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Tesi sul tema "Vibration"
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1
Zethson, Alexander. "Vibration". Thesis, Kungl. Musikhögskolan, Institutionen för jazz, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kmh:diva-950.
Testo completo
2
Kumar, Ashok. "Active structural-acoustic control of interior noise in vibro-acoustic cavities". Thesis, IIT Delhi, 2016. http://localhost:8080/iit/handle/2074/7036.
Testo completo
3
Kornienko, N. E., e A. P. Naumenko. "Strong Vibration-Electron Interactions and Vibration Band Enhancement in Vibrational Spectra of C60 Nanofilms and Singlewalled Carbon Nanotubes". Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35593.
Testo completoAbstract (sommario):
In Raman spectra in nanofilms of fullerene C60 with thickness about 150 – 250 nm it was found the en-hancement of vibrational bands Hg (1 ÷ 8) intensity at 2 ÷ 7 times in comparison with the microfilms with thickness 1 – 2 microns. It is shown that the inactive for icosahedral symmetry Ih Raman and IR vibrations Gg, u, Hu, F2g, u, and the lateral spectral components of the bands Hg (1 ÷ 8) increase in 5 – 50 times and more. This is due to an abnormal increasing of the resonant nonlinear interaction of the vibrational modes and the vibrational-electronic interaction, which leads to a change in the electronic states and the appear-ing of new electronic bands (EB) in the region of the vibrations. The change induced by the polymerization of EB in nanofilms C60 and intense laser pulses have been studied. . A nonmonotonic dependence of the EP intensity on the thickness of nanofilms has been established. The lineshape of the overtones 2Ag (2) and 2Hg (7) for fullerene C60 and increasing of overtone 2D in spectra of single-walled carbon nanotubes, as well as unusual changes anharmonisity their 2G and 2D bands varies with the frequency of the laser radi-ation have been studied.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35593
4
Trimble, A. Zachary. "Downhole vibration sensing by vibration energy harvesting". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39891.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (p. 117).
This thesis outlines the design of a prototype electromagnetic induction vibration energy harvesting device for use in a downhole environment. First order models of the necessary components for a generic vibration energy harvester are presented and used to predict the most sensitive parameters for the design of energy harvesting systems. A subset of the design tools created in MATLAB and Excel for vibration energy harvester design and first order optimization is introduced and used to aid in the design of an energy harvester specific to the downhole environment. The manufacture of a prototype design is documented and recommendations for future manufacturing processes are given. The prototype is then tested against the models. Based on the results, final conclusions and recommendations for future refinements are made, and other applications are suggested.
by A. Zachary Trimble.
S.M.
5
Shatov, MY, SV Joubert, CE Coetzee e IA Fedotoc. "Free vibration of rotating hollow spheres containing acoustic media". Elsevier, 2008. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001765.
Testo completoAbstract (sommario):
Abstract
When avibratingstructureisrotatedwithrespecttoinertialspace,thevibratingpatternrotatesatarateproportionalto
the inertialrateofrotation.Bryanfirstobservedthiseffectin1890.Theeffect,calledBryan’seffectinthesequel,has
numerous navigationalapplicationsandcouldbeusefulinunderstandingthedynamicsofpulsatingstarsandearthquake
series inastrophysicsandseismology.Bryan’sfactor(thecoefficientofproportionalitybetweentheinertialandvibrating
pattern rotationrates)dependsonthegeometryofthestructureandthevibrationmodenumber.The‘‘gyroscopiceffects’’
of ahollowisotropicsolidspherefilledwithaninviscidacousticmediumareconsideredhere,butthetheoryisreadily
adapted toahollowisotropicsolidcylinderfilledwithaninviscidacousticmedium.Alineartheoryisdevelopedassuming,
among othermildconditions,thattherotationrateisconstantandmuchsmallerthanthelowesteigenfrequencyofthe
vibrating system.Thuscentrifugalforcesareconsideredtobenegligible.Beforecalculatingsolutionsforthedisplacement
of aparticleintheisotropic,spherical,distributedbody,Bryan’sfactorisinterpretedusingacomplexfunction.Hereitis
demonstrated thatneitherBryan’seffectnorBryan’sfactorisinfluencedbyincludinglight,isotropic,viscousdampingin
the mathematicalmodel.Hencedampingisneglectedinthesequel.Twoscenariosarethenidentified.Firstly,wemay
assume thattheacousticmediumiscompletelyinvolvedintherotation(thespheroidalmode).Secondly,wemayassume
that theacousticmediumremainsstaticwithrespecttotheinertialreferenceframe(thetorsionalmode).Weinvestigatethe
spheroidal modeusinganumericalexperimentthatcomparestherotationalangularrateofasphere(filledwithaninviscid
acoustic medium)withthoseofitsvibratingpatternsatbothhighandlowvibrationfrequency.
6
Körning, Ljungberg Jessica. "Psychological responses to noise and vibration /". Umeå : Umeå universitet : Arbetslivsinstitutet, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-915.
Testo completo
7
Labbé, Julien. "Détection et étude de micro-déplacements des contacts sous contrainte vibratoire et leurs conséquences sur les matériaux et revêtements des connecteurs-automobiles". Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S146/document.
Testo completoAbstract (sommario):
Les vibrations issues du fonctionnement d'un véhicule automobile (moteur, route) sont transmises aux connecteurs électriques. Ces vibrations peuvent induire des déplacements relatifs entre certains des composants du connecteur à l’interface de contact. Les éléments en contact sont de diverses formes et diverses natures dont une partie femelle (dite clip) dans laquelle s’introduit une partie mâle (dite languette). Or, un déplacement relatif de quelques micromètres entre le clip et la languette est suffisant pour dégrader et ce de manière irréversible, l'interface de la zone de contact électrique (phénomène de fretting-corrosion). Il est donc nécessaire de connaître le comportement vibratoire interne d'un connecteur i.e. des connectiques pour préconiser sa meilleure son utilisation au sein d'un véhicule. Un banc d'essai sur pot vibrant a été réalisé dans le but de caractériser le comportement vibratoire d'un connecteur soumis à un profil vibratoire. Les mesures ont été réalisées par tribométrie en réalisant des orifices d'accès au clip et à la languette. De là, l'analyse des vibrations induites a mis en évidence des directions de déplacement multi-axiales des composants du connecteur et notamment celles d’un support du clip dit porte-clip, et ce malgré une vibration dont la direction est mono-axiale. L'analyse a également mis en évidence une correspondance vibratoire entre le clip et le porte-clip ainsi que des phénomènes de résonances. De là, une première approche sur une modélisation numérique, basée sur un système masse-ressort-amortisseur, a été proposée. Cette analyse permet de caractériser le comportement vibratoire général d'un connecteur sans dépendre du type de vibration appliquée. C'est une nouvelle approche dans la caractérisation de connecteurs électriques utilisés dans l’industrie automobile. Les éléments en contact d’un connecteur sont revêtus de matériaux qui les protègent des dégradations mécaniques et chimiques. Ces revêtements (de quelques micromètres d’épaisseur) peuvent être des matériaux nobles (or, argent,…) ou non nobles (étain, …). Le déplacement relatif entre un clip étamé et une languette étamée engendre la formation d'un troisième corps à l'interface de contact. Ce troisième corps est composé de débris oxydés qui perturbent la conduction des charges électriques. L'utilisation d'une atmosphère de di-azote (N2) et l’analyse de la tension de contact en fonction de l'emplacement du clip par rapport à la languette ont mis en évidence la dynamique des débris oxydés avec notamment leur évacuation hors de la zone de contact. De plus, l'analyse d'une zone de contact dégradée à la microsonde nucléaire a permis de doser l'oxygène et de mettre en valeur deux types d'oxydes de cuivre. Ces caractérisations permettent de mieux comprendre le phénomène de fretting-corrosion et ses conséquencesVibrations are generating from an operating vehicule (motor, road). Then, they are transmitted to electrical connectors. Therefor, these vibrations can induce relative displacements between some of the connector components. The components for the electrical contact are the female part (called a clip) and the male part (called the tongue).These components are coated with materials that protect them from mechanical and chemical degradation. These coatings (a few micrometers thick) can be noble materials (gold, silver,...) or not noble (tin). A relative displacement of a few micrometers between the clip and the tongue is sufficient to irreversibly degrade the interface of the electrical contact zone by fretting-corrosion phenomenon. It is therefore necessary to know the internal vibratory behavior of connectors in order to recommend its best use for a vehicle.A test bench is carried out in order to characterize the vibratory behavior of a connector subjected to a vibratory profile. The measurements are carried out by vibrometry by making holes access for the clip and the tongue. From there, the analysis of the induced vibrations has revealed multi-axial directions displacements of the components of the connector and in particulary the clip holder (external support of the clip), despite a vibration whose direction is mono-axial.The analysis also showed a vibratory correspondence between the clip and the clip holder and resonance phenomena. From there, a first approach on a numerical modeling, based on a system mass-spring-damper, has been proposed. This analysis makes it possible to characterize the general vibratory behavior of a connector without depending on the type of vibration applied. This is a new approach in the characterization of electrical connectors used in the automotive industry.The relative movement between the clip and the tongue induce formation of a third body at the contact interface. This third body is composed of tin oxidized remains which disturb the conduction of electrical charges due to their electrcail insulating characteristic. The use of a nitrogen atmosphere and the analysis of the contact voltage as a function of the location of the clip relative to the tongue have demonstrated the dynamics of the oxidized debris with, in particular, their evacuation out of the contact area. Moreover, the analysis by a nuclear microprobe of a zone degraded contact area enable the measurement of oxygen concentration. The results hilight two types of copper oxides. These characterizations make it possible to better understand the phenomenon of fretting-corrosion and its consequences
8
Sidbury, Jenny Elizabeth. "Analysis of Buckled and Pre-bent Columns Used as Vibration Isolators". Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/9641.
Testo completoAbstract (sommario):
Vibrations resulting from earthquakes, machinery, or unanticipated shocks may be very damaging and costly to structures. To avoid such damage, designers need a structural system that can dissipate the energy caused by these vibrations. Using elastically buckled struts may be a viable means to reduce the harmful effects of unexpected vibrations. Post-buckled struts can support high axial loads and also act as springs in a passive vibration isolation system by absorbing or dissipating the energy caused by external excitation. When a base excitation is applied, the buckled strut may act to reduce the dynamic force transmitted to the system, thus reducing the structural damage to the system.
Several models of buckled and pre-bent struts are examined with different combinations of parameters and end conditions. The models include pinned or fixed columns supporting loads above their buckling load, and columns with an initial curvature supporting various loads. The varying parameters include external damping, internal damping, and stiffness. The columns will be subjected to simple harmonic motion applied at the base or to a multi-frequency base excitation. The response of each model is measured by the deflection transmissibility of the supported load over a large range of frequencies. Effective models reduce the motion of the supported load over a large range of frequencies.Master of Science
9
Korneliusson, Marie, e Pernilla Lindell. "Vibration/accelerationsträning". Thesis, Halmstad University, School of Business and Engineering (SET), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-1120.
Testo completoAbstract (sommario):
Studien hade ett primärt och ett sekundärt syfte. Primära syftet var att genomföra en empirisk studie gällande vibration/accelerationsträning och undersöka om vibration/accelerationsträning påverkar styrka och balans. Sekundära syftet var att utföra en litteraturstudie och utvärdera positiva, negativa och uteblivna effekter av vibration/accelerationsträning.
I studien deltog från start av studien 16 stycken kvinnor med en medelålder på 45 år, varav tre stycken kvinnor fullföljde studien. Testpersonerna tränade tre gånger i veckan under åtta veckor. Träningsprogrammet som utfördes innehöll 14 stycken övningar och tog cirka 20 minuter att genomföra. Ett styrketest och ett balanstest utfördes före träningsperioden, efter fyra veckor och efter åtta veckors träning. Det utfördes mätningar på biceps-, lår-, midje- och stussomfång utfördes, samt vägning. Testpersonerna svarade även på en enkät före träningsperioden och en enkät efter avslutad träningsperiod.
Testpersonerna var 16 stycken vid första testtillfället. Vid andra testtillfället var endast tre stycken testpersoner kvar, vilka även genomförde hela studien. Resultaten för testperson ett var viktminskning och inga signifikanta förändringar på mätvärdena gällande biceps, midja, stuss och lår. Balans och styrkevärdena förbättrades på båda benen. Testperson två fick en liten viktökning, inga signifikanta förändringar i mätvärdena gällande biceps, stuss och lår. En signifikant minskning av midjeomfånget. Balansen försämrades signifikant medan styrkan förbättrades. Resultaten för testperson tre var en liten viktminskning, inga signifikanta förändringar i mätvärdena. Inga signifikanta förändringar gällande balans och styrka.
Vibration/accelerationsträning uppfyller idag inte alla krav som styrketräning innebär. Effekterna är inte helt klarlagda och kräver fler studier. Framtida studier som kommer att utföras på vibration/accelerationsträningen bör ha likvärdiga gruppsammansättningar vid jämförelser mellan olika träningsmetoder eller utvärdera effekterna endast från vibration/accelerationsträningen, för att få rättvisande testresultat. Viktigast är att utvärdera enskild individ.
10
Bury, A. S. "Torsional vibration". Thesis, Видавництво СумДУ, 2012. http://essuir.sumdu.edu.ua/handle/123456789/26042.
Testo completoAbstract (sommario):
Torsional vibration can be broadly described as the angular vibration of any object as a result of applied torque. It can be defined specifically as the periodic motion corresponding to a shaft, where the shaft is twisted about its axis, alternating from one direction to the other.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/26042
11
Park, Jeong Gyu. "Vibration suppression of ropeway carrier by dynamic vibration absorber". 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/149772.
Testo completoAbstract (sommario):
要旨には「Vibration Suppression of Ropeway Carrier by Optimally Tuned Passive Devices」とありKyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第9529号
工博第2115号
新制||工||1230(附属図書館)
UT51-2002-G287
京都大学大学院工学研究科精密工学専攻
(主査)教授 松久 寛, 教授 久保 愛三, 教授 吉村 允孝
学位規則第4条第1項該当
12
Jayasuriya, A. M. M. "Finite element modeling of blast vibrations and study of vibration control criteria". Ohio : Ohio University, 1989. http://www.ohiolink.edu/etd/view.cgi?ohiou1182438393.
Testo completo
13
Drezet, Cyril. "Récupération d'énergie vibratoire pour puce autonome sur conteneur". Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCD062.
Testo completoAbstract (sommario):
La société TRAXENS propose une solution innovante permettant le suivi de l'état d'un conteneur (position, température, chocs, etc.). Ce service est basé sur un capteur sans fil appelé TRAXENS-BOX dont la durée de vie doit être étendue avec un volume de batterie limité. La présence d'une quantité d'énergie vibratoire non négligeable dans l'environnement du conteneur multimodal oriente donc vers la récupération d'énergie vibratoire. L'objectif principal de ce travail de thèse est donc d'identifier une solution permettant de récupérer l'énergie vibratoire dans le contexte particulier du conteneur caractérisé notamment par des vibrations verticales, aléatoires et très basses fréquences.On commence donc par introduire un modèle complet de récupérateur d'énergie vibratoire électromagnétique basé sur un oscillateur à un degré de liberté avant d'étudier son comportement lorsqu'il est soumis à des excitations harmoniques puis aléatoires ; on peut alors en déduire des règles de dimensionnement permettant la conception d'un récupérateur d'énergie vibratoire linéaire hautes performances. Le modèle est ensuite utilisé pour prouver l'intérêt de l'introduction d'une non-linéarité de Duffing dans la raideur du récupérateur, notamment sous les vibrations du transport routier. La partie théorique se termine alors par une comparaison mettant en opposition plusieurs configurations de récupérateur dans le cadre de l'application TRAXENS-BOX ; la solution retenue est l'utilisation d'une raideur non-linéaire HSLD (High Static Low Dynamic).On propose ensuite la conception optimisée puis la fabrication d'un démonstrateur linéaire hautes performances qui nous permet de valider les règles de dimensionnement énoncés dans la partie théorique. Enfin, le démonstrateur est modifié de manière à obtenir un comportement HSLD et prouver la faisabilité de ce conceptTRAXENS company proposes an innovative solution to enable the monitoring of shipping containers (position, temperature, shocks, etc.). This service is based on a wireless sensor called TRAXENS-BOX whose lifetime must be extended by maintaining a small energy storage volume. In the environment of a shipping container, the presence a non-negligible amount of vibration makes energy harvesting a viable solution. The main objective of this work is to identify the means to scavenge vibration energy in the singular context of shipping container characterized by very low frequency, random and vertical vibration.First, a general electromagnetic vibration energy harvester model based on a single degree of freedom oscillator is introduced before analyzing its behavior when submitted to harmonic and random excitations ; rules to design high performances linear vibration energy harvester are then deduced. Henceforth, the model is used to prove the interest of introducing a Duffing nonlinearity in the harvester stiffness, especially under road induced vibration. The theoretical part ends with performance comparison between several harvester configurations within TRAXENS-BOX context ; the chosen solution is the use of a HSLD (High Static Low Dynamic) stiffness.Then, the design and fabrication of a linear high performances prototype is conducted to validate design rules drawn from the theoretical part. Finally, a HSLD stiffness is added to the prototype to prove the feasibility of this technique
14
Rafique, Sajid. "Piezoelectric vibration energy harvesting and its application to vibration control". Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/piezoelectric-vibration-energy-harvesting-and-its-application-to-vibration-control(d9edcedf-054e-4921-9ba3-5e015b9bbd8f).html.
Testo completoAbstract (sommario):
Vibration-based energy harvesting using piezoelectric materials have been investigated by several research groups with the aim of harvesting maximum energy and providing power to low-powered wireless electronic systems for their entire operational life. The electromechanical coupling effect introduced by the piezoelectric vibration energy harvesting (PVEH) mechanism presents modelling challenges. For this reason, there has been a continuous effort to develop different modelling techniques to describe the PVEH mechanism and its effects on the dynamics of the system. The overall aims of this thesis are twofold: (1) a thorough theoretical and experimental analysis of a PVEH beam or assembly of beams; (2) an in-depth analytical and experimental investigation of the novel concept of a dual function piezoelectric vibration energy harvester beam/tuned vibration absorber (PVEH/TVA) or 'electromechanical TVA' and its potential application to vibration control. The salient novel contributions of this thesis can be summarised as follows: (i) An in-depth experimental validation of a PVEH beam model based on the analytical modal analysis method (AMAM), with the investigations conducted over a wider frequency range than previously tested. (ii) The precise identification of the electrical loads that harvest maximum power and that induce maximum electrical damping. (iii) A thorough investigation of the influence of mechanical damping on PVEH beams. (iv) A procedure for the exact modelling of PVEH beams, and assemblies of such beams, using the dynamic stiffness matrix (DSM) method. (v) A procedure to enhance the power output from a PVEH beam through the application of a tip rotational restraint and the use of segmented electrodes. (vi) The theoretical basis for the novel concept of a dual function PVEH beam/TVA, and its realisation and experimental validation for a prototype device. A thorough experimental validation of a cantilever piezoelectric bimorph energy harvester without a tip mass is presented under random excitation. The study provided a deep insight into the effect of PVEH on the dynamics of the system for variations in electrical load. An alternative modelling technique to AMAM, based on the DSM, is introduced for PVEH beams. Unlike AMAM, the DSM is exact, since it is based on the exact solution to the bending wave equation. It also readily lends itself to the modelling of beams with different boundary conditions or assemblies of beams of different crosssections. AMAM is shown to converge to DSM if a sufficiency of modes is used. Finally, an in-depth theoretical and experimental investigation of a prototype PVEHbeam/TVA device is presented. This device comprises a pair of bimorphs shunted by R-L-C circuitry and can be used as a tuned mass damper (TMD) to attenuate a vibration mode of a generic structure. The optimal damping required by this TMD is generated by the PVEH effect of the bimorphs. Such a device combines the advantages of conventional mechanical and electrical TVAs, overcoming their relative disadvantages. The results demonstrate that the ideal degree of attenuation can be achieved by the proposed device through appropriate tuning of the circuitry, thereby presenting the prospect of a novel class of 'electromechanical' tuned vibration absorbers.
15
Meusch, John Carl. "Supine human response and vibration-suppression during whole-body vibration". Thesis, University of Iowa, 2012. https://ir.uiowa.edu/etd/2945.
Testo completoAbstract (sommario):
Whole-body vibration (WBV) has been identified as a stressor to supine patients with head and spinal injuries during medical transportation. Limited information is available on the dynamic effects of the long spinal board and stretcher in vibrating environments. This is the first study to investigate the transmission of vibration through the long spinal board, military stretcher, and supine human in relation to a control case with full-rigid support. A sample of eight healthy male participants was used in this study. Each was placed on a vibration platform using spinal immobilization. Random vibration was applied in the fore-aft, lateral, and vertical directions, and the transmission of vibration was computed for the head, sternum, and pelvis. In addition, a novel approach to assess relative motion between segments, called relative transmissibility, was introduced. Compared to full-rigid support, the long spinal board strapped to a standard military litter system showed a 50% increase in transmission of anterior-posterior vibration to the head and a 100% increase to the sternum at its resonance frequency of 5 Hz (p < 0.05, Wilcoxon) for vertical vibration. Use of the cervical collar during immobilization increased the head nodding and the relative head-sternum flexion-extension as a result of the input fore-aft (axial) whole-body vibration. Yet, head nodding was reduced from vertical (anterior-posterior) input vibration. Relative transmissibility has revealed that at 5 Hz, the acceleration difference between the head and sternum was 1.5 times the vertical (anterior-posterior) input acceleration using the spinal board upon the military litter. During air, ground, and hand transportation, WBV may occur around 5 Hz. Patients with head and spinal cord injuries may benefit from vibration-suppression designs that minimize (1) the overall transmission of vibration in each axis and (2) the relative accelerations between segments for the most common vibration frequencies that occur during transportation. Furthermore, vibration applied in each axis independently showed transmissibility results comparable to that of simultaneous stimuli in three axes. Although the effects of vibration are quantified in this study, transient shock type vibration should be investigated and future research should be done to fully understand the clinical significance and application of these results.
16
Lengoc, Lan. "Vibration of bandsaws". Thesis, University of Canterbury. Mechanical Engineering, 1990. http://hdl.handle.net/10092/6038.
Testo completoAbstract (sommario):
The aim of this thesis was to investigate the vibrational characteristics of wide band bandsaws.
Firstly, the vibration of bandsaw structures was considered.
A computer program was developed to predict the natural frequencies and mode shapes of three dimensional structures, consisting of beams, springs, viscous dampers, concentrated masses, and gyroscopic rotors. The method used was the dynamic stiffness method.
Some of the vibrational characteristics of the bandsaw structure were then established from experimental results and results obtained from the computer program. The gyroscopic effects on the bandsaw structure due to rotating pulleys were also examined.
Secondly, the dynamic stiffness method was used to solve the moving beam problem. The moving beam had been used previously to model the bandsaw blade. The dynamic stiffness method allowed complex problems to be analysed in a systematic manner.
A moving beam proved to be too crude a representation of a wide bandsaw blade at the level of detail being investigated. Therefore, attempts were made to model the dynamic behaviour of wide bandsaw blades with moving plates.
A general approach to the solution of the moving plate problem is presented in this thesis, it uses the extended Galerkin method to discretise the partial differential equation of motion and the boundary conditions into a quadratic eigenvalue problem. The solutions for this problem were obtained by using a linearisation technique.
The effects of in-plane stresses on bandsaw blades are considered in this thesis. Three cases are examined; a linearly distributed stress across the width of the blade due to wheel-tilting and/or backcrowning, a parabolic distributed stress across the width of the blade due to prestressing, and stresses induced by tangential cutting forces.
Parametric instabilities due to fluctuating tension, and due to periodic tangential cutting forces were investigated. The harmonic balance method was used on the discretised form of the moving plate equation to obtain the required instability regions.
Finally, the dynamic instability of a moving plate due to a nonconservative component of the tangential cutting force was considered. The method of solving this nonconservative problem was the same as that used to solve the conservative case.
17
Grampeix, Guillaume, e Guillaume Grampeix. "Vibration des bétons". Phd thesis, Université Paris-Est, 2013. http://tel.archives-ouvertes.fr/tel-00975153.
Testo completoAbstract (sommario):
Dans le domaine de la construction, le béton constitue le matériau le plus consommé. Afin de favoriser le remplissage des coffrages in situ, les bétons sont liquéfiés ponctuellement suite à l'insertion successive d'une aiguille vibrante. Malgré l'arrivée sur le marché des bétons très fluides à auto-plaçant, les bétons ordinaires représentent plus de 90% des formulations employés sur les chantiers. Cependant, les recommandations traditionnelles actuelles se basent sur des études établies au cours de la première moitié du siècle dernier. Ainsi, nous choisissons de les revisiter afin d'incorporer les progrès actuels sur la rhéologie des matériaux cimentaires. A partir d'une étude de la littérature, nous établissons les liens entre les caractéristiques mécaniques des matériels vibrants et le comportement en écoulement des bétons. Puis, dans le chapitre deux, nous mettons en évidence pour quelles consistances de matériau la vibration est réellement nécessaire. Par la suite, nous développons un modèle analytique simple afin de prédire le diamètre d'action d'un vibreur et nous le comparons à deux configurations de mises en œuvre. Enfin, nous proposons un temps minimal de vibration nécessaire au compactage du matériau et un temps maximal afin d'assurer un parement de qualité
18
Davis, Myers Abraham. "Visual vibration analysis". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107330.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 109-113).
This dissertation shows how regular cameras can be used to record and analyze the vibrations of visible objects. Through careful temporal analysis, we relate subtle changes in video to the vibrations of recorded surfaces, and use that information to reason about the physical properties of objects and the forces that drive their motion. We explore several applications of our approach to extracting vibrations from video - using it to recover sound from distant surfaces, estimate the physical properties of visible objects, and even predict how objects will respond to new, previously unseen forces. Our work impacts a variety of fields, ranging from computer vision, to long-distance structural health monitoring and nondestructive testing, surveillance, and even visual effects for film. By imaging the vibrations of objects, we offer cameras as low-cost vibration sensors with dramatically higher spatial resolution than the devices traditionally used in engineering. In doing so, we turn every camera into a powerful tool for vibration analysis, and provide an exciting new way to image the world.
by Myers Abraham Davis (Abe Davis)
Ph. D.
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Petri, Patrick Andreas 1979. "Vibration-induced rotation". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/36110.
Testo completoAbstract (sommario):
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.This thesis presents, explores, and documents the validation of a mechanical mechanism dubbed Vibration-Induced Rotation, or VIR. The tendency of threaded fasteners to move under the influence of vibrations is well known, but never before has the root cause been identified and investigated in search of beneficial consequences. The sense of rotation, speed, and force with which a threaded body moves in an appropriately vibrated medium is a function of the excitation. The principal kinematic and dynamic relationships governing VIR have been developed and experimentally affirmed. There is evidence for more complex modes of motion, but pure VIR remains the dominant response under a wide variety of conditions. Simplicity, robustness, and uniqueness suggest a multitude of possible applications, particularly in the areas of product assembly and fastener insertion. This thesis should provide a cornerstone in a new and promising field of application-oriented research.
by Patrick Andreas Petri.
S.B.
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Tew, David Peter. "Large amplitude vibration". Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619693.
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Udovychenko, N. M. "Machinery vibration diagnostics". Thesis, Сумський державний університет, 2013. http://essuir.sumdu.edu.ua/handle/123456789/33874.
Testo completoAbstract (sommario):
Vibration is a process that can not be measured, unlike its parameters. The machine can have high levels of vibration for three reasons:
– there is a strong source of vibration inside the machine;
– during spreading between source of vibration and the point of observation, vibration weakly damped or even increases due to good conductivity and transparency of the surrounding structures;
– there are two previous reasons simultaneously.
For solving the first problem we have to explore the physical nature of vibration inside the machine. For solving the second problem it's necessary to investigate the spread of vibrations out of the construction.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/33874
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Grampeix, Guillaume. "Vibration des bétons". Thesis, Paris Est, 2013. http://www.theses.fr/2013PEST1179/document.
Testo completoAbstract (sommario):
Dans le domaine de la construction, le béton constitue le matériau le plus consommé. Afin de favoriser le remplissage des coffrages in situ, les bétons sont liquéfiés ponctuellement suite à l'insertion successive d'une aiguille vibrante. Malgré l'arrivée sur le marché des bétons très fluides à auto-plaçant, les bétons ordinaires représentent plus de 90% des formulations employés sur les chantiers. Cependant, les recommandations traditionnelles actuelles se basent sur des études établies au cours de la première moitié du siècle dernier. Ainsi, nous choisissons de les revisiter afin d'incorporer les progrès actuels sur la rhéologie des matériaux cimentaires. A partir d'une étude de la littérature, nous établissons les liens entre les caractéristiques mécaniques des matériels vibrants et le comportement en écoulement des bétons. Puis, dans le chapitre deux, nous mettons en évidence pour quelles consistances de matériau la vibration est réellement nécessaire. Par la suite, nous développons un modèle analytique simple afin de prédire le diamètre d'action d'un vibreur et nous le comparons à deux configurations de mises en œuvre. Enfin, nous proposons un temps minimal de vibration nécessaire au compactage du matériau et un temps maximal afin d'assurer un parement de qualitéIn the field of construction, concrete is the most used material. In order to facilitate the casting process, concretes are liquefied punctually following the successive insertion of an internal vibrating poker. Despite the introduction of very fluid to self-compacting concrete, ordinary concrete represents more than 90% of the mix-design used on building sites. However, international recommendations are based on studies carried out during the first half of last century. Thus, we choose to investigate theses recommendations in order to incorporate the current progress on the rheology of cementitious materials. From a study of the literature, we establish the relationship between the mechanical properties of vibrating poker and the fresh behavior of concrete. Then, in chapter two, we determine, for which consistency, the vibration is really needed. Thereafter, we develop a simple analytical model to predict the diameter of action of internal poker and we compare two configurations of casting. Finally, we propose a minimum time of vibration required for compaction of the material and a maximum time to ensure a surface quality
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Moyka, Ana S. "Adaptive vibration absorber". Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-10052007-143216/.
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Koo, Jeong-Hoi. "Using Magneto-Rheological Dampers in Semiactive Tuned Vibration Absorbers to Control Structural Vibrations". Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/29023.
Testo completoAbstract (sommario):
Since their invention in the early 1900s, Tuned Vibration Absorbers (TVAs) have shown to be effective in suppressing vibrations of machines and structures. A vibration absorber is a vibratory subsystem attached to a primary system. It normally consists of a mass, a spring, and a damper. Mounted to the primary system, a TVA counteracts the motions of the primary system, "absorbing" the primary structure's vibrations. A conventional passive TVA, however, is only effective when it is tuned properly, hence, the name "tuned" vibration absorber. In many practical applications, inevitable off-tuning (or mistuning) of a TVA occurs because of the system's operating conditions or parameter changes over time. For example, the mass in a building floor could change by moving furnishings, people gathering, etc., which can "off-tune" TVAs. When TVAs are off-tuned, their effectiveness is sharply reduced. Moreover, the off-tuned TVAs can excessively amplify the vibration levels of the primary structures; therefore, not only rendering the TVA useless but also possibly causing damage to the structures. Off-tuning is one of the major problems of conventional passive TVAs.
This study proposes a novel semiactive TVA, which strives to combine the best features of passive and active TVA systems. The semiactive TVA in this study includes a Magneto-Rheological (MR) damper that is used as a controllable damping element, for providing the real-time adjustability that is needed for improving the TVA performance.
This study is conducted in two phases. The first phase provides a numerical investigation on a two-degree-of-freedom (2-DOF) numerical model in which the primary structure is coupled with a TVA. The numerical investigation considers four semiactive control methods for the MR TVAs, in addition to an equivalent passive TVA. These numerical models are optimally tuned using numerical optimization techniques to compare each TVA system. These tuned systems then serve as the basis for numerical parametric studies for further evaluation of their dynamic performance. The parametric study covers the effects of damping, as well as system parameter variations (off-tuning). The results indicates that semiactive TVAs are more effective in reducing the maximum vibrations of the primary structure and are more robust when subjected to off-tuning. Additionally, the numerical study identifies the "On-off Displacement-Based Groundhook control (on-off DBG)" as the most suitable control method for the semiactive TVA among control methods considered in this study.
For the second phase of this study, an experimental study is performed on a test setup, which represents a 2-DOF structure model coupled with an MR TVA. Using this setup, a series of tests are conducted in the same manner as the numerical study to evaluate the performance of the semiactive TVA. The primary purposes of the experiment are to further evaluate the most promising semiactive control methods and to serve as a "proof-of-concept" of the effectiveness of this MR TVA for floor vibration applications. The results indicate that the semiactive TVA with displacement-based groundhook control outperforms the equivalent passive TVA in reducing the maximum vibrations of the primary structure. This confirms the numerical result that identifies on-off DBG control method as the "best" control method for the MR TVA among four semiactive control schemes considered. The experimental robustness study is also conducted, focusing on the dynamic performance of both the passive and the semiactive TVAs when the mass of the primary system changes (mass off-tuning). The mass of the primary system varied from -23 % to +23 % of its nominal value by adding and removing external masses. The experimental results show that the semiactive TVA is more robust to changes in the primary mass than the passive TVA.
These results justify the benefits of the use of semiactive MR TVAs in structures, such as building floor systems. The off-tuning analysis further suggests that, in practice, semiactive TVAs should be tuned slightly less than their optimum in order to compensate for any added masses to the structure. Additionally, the lessons learned from the experimental study have paved the way for implementing the semiactive MR TVA on a test floor, which is currently in progress under a separate study.Ph. D.
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Reynolds, George Alexander. "REDUCTION OF VIBRATION BY OSCILLATING BOUNDARIES AND ITS APPLICATION IN ROTORDYNAMICS". Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1470319955.
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Cierocka, Joanna, e Jiayue Tang. "Vibrational tests of preloaded rubber vibration isolators : A cam controlled displacement excitation". Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-53703.
Testo completoAbstract (sommario):
Vibrations are very common phenomenon. It influences structures and generates acoustic noise which might be harmful to human beings. The vibration isolator was invented to reduce the effect from vibrations. However, the behavior of rubber material, which many vibration isolators are made of, is hard to predict. Consequently, vibration tests are needed to obtain the dynamic properties of rubber isolator.In this case, a six-year old LORD 2204-5 rubber isolator provided by Atlas Copco was tested. The aim of this paper is to obtain the FRF (Frequency Response Function) diagram which can describe the property of the rubber material. Moreover, the influence of aging of rubber material on the dynamic properties was studied.As the vibration test should simulate the working environment of the isolators that are both a static load from the structure and a dynamic force from the engine, a new excitation method was designed. The camshaft with the shape of an epitrochoid induced the sinusoidal signal of the isolator and the frame transferred the static load from the hydraulic machine. The artificial aging was performed in a hot air oven in 90°C for 42 hours, which according to Arrhenius equation should be equivalent to six years of natural aging. The vibration isolator was tested again after being aged.The obtained data showed that the aging process decreased the stiffness of the material. The results were corresponding with other studies regarding aging of rubber.
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Davis, Michael P. "Low-order modeling of freely vibrating flexible cables". Link to electronic thesis, 2001. http://www.wpi.edu/Pubs/ETD/Available/etd-0427101-130552.
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Hirunyapruk, Chompoonoot. "Vibration control using an adaptive tuned magneto-rheological fluid vibration absorber". Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/65677/.
Testo completoAbstract (sommario):
An adaptive tuned vibration absorber (ATVA) can be used to suppress unwanted vibrations. If the excitation frequency is time harmonic but the frequency changes with time, it is desirable to retune the ATVA so that the natural frequency of the ATVA always coincides with the excitation frequency. One way of achieving this is to adjust the stiffness of the ATVA. The key challenge is to change the stiffness in real-time. Tunable fluids such as Magneto-Rheological (MR) fluids, whose properties can be controlled by a magnetic field, may be used to address this challenge. The subject of this thesis is an ATVA exploiting the changeable properties of MR fluids in the pre-yield state. The ATVA is designed as a three-layer beam with elastic face plates and MR fluuid in the core. Electromagnets are attached to the top and the bottom layers to generate a magnetic field. By varying the current supplied to the electromagnets, the shear stiffness of the MR fluid and hence the stiffness of the ATVA can be varied. The vibration characteristics of the ATVA as a function of the magnetic field strength are predicted by a finite element model together with an empirical model for the shear modulus of the MR fluid and a model for the magnetic field applied to the fluid. An MR fluid-filled ATVA was manufactured and tested to validate the predictions. This ATVA design allows the natural frequency to be changed by 40.6%. The self-tuning of the MR fluid-filled ATVA can be achieved by integrating an adaptive-passive controller with the ATVA so that its stiffness can be continuously adjusted in real-time. The control aims to drive the cosine of phase angle between the velocities of the host structure and the ATVA to zero. Various control algorithms, i.e. non-linear proportional, derivative, and proportional-plus-derivative controls, are investigated. Computer simulations and experimental results demonstrate that the MR fluid-filled ATVA is able to retune itself in the order of 0.2 seconds. The ATVA can also maintain the tuned condition within a reasonably wide frequency range between 110 and 146 Hz in the face of changes in the forcing frequency. The MR fluid-filled ATVA has the potential to substantially reduce vibration of a host structure. The proportional-plus-derivative control was found to be the best control approach for the ATVA.
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Heilmann, John. "A dual reaction-mass dynamic vibration absorber for active vibration control". Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-09182008-063315/.
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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.
Testo completoAbstract (sommario):
Thesis (MEng) -- Stellenbosch University, 2014.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.
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.
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Brogren, Felix, e Peter Gustafsson. "VIBRATION ANALYSIS OF THE FLUE GAS FAN IN MÄLARENERGI’S UNIT 6 : Troubleshooting using CFD simulations in ANSYS to locate the origin of the vibration spikes and suggest solutions for a more optimized performance". Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-40030.
Testo completoAbstract (sommario):
The purpose of this study is to investigate the flue gas fan in Mälarenergi’s Unit 6 and try to find what is causing the vibrations increase. The Fast Fourier transform (FFT) method was used for this degree project. A comparison was made with previous studies using FFT in order to pinpoint the source of the problem with vibrations. After a possible source had been identified, a computational fluid dynamics (CFD) simulation was performed using ANSYS to visualize the problem. Two cases were simulated using two different turbulence models: the K-epsilon model and the Large-eddy simulation (LES) model. The result from the CFD simulations was compared with previous studies that used similar turbulence models. The flue gas fan’s high vibrations are most likely flow-induced. The simulation result indicates that LES model performed better than the Kepsilon model. The lack of validation in this degree work means that it is hard to know the accuracy of the model. Based on the simulation results the most promising solution seems to be inlet straighteners.Syftet med studien är att undersöka rökgasfläkten i Mälarenergis Unit 6 och att försöka hitta vad som orsakar vibrationsökningarna. Fast Fourier transform metoden har används i detta examensarbete. En jämförelse har gjorts med tidigare studier som använt FFT metoden för att kunna urskilja källan till vibrationsproblemet. Efter en rimlig källa hittades så utfördes en CFD-simulering i ANSYS för att visualisera problemet. Två fall simulerades med två olika turbulensmodeller: K-epsilon modellen och Largeeddy simulation modellen. Resultatet från CFD-simuleringarna jämfördes med tidigare studier som använt liknande metoder. Rökgasfläktens höga vibrationer är med störst sannolikhet flödesinducerad. Simuleringsresultatet indikerar att LES modellen utfördes bättre än Kepsilon modellen. Då det saknas en validering i form av flödesmätningar så är det svårt att säga hur lik modellen är med verkligheten. Baserat på resultatet från simuleringarna så verkar inloppsgaller vara den mest lovande lösningen.
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Sousa, Hairton de Jesus. "Uso da ferramenta "Full Spectrum" para detecção de danos em máquinas rotativas". [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263755.
Testo completoAbstract (sommario):
Orientador: Milton Dias JuniorDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-16T18:51:00Z (GMT). No. of bitstreams: 1 Sousa_HairtondeJesus_M.pdf: 5983507 bytes, checksum: bbd9b5a7613f605ecdda388d19949395 (MD5) Previous issue date: 2010
Resumo: Este trabalho consiste na aplicação das ferramentas de full spectrum na detecção de falhas em máquinas rotativas em cantraste com os half spectrum normalmente utilizados nas aplicações industriais. Nesta dissertação, o full spectrum é computado diretamente da manipulação das coordenadas complexas juntamente com o índice de forma e direcionalidade, que fornece uma informação clara sobre o movimento de precessão de qualquer seção do rotor. Inicialmente, utiliza-se um modelo de elementos finitos de um sistema rotativo a fim de se familiarizar com o seu comportamento dinâmico enquanto sujeito a forças de desbalanceamento Este modelo, que representa uma idealização do rotor usado na parte experimental deste trabalho, é constituído de dois mancais, um deles bastante macio e anisotrópico, e pode ser montado com duas configurações: com um e dois discos. Variando-se a velocidade de rotação e a distribuição espacial das forças de desbalanceamento foi possível identificar, ao longo do rotor, as seções que descreviam movimentos de precessão direta ou retrógrada. As mesmas análises realizadas no modelo numérico foram também conduzidas experimentalmente em uma bancada. Além disso, neste caso, foi também estudado o fenômeno do rubbing (roçamento), que ocorre quando o rotor toca (roça) o stator ou a parte interna dos mancais hidrodinâmicos. Neste experimentos a influência de dois parâmetros foram analizadas: a posição do estator ao longo do rotor - especialmente o movimento de precessão do ponto do eixo em contato com o estator - e a folga entre estator e rotor. Os dados adiquiridos foram analisados usando o full e o half spectrum e os mapas de ordem normal e direcional
Abstract: This work consists in the application of full spectrum tools in fault detection of rotating machinery in contrast to the half spectrum commonly used in industrial applications. In this dissertation, the full spectrum is computed directly from the manipulation of the complex coordinates together with the shape and directivity index, which provides clear information about the precessional motion of any part of the rotor. Initially, it is used a finite element model of a rotating system in order to get acquainted with its dynamic behavior while subjected to unbalance forces. This model, which represents an idealization of the rotor used in the experimental part the this work, has two bearings, one of them very soft and anisotropic, and can be assembled in two configurations: with one or two disks. Varying the rotational speed and the spatial distribution of the unbalance forces it was possible to identify, along the rotor, the stations describing forward or backward precessional motions. The same analyses performed on the numerical model were also experimentally conducted on an instrumented test rig. In this case, however, it was also studied the rubbing phenomenon, which occurs when the rotor hits (rubs) the stator or the internal part of the journal bearings. In these experiments the influence of two parameters were analyzed: the position of the stator along the rotor - especially the precessional motion of the shaft point in contact with the stator - and the stator gap. The acquired data were analyzed using the full and half spectrum and the full and half order map
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
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Al-Bugharbee, Hussein Razzaq. "Data-driven methodologies for bearing vibration analysis and vibration based fault diagnosis". Thesis, University of Strathclyde, 2016. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27458.
Testo completoAbstract (sommario):
Rolling element bearings (REBs) are one of the most critical mechanical components. Their failures can lead for catastrophic failures which might include great loss in economy or even in the lives of people. REBs are inherently dynamic and they demonstrate complex vibration behaviour where conventional vibration –based fault diagnosis methods might not give sensitive indicators of the presence of the defects. This thesis investigates the singular spectrum analysis (SSA) capabilities as completely data-based fault diagnosis method in REBs. The SSA is used to decompose the bearing vibration acceleration signals in a certain number of principal components having the trend, periodical components and structure-less noise. This thesis develops two methodologies to use SSA in different ways and for different purposes. The first methodology uses the SSA (i.e only the decomposition stage) to create a baseline space from healthy bearing vibration signals. Then, any new signals are projected onto this baseline space. From these projections, features are made and used for fault diagnosis purposes. In the second methodology, the SSA contributes to the development of an advanced signal pretreatment that efficiently improves representing the nonstationary bearing vibration signals by linear time invariant autoregressive (LTIVAR) model. Then the coefficients of LTIVAR model are used as features for fault diagnosis purposes. The two methodologies have been validated by using experimental data obtained from three different bearing test rigs. The data used in the analysis covers different defect locations and different defect severities. The results of both methodologies, in terms of correct classification, were compared to some other recent methodologies. In comparison, it is shown that both methodologies have a very good performance and they are superior to those methodologies. The thesis offers simple and efficient methodologies for a complete fault diagnosis in terms of fault detection, identification and severity estimation. Thus, these methodologies have a potential possibility for automation of the entire process of each method.
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Cheour, Khouloud. "Analyse du comportement en vibration de matériaux composites à fibres végétales". Thesis, Reims, 2017. http://www.theses.fr/2017REIMS022/document.
Testo completoAbstract (sommario):
Ce travail de thèse a pour objectif d’analyser le comportement en vibration des composites non-hybrides et hybrides lin-verre. Dans une première partie, une démarche d’analyse modale a été mise en place pour étudier le comportement mécanique et dynamique de ces matériaux. Ceci a permis d’une part, d’identifier les propriétés élastiques et les coefficients d’amortissement de ces composites à partir de leurs fréquences propres, et d’autre part, d’effectuer une comparaison avec les composites traditionnels. La deuxième partie de ce travail est consacrée à une modélisation de l’amortissement des composites non-hybrides et hybrides. Cette modélisation, basée sur la théorie des stratifiés avec cisaillement transverse, a été développée en utilisant la méthode des éléments finis. Plusieurs aspects ont été étudiés comme l’orientation des fibres, la séquence d’empilement, l’architecture des renforts, le choix des séquences d’empilement pour l’hybridation. Cette analyse a conduit enfin à optimiser les performances mécaniques et dissipatives des composites non hybrides et hybrides lin-verre.La dernière partie de ce travail est consacrée à l’étude d’un vieillissement caractérisé par une immersion des matériaux dans l’eau. Dans un premier temps, des essais de vibration ont été réalisés à différentes périodes d’immersion pour identifier l’impact de ce vieillissement sur les propriétés mécaniques et dissipatives des composites non hybrides et hybrides, ainsi que leur évolution en fonction de la durée d’immersion. Enfin, la réversibilité de ces propriétés a été également analysée en effectuant un cycle de vieillissement jusqu’à la saturation puis une opération de séchageThis PhD research work aimed at analysing the free vibration behaviour of non-hybrid and hybrid flax-glass composites. First, a modal analysis approach was developed to study the mechanical and dynamic behaviour of these materials. Their elastic and damping properties were identified from their natural frequencies and a comparison with the traditional composites was carried out. In the second part, a finite element modelling of the damping of non-hybrid and hybrid composites was implemented by considering the classical laminate theory, taking into account the transverse shear effects. Different topics were studied such as the fibres orientation, the stacking sequence, the reinforcement architecture, the choice of the stacking sequence layers for the hybridisation. This analysis resulted in optimising both mechanical and damping performances of non-hybrid composites and hybrid flax-glass composites. In the last part of this work, the effect of water ageing on the dynamical and mechanical properties of non-hybrid and hybrid glass-flax composites was studied. To this end, these composites were subjected to free vibrations at different ageing durations in order to identify the effect of water ageing on their mechanical and damping properties and their evolution with ageing time. Finally, a cycle of ageing until saturation was reached followed by a drying operation, which was carried out to analyse the reversibility of their properties
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James, Philippe Pierre. "A technique for the assessment of strength of coupling between statistical energy analysis subsystems". Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245304.
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Hilaire, Pierre. "Improved laser vibration ladar". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA359857.
Testo completoAbstract (sommario):
Thesis (M.S. in Applied Physics) Naval Postgraduate School, December 1998."December 1998." Thesis advisor(s): Robert C. Harney, Donald L. Walters. Includes bibliographical references (p. 43). Also available online.
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Backström, Daniel. "Vibration of sandwich beams". Doctoral thesis, KTH, Farkost och flyg, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4030.
Testo completoAbstract (sommario):
Some aspects and properties of the lateral vibration of sandwich beams are investigated, including the concept of apparent bending stiffness and shear modulus, allowing the sandwich beam dynamics to be approximately described by classical beam theory. A sixth order beam model is derived including boundary conditions, and the free and forced response of some beam configurations analyzed. The possibility of computing material parameters from measured eigenfrequencies, i. e. inverse analysis, is considered. The higher order model is also utilized for investigation of the energy propagation through sandwich composite beams and the transmission over different junctions.QC 20100630
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Marcollo, Hayden 1972. "Multimodal vortex-induced vibration". Monash University, Dept. of Mechanical Engineering, 2002. http://arrow.monash.edu.au/hdl/1959.1/7674.
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Backström, Daniel. "Vibration of sandwich beams /". Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4030.
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Vukasinovic, Bojan. "Vibration-induced droplet atomization". Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17237.
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James, Ashley Jean. "Vibration induced droplet ejection". Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17337.
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Kidner, Michael Roger Francis. "An active vibration neutraliser". Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299609.
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McKinnell, Robert James. "Active isolation of vibration". Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306465.
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Forta, Nazim Gizem. "Vibration intensity difference thresholds". Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/72167/.
Testo completoAbstract (sommario):
The intensity difference threshold is defined as ‘the difference in the intensity of two stimuli which is just sufficient for their difference to be detected’. The aim of this thesis is to advance understanding of the perception of vibration intensity differences in humans. In addition to increasing understanding of the tactile senses, knowledge of difference perception could inform various applications such as the optimisation of the vibration characteristics of vehicles and the design of human–machine interfaces involving communication via the sense of touch. Absolute thresholds for the perception of vibration in the glabrous skin have been modelled by ‘channels’ within the somatosensory system that predict the effects of vibration frequency, vibration magnitude, vibration duration and contact conditions. Difference thresholds are less well understood and there is little knowledge of their dependence on vibration characteristics and contact conditions. In this thesis, psychophysical methods were employed to determine the difference thresholds with various input conditions (whole-body vibration, foot-transmitted vibration, grasping a vibrating handle, and localised excitation of the hand and the forearm). Five experiments investigated the dependence of difference thresholds on vibration magnitude, vibration frequency, the responses of the somatosensory channels of the skin (especially the Pacinian and the non-Pacinian I channels) as well as the location of the vibration input, information from other sensory systems, and the presence of masking vibration. The first experiment tested the hypothesis that relative difference thresholds (i.e. the percentage change in vibration magnitude required for the change to be detected) for vertical whole-body vibration depend on the frequency and magnitude of the vibration. Relative difference thresholds were found to be independent of vibration magnitude except at the lowest frequency (2.5 Hz) and the highest frequency (315 Hz), where the change in motion may have been perceived by vision and hearing, respectively. The second and third experiments investigated the dependence of difference thresholds on the frequency and magnitude of hand-transmitted vibration and foot-transmitted vibration. The experiments produced similar results, with difference thresholds independent of the frequency of vibration and only dependent on the magnitude of vibration at 125 Hz, where higher magnitudes (18 dB sensation level and above) produced greater relative difference thresholds. The fourth experiment tested the hypothesis that a low-magnitude low-frequency masking vibration (at 16 Hz) would not affect high-frequency difference thresholds (at 125 Hz). It was found that the lowfrequency masker only increased difference thresholds when its magnitude was greater than 12 dB SL. The final experiment with localised vibration at the hand and arm tested the hypothesis that NPI and P channels have different relative difference thresholds. Overall, there was no significant difference between the relative difference thresholds of vibration mediated by the NPI channel (at 10 Hz) and the P-channel (at 125 Hz), but the relative difference thresholds of the P-channel tended to be lower than those of the NPI-channel, as in experiments II and III. Depending on the test conditions, the median unmasked relative difference thresholds were in a range from 0.1 to 0.6. There was a tendency for the relative difference thresholds to decrease with increasing contact area, with whole-body vibration producing the smallest relative difference thresholds and localised vibration producing the greatest relative difference thresholds. From the results of all five experiments, it was concluded that excitation area and cues from other senses were more likely to cause relative difference thresholds to depend on the frequency and magnitude of vibration, than any differences in discrimination capability between the P and NPI channels. Other findings include a possible reduction in the discrimination capability of the P-channel with increasing magnitude of vibration (in Experiments II and III) and the suggestion of lower relative differencethresholds for the NPII channel (in Experiment V).
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Zilletti, Michele. "Self-tuning vibration absorbers". Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/333270/.
Testo completoAbstract (sommario):
This thesis presents a theoretical and experimental study of self-tuning vibration control. Feedback design is often based on the assumption of time-invariance, which means that the controller has constant coefficients. Self-tuning control takes into account process changes in the response of the system under control by incorporating an adjusting mechanism which monitors the system, compares its status with the required one and adjusts the coefficients of the controller. In this thesis a self-tuning process is analysed for active and semi-active control of broadband vibration based on the maximisation of the power absorbed by the controller. The absorbed power can be locally estimated without using extra sensors to monitor the global response of the system under control. This is particularly advantageous in applications where many actuators are required, in which case each actuator and the collocated sensor can be treated as an independent self-tuneable unit. A theoretical analysis of vibration control using this approach is presented for lumped parameter systems and also for distributed systems, such as beam and panels. Different tuning strategies are compared in terms of the reduction of the global response of the system under control. An algorithm is then discussed that tunes the feedback gains of independent control units to maximise their individual absorbed powers. Experimental studies are then presented of a selftuning control system with two decentralised control units using velocity error signals and electromagnetic reactive actuators installed on an aluminium panel. In the second part of the thesis the analysis is extended to the use of inertial actuators. In this case the implementation of the self-tuning control based on the maximisation of the power absorbed is investigated using simulations of velocity feedback control and shunted inertial actuators.
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Hussein, Mohammed Farouk Mohammed. "Vibration from underground railways". Thesis, University of Cambridge, 2004. https://www.repository.cam.ac.uk/handle/1810/272112.
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Triplett, Angela L. "Vibration-Based Energy Harvesting". University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1226614650.
Testo completo
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Red, Wing Rodney D. "Adaptive tuned vibration absorber". Thesis, This resource online, 1997. http://scholar.lib.vt.edu/theses/available/etd-08252008-162250/.
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Su, Dan Kuan-Nien. "Bumblebee vibration activated foraging". Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p1467769.
Testo completoAbstract (sommario):
Thesis (M.S.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed September 15, 2009). Available via ProQuest Digital Dissertations. Includes bibliographical references (p. 27-29).
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Yamada, Shin'ya, Hisataka Sakakibara e Makoto Futatsuka. "Vibration Dose Disturbance Stage, and Examination Results and Subjective Symptoms in Vibration Syndrome". 名古屋大学医学部, 1995. http://hdl.handle.net/2237/6172.
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