Дисертації з теми "Acoustic finite element model"
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Hamiche, Karim. "A high-order finite element model for acoustic propagation." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/400677/.
Повний текст джерелаBolmsvik, Åsa. "Structural-acoustic vibrations in wooden assemblies: : Experimental modal analysis and finite element modelling." Doctoral thesis, Linnéuniversitetet, Institutionen för bygg- och energiteknik (BE), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-24562.
Повний текст джерелаDenna doktorsavhandling behandlar flanktransmission i flervåningshus med trästomme, inom det lågfrekventa området, främst 20-120 Hz. Det övergripande målet är att undersöka hur finita elementmetoden kan bidra i konstruktionsfasen för att utvärdera olika knutpunkters inverkan på flanktransmissionen. Två fältmätningar av accelerationer i trähus har utvärderats. I dessa har två olika lastkällor använts, i den första en stegljudsapparat och i den andra en elektrodynamisk vibrator (shaker). Det visades att shakern kan ge mer detaljerad information, men eftersom vibrationerna även sprider sig till omgivande byggnadsdelar vid fältmätningarna var det svårt att estimera tillförlitliga dämpningsdata även då shaker användes. Fältmätningarna följdes av två mätningar i laborationsmiljö. Dessa två experiment utvärderades med experimentell modalanalys, vilket ger egenmoder och dämpning hos strukturerna. Dämpningen för dessa trähuskonstruktioner varierar kraftigt med frekvens. Extra stora variationer registreras då en elastomer användes i knutpunkten mellan golv och vägg. Den totala dämpningen är generellt högre när elastomerer används i knutpunkten mellan golv och vägg i jämförelse med då knutpunkten är skruvad. Genom att analysera egenmoder och deras korrelationer (MAC), för samma trästruktur men med olika typer av knutpunkter, drogs slutsatsen att knutpunkten drastiskt förändrar strukturens dynamiska beteende. Flera finita elementmodeller av både fält- och laboratorieuppställningar har gjorts. I dessa har knutpunkterna mellan byggnadsdelar modellerats helt styvt eller med hjälp av fjädrar och dämpare. Visuella observationer av egenmoder och korrelationen dem emellan visar att det finns mer rotationsstyvhet i försöken än i finita elementmodellerna. Resultaten i denna doktorsavhandling har gett förståelse för hur knutpunkter i träkonstruktioner beter sig och kan simuleras med finit elementmodellering. Vidare kan resultaten bidra till utvecklingen av FE-modeller som kan användas för att kunna se de akustiska effekterna redan under konstruktionsstadiet. Dock behövs ytterligare forskning inom området.
Rumpler, Romain. "Efficient finite element approach for structural-acoustic applicationns including 3D modelling of sound absorbing porous materials." Phd thesis, Conservatoire national des arts et metiers - CNAM, 2012. http://tel.archives-ouvertes.fr/tel-00726915.
Повний текст джерелаHochman, Michael. "Investigation of acoustic crosstalk effects in CMUT arrays." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42782.
Повний текст джерелаRumpler, Romain. "Efficient Finite Element Approach for Structural-Acoustic Applications including 3D modelling of Sound Absorbing Porous Materials." Doctoral thesis, KTH, MWL Numerisk akustik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-90335.
Повний текст джерелаDans le contexte de lutte contre les nuisances sonores, cette thèse porte sur le développement de méthodes de résolution efficaces par éléments finis, pour des problèmes de vibroacoustique interne avec interfaces dissipatives, dans le domaine des basses fréquences. L’étude se limite à l’utilisation de solutions passives telles que l’intégration de matériaux poreux homogènes et isotropes, modélisés par une approche fondée sur la théorie de Biot-Allard. Ces modèles étant coûteux en terme de résolution, un des objectifs de cette thèse est de proposer une approche modale pour la réduction du problème poroélastique, bien que l’adéquation d’une telle approche avec le comportement dynamique des matériaux poreux soit à démontrer.Dans un premier temps, la résolution de problèmes couplés élasto-poro-acoustiques par sous-structuration dynamique des domaines acoustiques et poreux est établie. L’approche modale originale proposée pour les milieux poroélastiques, ainsi qu’une procédure de sélection des modes significatifs, sont validées sur des exemples 1D à 3D.Une deuxième partie présente une méthode combinant l’utilisation des modèles réduits précédemment établis avec une procédure d’approximation de solution par approximants de Padé. Il est montré qu’une telle combinaison offre la possibilité d’accroître les performances de la résolution (allocation mémoire et ressources en temps de calcul).Un chapitre dédié aux applications permet d’évaluer et comparer les approches sur un problème académique 3D, mettant en valeur leurs performances encourageantes. Afin d’améliorer les méthodes établies dans cette thèse, des perspectives à ces travaux de recherche sont apportées en conclusion.
QC 20120224
FP6 Marie-Curie Smart Structures
FP7 Marie-Curie Mid-Frequency
Zhang, Nan. "SCALE MODELS OF ACOUSTIC SCATTERING PROBLEMS INCLUDING BARRIERS AND SOUND ABSORPTION." UKnowledge, 2018. https://uknowledge.uky.edu/me_etds/119.
Повний текст джерелаRemillieux, Marcel C. "Development of a Model for Predicting the Transmission of Sonic Booms into Buildings at Low Frequency." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/27543.
Повний текст джерелаPh. D.
Day, Joseph L. "A modal approximation for the mutual radiation impedance for spherical sources and acoustic wave scattering using an improved ATILA Finite Element code." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA369783.
Повний текст джерела"September 1999". Thesis advisor(s): Clyde L. Scandrett, Steven R. Baker. Includes bibliographical references (p. 83-84). Also avaliable online.
Case, Justin J. "Numerical analysis of the vibration and acoustic characteristics of large power transformers." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/103702/1/Justin_Case_Thesis.pdf.
Повний текст джерелаMitchell, Morgan Adrienne. "Passive Noise Control in Incubators." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/51603.
Повний текст джерелаMaster of Science
Oberhardt, Tobias. "A micromechanical model for the nonlinearity of microcracks in random distributions and their effect on higher harmonic Rayleigh wave generation." Thesis, Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54365.
Повний текст джерелаTan-Kim, Antoine. "Contribution à l’étude du bruit acoustique d’origine magnétique en vue de la conception optimale de machines synchrones à griffes pour application automobile." Thesis, Compiègne, 2015. http://www.theses.fr/2015COMP2240/document.
Повний текст джерелаThis thesis aims at simulating and reducing the acoustic noise due to magnetic forces of claw-pole automotive alternators. It also aims at improving the understanding of the noise generation mechanisms. In the first part, the assembly of the claw-pole alternator and its different parts are described. The particularities of the acoustic noise of the alternator are also given. Then, the problem as well as the global approach, based on the vibro-acoustic simulation, are explained. The second part is a review of the studies on the acoustic noise from a magnetic origin of electrical machines. The models used to study these machines as well as the main noise reduction solutions are detailed. In the third part, new electromagnetic and vibro-acoustic models are developed. Two electromagnetic models are considered : a finite element model and a hybrid model which couples the finite element model with an analytical model. This analytical model computes the airgap magnetic flux density as the product of a permeance and a magnetomotive force functions. Each function takes the variations of the claw-pole geometry along the axial direction into account. Saturation and tangential forces are taken into account thanks to the finite element model. Then, a finite element mechanical model is developed. Three unknown parameters of the model are determined thanks to the correlation between the model and experimental data, namely : the equivalent materials of the stator stack and the windings and the contact conditions between the stator and the brackets. Finally, acoustic simulations are compared with measurements. A good correlation is achieved between simulated and measured noise peaks. In the fourth part, sensitivity studies are carried out in order to determine the most influential parameters on the acoustic noise of claw-pole alternators. These studies show the significant influence of the claw-pole geometry, the stator windings and the temperature on the acoustic noise. Structural modifications and studied faults have a smaller influence. Characteristics of the magnetic forces as well as the influences of radial and tangential forces are then detailed. In the end, optimizations with the finite element and the hybrid models are presented. A prototype is built and acoustic measurements show a 10 dB decrease of the sound power level
Zohora, Fatematuz. "Study of pipe leak fluid dynamic characteristics and their influences on acoustic emission generation." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/207823/1/Fatematuz_Zohora_Thesis.pdf.
Повний текст джерелаJardim, Maurício Ferreira [UNESP]. "Análise teórica e experimental vibro-acústica utilizando a técnica de matrizes compactas." Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/94549.
Повний текст джерелаCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Em muitos problemas do nosso cotidiano ocorre acoplamento entre a resposta acústica no interior de uma cavidade e a excitação estrutural em um de seus contornos flexíveis, bem como a resposta estrutural nestes contornos também está relacionada à fonte acústica da cavidade. Interior de automóveis, cabine de caminhões e fuselagem de aviões são apenas alguns exemplos práticos destes tipos de sistemas. Acoplamento implica que o comportamento dos sistemas acústico e estrutural não são independentes um do outro, e ambos devem ser considerados como um único sistema global. O propósito deste trabalho é avaliar a técnica de matrizes compactas na solução de problema de acoplamento vibroacústico em cavidades de geometria regular e irregular. Preliminarmente, a análise do acoplamento vibro-acústico é baseado no método dos elementos finitos e o conjunto de equações não simétricas que modela o movimento é discutida. A aproximação vibro-acústica por matrizes compactas é feita utilizando conceitos de impedância e mobilidade. No modelo de matrizes compactas, o acoplamento é obtido através da avaliação dos modos acústicos e estruturais desacoplados da cavidade e da estrutura flexível, respectivamente. Simulações numéricas utilizando o método dos elementos finitos e a técnica de matrizes compactas são apresentadas para modelos vibro-acústicos de geometria regular e irregular. Testes experimentais são realizados em uma cavidade irregular feita de PVC e aço. A metodologia de análise dos resultados é baseada nas FRF(s) definidas pelas relações entre a resposta em pressão acústica da cavidade e a força estrutural e entre a resposta em velocidade e a força estrutural aplicada sobre a superfície flexível. A comparação dos modelos numéricos e experimentais mostra o potencial da técnica de matrizes compactas.
In many systems of day-life occurs the coupling between the acoustical response in a cavity and a structural excitation on a flexible boundary, whereas the structural response in this same boundary is also related to acoustical excitation source. Car interiors, cabs of trucks and aircraft fuselage are a just a few practical examples of this sort of systems. Coupling implies that the acoustical and structural system behavior is not independent from each other, and therefore they must be considered as a global system behavior. The aim of this work is to evaluate a compact matrix formulation to solve vibro-acoustic problems in regular and irregular shape cavity. Preliminary, the vibro-acoustic coupling analysis is based on finite element method and the set of non-symmetric equation that represents the movement is discussed. The compact matrix formulation approaches have been done using impedance and mobility concepts. In compact matrix model, the coupling is obtained by evaluating the uncoupled acoustic modes and structural modes of the cavity and flexible structure, respectively. Numerical simulation using the finite element method and the compact matrix formulation are shown for regular and irregular shape cavity model. Experimental tests are evaluated in an irregular rigid cavity made of PVC and steel. The results analysis methodology is based on FRF(s) defined by the relationship between the pressure acoustic response in the cavity and structural force and between the velocity response and structural force applied on the flexible boundary. The comparison of numerical and experimental models shows the potential of the compact matrix formulation.
Leonet, Véronique Madeleine. "Participation à la coopération de méthodes de modélisation : application au calcul vibroacoustique." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10159.
Повний текст джерелаPelteku, Altin E. "Development of an electromagnetic glottal waveform sensor for applications in high acoustic noise environments." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0114104-142855/.
Повний текст джерелаKeywords: basis functions; perfectly matched layers; PML; neck model; parallel plate resonator; finite element; circulator; glottal waveform; multi-transmission line; dielectric properties of human tissues; radiation currents; weighted residuals; non-acoustic sensor. Includes bibliographical references (p. 104-107).
Jardim, Maurício Ferreira. "Análise teórica e experimental vibro-acústica utilizando a técnica de matrizes compactas /." Ilha Solteira : [s.n.], 2008. http://hdl.handle.net/11449/94549.
Повний текст джерелаBanca: Gustavo Luiz Chagas Manhães de Abreu
Banca: Edson Antonio Capello Sousa
Resumo: Em muitos problemas do nosso cotidiano ocorre acoplamento entre a resposta acústica no interior de uma cavidade e a excitação estrutural em um de seus contornos flexíveis, bem como a resposta estrutural nestes contornos também está relacionada à fonte acústica da cavidade. Interior de automóveis, cabine de caminhões e fuselagem de aviões são apenas alguns exemplos práticos destes tipos de sistemas. Acoplamento implica que o comportamento dos sistemas acústico e estrutural não são independentes um do outro, e ambos devem ser considerados como um único sistema global. O propósito deste trabalho é avaliar a técnica de matrizes compactas na solução de problema de acoplamento vibroacústico em cavidades de geometria regular e irregular. Preliminarmente, a análise do acoplamento vibro-acústico é baseado no método dos elementos finitos e o conjunto de equações não simétricas que modela o movimento é discutida. A aproximação vibro-acústica por matrizes compactas é feita utilizando conceitos de impedância e mobilidade. No modelo de matrizes compactas, o acoplamento é obtido através da avaliação dos modos acústicos e estruturais desacoplados da cavidade e da estrutura flexível, respectivamente. Simulações numéricas utilizando o método dos elementos finitos e a técnica de matrizes compactas são apresentadas para modelos vibro-acústicos de geometria regular e irregular. Testes experimentais são realizados em uma cavidade irregular feita de PVC e aço. A metodologia de análise dos resultados é baseada nas FRF(s) definidas pelas relações entre a resposta em pressão acústica da cavidade e a força estrutural e entre a resposta em velocidade e a força estrutural aplicada sobre a superfície flexível. A comparação dos modelos numéricos e experimentais mostra o potencial da técnica de matrizes compactas.
Abstract: In many systems of day-life occurs the coupling between the acoustical response in a cavity and a structural excitation on a flexible boundary, whereas the structural response in this same boundary is also related to acoustical excitation source. Car interiors, cabs of trucks and aircraft fuselage are a just a few practical examples of this sort of systems. Coupling implies that the acoustical and structural system behavior is not independent from each other, and therefore they must be considered as a global system behavior. The aim of this work is to evaluate a compact matrix formulation to solve vibro-acoustic problems in regular and irregular shape cavity. Preliminary, the vibro-acoustic coupling analysis is based on finite element method and the set of non-symmetric equation that represents the movement is discussed. The compact matrix formulation approaches have been done using impedance and mobility concepts. In compact matrix model, the coupling is obtained by evaluating the uncoupled acoustic modes and structural modes of the cavity and flexible structure, respectively. Numerical simulation using the finite element method and the compact matrix formulation are shown for regular and irregular shape cavity model. Experimental tests are evaluated in an irregular rigid cavity made of PVC and steel. The results analysis methodology is based on FRF(s) defined by the relationship between the pressure acoustic response in the cavity and structural force and between the velocity response and structural force applied on the flexible boundary. The comparison of numerical and experimental models shows the potential of the compact matrix formulation.
Mestre
Sánchez, Orgaz Eva María. "Advanced numerical techniques for the acoustic modelling of materials and noise control devices in the exhaust system of internal combustion engines." Doctoral thesis, Universitat Politècnica de València, 2016. http://hdl.handle.net/10251/64090.
Повний текст джерела[ES] Esta Tesis se centra en el desarrollo e implementación de métodos numéricos eficientes para el diseño y modelado de componentes de la línea de escape en motores de combustión interna. Merecen especial atención los silenciadores disipativos perforados de automóviles, ya que su comportamiento acústico puede sufrir variaciones importantes debidas a las variaciones de temperatura en el material absorbente, así como a las heterogeneidades de la fibra. Por tanto, se requieren técnicas numéricas que consideren estos casos para garantizar la precisión de los resultados. Se lleva a cabo una revisión bibliográfica que recoge los modelos de onda unidimensionales, así como modelos acústicos de materiales absorbentes y superficies perforadas. Sin embargo, las limitaciones de los primeros hacen indispensable el uso de modelos multidimensionales. Además se explora la posibilidad de usar nuevos elementos acústicos, cuyo objetivo es ser una alternativa potencial a los materiales absorbentes, que pueden tener un efecto negativo sobre la salud. La Tesis considera el uso de superficies microperforadas y sinterizadas. Estas últimas en algunos casos presentan una impedancia casi constante, cuyo valor depende, entre otras cosas, del espesor y la porosidad de las placas. Para evitar las limitaciones de los modelos de onda plana, se propone un enfoque en elementos finitos (EF) para el análisis acústico de silenciadores disipativos que incluyen un conducto con flujo medio axial uniforme y una cámara externa con una distribución heterogénea de material absorbente. Por otro lado, la variación de las propiedades también puede producirse por gradientes térmicos. En este caso, se propone una formulación híbrida de EF para silenciadores disipativos perforados que incluye: (1) Gradientes térmicos en el conducto central y la cámara; (2) Un conducto perforado que canaliza flujo medio axial no uniforme. Se ha implementado una formulación de EF para resolver la ecuación de ondas en términos de presión para el medio estacionario heterogéneo asociado a la cámara. Además, la ecuación asociada al conducto central, expresada en términos de potencial de velocidad acústica, permite la presencia de flujo axial no uniforme. El acoplamiento entre ambas regiones se ha realizado mediante un conducto perforado y su impedancia acústica y se ha adaptado para incluir la citada falta de homogeneidad. Se ha visto que las heterogeneidades pueden influir notablemente en la atenuación acústica de un silenciador, debiéndose incluir en los modelos teóricos. Las técnicas de optimización para componentes industriales de control de ruido son importantes, ya que producen elementos con mejores características. Los algoritmos evolutivos son técnicas emergentes capaces de obtener una solución, incluso cuando la optimización tradicional tiene dificultades. Las técnicas de optimización se combinan con el MEF para conseguir la máxima atenuación posible en el rango de frecuencias de interés. Se ha definido un problema de optimización de un silenciador multicámara y se han llevado a cabo varios análisis para obtener la configuración más adecuada para cada caso. Bajo ciertas hipótesis de uniformidad axial, se han considerado varias técnicas para reducir el coste computacional de un análisis 3D completo para silenciadores disipativos con gradientes de temperatura y flujo medio. Éstas se basan en la descomposición del campo acústico en modos axiales y transversales dentro de cada subdominio, y un procedimiento de acoplamiento de las expansiones modales en los cambios de sección del silenciador mediante las condiciones de continuidad de los campos acústicos. Se estudia la eficiencia computacional y precisión de las predicciones de las técnicas de acoplamiento, incluyendo colocación puntual en nodos y puntos de Gauss, así como ajuste modal. Todos ellos proporcionan predicciones precisas de la atenuación mejorando el coste
[CAT] Aquesta Tesi es centra en el desenvolupament i implementació de mètodes numèrics eficients per al disseny i modelatge de components de la línia d'escapament en motors de combustió interna. Mereixen especial atenció els silenciadors dissipatius perforats d'automòbils, ja que el seu comportament acústic pot patir variacions importants degudes a les variacions de temperatura en el material absorbent, així com a les heterogeneïtats de la fibra. Per tant, es requereixen tècniques numèriques que considerin aquests casos per garantir la precisió dels resultats. Es porta a terme una revisió bibliogràfica que recull els models d'ona unidimensionals, així com models acústics de materials absorbents i superfícies perforades. No obstant això, les limitacions dels primers fan indispensable l'ús de models multidimensionals. A més s'explora la possibilitat d'usar nous elements acústics amb l'objectiu que siguen una alternativa potencial als materials absorbents, que poden tenir un efecte negatiu sobre la salut. La Tesi considera l'ús de superfícies microperforades i sinteritzades. Aquestes últimes en alguns casos presenten una impedància gairebé constant. El seu valor depèn, entre altres coses, del gruix i la porositat de les plaques. Per evitar les limitacions dels models d'ona plana, es proposa un enfocament amb elements finits (EF) per a l'anàlisi acústic de silenciadors dissipatius que inclouen un conducte amb flux mig axial uniforme i una càmera externa amb una distribució heterogènia de material absorbent. D'altra banda, la variació de les propietats també es pot produir per gradients tèrmics. En aquest cas, es proposa una formulació híbrida d'EF per silenciadors dissipatius perforats que inclou: (1) Gradients tèrmics en el conducte central i la càmera; (2) Un conducte perforat que canalitza flux mig axial no uniforme. S'ha implementat una formulació d'EF per resoldre l'equació d'ones en termes de pressió per al medi estacionari heterogeni associat a la càmera. A més, l'equació associada al conducte central, expressada en termes de potencial de velocitat acústica, permet la presència de flux axial no uniforme. L'acoblament entre les dues regions s'ha realitzat mitjançant un conducte perforat i la seva impedància acústica i s'ha adaptat per incloure la esmentada falta d'homogeneïtat. S'ha vist que les heterogeneïtats poden influir notablement en l'atenuació acústica d'un silenciador i s'han d'incloure en els models teòrics. Les tècniques d'optimització per a components industrials de control de soroll són importants, ja que produeixen elements amb millors característiques. Els algoritmes evolutius són tècniques emergents capaces d'obtenir una solució, fins i tot quan l'optimització tradicional té dificultats. Les tècniques d'optimització es combinen amb el mètode d'elements finits (MEF) per aconseguir la màxima atenuació possible en el rang de freqüències d'interès. S'ha definit un problema d'optimització d'un silenciador multicàmera i s'han dut a terme diverses anàlisis per obtenir la configuració més adequada per a cada cas. Sota certes hipòtesis d'uniformitat axial, s'han considerat diverses tècniques per reduir el cost computacional d'una anàlisi 3D complet per silenciadors dissipatius amb gradients de temperatura i flux mig. Aquestes es basen en la descomposició del camp acústic en modes axials i transversals dins de cada subdomini, i un procediment d'acoblament de les expansions modals en els canvis de secció del silenciador mitjançant les condicions de continuïtat dels camps acústics. S'estudia l'eficiència computacional i precisió de les prediccions de les tècniques d'acoblament, incloent col·locació puntual en nodes i punts de Gauss, així com ajust modal. Tots ells proporcionen prediccions precises de l'atenuació millorant el cost computacional d'EF.
Sánchez Orgaz, EM. (2016). Advanced numerical techniques for the acoustic modelling of materials and noise control devices in the exhaust system of internal combustion engines [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/64090
TESIS
Uhrig, Matthias Pascal. "Numerical simulation of nonlinear Rayleigh wave beams evaluating diffraction, attenuation and reflection effects in non-contact measurements." Thesis, Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54368.
Повний текст джерелаIrfanoglu, Bulent. "Boundary Element-finite Element Acoustic Analysis Of Coupled Domains." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605360/index.pdf.
Повний текст джерелаKrishnapillai, Shankar. "Application of finite element models to powerflow calculations : a receptance approach." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297248.
Повний текст джерелаThomas, Sadiq. "Comprehensive finite element modelling of electromagnetic acoustic transducers." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509874.
Повний текст джерелаAssaad, Jamal. "Modélisation des transducteurs piézoélectriques haute fréquence à l'aide de la méthode des éléments finis." Valenciennes, 1992. https://ged.uphf.fr/nuxeo/site/esupversions/daff1271-db25-4894-82dd-828d666c589c.
Повний текст джерелаMeyer, Valentin. "Development of a substructuring approach to model the vibroacoustic behavior of submerged stiffened cylindrical shells coupled to non-axisymmetric internal frames." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI111/document.
Повний текст джерелаMany works can be found in the literature concerning the vibroacoustic modelling of submerged stiffened cylindrical shells, because of high interest in the industrial domain, in particular for aeronautical or naval applications. However, only a few of them take into account non-axisymmetric internal frames, as for instance engine foundations or floor partitions, that can play a role on the vibroacoustic behavior of the system. That is why a substructuring approach called the Condensed Transfer Function (CTF) approach is proposed in the first part of this thesis. The aim is to take advantage of both analytical models and element-based models, in order to be able to deal with the geometrical complexity, and to calculate at higher frequencies than with element-based methods only. The substructuring method is developed in the general case of thin mechanical structures coupled along curves. A set of orthonormal functions called condensation functions, which depend on the curvilinear abscissa along the coupling line, is considered. This set is then used as a basis for approximating and decomposing the displacements and the applied forces at the line junctions. Thanks to the definition and calculation of condensed transfer functions for each uncoupled subsystem and by using the superposition principle for passive linear systems, the behavior of the coupled subsystems can be obtained. The method is first developed and validated for plates and convergence criteria are defined in relation with the size of the basis of condensation functions. The CTF method is then applied to the case of a submerged stiffened cylindrical shell with non-axisymmetric internal frames. The system is partitioned in 3 types of subsystems: the submerged shell, the axisymmetric frames (stiffeners, bulkheads) and the non-axisymmetric frames. The submerged shell is described by a semi-analytical method based on the Flügge equations in the spectral domain. The axisymmetric frames are described by axisymmetric Finite Element models and the non-axisymmetric frames by Finite Element models. The CTF method is applied to different test cases in order to highlight the influence of non-axisymmetric internal frames on the vibroacoustic behavior of a submerged stiffened cylindrical shell, for different excitations particularly relevant in the naval domain: a point force, an acoustic plane wave, and a random pressure field (such as a diffuse sound field or a turbulent boundary layer for instance)
Meury, Patrick E. "Stable finite element boundary element Galerkin schemes for acoustic and electromagnetic scattering." lizenzfrei, 2007. http://e-collection.ethbib.ethz.ch/view/eth:30146.
Повний текст джерелаKlíma, Jaromír. "Výpočtové modelování funkce lidských hlasivek." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228702.
Повний текст джерелаPavlica, Ondřej. "Výpočtové modelování interakce kmitajících hlasivek s proudem vzduchu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229726.
Повний текст джерелаMurdoch, Brian. "Finite element-CAD integrated BOD model." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0005/MQ30525.pdf.
Повний текст джерелаRompré, Stéphane. "Finite element model of wood fibres." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=64106.
Повний текст джерелаRathi, Keshav L. "Finite element acoustic analysis of absorption silencers with mean flow." Thesis, Loughborough University, 1994. https://dspace.lboro.ac.uk/2134/26860.
Повний текст джерелаBetts, Juan Fernando. "Finite Element Study of Plane Wave Acoustic Phenomena in Ducts." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/9584.
Повний текст джерелаMaster of Science
Bermejo-Bermejo, Rodolfo. "A finite element model of ocean circulation." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26166.
Повний текст джерелаScience, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
Yin, John Zhihao. "Finite element model of cardiac electrical conduction." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/26859.
Повний текст джерелаGotin, Nathalie. "Finite Element Model Updating for Rotary Machinery." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/864.
Повний текст джерелаHamam, Zeina. "Simulation numérique et analyse de l'émission acoustique due à la rupture de fibre et à la décohésion à l'interface fibre/matrice dans un microcomposite." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI127.
Повний текст джерелаThis work focuses on the modeling of acoustic emission (AE) in a microcomposite made of carbon fiber and epoxy matrix. The main objective of this thesis is to quantify the influence of the propagation medium and of the sensor on the acoustic signal related to the breakage of a fiber, via finite element simulations carried out using the ABABQUS® software. Several studies, based on pattern recognition techniques, have shown that it is possible to correlate each AE signal to the different damage mechanisms (fiber breakage, matrix cracking, interfacial fiber / matrix debonding, delamination, etc. ). However, the acoustic signature is not universal; it strongly depends on the material, the structure, the sensors and the acquisition system. In the AE qualitative analysis, propagation and signal modifications are not taken into account. In this context, the validation of the acoustic signature is delicate and the results are difficult to generalize. A quantitative approach based on the simulation of AE and the entire acquisition chain is necessary in order to make the use of AE more reliable and to give robustness to the diagnosis and prognosis. In this work, a numerical model of the carbon fiber failure embedded in an epoxy matrix is established. This numerical model is validated by comparison with the experimental results. A parametric study is carried out in order to identify the effect of the different parts of the AE chain, in particular the effect of the propagation medium and of the sensor. An extension of this numerical model is also proposed in order to simulate another AE source, the interfacial fiber / matrix debonding. These numerical AE signals can be used in addition to experimental data to build libraries for life prediction approaches, based on machine learning methods in a PHM (Prognosis Heath management) type approach
Pereira, Da Silva Luciano. "Atténuation du bruit et des vibrations de structures minces par dispositifs piézoélectriques passifs : modèles numériques d'ordre réduit et optimisation." Thesis, Paris, CNAM, 2014. http://www.theses.fr/2015CNAM0944/document.
Повний текст джерелаPassive structural vibration and noise reduction by means of shunted piezoelectric patches is addressed in this thesis. The first part of the work concerns the finite element modeling of shunted piezoelectric systems. Firstly, an original finite element formulation, with only a couple of electric variables per piezoelectric patch (the global charge/ voltage), is analyzed and validated. Secondly, several reduced order models based on a normal mode expansion are proposed to solve the electromechanical problem. The convergence of these reduced order models is then analyzed for a resistive and a resonant shunt circuits. In the second part of the work, the concept of topology optimization, based on the Solid Isotropic Material with Penalization method (SIMP), is employed to optimize, in terms of damping efficiency, the geometry of piezoelectric patches as well as their placement on the host elastic structure. The proposed optimization procedure consists of distributing the piezoelectric material in such a way as to maximize the modal electromechanical coupling factor of the mechanical vibration mode to which the shunt is tuned, independently of the choice of electric circuit components. Numerical examples validate and demonstrate the potential of the proposed approach for the design of piezoelectric shunt devices. Finally, the last part of the work concerns the numerical modeling of noise and vibration reduction of thin structures in the low frequency range by using shunted piezoelectric elements. An efficient approach that can be applied to any thin continuous plates in an infinite baffle, independently of the boundary conditions, is proposed. An application example of a thin plate with reinforcements is presented and analyzed
Wilson, Kelly A. "Finite Element Analysis of Breast Implants." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/32972.
Повний текст джерелаMaster of Science
Le, Gall Thomas. "Simulation de l'émission acoustique : Aide à l'identification de la signature acoustique des mécanismes d'endommagement." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI005/document.
Повний текст джерелаAcoustic emission (AE) is a non-destructive testing technique consisting in measuring and interpreting the acoustic signature of damage mechanisms. In a conventional treatment approach (phenomenological approach), the interpretation of data measured by AE is based on empirical correlations between the source (the damage mechanism) parameters and the measured signal. Therefore, the modifications due to the acquisition chain of acoustic emission are ignored. Yet, propagation of the waves in the material, measures made by the sensor and signal treatments made by the acquisition system modify the signal and the information it carries. As a consequence, identification of the source and comparison with results from other tests made in different conditions are difficult. To find a solution to these problems, one can take into account the different steps of the acquisition chain. This is the goal of Quantitative Acoustic Emission (QAE). This approach is based on modelling techniques to evaluate the impact of each step of the acquisition chain on the AE signal. The first part of this study concerns the experimental validation of the modelling techniques that were used in simulating the steps of the acquisition chain. The Finite Element Method (FEM) is used in simulating the signal propagation inside the material. The sensor effect on the signal is simulated by its sensitivity function, measured by the reciprocity method and used as a transfer function. The second part deals with using these techniques to evaluate the impact of simple AE sources on the AE signal. These simple sources are considered as a point source and modelled by dipole forces. Three tensile specimen geometries are studied: a first specimen that can be compared to a plate, a second specimen that can be compared to a beam and a third specimen of intermediate dimensions. The obtained results show the mechanical waves propagate inside the specimens as modes. These modes depend on the specimen geometry. Each source excites the wave propagation modes in a different manner. Consequently, studying the excited modes, one can gather useful information on the AE source to identify it. In addition, this study highlighted relevant signal parameters to identify AE sources. The correlation of these parameters allows segregating the signals as a function of the source. These results obtained at the material surface don’t take into account the sensor modifications on the signal. The sensor modifies the modal signature of the sources as well as the value of the calculated parameters. This leads to more difficulties in identifying the AE sources
Di, Meglio Alberto. "Finite element-boundary elements modelling of acoustic scattering from viscoelastic anechoic structures." Thesis, University of Birmingham, 2000. http://etheses.bham.ac.uk//id/eprint/488/.
Повний текст джерелаShah, Jimit. "Vibro-Acoustic Studies on Damped Panels Using Finite and Boundary Element Methods." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1420207337.
Повний текст джерелаCodina, Rovira Ramon. "A finite Element model for incompressible flow problems." Doctoral thesis, Universitat Politècnica de Catalunya, 1992. http://hdl.handle.net/10803/5915.
Повний текст джерелаLe, Roux Daniel Y. "A semi-Lagrangian finite element barotropic ocean model." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ44492.pdf.
Повний текст джерелаLevin, Robert Ian. "Dynamic Finite Element model updating using neural networks." Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264075.
Повний текст джерелаWaters, Timothy Paul. "Finite element model updating using frequency response functions." Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294617.
Повний текст джерелаTerrell, Michael John. "Constrained generic substructures in finite element model updating." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430175.
Повний текст джерелаGorman, John P. (John Patrick) 1973. "Finite element model of thermoelastic damping in MEMS." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8458.
Повний текст джерелаIncludes bibliographical references (p. 111).
Damping in MEMS resonators was studied experimentally and numerically. Quality factor measurements were performed on Draper gyroscopes made from boron doped silicon wafers with varying amount of germanium (0%, 2%, 23%, 30% ). The quality factors of gyroscopes with germanium were measured to be lower than those without germanium, due to increased anelastic damping. Specifically, the decreased thermal conductivity in the devices with germanium causes those devices to experience thermoelastic damping of a greater magnitude than the germanium-free devices. The amount of damping exhibited is found to be well explained by existing analytical expressions for thermoelastic dissipation in a beam model. The governing equations of thermo elasticity dictate that the amount of damping that a resonator undergoes is a function of both material properties as well as device geometry. Damping will become greatest at operating cycle times that are of the same scale as the thermal relaxation times of the device material. Due to the fact that analytical expressions exist for only a few simple geometries, a finite element model was developed to evaluate thermoelastic damping in more complicated geometries. The finite element model is demonstrated to be in good qualitative agreement with the analytical expressions, and is used to analyze the impact of design modifications such as the addition of fillets and anchors to a simple beam model. It is shown that depending on the size scale of the resonator (which dictates the amount of internal damping), these geometric modifications may either hinder or improve resonator damping characteristics.
by John P. Gorman.
S.M.
Liu, Jiawei. "SIMULATION OF WHISTLE NOISE USING COMPUTATIONAL FLUID DYNAMICS AND ACOUSTIC FINITE ELEMENT SIMULATION." UKnowledge, 2012. http://uknowledge.uky.edu/me_etds/9.
Повний текст джерелаLiu, Zhaowei. "An isogeometric coupled boundary element method and finite element method for structural-acoustic analysis through loop subdivision surfaces." Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/38988/.
Повний текст джерелаEriksson, Daniel. "A Mass Conserving Wind Model Evaluation With Finite Element." Thesis, Umeå universitet, Institutionen för fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-80406.
Повний текст джерелаDetta arbete testar och utvärderar en metod for att approximera ett stationärt vind fält i en urban miljö i syfte att användas for spridnings beräkningar. Istället for att använda Navier Stokes ekvation används en massbevarande modell. Denna modell använder empirisk information for att approximera vind fältet. Fältet görs sedan massbevarande. Detta arbete visar att det ar möjligt att lösa modellen med Finita Element och Comsol Multiphysics för stora urbana miljöer på kort tid. Jämförelser med vindtunnel experiment visar att de stora virvlarna är synliga men att hastigheterna är lägre. Bland de iterativa lösarna som användes presterade Multigrid och Conjugat Gradient metoden bäst. En urban miljö med 2 100 000 frihetsgrader hade en lösningstid på ca 3 minuter.
Giavaras, Alexandros. "A finite element model for the permeability of textiles." Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546289.
Повний текст джерела