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Meyer, Arnd, e Peter Nestler. "Mindlin-Reissner-Platte: Einige Elemente, Fehlerschätzer und Ergebnisse". Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200601589.
Testo completo
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Pokojovy, Michael [Verfasser]. "Zur Theorie Wärmeleitender Reissner-Mindlin-Platten / Michael Pokojovy". Konstanz : Bibliothek der Universität Konstanz, 2011. http://d-nb.info/1037311981/34.
Testo completo
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Sakami, Siham. "Modélisation numérique des structures composites multicouches à l’aide d’une approche discrète au sens de Mindlin. Le modèle DDM (Displacement Discrete Mindlin)". Reims, 2008. http://theses.univ-reims.fr/exl-doc/GED00000982.pdf.
Testo completoAbstract (sommario):
Ce travail de thèse consiste le développement d’un élément fini de plaque et de coque courbe géométriquement simple (4 nœuds), basé sur une nouvelle approche variationnelle appelée DDM (Displacement Discrete Mindlin). Il prend en compte l’effet du cisaillement transversal CT à travers l’épaisseur. Le modèle DDM introduit de manière discrète deux hypothèses de Mindlin. La première hypothèse est cinématique, elle consiste à introduire sous la forme d’une intégrale de contour une équation cinématique de la déformation de CT. Elle permet l’élimination du verrouillage en CT sans introduire des fonctions bulles ou sans recourir à l’intégration réduite ou sélective. Il s’agit de l’approche des déformations de CT de substitution, connue sous le nom de « ANS method : Assumed Natural Strains ». La seconde hypothèse fait appel à deux lois de comportement, l’une en flexion et l’autre en CT, et deux équations d’équilibre d’une plaque en flexion/CT. Elle a pour principal avantage une élimination locale des degrés de libertés de rotation, introduits initialement au milieu d’un bord élémentaire par le biais d’une approximation quadratique des rotations de la normale à la surface moyenneThe present work of the thesis deals with the theoretical formulation and the evaluation of a new first order finite element for multilayered/sandwich plates and shells. It’s based on a displacement variational model that we consider as discrete, insofar as we introduce kinematic and mechanical hypothesises in a discrete manner. This model, labelled DDM (Discrete Displacement Mindlin), leads to a finite element which is geometrically simple (4 node) and efficient, owing to the linearity of bending curvatures obtained from a quadratic approximation of the normal rotations to the plate mid-surface. The new element takes into account the transverse shear effects along thickness direction and gives thin plate results when the ratio L/h (Length/ thickness) becomes big. It has been successfully validated across some known testing problems, from thin to thick laminated and sandwich
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Sakami, Siham Ayad Rezak. "Modélisation numérique des structures composites multicouches à l'aide d'une approche discrète au sens de Mindlin. Le modèle DDM (Displacement Discrete Mindlin)". Reims : S.C.D. de l'Université, 2008. http://scdurca.univ-reims.fr/exl-doc/GED00000982.pdf.
Testo completo
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Zhang, Lei, University of Western Sydney, of Science Technology and Environment College e School of Engineering and Industrial Design. "Exact solution for vibration of stepped circular Mindlin plates". THESIS_CSTE_EID_Zhang_L.xml, 2002. http://handle.uws.edu.au:8081/1959.7/64.
Testo completoAbstract (sommario):
This thesis presents the first-known exact solutions for vibration of stepped circular Mindlin plates. The considered circular plate is of several step-wise variation in thickness in the radial direction. The Mindlin first order shear deformable plate theory is employed to derive the governing differential equations for the annular and circular segments. The exact solutions to these differential equations may be expressed in terms of the Bessel functions of the first and second kinds and the modified Bessel functions of the first and second kinds. The governing homogenous system of equations is assembled by implementing the essential and natural boundary conditions and the segment interface conditions. Vibration solutions are presented for circular Mindlin plates of different edge support conditions and various combinations of step-wise thickness variations. These exact vibration results may serve as important benchmark values for researchers to validate their numerical methods for such circular plate problemsMaster of Engineering (Civil)
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Zhang, Lei. "Exact solution for vibration of stepped circular Mindlin plates". Thesis, View thesis, 2002. http://handle.uws.edu.au:8081/1959.7/64.
Testo completoAbstract (sommario):
This thesis presents the first-known exact solutions for vibration of stepped circular Mindlin plates. The considered circular plate is of several step-wise variation in thickness in the radial direction. The Mindlin first order shear deformable plate theory is employed to derive the governing differential equations for the annular and circular segments. The exact solutions to these differential equations may be expressed in terms of the Bessel functions of the first and second kinds and the modified Bessel functions of the first and second kinds. The governing homogenous system of equations is assembled by implementing the essential and natural boundary conditions and the segment interface conditions. Vibration solutions are presented for circular Mindlin plates of different edge support conditions and various combinations of step-wise thickness variations. These exact vibration results may serve as important benchmark values for researchers to validate their numerical methods for such circular plate problems
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Zhang, Lei. "Exact solution for vibration of stepped circular Mindlin plates /". View thesis, 2002. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030714.140725/index.html.
Testo completoAbstract (sommario):
Thesis (M. E.) (Civil) -- University of Western Sydney, 2002.A thesis submitted for the degree of Master of Engineering (Civil), School of Engineering and Industrial Design, University of Western Sydney, 2002. Bibliography : p. 42-46.
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Souza, Pammella Queiroz de. "Limites assintóticos e estabilidade para o sistema de Mindlin-Timoshenko". Universidade Federal da Paraíba, 2016. http://tede.biblioteca.ufpb.br:8080/handle/tede/9256.
Testo completoAbstract (sommario):
Submitted by ANA KARLA PEREIRA RODRIGUES (anakarla_@hotmail.com) on 2017-08-15T11:54:12Z
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
This thesis is concerned with the dynamics of Mindlin-Timoshenko system for beams and plates. We study issues relating to the asymptotic limit in relation to the parameters and decay rates. In the context of asymptotic limit, as the main result, we present a positive response to the conjecture made by Lagnese and Lions in 1988, where the Von-Kármán model is obtained as singular limit when k tends to infinity, the Mindlin-Timoshenko system. Introducing appropriate damping mechanisms (internal and boundary), we also show that the energy of solutions for the Mindlin-Timoshenko system has decay properties exponential and polynomial, with respect to the parameters.
Esta tese aborda a dinâmica do sistema de Mindlin-Timoshenko para vigas e placas. Estudamos questões relacionadas com o limite assintótico em relação aos parâmetros e as taxas de decaimento. No contexto do limite assintótico, como resultado principal, apresentamos uma resposta positiva à conjectura feita por Lagnese e Lions em 1988, onde o modelo de Von-Kármán é obtido como limite singular, quando k tende ao infinito, do sistema de Mindlin-Timoshenko. Introduzindo mecanismos de amortecimento apropriados (internos e de fronteira), também mostramos que, sob certas condições, a energia de solução do sistema de Mindlin-Timoshenko tem propriedades de decaimento exponencial e polinomial com relação aos parâmetros.
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Chen, Xie. "Analysis of the arbitrary Mindlin plate by spline finite strip method". Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6577.
Testo completo
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Meyer, Arnd, e Peter Nestler. "Mindlin-Reissner-Platte : Vergleich der Fehlerindikatoren in Bezug auf die Netzsteuerung". Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200601638.
Testo completoAbstract (sommario):
Es werden die vorgestellten Fehlerindikatoren in Bezug auf die Netzsteuerung anhand von drei Beispielen analysiert. Im weiteren werden auch die einzelen MITC-Elemente und ihre Besonderheiten bei dieser Analyse der Netzsteuerung mit berücksichtigt. Als Abschluss werden einige spezielle Fehlerindikatoren vorgestellt, die für die weitere Entwicklung einige interessante Eigenschaften aufzeigen.
Im zweiten Teil geht es um die Auswertung mit dem speziellen Ziel der Findung einer optimalen Netzsteuerung. Dabei wird auf die Besonderheiten der Elemente eingegangen sowie auf die Plattendicke und auf ihre Wirkung bei den Fehlerindikatoren. Mit diesen Erkenntnissen wird ein spezieller Fehlerindikator vorgestellt, der die Vorteile aller Fehlerindikatoren aus Teil I vereint.
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ARAÚJO, Adelma Ferreira de. "Rubens Borba de Moraes e José Mindlin: bibliofilia como patrimônio informacional". Universidade Federal de Pernambuco, 2017. https://repositorio.ufpe.br/handle/123456789/25239.
Testo completoAbstract (sommario):
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Apresenta um estudo sobre bibliofilia a partir das memórias de Rubens Borba de Moraes e José Mindlin, destacando a importância de ambos para a preservação da memória escrita, a partir da formação das bibliotecas de coleções de livros raros, em especial à coleção Brasiliana. O posicionamento de disponibilizar para o público os acervos desenvolvidos durante anos pelos bibliófilos em destaque, traz uma nova proposta de pensar a bibliofilia como patrimônio informacional, idealizando um sentido utilitário à coleção com a criação da Brasiliana USP, em oposição a práticas correntes de fragmentação ou desuso das coleções. Quanto à metodologia foram utilizados materiais bibliográficos, tratando-se de uma pesquisa exploratória. Foram explanados assuntos sobre a história do livro, tipografia, colecionismo, livros raros, hábito de leitura e digitalização de acervos. A biografia dos bibliófilos auxiliou na contextualização da trajetória da formação das bibliotecas de livros raros. Houve também a aplicação dos pressupostos teóricos da biblioteconomia que tratam da seleção e aquisição de materiais bibliográficos; formação e desenvolvimento de coleções; organização, disponibilização e recuperação da informação e preservação da memória organizacional para assim haver uma interlocução da Ciência da Informação com a bibliofilia.
This research aims at analyzing bibliophily based upon the memories of Rubens Borba de Moraes and José Mindlin, thus pinpointing the importance of both theorists towards written memory preservation by the formation of rare book collection libraries, especially “Brasiliana” collection. The perspective of making the developed repository available to the public throughout the years present a new proposal of redefining bibliophily as informational heritage, thus idealizing an utilitarian sense to the collection with the USP Brasiliana creation, in opposition to the current practices of fragmentation and misuse of collections. As for the methodology, bibliographic materials were used due to the descriptive aspect of the research. Subjects concerning the history of the book, typography, collectionism, rare books, reading habits and collection digitalization were explained through. The bibliophile biografies helped in the formation path contextualization of rare book libraries. Informational theory corollaries towards selection and acquisition of bibliographic materials, collection formation and development, organization, availability, information recovery and organizational memory preservation so as to provide a crossroad between Information Science and bibliophily.
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Verhille, Emmanuel. "Méthodes d’éléments finis a posteriori pour les équations de Reissner-Mindlin". Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10032/document.
Testo completoAbstract (sommario):
Ce travail est consacré à l’étude d’estimateurs d'erreur a posteriori de type flux équilibrés et résiduels pour la résolution des équations de Reissner-Mindlin par la méthode des éléments finis. Le mémoire débute par l'introduction du problème aux limites et de son analyse de convergence a priori par la méthode des éléments finis. Nous construisons alors pour une discrétisation conforme un estimateur a posteriori de type flux équilibrés fiable, efficace et robuste en l'épaisseur de la plaque t. Nous obtenons finalement une constante multiplicative égale à 1 pour la fiabilité. Des tests numériques illustrent nos résultats pour différents maillages. Puis nous abordons le cas d’une discrétisation non-conforme, où nous proposons un estimateur a posteriori de type résiduel, utilisant une régularisation de la solution discrète. Des tests numériques illustrent également nos résultats. La suite du travail reprend la discrétisation conforme en construisant un estimateur a posteriori défini à partir de la résolution de problèmes localisés sur les patchs de la triangulation, menant à un choix plus consistant avec le problème aux limites. Le dernier chapitre est consacré à l'estimation a posteriori pour le problème aux valeurs propres de Reissner-Mindlin. L’estimateur obtenu est fiable et efficace pour la norme de l'erreur entre les vecteurs propres, permettant également de majorer l’erreur commise entre les valeurs propres. Des tests numériques illustrent nos résultatsThis work is devoted to the study of equilibrated fluxes and residual a posteriori error estimators for the finite element resolution of the Reissner-Mindlin system. This report begins by the introduction of the boundary value problem and of its a priori convergence analysis in the finite element method context. Then, an equilibrated fluxes a posteriori estimator is built for a conform discretization, which is proven to be reliable, efficient and robust on the plate thickness t. We finally obtain a multiplicative constant equal to 1 for the reliability. Numerical tests illustrate our results on different meshes. Then, we address the non-conforming discretization case, where a residual a posteriori estimator is proposed using a regularisation of the discrete solution. Numerical tests also illustrate our results. Next we come back to the conform discretization by building an a posteriori estimator defined from localised problems resolution on stars, leading to a consistent choice with the boundary value problem. The last chapter is devoted to an a posteriori estimation for the Reissner-Mindlin eigenvalues problem. The obtained estimator is reliable and efficient for the error norm between the eigenvectors, also allowing to evaluate the error between the eigenvalues. Numerical tests illustrate our results
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Garcia, Oscar Alfredo. "Método sem malha hp-clouds na análise de placas Reissner-Mindlin /". Florianópolis, SC, 1999. http://repositorio.ufsc.br/xmlui/handle/123456789/80583.
Testo completoAbstract (sommario):
Dissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico.Made available in DSpace on 2012-10-18T16:22:26Z (GMT). No. of bitstreams: 0Bitstream added on 2016-01-09T03:10:48Z : No. of bitstreams: 1 152867.pdf: 9778338 bytes, checksum: c30545b168e61f3226516bc396c6b237 (MD5)
O conteúdo deste trabalho trata da aplicação do método sem malha hp-Clouds ou simplesmente método de nuvens (C. A. Duarte e J. T. Oden [8]) à solução de problemas de placas de Reissner-Mindlin.
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Ben, thaier Mehdi. "Modélisation numérique de plaques et de coques composites à l'aide d'une approche au sens de Reissner-Mindlin enrichie pour les problèmes mécanique et piézo-mécanique". Thesis, Paris 10, 2010. http://www.theses.fr/2010PA100054/document.
Testo completoAbstract (sommario):
Ce travail concerne le développement d’un outil numérique pour résoudre des problèmes de plaques et de coques mécaniques et piézo-électriques multicouches. En d’autres termes, nous développons des éléments finis basés sur le modèle de Reissner-Mindlin pour l’analyse des problèmes mécaniques et piézoélectriques de plaques et de coques multicouches. Cet outil doit être le moins coûteux en termes de degrés de liberté, simple à utiliser pour modéliser le problème, sans aucune pathologie numérique classique et satisfaisant :vitesse de convergence et efficacité.Dans le domaine des éléments finis, il existe une théorie appelée La « théorie des déformations du cisaillement du premier ordre »(FSDT), utilisée pour résoudre des problèmes purement mécanique prenant en compte l’effet des contraintes en cisaillement transverse. Dans cette théorie, cinq degrés de liberté (trois translations et deux rotations), sont à chercher.Prenant en compte l’hypothèse d’une approximation du déplacement au niveau de la surface moyenne, en utilisant la loi constitutive 2D.Dans ce travail, nous présentons l’extension piézoélectrique de cette théorie pour des éléments finis quadratiques à huit nœuds pour résoudre des problèmes de plaques et de coques multicouches. En effet, la nouveauté dans ce travail est celle de considérer une loi constitutive 3D afin de calculer non seulement le déplacement transversal au niveau du plan moyen de chaque couche mais aussi les déplacements transversaux en surface supérieure et en surface inférieure de chaque couche. Cette approximation de l’épaisseur fait intervenir deux nouveaux degrés de liberté, qui seront très importants dans l’étude des plaques et des coques épaisses et semi épaisses.Le déplacement mécanique est approximé en utilisant une approche Equivalent Single Layer(ESL) et le potentiel électrique est , quant à lui, approximé par une approche LayerWise (LW).Cette évolution est proposée afin d’acquérir un bon compromis entre le minimum de degrés de liberté et le maximum d’efficacité. D’une part, l’approximation par élément fini pour le potentiel électrique, respectant les coordonnées de l’épaisseur est représenté par une variation linéaire au niveau de chaque couche. D’autres part ce potentiel est constant par élément en chaque interface, ce qui réduit le nombre d’inconnus pour la recherche du potentiel électrique résultant. Plusieurs tests numériques sont présentés dans le but d’évaluer les éléments mécanique et piézoélectrique de plaque PQ8P7 et PQ8P7PZ et de coque CQ8P8 et CQ8P8PZ ainsi que leurs capacités de résoudre les problèmes physiques auxquels ils sont dédiés, en comparant nos résultats aux solutions de référenceThe aim of this work is to develop a computational tool for a multilayred piezolelectic plates and shells: a low cost tool, simple to use and very efficient for both convergence velocity and accuracy, without any classical numerical pathologies. In the field of finite elements, there is atheory, called "First-order-shear deformation theories (FSDT) used for the mechanical part in much reserches, taking in account the transverse shear stress effects. There are only five unknows generalized displacement, taking the hypothesis of the midsurface displacement approximation using a 2D constitutive law. In This work we present the piezo electric extension of the FSDT eight nodes plate/shell finite element using seven unknows genralized displacement. Two new mechanical unknowns are added to approximate the thickness in the top and the bottom of the /shell, considering a 3D constitutive law, wich is very interesting study especialy for the thick plate/shell modelisation. The mechanical displacement is approximated using the equivalent single layer approch (ESL) and the electric potential is approximated using the layerwise approch (LW).An evolution is proposed in order to access the best compromise between minimum number of degrees of freedom and maximum efficiency. On one hand, a finite element approximation for the electric potential with respect to the thickness coordinate are presented a linear variation in each layer. On the other hand, the in-plane variation is constant on the elementary domain at each interface layer. The use of a constant value reduces the number of unknown electric potentials. Furthermore, at the post processing level, the transverse shear stress are deduced using the equilibrium equations.Numerous tests are presented in order to evoluate that capability of these electric potential approximations to give accurate results with respect to piezoelasticity or finite element reference solutions
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BATISTA, ANTONIO JOSE DE SENA. "ARCHITECTS WITHOUT HALO: THE ACTION OF M.M.M. ROBERTO AND HENRIQUE MINDLIN ASSOCIATED ARCHITECTS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2013. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=34834@1.
Testo completoAbstract (sommario):
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROA historiografia da Arquitetura Moderna Brasileira tende a privilegiar a construção de uma coerência ficcional que determina grupos aos quais todos arquitetos atuantes naquele período são anexados. No entanto, uma análise mais detalhada traz à tona a existência de múltiplas formas de ação que não concorrem para tal unidade fictícia. Dentre eles estão os arquitetos que trabalham prioritariamente para o mercado da construção civil, que lhes impõe regras, meios, relações econômicas, que contaminam seu modo de operação projetual. Essa tese busca, através da análise de dois escritórios de arquitetura cariocas – MMMRoberto e Henrique Mindlin Arquitetos Associados - perceber de que maneiras as imposições do mercado alteram a obra de tais escritórios, fazendo-os adquirir características de concepção de projeto e de organização funcional que os torne distintos de outros escritórios atuantes no mesmo período.
The historiography of Brazilian Modern Architecture tends to favor the construction of a fictional coherence; determining groups to which all architects that have worked in that period are attached to. However, a more detailed analysis brings to light the existence of multiple forms of action that do not compete for this fictitious unity. Among them, architects who work primarily for the construction market, which imposes rules, resources, economic relations, that contaminate their modus operandi. This thesis tries to determinate by the analyses of two modern architectural offices – MMMRoberto and Henrique Mindlin Arquitetos Associados - in which ways the market impositions do change the work of these architectural firms, leading them to acquire different design characteristics and organizational methods.
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Sodré, João Clark de Abreu. "Roteiros americanos: as viagens de Mindlin e Artigas pelos Estados Unidos , 1943-1947". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/16/16133/tde-19122016-143604/.
Testo completoAbstract (sommario):
A tese investiga as possíveis aproximações entre arquitetura e viagens de formação a partir das experiências de deslocamentos de dois arquitetos de São Paulo pelos Estados Unidos, entre 1943 e 1947. Formados respectivamente pelas escolas de engenharia do Mackenzie e da USP na década anterior, Henrique Mindlin (1911-1971) e João Vilanova Artigas (1915-85) empreenderam suas viagens aos EUA em anos decisivos de modelagem de sua atitude e liderança no campo profissional, de modernização do campo arquitetônico no Brasil, bem como de ampliação dos mecanismos de cooperação entre os dois países. Propõe-se entender estas viagens tanto em seus aspectos comuns, como um expediente caro à própria história da arquitetura, quanto nas particularidades de cada uma delas, dos arquitetos que as empreenderam, dos itinerários que desenvolveram e no momento mesmo em que o fizeram.The thesis investigates the possible approximations between architecture and training trips based on the experiences of two US architects traveling from São Paulo between 1943 and 1947. They were graduated respectively from Mackenzie and USP engineering schools in the previous decade, Henrique Mindlin (1911-1971) and João Vilanova Artigas (1915-85) undertook their travels to the United States in decisive years modeling their attitude and leadership in the professional field of modernizing the architectural field in Brazil, as well as expanding cooperation mechanisms between The two countries. It is proposed to understand these journeys both in their common aspects, as a costly expedient for the history of architecture itself, as well as the particularities of each one of them, the architects who carried them out, the itineraries they developed and the moment they did so.
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Rosa, Vitor Sales Dias da. "Análise de sensibilidade topológica do modelo de flexão de placas de Reissner-Mindlin". Laboratório Nacional de Computação Científica, 2015. https://tede.lncc.br/handle/tede/222.
Testo completoAbstract (sommario):
Submitted by Maria Cristina (library@lncc.br) on 2015-11-25T12:00:01Z
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes)
The topological derivative concept has been proved to be useful in many relevant applications such as topology optimization, inverse problems, image processing, multi-scale constitutive modeling, fracture mechanics and damage evolution modeling. The topological asymptotic analysis has been fully developed for a wide range of problems modeled by partial di erential equations. On the other hand, the topological derivatives associated with coupled problems have been derived only in their abstract forms. In this paper, therefore, we deal with the Reissner-Mindlin plate bending model, which is written in the form of a coupled system of partial di erential equations. In particular, the topological asymptotic analysis of the associated total potential energy is developed and the topological derivative with respect to the nucleation of a circular inclusion is derived in its closed form.Finally, we provide the estimates for the remainders of the topological asymptotic expansion and perform a complete mathematical justi cation for the derived formulas.
O conceito de derivada topológica tem se mostrado útil em muitas aplicações, tais como otimização topológica, problemas inversos, processamento de imagens, modelagem constitutiva multi-escala, mecânica da fratura e modelagem da evolução de dano. A análise assintótica topológica foi amplamente desenvolvida para uma grande variedade de problemas modelados por equações diferenciais parciais. Por outro lado, a derivada topológica associada a problemas acoplados é conhecida apenas em sua forma abstrata. Neste trabalho, portanto, considera-se o modelo de flexão de placa de Reissner-Mindlin, que é escrito na forma de um sistema acoplado de equações diferenciais parciais. Em particular, a análise assintótica topológica da energia potencial total associada é desenvolvida e a derivada topológica com relação a nucleação de uma inclusão circular é obtida na sua forma fechada. Finalmente, os resíduos da expansão assintótica topológica são estimados e uma justificativa matemática completa para a derivada topológica é apresentada.
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Sedira, Lakhdar. "Contribution à la Modélisation de Composites 2D/3D à l'Aide d'Eléments Finis Spéciaux". Thesis, Reims, 2013. http://www.theses.fr/2013REIMS019/document.
Testo completoAbstract (sommario):
La présente thèse doctorale traite de la formulation et l'évaluation élément fini d'un model variationel de Mindlin discret et modifié pour l'analyse du comportement statique et dynamique, linéaire et non linéaire des plaques et coques composites. Incluant des termes additionnels de type zigzag, en vue d'améliorer la précision de contraintes, le modèle a été reformulé afin de prendre en considération la variation linéaire par couche du déplacement. En conséquence, deux éléments finis de plaques et coques à quatre nœuds, baptisés respectivement DMQP et DMQS (Discret Mindlin Quadrilateral Plates/ Shells), améliorés par un champ de rotations quadratique ont été développés et validés sur les codes de calcul REFLEX et ABAQUS. Dans une seconde version, les deux éléments avec un effet de zigzag ont été développés et validés à travers quelques tests statiques et dynamiques connus de la littérature. Les résultats montrent une indépendance vis-à-vis de la correction du cisaillement transverse et une précision des contraintes meilleure à celle obtenue par rapport le modèle initial (sans l'effet de zigzag).Les résultats satisfaisants de ce modèle constatés à travers les cas-tests linéaires de coque isotropes, nous ont motivés à étendre la présente approche aux applications non-linéaires géométriques. Un élément isoparamétrique courbe de coque a été développé à cet effet, avec l'hypothèse des petites déformations élastiques et grands déplacements et rotations modérées. Il est géométriquement simple et ne possède que quatre nœuds aux sommets et 6 ddl/nœud. Le calcul élémentaire de la matrice de rigidité tangente consiste à associer la partie linéaire du modèle de coque courbe (DMQS) avec celle non linéaire de l'élément standard Q4 de membrane. Une formulation lagrangienne actualisée à chaque itération (FLAI) a été utilisée avec la méthode de résolution de Newton-Raphson. Quelques tests standards non-linéaires des structures coques sont présentés, ils montrent un très bon comportement global et une convergence meilleure que celle d'éléments pareilsThis doctoral thesis deals with the finite element formulation and evaluation of a modified Mindlin's discrete variational model for static, dynamic, linear and non-linear composite plates and shells analysis. Including additional terms of zigzag type, in order to improve the accuracy of stress, the model has been reformulated to take into account the linear picewise of displacement variation. Consequently, two finite plate and shell elements with four nodes, called DMQP and DMQS (Discrete Quadrilateral Mindlin Plates and Shells respectively), enhanced by quadratic field rotations, have been developed and validated under REFLEX and ABAQUS codes.Both elements including the zigzag effect have been also developed in a second version, and validated through several static and dynamic test problems known from the literature, highlighting the independence towards the transverse shear correction and in particular the stress accuracy with respect to the initial model without the zigzag effect.The satisfactory results of this model found through cases of linear isotropic shell tests, motivated us to extend this approach to the non-linear geometric applications. An isoparametric curve element of shell has been developed for this purpose, where small elastic deformation assumptions of and large displacements and moderate rotations are adopted. It is geometrically simple and has only four nodes at corners and 6 DOF/node. The elementary calculation of the tangent stiffness matrix consists in combining the linear part of the curved shell element (DMQS) with that of the membrane Q4 non-linear part. An Updated Lagrangian Formulation at each Iteration (ULFI) is used with Newton-Raphson resolution Method. Some standard tests of nonlinear geometrical shell structures are presented; they show a very good convergence and global behavior better than such elements
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Kobrich, Echavarri Philip. "Esquema numérico de proyección nodal para la placa de Reissner-Mindlin utilizando métodos sin malla". Tesis, Universidad de Chile, 2017. http://repositorio.uchile.cl/handle/2250/147127.
Testo completoAbstract (sommario):
Ingeniero Civil MecánicoEn la práctica de la ingeniería el método de elementos finitos o MEF se utiliza para realizar cálculos cuando resulta difícil o ineficiente obtener una solución analítica. En los últimos años se ha popularizado el uso de los métodos sin malla ya que estos entregan soluciones más exactas además de ser menos sensibles a las distorsiones de los elementos. Esto último se debe a que los métodos sin malla utilizan un vecindario de nodos para construir la aproximación de las variables, eliminando la necesidad de conexiones elementales (mallado) entre los nodos. La placa de Reissner-Mindlin (RM) se utiliza para el análisis de esfuerzos y deformaciones en placas gruesas. Este modelo supone que la deformación a lo largo del espesor varía en forma lineal además supone que la componente σzz del esfuerzo es nula.Sin embargo, la placa RM presenta el problema de bloqueo por corte, donde la rigidez de la placa aumenta drásticamente a medida que se disminuye el espesor. El objetivo de este trabajo es solucionar el bloqueo por corte mediante la proyección nodal, la cual ya ha sido utilizada para solucionar el bloqueo volumétrico en elasticidad incompresible (análogo al bloqueo por corte). Para este propósito se formula la proyección nodal para el problema de la placa RM. La proyección nodal se formula a partir de la formulación mixta eliminando los grados de libertad de corte S a partir de la discretización de los desplazamientos adyacentes disminuyendo el número de ecuaciones por resolver. Se implementa el esquema para la proyección nodal sin malla con funciones de base de máxima entropía utilizando el software Matlab. Se realizaron experimentos numéricos sobre problemas cuya solución analítica es conocida y se evaluó la convergencia y sensibilidad a distorsiones para la proyección nodal y métodos tradicionales. La proyección nodal converge óptimamente para la norma L2 del error y para la semi-norma H1 del error. La proyección nodal es menos sensible a distorsiones geométricas en la malla base que métodos MEF tradicionales. Se concluye que la proyección nodal soluciona el problema de bloqueo por corte utilizando métodos sin malla. Se consigue una mejor convergencia con respecto a los métodos tradicionales además de disminuir la sensibilidad a distorsiones geométricas.
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Sanches, Luiz Carlos Facundo. "Uma resolução de placas com a teoria de Mindlin atraves do metodo dos elementos de contorno". [s.n.], 1998. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258074.
Testo completoAbstract (sommario):
Orientador: Leandro Palermo JuniorDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil
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Resumo: o presente trabalho dedica-se ao estudo da formulação do Método dos Elementos de Contorno para o problema de flexão de placas homogêneas e isotrópicas através da teoria de Mindlin. A análise é feita em regime elástico linear mediante a hipótese de pequenas deformações e com equilíbrio na posição indeslocada. É apresentado o desenvolvimento da teoria de Mindlin que inclui o efeito da deformação por cortante no equilíbrio mas, necessita do atendimento das três condições fisicas na borda da placa. São resolvidos problemas envolvendo placas finas e moderadamente espessas e os resultados comparados com os disponíveis na literatura. Apresentam-se soluções fundamentais para as teorias de Reissner e Mindlin, necessárias na aplicação do Método dos Elementos de Contorno. Adicionalmente, são propostas duas soluções fundamentais que tendem às soluções de Danson e Benzine-Stern de placas finas quando a espessura reduz-se a zero. O tratamento numérico foi feito através da formulação direta do Método dos Elementos de Contorno, utilizando-se elementos isoparamétricos lineares e gerando-se as equações integrais em pontos de colocação fora do domínio da placa
Abstract: This study analyzes the bending of moderately thick plates using the Boundary Element Method. The Mindlin 's theory was applied to an isotropic and homogeneous constitutive material. The equilibrium was made at the initial position with the small strain hypothesis. Mindlin's theory takes into account the shear effect in the equilibrium position and three conditions should be attending. Several examples were solved for thin and thick plates with the purpose to show the accuracy of the presented formulation. Some fundamental solutions were analyzed inc1udingthe well know solution to solve Reisssner's plate with BEM. In addition, two fundamental solutions were proposed and they approaches to the Danson and Bezine-Stern solutions for thin plates when the thickness approaches to zero. The direct Boundary Element Method was used with isoparametric linear elements and the integral equations were computed with the collocation points placed out of the domain
Mestrado
Estruturas
Mestre em Engenharia Civil
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Pereira, Carlos Eduardo Leite 1975. "Formulação variacional e aproximação por elementos finitos dos modelos de placa de Kirchhoff e Reissner-Mindlin". [s.n.], 2002. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263493.
Testo completoAbstract (sommario):
Orientador : Marco Lucio BittencourtDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-08-01T19:19:56Z (GMT). No. of bitstreams: 1 Pereira_CarlosEduardoLeite_M.pdf: 5572640 bytes, checksum: 45c5cb6b60e51ad992bd747fb7f167fe (MD5) Previous issue date: 2002
Resumo: O presente trabalho tem por objetivo desenvolver a formulação variacional dos modelos de placa de Kirchhoff, incluindo o efeito de membrana, e de Reissner-Mindlin. Ambos os modelos são formulados utilizando-se a mesma metodologia. Primeiramente, definem-se as hipóteses cinemáticas dos modelos, considerando-se pequenos deslocamentos. Em seguida, deduzem-se os campos de deformação e de movimentos rígidos compatíveis com a cinemática. O conceito de trabalho interno é utilizado com o objetivo de encontrar os esforços internos compatíveis com a cinemática dos modelos. Em seguida, o Princípio dos Trabalhos Virtuais (PTV) é utilizado, a fim de caracterizar os esforços externos e os Problemas de Valor de Contorno (PVC) de equilíbrio. Conhecidos esses PVCs, a equação constitutiva de um material elástico, linear, isotrópico e homogêneo é utilizada para obter as relações entre os campos de tensão e de deformação dos modelos de placa, assim como os PVCs ou forma forte em termos da cinemática. As formas fracas das equações diferenciais dos modelos são então aproximadas pelo Método dos Elementos Finitos. Finalmente, considerações sobre os elementos de placa são apresentadas
Abstract: The present work aims to present the variational formulation of the Kirchhoff plate model with membrane effect and the Reissner-Mindlin plate model. Both models are formulated using the same methodology. First, it is defined the kinematic hypotheses of the models for small displacements. After that, the strain and rigid displacement fields compatible with the kinematic hypotheses are obtained. The internal work concept is used to find the internal forces compatible with the kinematic hypotheses of the models. The Virtual Work Principle is used to find the external forces and the equilibrium Boundary Value Problems (BVP). The constitutive equation of the elastic, linear, isotropic and homogeneous material is used to obtain the relations between the stress and strain fields. Based on that, BVPs in terms of the kinematics are obtained. The weak forms of the differential equation are approximated by Finite Element Method. Finally, comments about plate elements are presented.
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
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Westphal, Junior Tancredo. "Abordagem direta dos modelos de placa de Reissner e Mindlin pelo metodo dos elementos de contorno". reponame:Repositório Institucional da UFSC, 1990. https://repositorio.ufsc.br/xmlui/handle/123456789/157617.
Testo completoAbstract (sommario):
Dissertação (mestrado) - Universidade Federal de Santa Catarina. Centro TecnologicoMade available in DSpace on 2016-01-08T16:32:11Z (GMT). No. of bitstreams: 1 83703.pdf: 2202169 bytes, checksum: 64994ccb384c9d21ea93a1e14e502a49 (MD5) Previous issue date: 1990
A aplicação do método dos resíduos ponderados ao modelo de placa de reissner resulta num conjunto de equações integrais. Uma simplificação destas equações fornece aquelas correspondentes ao modelo de placa de Mindlin. A formulação é então unificada para os dois modelos. A solução fundamental é determinada pelo método de Hörmander. Pela teoria das distribuições verifica-se que a solução fundamental é composta de funções essenciais e complementares (ou livres). Os coeficientes das funções livres são estudados através de alguns experimentos numéricos, pela aplicação do método dos elementos de contorno. Uma simplificação do tensor e deslocamento fundamental conduz a uma equiparação com o correspondente tensor associado ao modelo de placa de Kirchhofp. Um sistema de equações é obtido pelo método da colocação, e o estudo numérico é efetuado usando funções de interpolação isoparamétricas constantes, lineares ou quadráticas. As integrais são calculadas numericamente por quadratura gaussiana, sendo antes aplicado um procedimento especial de regularização sobre as integrais singulares. Os valores principais são obtidos pela imposição de deslocamentos unitários de corpo rígido. Quando o carregamento é uniformemente distribuído sobre a placa, a integral no domínio é convertida numa integral sobre o contorno. Contudo, esta transformação é opicional, pois assim podem ser considerados problemas com carregamento genérico.
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Ramos, Ana Paula Ferreira. "Análise da interação estaca-solo-superestrutura com o acoplamento MEC-MEF". Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-19112013-220957/.
Testo completoAbstract (sommario):
Fundações do tipo radier estaqueado são aquelas formadas pelos elementos estruturais de placa e estacas (elementos de barras) e o solo . Ao contrário de outras tipos de fundações, onde a carga da superestrutura é transferida ao solo pelo radier ou pelas estacas apenas, no radier estaqueado a contribuição das estacas, bem como a do radier são consideradas. As estacas transferem as cargas da superestrutura ao solo e, assim, permitem a redução dos recalques de uma forma muito econômica. O objetivo do presente trabalho é a análise da interação solo-estrutura através do acoplamento MEC-MEF. O solo é considerado um semi-espaço homogêneo, elástico e linear governado pela equação de Navier e modelado pelo Método dos Elementos de Contorno (MEC), admitindo a solução fundamental de Mindlin. As estacas são modeladas pelo Método dos Elementos Finitos (MEF) e cada elemento possui quatro nós. Além disso, as estacas podem receber forças horizontais, verticais e momentos. A tensão de cisalhamento ao longo da estaca é aproximada por um polinômio do segundo grau e as forças na direção horizontal são aproximadas por um polinômio do quarto grau. O elemento de fundação que faz a ligação do pilar com a estaca é representado por uma placa de grande rigidez, que apresenta o comportamento de um bloco. A interação entre o radier estaqueado e o solo é feita através da reação resultante da interação estaca-solo, nos nós com estaca. A interface radier-solo é dividida em elementos triangulares e para a reação do solo considera-se a variação linear ao longo de cada elemento. A superestrutura é modelada pelo MEF. Vários exemplos de interação solo-estrutura são estudados nesta tese, e mostram que as soluções obtidas a partir do programa computacional desenvolvido no presente trabalho denominado SSI estão de acordo com outros autores.Piled raft foundations are structures consisting of piles, the raft and the soil. Unlike classical foundation design where the building load is either transferred by the raft or the piles alone, in a piled raft foundation the contribution of the piles as well as the raft is taken into account. The piles transfer a part of the building loads into the soil and thereby allow the reduction of settlement in a very economic way. The objective of the present work is the analysis of soil-structure interaction using BEM-FEM coupling. The soil, assumed to be an elastic linear homogeneous half space is governed by Navier\'s equation and it is modeled by the Boundary Elements Method (BEM) using Mindlin\'s fundamental solution. The piles are modeled by the Finite Element Method (FEM) with four nodes each. In addition, the piles can received horizontal and vertical forces and bending moments. The shear traction along the pile is approximated by a second-degree polynomial and the tractions in the horizontal direction are approximated by a fourth degree polynomial. The cap of the pile group is assumed to be rigid. The interaction between the raft and soil is made through the subgrade reaction. The soil-cap interface is divided into triangular elements and the subgrade reaction is assumed to vary linearly across each element. The building\'s structure is modeled by FEM. Several soil structure interaction examples are studied in this thesis, and they show that the solutions obtained from program SSI are in good agreement with others authors.
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Canisius, Tantirimudalige Don Gerard. "A Mindlin finite strip for the analysis of rectangular containers and continuous plates with elastically restrained supports". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30605.
Testo completoAbstract (sommario):
A first order shear deformable finite strip with support displacements is introduced. Both nonlinear geometric effects and initial deflections may be considered. Support displacements are introduced by the use of a set of basis functions for support degrees of freedom. Each basis function is obtained by the solution of a Timoshenko beam under a unit displacement of the respective support degree of freedom. They are combined with the standard beam functions. The new finite strip can be applied to the analysis of rectangular containers and continuous plates with elastically restrained supports. The elastic restraints are introduced with independent springs acting along supports and nodal lines. The finite strip is extended to the analysis of unsymmetrically laminated clamped composite plates by the definition of equivalent elasticity modulii to find the basis functions.
The new finite strip is used in the analysis of rectangular containers. It is shown that compressive horizontal forces exist in the walls of flexible containers filled with a liquid. This can only be predicted by the simultaneous consideration of the movement of the wall corners and the geometric nonlinearities, as can be done with the present model.
A 'mode transition finite strip' which has unequal numbers of modes in the nodal lines is introduced. It can be used to economize the finite strip analysis of plates with loads that need a large number of modes, but spread only across a few of the strips. Also a study of the determination of transverse shear stresses by the use of the equilibrium equations and the displacement solution is made, resulting in some important and interesting observations.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Qi, Hai. "Free vibration analysis of rectangular Mindlin plates resting on uniform elastic edge supports by the superposition method". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq20943.pdf.
Testo completo
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Yu, Jian-Hua. "Etude statique, dynamique et de la stabilité des plaques nervurées à partir de la formulation de mindlin". Besançon, 1986. http://www.theses.fr/1986BESA2010.
Testo completoAbstract (sommario):
Etude du comportement statique d'une plaque nervurée rectangulaire en appui simple en fonction des divers paramètres géométriques introduits. Etude paramétrique des vibrations de la plaque précédente, puis du flambage. Etude du comportement dynamique d'une plaque nervurée rectangulaire en appui simple sous l'influence de forces situées dans son plan moyen
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Yu, Jian-Hua. "Etude statique, dynamique et de la stabilité des plaques nervurées à partir de la formulation de Mindlin". Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb376019065.
Testo completo
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Munoz, Rojas Pablo Andres. "Desenvolvimentos na aplicação do metodo da função de Green local modificado a problemas de placa de Mindlin". reponame:Repositório Institucional da UFSC, 1994. https://repositorio.ufsc.br/xmlui/handle/123456789/157860.
Testo completoAbstract (sommario):
Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro TecnologicoMade available in DSpace on 2016-01-08T18:50:37Z (GMT). No. of bitstreams: 1 98094.pdf: 3771901 bytes, checksum: f5381c3413d44bf0f67064f276b7c0ac (MD5) Previous issue date: 1994
Análise da aplicação do Método da Função de Green Local Modificado - MLGFM para problemas de flexão de placas de Mindlin e desenvolvimento da formulação do mesmo método para problemas de vibração livre destas placas. O MLGFM é apresentado como uma particularização do Método dos Resíduos Ponderados e uma extensão do Método dos Elementos de Contorno de Galerkin. Apontam-se algumas dificuldades na imposição das condições de contorno em pontos de descontinuidade do vetor normal à superfície. Verifica-se a existência do fenômeno do locking na modelagem de placas finas com a teoria de Mindlin. Constata-se que o MLGFM fornece a mesma qualidade de resultados que o Método dos Elementos Finitos para deslocamentos, enquanto que a determinação de esforços - vetor tração - converge mais rapidamente com o MLGFM. O comportamento de convergência para deslocamentos e esforços é explicado por uma abordagem alternativa na formulação do método. Esta abordagem evidencia que o erro da solução aproximada é minimizado apenas no interior de cada célula de Green, e não no seu contorno. No referente a problemas de vibração livre, são empregados vários esquemas de diagonalização de matriz massa. Nesta parte é empregada a função de Green correspondente à parte estática do operador diferencial envolvido. Comparam-se os resultados com os fornecidos com o Método dos Elementos Finitos e com alguns da bibliografia afim.
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Albuquerque, Arthur Álax de Araújo. "Implementação de elementos finitos de barra e placa para a análise de esforços em tabuleiros de pontes por meio de superfícies de influência". Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-28072014-093844/.
Testo completoAbstract (sommario):
Este trabalho consiste em analisar os esforços em tabuleiros de pontes por meio de superfícies de influência. Para isto, o método dos elementos finitos (MEF) é utilizado e os resultados são comparados com os das tabelas de Rüsch. Os elementos finitos de barra, representando longarinas e transversinas, e placa, as lajes do tabuleiro, são implementados no código SIPlacas. Estes elementos finitos são formulados pelas teorias de viga Timoshenko e placa Reissner-Mindlin, respectivamente. Estes apresentam problema de travamento de força cortante (Shear Locking), que é contornado por duas propostas: o artifício matemático da integração reduzida e elementos finitos com campo assumido de deformação de força cortante (CADFC). Verifica-se que os elementos com aproximações quadráticas para os deslocamentos e com CADFC são os que melhor se adequam à proposta de análise da presente pesquisa. Tais elementos apresentam convergência de resultados considerando estruturas com baixa discretização. Os resultados analisados foram o deslocamento, momento fletor e força cortante. Posteriormente realiza-se um estudo de caso de uma ponte em viga. O tabuleiro da ponte é calculado utilizando-se as tabelas de Rüsch e o código SIPlacas. O cálculo dos esforços pelo SIPlacas é realizado de três maneiras. Na primeira consideram-se os painéis de lajes do tabuleiro isolados; na segunda o tabuleiro está sobre apoios não deslocáveis; e na terceira, o tabuleiro apresenta-se com vigas acopladas. Foi concluído que a terceira configuração, cuja representação melhor se aproxima da estrutura real de análise, apresentou os menores esforços internos.This work aims at the analysis of bridge deck stresses through influence surfaces. The finite element method (FEM) is used and the results are compared with those of Rüsch\'s tables. The bar and plate finite elements represent stringers, cross beams and slabs bridge deck. These finite elements are implemented in the SIPlacas code and the theories of Timoshenko beam and Reissner-Mindlin plate are used to theirs formulation. The Shear Locking problem is solved by two proposals: reduced integration and definition of element with transversal shear strain assumed (TSSA). The elements with quadratic approximations for the displacements and TSSA are the best suited to the proposed analysis of this research. Such elements have convergence of results considering structures with low discretization. Displacement, bending moment and shear force were the results analyzed. Subsequently a case study on a beam bridge was carried out. The bridge deck is calculated using Rüsch\'s tables and SIPlacas code. The calculation of the internal forces by SIPlacas is performed in three ways. The first one considers the slabs isolated panels; the second, the slab deck is on a rigid support; and third, the slab deck is on deformable supports. It was concluded that the third configuration showed the lowest internal forces. This configuration is the optimum representation to the structure analysis.
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Hijjar, Jorge Roberto Abrahão. "Análise de problemas da elasticidade tridimensional pelo método dos elementos de contorno com a utilização da solução fundamental de Mindlin". Universidade Federal do Rio de Janeiro, 1987. http://hdl.handle.net/11422/3715.
Testo completoAbstract (sommario):
Submitted by Fatima Fonseca (fatima.fonseca@sibi.ufrj.br) on 2018-03-08T17:06:52Z
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166425.pdf: 1129767 bytes, checksum: 922953947a9844b65d6a9f23a3538a5a (MD5)Made available in DSpace on 2018-03-08T17:06:52Z (GMT). No. of bitstreams: 1 166425.pdf: 1129767 bytes, checksum: 922953947a9844b65d6a9f23a3538a5a (MD5) Previous issue date: 1987-03
O presente trabalho trata da análise de problemas da elasticidade tridimensional pelo método dos elementos de contorno, com a utilização da solução fundamental de Mindlin. Para tanto, uma formulação teórica e um programa de computador baseado nesta foram desenvolvidos. Por ter sido empregada a solução fundamental proposta por Mindlin [1] para semi-espaços infinitos, é obtida uma grande eficiência na solução de problemas desta natureza. Os resultados finais da análise são caracterizados pelos deslocamentos e forças de superfície dos pontos de contorno do corpo e deslocamentos e tensões de pontos internos do mesmo. Finalmente, alguns exemplos e conclusões são apresentados.
This work deals with the analysis of threedimensional elasticity problems with the boundary element method using Mindlin's fundamental solution. Hence, a theoretical formulation and a computer program based on it were developed. Since Mindlin's fundamental solution is for a half-space, a good efficiency in the solution of that kind of problems is obtained. The final results of the analysis are displacements and tractions on the boundary of the body and displacements and stresses at internal points. Finally, some test cases are analysed and conclusions are presented.
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Dornisch, Wolfgang Verfasser], Sven [Akademischer Betreuer] [Klinkel, Manfred [Akademischer Betreuer] Bischoff e Friedrich [Akademischer Betreuer] Gruttmann. "Interpolation of Rotations and Coupling of Patches in Isogeometric Reissner-Mindlin Shell Analysis / Wolfgang Dornisch ; Sven Klinkel, Manfred Bischoff, Friedrich Gruttmann". Aachen : Universitätsbibliothek der RWTH Aachen, 2015. http://d-nb.info/1126124044/34.
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Dornisch, Wolfgang [Verfasser], Sven [Akademischer Betreuer] Klinkel, Manfred [Akademischer Betreuer] Bischoff e Friedrich [Akademischer Betreuer] Gruttmann. "Interpolation of Rotations and Coupling of Patches in Isogeometric Reissner-Mindlin Shell Analysis / Wolfgang Dornisch ; Sven Klinkel, Manfred Bischoff, Friedrich Gruttmann". Aachen : Universitätsbibliothek der RWTH Aachen, 2015. http://d-nb.info/1126124044/34.
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Luersen, Marco Antonio. "Problemas de contato unilateral em placas semi-espessas sujeitas a grandes deflexões". reponame:Repositório Institucional da UFSC, 1994. https://repositorio.ufsc.br/xmlui/handle/123456789/157894.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro TecnologicoMade available in DSpace on 2016-01-08T19:17:06Z (GMT). No. of bitstreams: 1 99944.pdf: 1541003 bytes, checksum: 1ce956e07d2631dcb9abbc0ea25132e0 (MD5) Previous issue date: 1994
Formulação e análise de problemas de contato em placas utilizando o Método dos Elementos Finitos. A teoria de placas semi-espessas ou teoria de Mindlin-Reissner é utilizada, e a versão lagrangiana atualizada do princípio dos trabalhos virtuais é adotada para o tratamento da não-linearidade advinda do fato da estrutura poder sofrer grandes deflexões. A desigualdade variacional, característica do problema de contato, é resolvida fazendo-se uso do método da penalidade.
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Haidar, Mohamed. "Modelling of failure mechanisms for corrugated board". Thesis, KTH, Hållfasthetslära (Inst.), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176010.
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The present work describes the construction of a semi-analytical model for prediction of buckling loads in simply supported corrugated paperboard panels. The model accounts for transverse shear, due to the weakness of the core in such plates compared to the facings. This was done utilizing energy relations and rst order transverse shear. The panel was homogenised using laminate theory. A detailed model using FEM was derived in order to validate the predictive capabilities of the analytical model. Experimental testing was performed to estimate the accuracy of both theoretical models, and assess the limitation of the analytical model. All modes of analysis showed good agreement for cubic boxes. Further investigation into expanding the scope of the analytical model was carried out and commented on.
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Willoughby, David Scott. "An Investigation into Isogeometric Blended Shells". BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6565.
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Improvements to isogeometric blended shells are introduced which blend traditional Reissner-Mindlin shells, and Kirchhoff-Love shells, with an exact interpolation of the shell director increment. A gradient extraction operator is introduced which allows derivatives of basis functions to be exactly expressed as a linear combination of the basis functions themselves. Several benchmarks are investigated and the new blended shell is compared with different shell elements in ABAQUS and NASTRAN. In addition, the effect of different quadrature schemes is included in the comparisons. The new isogeometric blended shell performs comparably in some benchmarks, and even outperforms commercial shell finite elements in some benchmarks. Future improvements to the formulation are discussed.
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下田, 昌利, Masatoshi SHIMODA, 二郎 辻, Jiro TSUJI, 康宏 神田, Yasuhiro KANDA, 秀幸 畔上 e Hideyuki AZEGAMI. "固有振動数制約付き Mindlin 板・シェル構造の重量最小形状設計". 日本機械学会, 2003. http://hdl.handle.net/2237/12172.
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Lei, Zhen. "Isogeometric shell analysis and optimization for structural dynamics". Thesis, Ecully, Ecole centrale de Lyon, 2015. http://www.theses.fr/2015ECDL0028/document.
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Cette thèse présente des travaux effectués dans le cadre de l'optimisation de forme de pièces mécaniques, sous critère dynamique, par approche isogéométrique. Pour réaliser une telle optimisation nous mettons en place dans un premier temps les éléments coque au travers des formulations Kirchhoff-Love puis Reissner-Minlin. Nous présentons une méthode permettant d'atteindre les vecteurs normaux aux fibres dans ces formulations au travers de l'utilisation d'une grille mixte de fonctions de base interpolantes, traditionnellement utilisées en éléments finis, et de fonction non interpolantes issues de la description isogéométrique des coques. Par la suite, nous détaillons une méthode pour le couplage de patch puis nous mettons en place la méthode de synthèse modale classique dans le cadre de structures en dynamique décrites par des éléments isogéometriques. Ce travail établit une base pour l'optimisation de forme sous critères dynamique de telles structures. Enfin, nous développons une méthode d'optimisation de forme basée sur le calcul du gradient de la fonction objectif envisagée. La sensibilité de conception est extraite de l'analyse de sensibilité au niveau même du maillage du modèle, qui est obtenue par l'analyse discrète de sensibilité. Des exemples d'application permettent de montrer la pertinence et l'exactitude des approches proposéesIsogeometric method is a promising method in bridging the gap between the computer aided design and computer aided analysis. No information is lost when transferring the design model to the analysis model. It is a great advantage over the traditional finite element method, where the analysis model is only an approximation of the design model. It is advantageous for structural optimization, the optimal structure obtained will be a design model. In this thesis, the research is focused on the fast three dimensional free shape optimization with isogeometric shell elements. The related research, the development of isogeometric shell elements, the patch coupling in isogeometric analysis, the modal synthesis with isogeometric elements are also studied. We proposed a series of mixed grid Reissner-Minlin shell formulations. It adopts both the interpolatory basis functions, which are from the traditional FEM, and the non-interpolatory basis functions, which are from IGA, to approximate the unknown elds. It gives a natural way to define the fiber vectors in IGA Reissner-Mindlin shell formulations, where the non-interpolatory nature of IGA basis functions causes complexity. It is also advantageous for applying the rotational boundary conditions. A modified reduce quadrature scheme was also proposed to improve the quadrature eficiency, at the same time, relieve the locking in the shell formulations. We gave a method for patch coupling in isogeometric analysis. It is used to connect the adjacent patches. The classical modal synthesis method, the fixed interface Craig-Bampton method, is also used as well as the isogeometric Kirchhoff-Love shell elements. The key problem is also the connection between adjacent patches. The modal synthesis method can largely reduce the time costs in analysis concerning structural dynamics. This part of work lays a foundation for the fast shape optimization of built-up structures, where the design variables are only relevant to certain substructures. We developed a fast shape optimization framework for three dimensional thin wall structure design. The thin wall structure is modelled with isogeometric Kirchhoff-Love shell elements. The analytical sensitivity analysis is the key focus, since the gradient base optimization is normally more fast. There are two models in most optimization problem, the design model and the analysis model. The design variables are defined in the design model, however the analytical sensitivity is normally obtained from the analysis model. Although it is possible to use the same model in analysis and design under isogeomeric framework, it might give either a highly distorted optimum structure or a unreliable structural response. We developed a sensitivity mapping scheme to resolve this problem. The design sensitivity is extracted from the analysis model mesh level sensitivity, which is obtained by the discrete analytical sensitivity analysis. It provides exibility for the design variable definition. The correctness of structure response is also ensured. The modal synthesis method is also used to further improve the optimization eficiency for the built-up structure optimization concerning structural dynamics criteria
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Rodrigues, Marcelo Ricardo Bertoni. "Soluções analíticas para flambagem de placas laminadas retangulares simplesmente apoiadas". Instituto Tecnológico de Aeronáutica, 2004. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=680.
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Materiais compósitos avançados, que consistem basicamente de fibras de alta resistência e rigidez embebidas em um material matriz, têm revolucionado projetos de aeronaves, pois permitem significante economia de peso e conseqüente ganho de performance. Esses materiais são geralmente empregados na forma de placas laminadas, produzidas pela junção de várias camadas de material compósito, variando-se a orientação das fibras. Desta forma ée possível obter-se um componente estrutural com resistência e rigidez adequadas em cada direção, atendendo mais eficientemente às solicitações de serviço. Neste trabalho são estudadas soluções analíticas para flambagem de placas laminadas retangulares simplesmente apoiadas, submetidas a carregamento biaxial. São apresentados estudos paramétricos e comparações entre cargas de flambagem obtidas com a teoria clássica e a teoria de primeira ordem. A teoria clássica superestima cargas de flambagem e os erros resultantes são significativos em placas espessas. Os maiores erros encontrados aproximam-se de 100% para placas com a razão largura / espessura igual a 10 e baixos módulos de cisalhamento transversal, considerados infinitos pela teoria clássica.
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Adam, Cédric. "Une contribution à l'analyse isogéométrique statique et dynamique des structures". Palaiseau, Ecole polytechnique, 2015. http://www.theses.fr/2015EPXX0004.
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Dallot, Julien. "Modélisation des structures multicouches en analyse limite : application au renforcement de matériau quasi-fragile-acier". Phd thesis, Ecole des Ponts ParisTech, 2007. http://pastel.archives-ouvertes.fr/pastel-00003625.
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Dans le domaine du génie civil et de la construction, ainsi que de l'industrie, les structures hétérogènes multicouches sont très utilisées. L'une des demandes formulées par les ingénieurs pour concevoir de telles structures est aussi la connaissance des charges limites qu'elles peuvent supporter. Des méthodes d'homogénéisation des plaques et poutres multicouches en analyse limite ont ainsi été développées. Elles conduisent respectivement à des cinématiques de Love-Kirchhoff ou d'Euler-Bernoulli pour la structure homogène équivalente. Afin de prendre en compte les effets de cisaillement, de nouveaux modèles de plaques et de poutres multiparticulaires ont été proposés et justifiés. Après une validation par éléments finis de ces modèles, on les applique au cas des poutres en béton armé renforcées. Ils permettent d'avoir une estimation rapide des chargements maximaux supportables et de construire ainsi un outil de dimensionnement à l'Etat Limite Ultime pour de telles structures.
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Liu, Youhua. "Efficient Methods for Structural Analysis of Built-Up Wings". Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/77972.
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The aerospace industry is increasingly coming to the conclusion that physics-based high-fidelity models need to be used as early as possible in the design of its products. At the preliminary design stage of wing structures, though highly desirable for its high accuracy, a detailed finite element analysis(FEA) is often not feasible due to the prohibitive preparation time for the FE model data and high computation cost caused by large degrees of freedom. In view of this situation, often equivalent beam models are used for the purpose of obtaining global solutions. However, for wings with low aspect ratio, the use of equivalent beam models is questionable, and using an equivalent plate model would be more promising.
An efficient method, Equivalent Plate Analysis or simply EPA, using an equivalent plate model, is developed in the present work for studying the static and free-vibration problems of built-up wing structures composed of skins, spars, and ribs. The model includes the transverse shear effects by treating the built-up wing as a plate following the Reissner-Mindlin theory (FSDT). The Ritz method is used with the Legendre polynomials being employed as the trial functions. Formulations are such that there is no limitation on the wing thickness distribution. This method is evaluated, by comparing the results with those obtained using MSC/NASTRAN, for a set of examples including both static and dynamic problems.
The Equivalent Plate Analysis (EPA) as explained above is also used as a basis for generating other efficient methods for the early design stage of wing structures, such that they can be incorporated with optimization tools into the process of searching for an optimal design. In the search for an optimal design, it is essential to assess the structural responses quickly at any design space point. For such purpose, the FEA or even the above EPA, which establishes the stiffness and mass matrices by integrating contributions spar by spar, rib by rib, are not efficient enough.
One approach is to use the Artificial Neural Network (ANN), or simply called Neural Network (NN) as a means of simulating the structural responses of wings. Upon an investigation of applications of NN in structural engineering, methods of using NN for the present purpose are explored in two directions, i.e. the direct application and the indirect application. The direct method uses FEA or EPA generated results directly as the output. In the indirect method, the wing inner-structure is combined with the skins to form an "equivalent" material. The constitutive matrix, which relates the stress vector to the strain vector, and the density of the equivalent material are obtained by enforcing mass and stiffness matrix equities with regard to the EPA in a least-square sense. Neural networks for these material properties are trained in terms of the design variables of the wing structure. It is shown that this EPA with indirect application of Neural Networks, or simply called an Equivalent Skin Analysis (ESA) of the wing structure, is more efficient than the EPA and still fairly good results can be obtained.
Another approach is to use the sensitivity techniques. Sensitivity techniques are frequently used in structural design practices for searching the optimal solutions near a baseline design. In the present work, the modal response of general trapezoidal wing structures is approximated using shape sensitivities up to the second order, and the use of second order sensitivities proved to be yielding much better results than the case where only first order sensitivities are used. Also different approaches of computing the derivatives are investigated. In a design space with a lot of design points, when sensitivities at each design point are obtained, it is shown that the global variation in the design space can be readily given based on these sensitivities.Ph. D.
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Loibl, Michael. "Implementation and validation of an isogeometric hierarchic shell formulation". Thesis, KTH, Bro- och stålbyggnad, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-264764.
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Within this thesis, thin walled shell structures are discussed with modern element formulationsin the context of the Isogeometric Analysis (IGA). IGA was designed to achieve a directinterface from CAD to analysis. According to the concept of IGA, Non-Uniform RationalB-Splines (NURBS) are used as shape functions in the design and the analysis. Dependingon the polynomial order, NURBS can come along with a high order continuity. Therefore,the curvature of a shell surface can be described directly by the shape function derivativeswhich is not possible within the classical Finite Element Analysis (FEA) using linear meshes.This description of the curvature gives rise to the application of the Kirchho-Love shellformulation, which describes the curvature stiness with the dierentiation of the spatialdegrees of freedom. Based upon this, the formulation can be enhanced with further kinematicalexpressions as the shear dierence vector, which leads to a 5-parameter Reissner-Mindlinformulation. This kinematic formulation is intrinsically free from transverse shear lockingdue to the split into Kirchho-Love and additional shear contributions. The formulation canbe further extended to a 7-parameter three-dimensional shell element, which considers volumetriceects in the thickness direction. Two additional parameters are engaged to describethe related thickness changes under load and to enable the use of three-dimensional materiallaws. In general, three-dimensional shell elements suer from curvature thickness and Poisson'sthickness locking. However, these locking phenomena are intrinsically avoided by thehierarchic application of the shear dierence vector and the 7th parameter respectively. The3-parameter Kirchho-Love, the 5-parameter Reissner-Mindlin and the 7-parameter 3D shellelement build a hierarchic family of model-adaptive shells.This hierarchic family of shell elements is presented and discussed in the scope of this thesis.The concept and the properties of the single elements are elaborated and the dierences arediscussed. Geometrically linear and non-linear benchmark examples are simulated. Convergencestudies are performed and the results are validated against analytical solutionsand solutions from literature, taking into account deections and internal forces. Furthermore,the dierent locking phenomena which occur in analyses with shell formulations areexamined. Several test cases are designed to ensure a validated implementation of the hierarchicshell elements. The element formulations and further pre- and postprocessing featuresare implemented and validated within the open-source software environment Kratos Multi-physics.
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Vlachová, Jana. "Studium parciálního skluzu v kapalinách s využitím vysokofrekvenčních střižných kmitů". Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2014. http://www.nusl.cz/ntk/nusl-217053.
Testo completoAbstract (sommario):
Byl studován kontakt mezi koulí a deskou pod tangenciálním zatížením ve vodě. Jako zdroj střižných kmitů byl použit akustický rezonátor (křemíkové mikrováhy – QCM). Kontakt koule s povrchem resonátoru indukuje změnu resonanční frekvence a šířky pásma. Byla měřena změna frekvence f a změna šířky pásma v závislosti na amplitudě oscilací. S rostoucí amplitudou docházelo k poklesu f a růstem , což je chování typické pro parciální skluz. Díky aplikaci Cattaneo-Mindlinova modelu byl vypočítán kontaktní poloměr a třecí koeficient. Kontaktní poloměr při nízké amplitudě stoupal při zvětšujícím se normálovým zatížením. Tato závislost se dobře shodovala s JKR modelem. Třecí koeficient se nacházel v odpovídajícím rozsahu. Při zvyšování externí normálové síly, docházelo k nepatrnému snižování hodnoty třecího koeficientu. Toto chování je vysvětleno příspěvkem adhezivních sil k totální normálové síle. Výpočtem byly získány dva typy třecích koeficientů, první ze změny frekvence f a druhý ze změny šířky pásma . Tyto dvě hodnoty se spolu shodovaly z ± 20 % pro měření prováděná ve vodě, zatímco pro dvě měření prováděných na hydrofilním povrchu ve vzduchu se lišila. Tento nesoulad poukazuje na nedostatek Cattaneo Mindlinovy teorie a mohl by být vysvětlen přítomností kapilárních sil.
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Andrade, Rebecca Cardelli de. "Uma analise das soluções fundamentais aplicaveis as placas espessas pelas teorias de Reissner e Mindlin e suas relações com a teoria classica para uso no metodo dos elementos de contorno". [s.n.], 2001. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258073.
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Orientador : Leandro Palermo JuniorDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil
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Resumo: O presente trabalho trata de soluções fundamentais de placas segundo as teorias de Reissner e Mindlin, necessárias para a aplicação do Método dos Elementos de Contorno na solução do problema. O problema estudado é de flexão de placas homogêneas e isotrópicas, em regime elástico linear, mediante a hipótese de pequenas deformações e com equilíbrio na posição indeslocada. Para o Método dos Elementos de Contorno, são utilizados elementos isoparamétricos lineares e é aplicada a formulação direta. Apresenta-se o desenvolvimento da teoria de Reissner/Mindlin através da formulação de Weeën, e um estudo com a formulação alternativa de Palermo Jr. para a teoria de Mindlin. Essa formulação alternativa trata da conexão da teoria de Mindlin com a teoria clássica, sendo uma somatória da teoria clássica com o efeito da deformação devido à força cortante. Foram incluídas as expressões das soluções fundamentais em coordenadas normal e tangencial ao contorno da placa. São resolvidos problemas envolvendo placas finas e espessas para analisar o efeito da variação de parâmetros livres da solução fundamental. Adicionalmente, é mostrada a importância da consideração do efeito da deformação por cortante no cálculo de placas
Abstract: The present report describes the fundamental solutions for plates in Reissner and Mindlin's theories, used in the application of the Boundary Element Method. The problem consists in the bending of a homogeneous and isotropic plate, in the linear elastic range and with the small strain hypothesis. The Boundary Element Method is based on the direct formulation and it was used isoparametric linear element. The development of Reissner/Mindlin's theory according to Weeën's formulation is shown and the alternative formulation for Mindlin's theory presented by Palermo Jr. is studied and tested. This alternative formulation establishes the connection between Mindlin's theory and the classical theory, and Mindlin's theory is obtained as a sum of the expressions of the classical theory plus a correction due to the shear deformation effect. The alternative formulation also permits the analysis in boundary coordinates. Problems involving thin and thick plates are studied and the effect of the free parameter of the fundamental solution is tested. Finally, the importance of considering the shear deformation effect in the analysis of plate is shown
Mestrado
Mestre em Engenharia Civil
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Sousa, Neto Gilcenio Rodrigues de. "Controlabilidade, problema inverso, problema de contato e estabilidade para alguns sistemas hiperbólicos e parabólicos". Universidade Federal da Paraíba, 2016. http://tede.biblioteca.ufpb.br:8080/handle/tede/9307.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
In this thesis we study controllability results, asymptotic behavior and inverse problem related to some problems of the theory of partial di erential equations. Two particular systems are the focus of the study: the Mindin-Timoshenko system, describing the vibrational motion of a plate or a beam, and the phase eld system describing the temperature and phase of a medium having two distinct physical states. The rst chapter is devoted to the study of the 1-D Mindlin-Timoshenko system with discontinuous coe cient. A Carleman inequality is obtained under the assumption of monotonicity on the beam speed. Subsequently, two applications are provided: the controllability of the control system acting on the boundary and Lipschitzian stability of the inverse problem of recovering a potential from a single measurement of the solution. In the second chapter we consider a contact problem characterized by the behavior of a two-dimensional plate whose board makes contact with a rigid obstacle. The formulation of this problem is presented by the 2-D Mindlin-Timoshenko system with boundary conditions and suitable damping terms. Concerning such system, is proved via penalty techniques, the existence of solution and that the system energy has exponential decay when the time approaches in nity. In the third chapter, the study is aimed at a nonlinear phase- eld system de ned in a real open interval. Here we present some controllability results when a single control acts, by means of Dirichlet conditions, on the temperature equation of the system on one of the endpoints of the interval. To prove the results is used the method of moments, plus a spectral study of operators associated to the system and xed point theory to deal with the nonlinearity.
Nesta tese estudamos resultados de controlabilidade, comportamento assintótico e problema inverso relacionados a alguns problemas da teoria de equações diferenciais parciais. Dois sistemas particulares são foco do estudo: o sistema de Mindin-Timoshenko, que descreve o movimento vibratório de uma placa ou viga, e o sistema de campo de fases que descreve a temperatura e a fase de um meio onde ocorrem dois estados físicos distintos. O primeiro capítulo é dedicado ao estudo do sistema de Mindlin-Timoshenko 1-D com coe ciente descontínuos. Uma desigualdade de Carleman é obtida sob a hipótese de monotonicidade sobre velocidade da viga. Posteriormente, são fornecidas duas aplicações: a controlabilidade do sistema com controles agindo na fronteira e a estabilidade Lipschitziana do problema inverso de recuperar um potencial através de uma única informação obtida sobre a solução. No segundo capítulo consideramos um problema de contato caracterizado pelo comportamento de uma placa bidimensional cujo bordo faz contato com um obstáculo rígido. A formulação deste problema é apresentada pelo sistema de Mindlin-Timoshenko 2-D com condi ções de fronteira e termos de amortecimento (damping) adequados. Sobre tal sistema, é provada, através de técnicas de penalização, a existência de solução e, posteriormente, que sua energia possui decaimento exponencial quando o tempo tende ao in nito. No terceiro capítulo o estudo é voltado a um sistema de campo de fases não-linear de nido em um intervalo aberto real. Neste espaço apresentamos alguns resultados de controlabilidade quando um único controle age, sob condições de Dirichlet, na equação da temperatura em um dos bordos do intervalo. Para provar os resultados é utilizado o método dos momentos, além de uma estudo espectral de operadores associados ao sistema e teoria de ponto xo para lidar com a não-linearidade.
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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.
Testo completoAbstract (sommario):
Cette thèse est consacrée à la modélisation de la propagation des ondes planes dans les plaques multicouches infinies, dans le cadre de l'élasticité linéaire. L’objet du travail est de trouver une approximation analytique ou semi-analytique des relations de dispersion des ondes lorsque le rapport de l'épaisseur de la plaque sur la longueur d'onde est petit. Ces relations de dispersion, liant la fréquence angulaire et le nombre d'onde, fournissent des informations clés sur les caractéristiques de propagation des différents modes. On propose dans cette thèse deux modélisations : le modèle du Bending-Gradient et la méthode des développements asymptotiques. La pertinence de ces méthodes est testée en comparant leurs prédictions à celles des théories de plaques bien connues, et à des résultats de référence obtenus par la méthode des éléments finis. Au préalable, dans la première partie de la thèse, une justification mathématique de la théorie du Bending-Gradient dans le cadre statique est réalisée à l’aide des méthodes variationnelles. Il s'agit d'abord d'identifier les espaces mathématiques dans lesquels les problèmes variationnels du Bending-Gradient sont bien posés. Puis, des théorèmes d'existence et d'unicité des solutions correspondantes sont ensuite formulés et prouvés. La deuxième partie est consacrée à la formulation des équations du mouvement du Bending-Gradient. Des simulations numériques sont effectuées pour plusieurs types d'empilements, permettant ainsi de tester la validité du modèle pour la modélisation de la propagation des ondes de flexion. La troisième partie est dédiée à l'analyse asymptotique des équations tridimensionnelles du mouvement, menée à bien grâce à la méthode des développements asymptotiques, le petit paramètre étant le rapport de l'épaisseur sur la longueur d'onde. En supposant que les champs tridimensionnels s'écrivent comme des séries en puissance du petit paramètre, on obtient une succession de problèmes à résoudre en cascade. La validité de cette méthode est évaluée par comparaison avec la méthode des éléments finisThis 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
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Shimizu, Derek S. "Mindlink Coordinators, LLC". Thesis, California State University, Long Beach, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10262963.
Testo completoAbstract (sommario):
In the state of California, about one in six adults suffer from some sort of mental illness and about one in twenty of those suffer from a serious mental illness (SMI). In the County of Los Angeles, about 4.5% of the county’s roughly 9.8 million residents suffer from a serious mental illness. Through most of history, mental health care and primary health care have represented two independent systems. The two independent systems have resulted in a double standard of quality of care, accessibility of care, and social stigmas of care. The disconnect leaves mental health care inferior to physical care, where mental illnesses are easily overlooked carrying negative social stigmas with little access. MindLink Coordinators, LLC, a not-for-profit mental health care coordinating organization, looks to bridge a major gap between mental health care and primary health care through care coordination and technology. In conjunction with care coordination, MindLink will provide various services for patients with mental illnesses. MindLink’s purpose will start with serving the Los Angeles County area with the hope of eventually serving patients throughout the state of California.
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Júnior, Faustino Sanches. "Desenvolvimento de modelos numéricos para a análise de estruturas de pavimentos de edifícios". Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-31032016-121303/.
Testo completoAbstract (sommario):
Este trabalho fornece uma contribuição à análise estrutural não-linear de pavimentos de edifícios de concreto armado com o emprego do Método dos Elementos Finitos. A deformação por esforço cortante é considerada, portanto as teorias de Timoshenko e de Reissner-Mindlin são empregadas nas formulações dos elementos de barra e de placa, respectivamente. As posições dos elementos de barra e de placa são independentes e, portanto, podem ser definidas em diferentes planos. Em conseqüência do exposto, o efeito de membrana deve ser necessariamente considerado na modelagem do pavimento. Para completar o modelo mecânico, as não-linearidades físicas descrevem o comportamento do concreto e do aço. A deterioração do concreto no cisalhamento é também considerada através de um modelo simplificado que é proposto para a modelagem do cisalhamento em condições de serviço.This work gives a contribution to the non-linear structural analysis of reinforced concrete buildings floors using the Finite Element Method. The shear strain components are taken into account by adopting the Timoshenko\'s beam theory together with and the Reissner-Mindlin\'s theory for plate bending. Bar and plate element position are independent and therefore can be defined at different planes. As several level are considered when defining the structure membrane effects are necessary considered. In order to complete the mechanical model, physical non-linearities are also assumed to describe concrete and steel behaviours. The deterioration of the concrete material in shear is also taken account. For this purpose, a simplified model is adopted to compute approximately the damaged shear component in the steel direction.
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Hache, Florian. "Vibration of nonlocal carbon nanotubes and graphene nanoplates". Thesis, Lorient, 2018. http://www.theses.fr/2018LORIS487/document.
Testo completoAbstract (sommario):
L’étude analytique proposée porte sur le comportement en vibration de nanotubes de carbone et de nanoplaques de graphène. Pour ce faire, il s’agira dans un premier temps d’étudier les traditionnelles théories de Bresse-Timoshenko pour les poutres et de Uflyand-Mindlin pour les plaques. Des modèles de cisaillement alternatifs sont développés, notamment basés sur des approches asymptotiques issues du milieu élastique tri-dimensionnel. Les interactions interatomiques, ne pouvant pas être négligées à une échelle nanoscopique, seront ensuite prises en compte dans les modèles à travers la présence de paramètres non locaux. Ainsi, différentes approches continues seront considérées : phénoménologiques, asymptotiques et continualisées. Ce dernier type d’approche est récent et est basé sur le développement de modèles continus à partir des équations discrètes de poutres et plaques épaisses et de l’utilisation des approximants de Padé et des développements en séries de Taylor. Pour chaque modèle développé au cours de cette étude, les fréquences propres seront déterminées pour différentes conditions aux limites. Il s’agira ainsi de définir le meilleur cadre pour l’utilisation de chaque modèle et de déterminer l’éventuelle supériorité d’un modèle sur les autresThis thesis deals with the analytical study of vibration of carbon nanotubes and graphene plates. First, a brief overview of the traditional Bresse-Timoshenko models for thick beams and Uflyand- Mindlin models for thick plates will be conducted. It has been shown in the literature that the conventionally utilized mechanical models models overcorrect the shear effect and that of rotary inertia. To improve the situation, two alternative versions of theories of beams and plates are proposed. The first one is derived through the use of equilibrium equations and leads to a truncated governing differential equation in displacement. It is shown, by considering a power series expansion of the displacement, that this is asymptotically consistent at the second order. The second theory is based on slope inertia and results in the truncated equation with an additional sixth order derivative term. Then, these theories will be extended in order to take into account some scale effects such as interatomic interactions that cannot be neglected for nanomaterials. Thus, different approaches will be considered: phenomenological, asymptotic and continualized. The basic principle of continualized models is to build continuous equations starting from discrete equations and by using Taylor series expansions or Padé approximants. For each of the different models derived in this study, the natural frequencies will be determined, analytically when the closed-form solution is available, numerically when the solution is given through a characteristic equation. The objective of this work is to compare the models and to establish the eventual superiority of a model on others
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Sakanaka, Sandra Hiromi. "Determinação de frequencias naturais e cargas criticas em placas incluindo o efeito da deformação por cortante com o metodo dos elementos de contorno". [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257772.
Testo completoAbstract (sommario):
Orientador: Leandro Palermo JrDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-09T15:27:34Z (GMT). No. of bitstreams: 1 Sakanaka_SandraHiromi_M.pdf: 2300706 bytes, checksum: bf530823f185b6dbee7f56dd83d01a67 (MD5) Previous issue date: 2006
Resumo: A análise de vibração livre e de instabilidade de placas finas e placas moderadamente espessas é apresentada através do método dos elementos de contorno (MEC) considerando o efeito da deformação pela força cortante e, particularmente para o cálculo de freqüências naturais, o efeito da inércia rotatória é também considerado. A formulação da solução fundamental é baseada na teoria de Mindlin (1951) mas resultados para a teoria de Kirchhoff (1850) também podem ser obtidos [Palermo Jr. (2000)]. O presente trabalho usa a técnica da iteração inversa através do coeficiente de Rayleigh para a determinação das menores freqüências naturais e cargas críticas de instabilidade das placas. A implementação numérica emprega elementos de contorno isoparamétricos lineares contínuos e descontínuos. Elementos constantes de domínio são usados. Os parâmetros nodais são posicionados nos extremos dos elementos e os pontos de carregamento dos elementos descontínuos são deslocados para o interior a uma distância igual a um quarto do comprimento do elemento. Expressões analíticas das integrais de contorno são desenvolvidas para os casos em que o elemento contém o ponto de carregamento e integração numérica de Gauss-Legendre é feita nos outros casos. As integrais de domínio foram transformadas em integrais de contorno para cada célula e foram tratadas como cargas de superfície atualizadas através de um processo iterativo. Os resultados obtidos foram comparados com valores encontrados na literatura para demonstrar a precisão do presente trabalho
Abstract: Free-vibration analysis and static buckling loads analysis of thin and thick plates considering the shear deformation effects using the Boundary Element Method (BEM) is presented. For the calculation of natural frequencies, the rotatory inertia is also counted. The formulation of the fundamental solution considers Mindlin¿s plates but results according to the classic theory can also be obtained [Palermo Jr. (2000)]. The present article makes use of the inverse iteration with Rayleigh coefficient to determine the smallest natural frequencies and the smallest static buckling loads of the plates. The numerical implementation employed continuous or discontinuous isoparametric linear boundary elements according to the characteristics of the problem to be solved. Constant domain elements are used. Nodal parameters have been placed at the ends of the elements and the source point of the discontinuous elements were positioned at a distance equal to one quarter of the element length. Analytical expressions have been employed in the integration on elements containing the source point and Gauss-Legendre numerical integration scheme otherwise. The domain integrals containing the inertia effects or nonlinear effect have been transformed into boundary integrals for each cell and were treated as surface loads updated in an iterative process. The obtained results were compared to those in literature to demonstrate the precision of this proposal
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Mestre em Engenharia Civil