Дисертації з теми "Spectral Stochastic Finite Element Method"
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Spectral Stochastic Finite Element Method".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
Fink, Sebastian [Verfasser]. "Simulation of elastic-plastic material behaviour with uncertain material parameters : a spectral stochastic finite element method approach / Sebastian Fink." Hannover : Technische Informationsbibliothek (TIB), 2015. http://d-nb.info/1095501860/34.
Повний текст джерелаStarkloff, Hans-Jörg. "Stochastic finite element method with simple random elements." Universitätsbibliothek Chemnitz, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200800596.
Повний текст джерелаParvini, Mehdi. "Pavement deflection analysis using stochastic finite element method." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0014/NQ42757.pdf.
Повний текст джерелаParvini, Mehdi. "Pavement deflection analysis using stochastic finite element method /." *McMaster only, 1997.
Знайти повний текст джерелаXiao, Dong Wen. "Efficiency analysis on element decomposition method for stochastic finite element analysis." Thesis, University of Macau, 2000. http://umaclib3.umac.mo/record=b1636334.
Повний текст джерелаAntypas, Dionyssios. "Structural response modelling using the stochastic finite element method." Thesis, Imperial College London, 2002. http://hdl.handle.net/10044/1/8314.
Повний текст джерелаLi, Chenfeng. "Stochastic finite element modelling of elementary random media." Thesis, Swansea University, 2006. https://cronfa.swan.ac.uk/Record/cronfa42770.
Повний текст джерелаNešpůrek, Lukáš. "STOCHASTIC CRACK PROPAGATION MODELLING USING THE EXTENDED FINITE ELEMENT METHOD." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-233900.
Повний текст джерелаWeber, Marc Anton. "Stochastic structural analysis of engineering components using the finite element method." Doctoral thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/8476.
Повний текст джерелаThis thesis investigates probabilistic and stochastic methods for structural analysis which can be integrated into existing, commercially available finite element programs. It develops general probabilistic finite element routines which can be implemented within deterministic finite element programs without requiring major code development. These routines are implemented in the general purpose finite element program ABAQUS through its user element subroutine facility and two probabilistic finite elements are developed: a three-dimensional beam element limited to linear material behaviour and a two-dimensional plane element involving elastic-plastic material behaviour. The plane element incorporates plane strain, plane stress and axisymmetric formulations. The numerical accuracy and robustness of the routines are verified and application of the probabilistic finite element method is illustrated in two case studies, one involving a four-story, two-bay frame structure, the other a reactor pressure vessel nozzle. The probabilistic finite element routines developed in this thesis integrate point estimate methods and mean value first order methods within the same program. Both methods require a systematic sequence involving the perturbation of the random parameters to be evaluated, although the perturbation sequence of the methods differ. It is shown that computer-time saving techniques such as Taylor series and iterative perturbation schemes, developed for mean value based methods, can also be used to solve point estimate method problems. These efficient techniques are limited to linear problems; nonlinear problems must use full perturbation schemes. Finally, it is shown that all these probabilistic methods and perturbation schemes can be integrated within one program and can follow many of the existing deterministic program structures and subroutines. An overall strategy for converting deterministic finite element programs to probabilistic finite element programs is outlined.
Huh, Jungwon. "Dynamic reliability analysis for nonlinear structures using stochastic finite element method." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/289087.
Повний текст джерелаKlenow, Bradley. "Finite and Spectral Element Methods for Modeling Far-Field Underwater Explosion Effects on Ships." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/37648.
Повний текст джерелаPh. D.
Zhou, Yiguang. "Efficient stochastic finite element method for the reliability analysis of nonlinear frame structures." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/185746.
Повний текст джерелаMardyanto, Mas Agus. "A solution to an inverse problem of groundwater flow using stochastic finite element method." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/29139.
Повний текст джерелаGao, Liwei. "Stochastic finite element method for the reliability analysis of nonlinear frames with PR connections." Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186898.
Повний текст джерелаLan, Shuang Wen. "Stochastic finite element analysis of structures with elementary stiffness matrix decomposition method and exponential polynomial moment method." Thesis, University of Macau, 2010. http://umaclib3.umac.mo/record=b2148241.
Повний текст джерелаFitzgerald, Anthony P. "A general variational principle for random and fields in elastic solid mechanics." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/21462.
Повний текст джерелаGuo, Xiu Xiu. "Finite element analysis of nonlinear stochastic oscillators with Poisson white noise excitation." Thesis, University of Macau, 2010. http://umaclib3.umac.mo/record=b2182943.
Повний текст джерелаScinocca, Francisco. "Uncertainty quantification of aircraft modal analysis using perturbation technique in the stochastic finite element method." Instituto Tecnológico de Aeronáutica, 2012. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=2062.
Повний текст джерелаJeong, Gi Young. "Tensile Properties of Loblolly Pine Strands Using Digital Image Correlation and Stochastic Finite Element Method." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/29563.
Повний текст джерелаPh. D.
Zeng, Wei. "Advanced Development of Smoothed Finite Element Method (S-FEM) and Its Applications." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439309306.
Повний текст джерелаBirgersson, Fredrik. "Prediction of random vibration using spectral methods." Doctoral thesis, KTH, Aeronautical and Vehicle Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3694.
Повний текст джерелаMuch of the vibration in fast moving vehicles is caused bydistributed random excitation, such as turbulent flow and roadroughness. Piping systems transporting fast flowing fluid isanother example, where distributed random excitation will causeunwanted vibration. In order to reduce these vibrations andalso the noise they cause, it is important to have accurate andcomputationally efficient prediction methods available.
The aim of this thesis is to present such a method. Thefirst step towards this end was to extend an existing spectralfinite element method (SFEM) to handle excitation of planetravelling pressure waves. Once the elementary response tothese waves is known, the response to arbitrary homogeneousrandom excitation can be found.
One example of random excitation is turbulent boundary layer(TBL) excitation. From measurements a new modified Chase modelwas developed that allowed for a satisfactory prediction ofboth the measured wall pressure field and the vibrationresponse of a turbulence excited plate. In order to model morecomplicated structures, a new spectral super element method(SSEM) was formulated. It is based on a waveguide formulation,handles all kinds of boundaries and its elements are easily putinto an assembly with conventional finite elements.
Finally, the work to model fluid-structure interaction withanother wave based method is presented. Similar to the previousmethods it seems to be computationally more efficient thanconventional finite elements.
Karavelić, Emir. "Stochastic Galerkin finite element method in application to identification problems for failure models parameters in heterogeneous materials." Thesis, Compiègne, 2019. http://www.theses.fr/2019COMP2501.
Повний текст джерелаThis thesis deals with the localized failure for structures built of heterogeneous composite material, such as concrete, at two different scale. These two scale are latter connected through the stochastic upscaling, where any information obtained at meso-scale are used as prior knowledge at macro-scale. At meso scale, lattice model is used to represent the multi-phase structure of concrete, namely cement and aggregates. The beam element represented by 3D Timoshenko beam embedded with strong discontinuities ensures complete mesh independency of crack propagation. Geometry of aggregate size is taken in agreement with EMPA and Fuller curve while Poisson distribution is used for spatial distribution. Material properties of each phase is obtained with Gaussian distribution which takes into account the Interface Transition Zone (ITZ) through the weakening of concrete. At macro scale multisurface plasticity model is chosen that takes into account both the contribution of a strain hardening with non-associative flow rule as well as a strain softening model components for full set of different 3D failure modes. The plasticity model is represented with Drucker-Prager yield criterion, with similar plastic potential function governing hardening behavior while strain softening behavior is represented with St. Venant criterion. The identification procedure for macro-scale model is perfomed in sequential way. Due to the fact that all ingredients of macro-scale model have physical interpretation we made calibration of material parameters relevant to particular stage. This approach is latter used for model reduction from meso-scale model to macro-scale model where all scales are considered as uncertain and probability computation is performed. When we are modeling homogeneous material each unknown parameter of reduced model is modeled as a random variable while for heterogeneous material, these material parameters are described as random fields. In order to make appropriate discretizations we choose p-method mesh refinement over probability domain and h-method over spatial domain. The forward model outputs are constructed by using Stochastic Galerkin method providing outputs more quickly the the full forward model. The probabilistic procedure of identification is performed with two different methods based on Bayes’s theorem that allows incorporating new observation generated in a particular loading program. The first method Markov Chain Monte Carlo (MCMC) is identified as updating the measure, whereas the second method Polynomial Chaos Kalman Filter (PceKF) is updating the measurable function. The implementation aspects of presented models are given in full detail as well as their validation throughthe numerical examples against the experimental results or against the benchmarks available from literature
Pondugala, Lakshmi Vara Prasad. "Stochastic J-integral and reliability of composite laminates based on a computational methodology combining experimental investigation, stochastic finite element analysis and maximum entropy method." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0017/MQ54327.pdf.
Повний текст джерелаFeng, Jianwen. "Probabilistic modelling of heterogeneous media." Thesis, Swansea University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.644724.
Повний текст джерелаChoi, Jiduck. "Investigation of the dynamic behavior of a cable-harnessed structure." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/49114.
Повний текст джерелаPh. D.
Pontaza, Juan Pablo. "Least-squares variational principles and the finite element method: theory, formulations, and models for solid and fluid mechanics." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/288.
Повний текст джерелаBarua, Ananda. "Mesoscale computational prediction and quantification of thermomechanical ignition behavior of polymer-bonded explosives (PBXs)." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49028.
Повний текст джерелаChang, Chia-Jung. "Statistical and engineering methods for model enhancement." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44766.
Повний текст джерелаKini, Satish D. "An approach to integrating numerical and response surface models for robust design of production systems." Columbus, Ohio : Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1080276457.
Повний текст джерелаTitle from first page of PDF file. Document formatted into pages; contains xviii, 220 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: R. Shivpuri, Dept. of Industrial, Welding and Systems Engineering. Includes bibliographical references.
Nascimento, Fábio Fialho do 1983. "Análise estocástica linear de estruturas complexas usando meta-modelo modal." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265736.
Повний текст джерелаDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-28T14:26:32Z (GMT). No. of bitstreams: 1 Nascimento_FabioFialhodo_M.pdf: 3796792 bytes, checksum: 3a40db657ae4ddf5e1331783c582bd04 (MD5) Previous issue date: 2015
Resumo: Este trabalho tem como objetivo geral investigar abordagens para a análise de incerteza em problemas de dinâmica estrutural, de forma computacionalmente eficiente, no contexto industrial. Neste sentido, utilizou-se um metamodelo, baseado no método da superfície de resposta, para simplificar a etapa do cálculo dos modos e das frequências naturais na análise de resposta em frequência da estrutura. Para viabilizar a análise de grandes modelos, a solução de elementos finitos foi realizada pelo Nastran®. O MatLab® foi utilizado para manipular os autovalores e autovetores, e calcular as FRFs. Já o processo de amostragem das variáveis, a preparação da superfície de resposta e a integração com os demais aplicativos, foram realizados por meio do Isight®. Inicialmente, a abordagem foi avaliada em um modelo simples de um para-brisa veicular, com espessura, modo de elasticidade e densidade como parâmetros incertos. Posteriormente, o método foi aplicado para um modelo de uma estrutura veicular com milhares graus de liberdade. Neste caso, as variáveis aleatórias consideradas foram espessuras de vinte peças estampadas. Todas as variáveis foram consideradas com distribuição normal. Para quantificar a incerteza na resposta dinâmica, a simulação por Monte Carlo foi conduzida em conjunto com o metamodelo. A variabilidade das frequências naturais e da FRF é comparada com o resultado do Monte Carlo direto
Abstract: This work has as general objective to investigate approaches for uncertainty analysis in structural dynamics problems in a computational efficient manner in an industrial context. In this sense, we used a metamodel based on the response surface method to simplify the process of modes and natural frequencies calculation for frequency response analysis of a structure. In order to make the process feasible for large models, the finite element solution was performed using Nastran®. MatLab® was used to manipulate the eigenvalues and eigenvectors and calculate the FRFs. Isight® was responsible for the variable sampling process, response surface preparation and integrating other applications as well. Initially, the approach was assessed in a simple model of a car windshield with its thickness, Young¿s modulus and material density as uncertain parameters. Later the method was applied to a vehicle structure model with thousands degrees of freedom. In this case, the random variables considered were thicknesses of twenty stamped parts. Gaussian distribution was considered for all variables. For the purpose of uncertainty quantification in the dynamic response, Monte Carlo simulation was performed over the metamodel. The variability of the natural frequencies and FRF is compared against to direct Monte Carlo results
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
Fukasaku, Kotaro. "Explorative study for stochastic failure analysis of a roughened bi-material interface: implementation of the size sensitivity based perturbation method." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41114.
Повний текст джерелаKocer, Bilge. "Vibration Fatigue Analysis Of Structures Under Broadband Excitation." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612061/index.pdf.
Повний текст джерелаs response to the loading will not be linear. Therefore, in the analysis of such situations, frequency domain fatigue analysis techniques are used which take the dynamic properties of the structure into consideration. Vibration fatigue method is also fast, functional and easy to implement. In this thesis, vibration fatigue theory is examined. Throughout the research conducted for this study, the ultimate aim is to find solutions to problems arising from test application for the loadings with nonzero mean value bringing a new perspective to mean stress correction techniques. A new method is developed to generate a modified input loading history with a zero mean value which leads in fatigue damage approximately equivalent to damage induced by input loading with a nonzero mean value. A mathematical procedure is proposed to implement mean stress correction to the output stress power spectral density data and a modified input loading power spectral density data is obtained. Furthermore, this method is improved for multiaxial loading applications. A loading history power spectral density set with zero mean but modified alternating stress, which leads in fatigue damage approximately equivalent to the damage caused by the unprocessed loading set with nonzero mean, is extracted taking all stress components into account using full matrixes. The proposed techniques&rsquo
efficiency is discussed throughout several case studies and fatigue tests.
Meinecke, Lina. "Stochastic Simulation of Multiscale Reaction-Diffusion Models via First Exit Times." Doctoral thesis, Uppsala universitet, Avdelningen för beräkningsvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-284085.
Повний текст джерелаZhu, Lailai. "Simulation of individual cells in flow." Doctoral thesis, KTH, Stabilitet, Transition, Kontroll, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-142557.
Повний текст джерелаQC 20140313
Gupta, Sayan. "Vibration Analysis Of Structures Built Up Of Randomly Inhomogeneous Curved And Straight Beams Using Stochastic Dynamic Stiffness Matrix Method." Thesis, Indian Institute of Science, 2000. https://etd.iisc.ac.in/handle/2005/224.
Повний текст джерелаGupta, Sayan. "Vibration Analysis Of Structures Built Up Of Randomly Inhomogeneous Curved And Straight Beams Using Stochastic Dynamic Stiffness Matrix Method." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/224.
Повний текст джерелаPranjal, Pranjal. "Optimal iterative solvers for linear systems with stochastic PDE origins : balanced black-box stopping tests." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/optimal-iterative-solvers-for-linear-systems-with-stochastic-pde-origins-balanced-blackbox-stopping-tests(4fd0d668-3271-4615-9def-07fc9fe2ea9e).html.
Повний текст джерелаKokrda, Lukáš. "Optimalizace stavebních konstrukcí s pravděpodobnostními omezeními." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232181.
Повний текст джерелаNóbrega, Edilson Dantas 1985. "Análise de modelos de barra de alta ordem usando métodos das fatias de guia de ondas." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265804.
Повний текст джерелаDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-27T14:11:06Z (GMT). No. of bitstreams: 1 Nobrega_EdilsonDantas_M.pdf: 12912450 bytes, checksum: 790ec696a10ed45d5c22747b666dea61 (MD5) Previous issue date: 2015
Resumo: A fim de superar as limitações atuais na análise dinâmica de estruturas em médias e altas frequências e tirando proveito da natureza periódica de muitas destas estruturas, nos últimos anos, foram desenvolvidos métodos de guia de ondas. São modelos obtidos a partir de fatias das guia de ondas e modeladas pelo Método dos Elementos Finitos (MEF) e pelo Método do Elemento Espectral (SEM), também conhecidos como Método de Propagação de Ondas por Elementos Finitos (Wave Finite Element Method - WFEM) e Método de Propagação de Ondas por Elementos Espectrais (Wave Spectral Element Method - WSEM), respectivamente. Exemplos de guia de ondas podem ser encontrados em diferentes tipos de estruturas tais como, os trilhos de trem, tubulações e até mesmo em estruturas complexas tipo a fuselagem de um avião e outras. Este trabalho apresenta uma extensão destes métodos de guias de ondas para a modelagem com elementos de barra de alta ordem. Os métodos foram implementados computacionalmente em códigos Matlab e os resultados são comparados com os do Método do Elemento Espectral (Spectral Element Method - SEM), do Método dos Elementos Finitos e com os do modelo analítico da Placa de Rayleigh-Lamb. Três elementos de barra de alta ordem são formulados: o modelo de Love (ou de Um modo), o modelo de Mindlin-Herrmann (ou de Dois modos) e o modelo de Doyle (ou de Três modos). O método é avaliado através de exemplos simulados computacionalmente e os resultados são analisados e comparados com aqueles da literatura
Abstract: In order to overcome the current limitations in the dynamic analysis of structures at middle and high frequencies and taking advantage of the periodic nature of many of these structures, in recent years, waveguide methods were developed. Models are obtained from slices of patterned waveguides, were developed by Finite Element Method (FEM) and Spectral Element Method, also known as Wave Finite Element Method - WFEM and Wave Spectral Element Method - WSEM. Examples of waveguides can be found in different types of structures such as the railroad tracks, pipelines and even complex structures like the fuselage of an airplane and others. This work presents an extension of these waveguides methods to model high order rod elements. The methods were implemented in Matlab codes and the results are compared with Spectral Element Method - SEM, Finite Element Method and the analytical Rayleigh-Lamb plate model. Three high order bar elements are formulated: the Love's model (or one mode), the Mindlin-Herrmann's model (or two modes) and the Doyle's model (or three modes). The method is evaluated through computationally simulated examples and the results are analyzed and compared with those of the literature
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
Nguyen, Truong B. "Efficient Numerical Methods For Chemotaxis And Plasma Modulation Instability Studies." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1564487925507593.
Повний текст джерелаShang, Shen. "Stochastic Material Characterization of Heterogeneous Media with Randomly Distributed Material Properties." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1352579058.
Повний текст джерелаČajánek, Michal. "Modely stochastického programování v inženýrském návrhu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228544.
Повний текст джерелаSTEFANONI, Filippo. "DUROTAXIS MODELLING FOR TISSUE ENGINEERING APPLICATIONS." Doctoral thesis, Università degli studi di Ferrara, 2010. http://hdl.handle.net/11392/2389166.
Повний текст джерелаMoraes, Elson Cesar 1976. "Análise de cavidades acústicas em médias e altas frequências usando métodos de energia." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265790.
Повний текст джерелаTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-27T18:23:30Z (GMT). No. of bitstreams: 1 Moraes_ElsonCesar_D.pdf: 11465202 bytes, checksum: 1ad71136d449760c1a551cda489beaca (MD5) Previous issue date: 2015
Resumo: Neste trabalho, estudam-se fenômenos de propagação de ondas acústicas em cavidades unidimensionais e bidimensionais e se propõe uma metodologia para a análise do comportamento acústico com o objetivo de identificar a propagação de onda nessas estruturas em médias e altas frequências. Para isso se utilizou os métodos originados da Análise de Fluxo de Energia (EFA) que têm como variáveis primárias a densidade de energia e fluxo de energia. Duas formulações foram usadas para resolver as equações diferenciais de energia aproximada derivada do EFA: o Método dos Elementos Finitos de Energia (EFEM) e o Método do Elemento Espectral de Energia (ESEM). O Método do Elemento Espectral (SEM) foi outra formulação estudada para resolver as equações diferenciais de propagações de ondas em cavidades acústicas unidimensionais, bem como para validar a metodologia proposta. Diferentes tipos de cavidades acústicas unidimensionais foram investigadas e implementas tais como: guia de onda simples, guia de onda com descontinuidade geométrica e guia de onda com descontinuidade das propriedades médias. Para isso, desenvolveu-se relações de acoplamento que descrevem essas descontinuidades acústicas. Um exemplo simulado envolvendo uma cavidade acústica retangular fechada é analisado com ESEM e os resultados são comparados com aqueles obtidos pelo EFA, EFEM e a Solução Analítica Acústica (SAA) da equação forçada de Helmholtz para cavidades retangulares bidimensionais fechadas. Uma investigação experimental do comportamento acústico de uma cavidade acústica bidimensional fechada foi realizada para verificar e validar os resultados do ESEM. De maneira geral, se observou que os resultados obtidos pelos modelos simulados apresentaram um comportamento semelhante ao resultado encontrado experimentalmente
Abstract: In this research, propagation phenomena of acoustic waves in one-dimensional and two-dimensional cavities is investigated and a methodology, based on energy methods, is proposed to predict acoustic response of these structures, at mid and high frequencies. These methods, originated from Energy Flow Analysis, use as primary variables the energy density and the energy flow. Two methodologies are used to solve approximated energy differential equations derived from EFA: Energy Finite Element Method (EFEM) and Energy Spectral Element Method (ESEM). The Spectral Element Method (SEM), is used to solve the wave propagation differential equations of acoustic in one-dimensional cavities, moreover this method is applied to validate the proposed methodology. Different acoustics cavities were investigated, such as simple waveguide, waveguide with geometric discontinuity and waveguide with discontinuity of the average properties. To this purpose, coupling relationships that represent those discontinuities are developed. A simulated example involving a closed rectangular acoustic cavity is analyzed with ESEM and the results are compared with those obtained by EFA, the Energy Finite Element Method (EFEM) and the acoustic analytical solution (SAA) of forced Helmholtz equation for rectangular two-dimensional closed cavities. An experimental investigation of acoustic response of a closed two-dimensional acoustic cavity was performed to verify the results of ESEM. The simulated models results, calculated in terms of energy variables, to analyze cavity, showed a good agreement with the experimental result
Doutorado
Mecanica dos Sólidos e Projeto Mecanico
Doutor em Engenharia Mecânica
Yin, Qi. "Prise en compte de la variabilité dans les calculs par éléments finis des structures composites en régime statique ou vibratoire." Thesis, Compiègne, 2016. http://www.theses.fr/2016COMP2304/document.
Повний текст джерелаThe manufacture of composite structures leads to a high variability of mechanical parameters. The objective of this work is to develop economic and robust methods to study the variability of the static or dynamic response of composite structures modeled by finite elements, taking into account uncertain material (elastic moduli, Poisson's ratios, densities... ) and physical (thicknesses and fiber orientations) properties. Two methods are developed: the Certain Generalized Stresses Method (CGSM) and the Modal Stability Procedure (MSP). The CGSM considers a mechanical assumption, the generalized stresses are assumed to be independant of uncertain parameters. lt allows to evaluate the variability of static response. The MSP, proposed to study the variability of structures in dynamics, is based on the assumption that the modes shapes are insensitive to uncertain parameters. These mechanical assumptions and only one fïnite element analysis allow to construct a metamodel used in a Monte Carlo simulation. As a result, the computational cost is reduced considerably. Moreover, they are not limited by the number of considered parameters or the level of input variability, and are compatible with standard finite element software. Four academic examples of composite plate and shell are treated with the CGSM, while two academic examples of composite square plate and an example of stiffened plate are studied by the MSP. The variability of static response (displacement and failure criterion) and dynamic response (natural frequency), namely mean value, standard deviation, coefficient of variation and distribution, is evaluated. The results obtained by the proposed methods are compared with those obtained by the direct Monte Carlo simulation, considered as the reference method. The comparison shows that the proposed methods provide quite accurate results and highlights their high computational efficiency. An error indicator is also proposed, which allows to provide an estimation of the error level of the results obtained by the CGSM or MSP compared to the reference method, without performing a large number of finite element analyses
Chen, Silin. "Reliability-based design of concrete-filled steel tubular (CFST) truss systems by advanced analysis." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/24557.
Повний текст джерелаBari, Md Wasiul. "Modelling of ground improvement by vertical drains in highly variable soils." Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/2593.
Повний текст джерелаDe, Abreu Corrêa Lúcio. "Large scale numerical wave propagation in a randomly-fluctuating continuum model of ballasted railway tracks." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC018/document.
Повний текст джерелаThe stronger competition with other means of transportation has increased the demand for performance in the railway industry. One way to achieve higher performance is using accurate numerical models to design/predict railways tracks behaviour. Two classes of numerical models are commonly used to predict the behaviour of these systems: (i) discrete approaches and (ii) continuum approaches. In the former, each grain of the ballast is represented by a rigid body and interacts with its neighbours through nonlinear contact forces using, for example, the nonsmooth contact dynamics method. Due to computational limits, this kind of method can only solve a few meters-length of ballast. The coupling with the soil under the ballast layer and with the sleepers also remains an open problem. In continuum approaches, the ballast is replaced by a homogenized continuum and the classical Finite Element (FE) Method (or similar) is used. However, they are normally used with homogeneous mechanical parameters, so that they do not represent fully the heterogeneity of the strains and stresses within the ballast layer. We investigate in this thesis an alternative approach using a stochastic heterogeneous continuum model, that can be solved with a FElike method while retaining to a large degree the heterogeneity of the stress and strain fields. The objective of this continuous model is to represent statistically the heterogeneity of the stress field in a continuum model as well as in a discrete granular model. To do this, the mechanical properties are represented using random fields. The present thesis is divided into three parts: (1) the construction of the model and the identification of the parameters of the continuum material (first-order marginal density, mean, variance, correlation model, and correlation length); (2) wave propagation in a ballasted railway track. (3) preliminary exploration of two experimental datasets. The first part sets the randomly-fluctuating continuum model and identifies the parameters of our continuum model on small cylindrical samples of discrete ballast. Continuum models equivalent to the discrete samples are generated and solved using the FE method, and the stochastic field used as mechanical properties. An optimization process is used to find a normalized variance for the stochastic heterogeneous material. The second part of this work concentrates on the solution of the dynamical equations on a large-scale model of a ballasted railway track using the Spectral Element Method. The influence of the heterogeneity is highlighted and studied. As a result, dispersion curves are obtained. Finally, the third part presents two distinct datasets of experimental measurements on ballast material: (1) a ballast box; (2) a train passage in a segment of ballasted railway track. Mobility curves were extracted from the ballast box experiment. An inverse problem was solved in order to estimate the homogenized wave velocity and local wave velocity in the medium. The trains pass-by recorded for the analysis of the vibration at medium frequencies
Bejjani, Nadine. "Wave propagation in multilayered plates : the Bending-Gradient model and the asymptotic expansion method." Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC1025.
Повний текст джерелаThis thesis is dedicated to the modelling of plane wave propagation in infinite multilayered plates, in the context of linear elasticity. The aim of this work is to find an analytical or semi-analytical approximation of the wave dispersion relations when the ratio of the thickness to the wavelength is small. The dispersion relations, linking the angular frequency and the wave number, provide key information about the propagation characteristics of the wave modes. Two methods are proposed in this thesis: the Bending-Gradient model and the asymptotic expansion method. The relevance of these methods is tested by comparing their predictions to those of well-known plate theories, and to reference results computed using the finite element method. Preliminarily, the first part of the thesis is devoted to the mathematical justification of the Bending-Gradient theory in the static framework using variational methods. The first step is to identify the mathematical spaces in which the variational problems of the Bending-Gradient are well posed. A series of existence and uniqueness theorems of the corresponding solutions are then formulated and proved. The second part is dedicated to the formulation of the equations of motion of the Bending-Gradient theory. Numerical simulations are realized for different types of layer stacks to assess the ability of this model to correctly predict the propagation of flexural waves. The third part is concerned with the asymptotic analysis of the three-dimensional equations of motion, carried out using the asymptotic expansion method, the small parameter being the ratio of the thickness to the wavelength. Assuming that the three-dimensional fields can be written as expansions in power of the small parameter, a series of problems which can be solved recursively is obtained. The validity of this method is evaluated by comparison with the finite element method
Nguyen, Cong Uy. "Hybrid stress visco-plasticity : formulation, discrete approximation, and stochastic identification." Thesis, Compiègne, 2022. http://www.theses.fr/2022COMP2695.
Повний текст джерелаIn this thesis, a novel approach is developed for visco-plasticity and nonlinear dynamics problems. In particular, variational equations are elaborated following the Helligner-Reissner principle, so that both stress and displacement fields appear as unknown fields in the weak form. Three novel finite elements are developed. The first finite element is formulated for the axisymmetric problem, in which the stress field is approximated by low-order polynomials such as linear functions. This approach yields accurate solutions specifically in incompressible and stiff problems. In addition, a membrane and plate bending finite element are newly designed by discretizing the stress field using the lowest order Raviart-Thomas vector space RT0. This approach guarantees the continuity of the stress field over an entire discrete domain, which is a significant advantage in the numerical method, especially for the wave propagation problems. The developments are carried out for the viscoplastic constitutive behavior of materials, where the corresponding evolution equations are obtained by appealing to the principle of maximum dissipation. To solve the dynamic equilibrium equations, energy conserving and decaying schemes are formulated correspondingly. The energy conserving scheme is unconditional stable, since it can preserve the total energy of a given system under a free vibration, while the decaying scheme can dissipate higher frequency vibration modes. The last part of this thesis presents procedures for upscaling of the visco-plastic material behavior. Specifically, the upscaling is performed by stochastic identification method via Baysian updating using the Gauss-Markov-Kalman filter for assimilation of important material properties in the elastic and inelastic regimes