission through piled foundations." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339629.
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Bisht, Saurabh Singh. "Vibration Measurement Based Damage Identification for Structural Health Monitoring." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/77301.
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The focus of this research is on the development of vibration response-based damage detection in civil engineering structures. Modal parameter-based and model identification-based approaches have been considered. In the modal parameter-based approach, the flexibility and curvature flexibility matrices of the structure are used to identify the damage. It is shown that changes in these matrices can be related to changes in stiffness values of individual structural members. Using this relationship, a method is proposed to solve for the change in stiffness values. The application of this approach is demonstrated on the benchmark problem developed by the joint International Association of Structural Control and American Society of Civil Engineers Structural Health Monitoring task group. The proposed approach is found to be effective in identifying various damage scenarios of this benchmark problem. The effect of missing modes on the damage identification scheme is also studied.
The second method for damage identification aims at identifying sudden changes in stiffness for real time applications. It is shown that the high-frequency content of the response acceleration can be used to identify the instant at which a structure suffers a sudden reduction in its stiffness value. Using the Gibb's phenomenon, it is shown why a high-pass filter can be used for identifying such damages. The application of high-pass filters is then shown in identifying sudden stiffness changes in a linear multi-degree-of-freedom system and a bilinear single degree of freedom system. The impact of measurement noise on the identification approach is also studied. The noise characteristics under which damage identification can or cannot be made are clearly identified. The issue of quantification of the stiffness reduction by this approach is also examined. It is noted that even if the time at which the reduction in stiffness happens can be identified, the quantification of damage requires the knowledge of system displacement values. In principle, such displacements can be calculated by numerical integration of the acceleration response, but the numerical integrations are known to suffer from the low frequency drift error problems. To avoid the errors introduced due to numerical integration of the acceleration response, an approach utilizing the unscented Kalman filter is developed to track the sudden changes in stiffness values. This approach is referred to as the adaptive unscented Kalman filter (AUKF) approach. The successful application of the proposed AUKF approach is shown on two multi-degree of freedom systems that experience sudden loss of stiffness values while subjected to earthquake induced base excitation.<br>Ph. D.
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Di, Maio Dario. "SLDV technology for measurement of mistuned bladed disc vibration." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/1299.
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Bladed discs are very sensitive structures and the amplitude vibration of each blade can vary significantly from blade to blade due to a series of factors such as geometrical inhomogeneity between blades or material properties. These factors lead to bladed disks mistuned thus the forced response amplitudes can be much higher than the level predicted for a tuned assembly. Designed models need to be “validate” to predict the response of a real bladed disc within the tolerances set by the manufactures and this process is very expensive as well as difficult. The validation process needs “reference data” as fundamental input against what all predictions can be compared and validated. Data that can be provided both under stationary conditions and under rotating conditions and the latter is the most difficult to achieve, especially for bladed disc assemblies which are very sensitive to any structural modification as it could be attaching a transducer to measure vibrations. There are contact-less measurement techniques available which, however, provide limited information because they can measure only limited areas of the vibrating structures. The aim of this study is to design measurement methods, using a standard Scanning Laser Doppler Vibrometer (SLDV) and to integrate it into a software platform which will be able to handle a series of measurement tasks both under stationary and rotating conditions. The main contribution of this thesis is to extend the use of Continuous Scanning LDV (CSLDV) to the rotating structures, such as bladed discs, thus to perform synchronous measurements. Hence, a bladed disc is needed to be designed to perform vibration predictions and measurements and a mathematical model of the measurement test to control, critically, all possible sources of errors involved in measurement under rotating conditions; all these to produce a robust measurement method. While the primary focus is the measurement method, the study also extends to evaluation of the sensitivity properties of the bladed disk test pieces that are the object of the measurement tool.
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Walter, Patrick L. "OPTIMIZING FLIGHT SHOCK AND VIBRATION MEASUREMENT BY RF LINKS." International Foundation for Telemetering, 1998. http://hdl.handle.net/10150/609222.
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International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California<br>Acquiring shock and vibration data from flight vehicles through rf telemetry links has numerous associated challenges. Yet, these measurements are important to establish environmental specifications to provide a basis for system or component design and testing. The principal limitation in acquiring these measurements is the frequency bandwidth available for data transmission. This limited bandwidth is often responsible for invalid data being accepted as valid. This work provides a brief review of time and frequency division multiplexing to identify the potential error contributors to shock and vibration measurements. Its focus is on the design of acceleration measurement systems to eliminate these errors and optimize individual measurement channel performance.
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Chan, Alfred. "Vocal fold vibration measurements using laser Doppler vibrometry." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106574.
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The objective of this study was to measure the velocity of the superior surface of human vocal folds during phonation using laser Doppler vibrometry (LDV). A custom-made endoscopic laser beam deflection unit was designed and fabricated. An in vivo clinical experimental procedure was developed and performed at the Montreal General Hospital Voice Laboratory in order to simultaneously collect velocity data from the LDV and video from endoscopy. The velocity along the direction of the laser beam, ie. the inferior-superior direction, was captured and found to be synchronous with electroglottograph (EGG) and sound level meter data. Recorded phonation onset/offset times were found to be commensurate with reported data obtained using EGG and high-speed imaging. The vibration energy of the vocal folds was determined to be significant up to a frequency of 3 kHz. The velocity amplitude was found to be approximately 45 mm/s and was consistent between subjects. A sparse map of the vocal fold surface velocity was obtained, which showed that the velocity amplitude did not change significantly with location. Different characteristic vibration waveforms were identified and attributed to the presence of a mucosal wave over the vocal fold surface. Laser Doppler vibrometry offers potential as a diagnostic tool for the early detection of vocal disorders. It may provide online biofeedback for voice professionals, and help them to tune their laryngeal tension to obtain the desired voice output.<br>La présente étude avait pour but de mesurer directement la vitesse des cordes vocales de la voix humaine en utilisant la vibrométrie laser (VL). Une buse endoscopique pour la re-direction du faisceau laser a été conçue et construite. Un protocole expérimental de mesures en clinique a été développé et mis en oeuvre afin d'obtenir des signaux de vitesse simultanément avec des images vidéoendoscopiques. Les mesures furent prises au laboratoire de la voix de l'Hôpital Général de Montréal. La vitesse mesurée est dans l'axe du faisceau laser, soit dans la direction inférieure-supérieure. Des signaux synchrones provenant d'un électroglottogramme (EGG) et d'un microphone furent recueillis pour fins de comparaisons et de vérifications. Les signaux provenant du VL sont parfaitement corrélés et consistants avec les signaux du EGG et microphone ainsi que les informations provenant du vidéo. L'énergie vibratoire semble être présente dans un bande de fréquence allant jusqu'à 3 kHz. La vitesse est de 45 mm/s dans les trois cas étudiés, pour toute fréquence, amplitude et position. Différents modes vibratoires avec des formes d'ondes distinctes furent identifiés, probablement dus à la propagation d'ondes sur la surface supérieure des cordes vocales. Les résultats suggèrent que l'utilisation du VL pourrait mener à des applications intéressantes pour la détection de problèmes tels que des lésions. La VL pourrait aussi sans doute fournir une rétroaction à des professionnels de la voix qui leur permettrait d'ajuster la tension et la position de leur cordes vocales afin d'obtenir le timbre ou l'intonation désirée.
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He, Zinan. "Vibration measurements on the widely exposed gerbil eardrum." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107722.
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Hearing loss is one of the most common birth defects. Early identification of hearing loss is very important because even a mild hearing loss can seriously delay language development and compromise communication, educational and social capabilities. Tympanometry is a promising tool to identify conductive hearing loss through examining the eardrum responses. However, current clinical results are unsatisfactory due to our inadequate knowledge of the complex mechanics of the middle ear. The vibration pattern of the eardrum is a critical factor for understanding tympanometry and the underlying sound transmission in the middle ear. However, very few experimental studies have investigated the vibration patterns of the eardrum.This study involves in vivo measurements of gerbil eardrum vibrations using laser Doppler vibrometry. An experimental approach to widely expose the eardrum has been developed. This wider exposure allows measurements to be taken on a larger area so as to better characterize the vibration pattern across the eardrum.<br>Les troubles de l'audition sont un des plus communs défauts de naissance. Il est très important d'identifier rapidement les troubles de l'audition car même un trouble léger peut retarder de façon sérieuse le développement du langage et compromettre la communication ainsi que les capacités éducatives et sociales. La tympanométrie est un outil prometteur pour identifier la surdité de transmission. Cependant, les résultats cliniques actuels ne sont pas satisfaisants en raison de notre connaissance inadéquate du mécanisme complexe de l'oreille moyenne. La caracterisation des vibrations du tympan est un facteur critique dans la compréhension de la tympanométrie et de la transmission sous-jacente des sons dans l'oreille moyenne. Cependant, peu d'études expérimentales ont investigué les vibrations du tympan.Cette étude implique la mesure in vivo des vibrations du tympan de la gerbille à l'aide d'un vibromètre à laser Doppler. Une approche expérimentale visant à largement exposer le tympan a été développée. Cette large exposition permet de prendre les mesures sur une plus grande surface dans le but de mieux caractériser les vibrations du tympan.
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Martarelli, Milena. "Exploiting the laser scanning facility for vibration measurements." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248035.
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