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Dissertations / Theses on the topic 'Solid Mechanic'
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Inácio, Vanessa Pinheiro. "Caracterização da madeira de Eucalyptus botryoides. Avaliação da sua potencialidade para madeira sólida." Master's thesis, ISA, 2014. http://hdl.handle.net/10400.5/6773.
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Mestrado em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de Agronomia<br>The use of Eucalyptus as solid wood can be a solution to increase the economic viability of our forests due to its rapid growth, good adaptability, low cost of production and physical and mechanical properties favorable to a variety of uses. The aim of this work is to make a biometric study of fibers and characterize the mechanical properties along with the spiral grain detection on Eucalyptus botryoides wood, a specie with only a few studies but with great potential to replace imported timber of high commercial value for solid purposes. Trees of 4 and 6 years old were studied and characterized its fibers, density, modulus of elasticity for static bending, axial compression, Janka hardness and spiral grain. The fibers length and wall thickness had expected values and variations. The 4 year’s timber revealed a more efficient mechanical behavior than the 6 year’s because despite the lower density, the mechanical properties were surprising for its lightness, and also showed no spiral grain. The results obtained in this work points towards evidence of a favorable behavior of Eucalyptus botryoides regarding its use on solid wood products.
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Cavalli, Cléo. "O desafio do gerenciamento dos resíduos sólidos industriais no Rio Grande do Sul frente à legislação ambiental : um estudo para o setor metalmecânico." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/127925.
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O presente trabalho se propôs a analisar um conjunto de empresas do setor metalmecânico, de maneira a verificar possíveis variações no cenário da disposição final dos Resíduos Sólidos Industriais (RSI) após a publicação da Política Nacional de Resíduos Sólidos (PNRS). Foram entrevistadas 22 empresas do setor metalmecânico e 6 Aterros e Centrais de Disposição Final, todas com localização no estado do Rio Grande do Sul. A seleção das empresas deu-se através do estabelecimento de alguns critérios, e estas foram subdividas em 3 amostras: Amostra A (empresas do setor metalmecânico que deixaram de enviar RSI para disposição final antes de 2010), Amostra B (empresas do setor metalmecânico que deixaram de enviar RSI para disposição final no período entre os anos de 2010 e 2014, ou que ainda continuam destinando resíduos para disposição final até a data da pesquisa) e Amostra C (aterros e centrais de disposição final). O procedimento metodológico consistiu na aplicação de um instrumento de coleta de dados através de entrevistas presenciais ou por telefone com profissionais da área ambiental de cada empresa. Os dados foram coletados entre os meses de outubro/2014 a abril/2015 e limitaram-se ao período entre os anos de 2010 a 2014. Os resultados estão apresentados em dois capítulos, sendo que o primeiro refere-se a uma análise global segmentado por amostra de empresa, e o segundo é dedicado às empresas da Amostra B. Os principais resultados encontrados nas empresas da Amostra B apontam reduções no envio dos RSI para disposição final, principalmente dos resíduos classe I, e pode-se verificar um aumento de envio dos classe II. Na Amostra C foi possível verificar uma expressiva diminuição no recebimento dos resíduos classe I e por outro lado, aumento dos resíduos classe II, até o ano de 2013. Os principais fatos que justificam este cenário de disposição final no Estado, referem-se a publicações legais, como a Portaria nº 16 da FEPAM/RS que proíbe o envio de resíduos com características de inflamabilidade para disposição final e também a preocupação com a não geração de passivos ambientais.<br>The purpose of this study was to analyze the possible variations on the of Industrial Solid Waste (ISW) disposal scenario from metal-mechanic companies after the publication of the National Solid Waste Policy (NSWP). 22 companies from metal-mechanic sector and 6 landfills/final disposal plants were interviewed, all those in the state of Rio Grande do Sul - Brazil. Criteria were established for companies selection in which have been subdivided into three samples: Sample A (metal-mechanic companies that stopped sending ISW before 2010), Sample B (metal-mechanic companies stopped sending ISW in the period between 2010 and 2014, or that are still sending waste for disposal until the date of the survey) and Sample C (landfills and final disposal plants). The used methodology was the application of a survey instrument through professional interviews or by telephone in the environmental departments of each company. Data were collected between the months of 2014, October to 2015, April and limited to the period of 2010 to 2014. The presented results are in two chapters. The first relates to a comprehensive analysis segmented by each company of the sample, and the second is dedicated to the Sample B companies. The main results in Sample B companies indicate ISW shipping reductions for disposal, mainly of the hazardous waste, and there is a increasing shipment of non-hazardous waste. In the Sample C was verified a significant decreasing in the receipt of hazardous waste and, in the other hand, a increasing of non-hazardous waste by the year 2013. The main facts which justify this disposal scenario in the state, refers to the legal publications, like FEPAM/RS no 16 Administrative Rule that prohibits the flammability waste disposal as well the concern about environmental liabilities non generation.
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Qian, Jing. "Discrete gradient method in solid mechanics." Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/261.
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The discrete gradient method is proposed as a novel numerical tool to perform solid mechanics analysis directly on point-cloud models without converting the models into a finite element mesh. This method does not introduce continuous approximation of the primary unknown field variables; instead, it computes the gradients of the field variables at a node using discrete differentials involving a set of neighboring nodes. The discrete gradients are substituted into Galerkin weak from to derive the algebraic governing equations for further analysis. Therefore, the formulation renders a completely discrete computation that can conduct mechanical analysis on point-cloud representations of patient-specific organs without resorting to finite element method.
Since the method is prone to rank-deficient instability, a stabilized scheme is developed by employing penalty that involves a minor modification to the method. The difference between nodal strain and subcell strain is penalized to prevent the appearance of zero average strain.
This dissertation delineates the theoretical underpins of the method and provides a detailed description of its implementation in two and three-dimensional elasticity problem. Several benchmark numerical tests are presented to demonstrate the accuracy, convergence, and capability of dealing with compressibility and incompressibility constraint without severe locking. An efficient method is also developed to automatically extract point-cloud models from medical images. Two and three-dimensional examples of biomedical applications are presented too.
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Dev, Bodhayan. "Characterization of Ceramic/Glass Composite Seals for Solid Oxide Fuel Cells." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1400847202.
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Iqbal, Zamin. "Variational methods in solid mechanics." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301901.
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Bao, Tianxin. "Suspension of Solid Mixtures by Mechanical Agitation." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1332422512.
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Miller, Erin Ashley. "Structure and mechanics of solid foam /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/9633.
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Samami, Hassan. "Solid mechanics of degrading bioresorbable polymers." Thesis, University of Leicester, 2016. http://hdl.handle.net/2381/37787.
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Bioresorbable polymers have been successfully used in clinical applications for many decades. They are those types of polymers that degrade into the human body and often don’t need to be removed out of the body, because their degradation products metabolise and enter the general metabolic pathways. However, there has been an increasing demand for better reliability and degradation control of bioresorbable polymeric devices causing researchers to abandon trial-and-error approaches to model-based methods. The mathematical or computer-based techniques for modelling of the mechanical properties are currently in their infancy or non-existent. This study aims to build a model to express the change in mechanical properties and detecting the degradation distribution within degrading bioresorbable polymers. It consists of three main parts. The first part reviews the literature for the most commonly used bioresorbable polymers and their applications. It also reviews the existing mathematical models for biodegradation. The experimental data of six PLLA films are also reviewed to provide insight into changes in mechanical properties of degrading bioresorbable polymers during hydrolytic degradation. The review shows that the mechanical properties are highly affected by the changes in molecular weight and crystallization. The second part presents a constitutive law for prediction of the elastic moduli, tensile strength and Poisson’s ratio of amorphous and semi-crystalline bioresorbable polymers based on the novel idea of formation cavity and crystal inclusions within degrading bioresorbable polymers. The results of using the constitutive law show that it can fit the experimental data fairly well. The third part presents a vibration-based study that shows the curvature mode shapes can successfully reveal the degradation distribution within, for instance, a simple cantilever beam or a coronary stent. This study also presents a chapter for computer modelling of the degradation behaviour of polyester-based tissue scaffolds using a degradation model developed in the University of Leicester.
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Perez, Gavilan Escalante Juan Jose. "Galerkin boundary elements in solid mechanics." Thesis, Queen Mary, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395674.
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Zenit, Camacho José Roberto Hunt Melany L. "Collisional mechanics in solid-liquid flows /." Diss., Pasadena, Calif. : California Institute of Technology, 1998. http://resolver.caltech.edu/CaltechETD:etd-08122005-140811.
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Mercier, Sylvain. "Fast nonlinear solvers in solid mechanics." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30305/document.
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La thèse a pour objectif le développement de méthodes performantes pour la résolution de problèmes non linéaires ne mécanique des solides. Il est coutume d'utiliser une méthode de type Newton qui conduit à la résolution d'une séquence de systèmes linéaires. De plus, la prise en compte des relations linéaires imposées à l'aide de multiplicateurs de Lagrange confère aux matrices une structure de point-selle. Dans un cadre plus général, nous proposons, étudions et illustrons deux classes d'enrichissement de préconditionneurs (limited memory preconditioners) pour la résolution de séquences de systèmes linéaires par une méthode de Krylov. La première est un extension au cas symétrique indéfini d'une méthode existante, développée initialement dans le cadre symétrique défini positif. La seconde est plus générale dans le sens où elle s'applique aus systèmes non symétriques. Ces deux familles peuvent être interprétées comme des variantes par blocs de formules de mise à jour utilisées dans différentes méthodes d'optimisation. Ces techniques ont été développées dans le logiciel de mécanique des solides Code_Aster (dans un environnement parallèle distribué via la bibliothèque PETSc) et sont illustrées sur plusieurs études industrielles. Les gains obtenus en terme de coût de calcul sont significatifs (jusqu'à 50%), pour un surcoût mémoire négligeable<br>The thesis aims at developing efficient numerical methods to solve nonlinear problems arising un solid mechanics. In this field, Newton methods are currently used, requiring the solution of a sequence of linear systems. Furthermore, the imposed linear relations are dualized with the Lagrange multipliers, leading to matrices with a saddle point structure. In a more general framework, we propose two classes of preconditioners (named limited memory preconditioners) to solve sequences of linear systems with a Krylov subspace method. The first class is based on an extension of a method initially developed for symmetric positive definite matrices to the symmetric indefinite case. Both families can be interpreted as block variants of updating formulas used in numerical optimization. They have been implemented into the Code_Aster solid mechanics software (in a parallel distributed environement using the PETSc library). These new preconditioning strategies are illustrated on several industrial applications. We obtain significant gains in computational cost (up to 50%) at a marginal overcost in memory
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Collins, Kimberlee C. (Kimberlee Chiyoko). "Experimental investigations of solid-solid thermal interface conductance." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61600.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 70-84).<br>Understanding thermal interface conductance is important for nanoscale systems where interfaces can play a critical role in heat transport. In this thesis, pump and probe transient thermoreflectance methods are used to measure the thermal interface conductance between solid materials. Two experimental studies of thermal interface conductance are presented, each revealing the complexity of phonon interactions at interfaces which are inadequately captured by current models of phonon transmissivity. The first study considers interfaces of different metals with graphite, and finds that atomic-scale roughness at the interface could be appreciably influencing the heat transport due to the extreme anisotropy of graphite. The thermal interface conductance of graphite is found to be similar to that of diamond, suggesting that when estimating the thermal interface conductance between metal and multi-walled carbon nanotubes (MWCNTs), a reasonable assumption may be that the conductance with the side walls of the MWCNTs is similar to the conductance with the ends of the MWCNTs. The second study considered aluminum on diamond interfaces where the diamond samples were functionalized to have different chemical surface terminations. The surface termination of the diamond is found to significantly influence the heat flow, with oxygenated diamond, which is hydrophilic, exhibiting four times higher thermal interface conductance than hydrogen-treated diamond, which is hydrophobic. Microstructure analysis determined that the Al film formed similarly, independent of diamond surface termination, suggesting that differences in interface bonding likely caused the observed difference in thermal interface conductance, a phenomenon which is not captured in current models of solid-solid phonon transmissivity.<br>by Kimberlee Chiyoko Collins.<br>S.M.
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Cardew, George Evelyn. "A local grid method in solid mechanics." Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420779.
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Eisenberg, David Phillip. "Solid Mechanics Effects in Cryopreservation Via Vitrification." Research Showcase @ CMU, 2015. http://repository.cmu.edu/dissertations/633.
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Cryopreservation via vitrification is the most promising means for long-term preservation of bulky tissues and organs. While the road to successful cryopreservation is paved with obstacles, of paramount importance is thermo-mechanical stress, which can lead to fracture. In order to model the mechanical stress within a vitrifying domain during cryopreservation, the relevant thermal and mechanical properties must be explored. Toward that end, mechanical properties, such as coefficient of thermal expansion and Young’s modulus were measured in the cryogenic temperature range for a new class of cryoprotective cocktail involving DP6 (a less concentrated variant of VS55 without formamide) combined with synthetic ice modulators. A synthesis of material models and properties, some measured in the current research work and others available from the literature, were incorporated into finite element models in order to model thermo-mechanical stress. An array of representative cases has been selected to investigate the effects of a spectrum of thermal histories on the resultant mechanical stress. In particular, a temperature hold near the glass transition temperature (i.e. annealing) has shown to significantly decrease the amount of mechanical stress. Other representative cases have been used to investigate the effects of volumetric warming on mechanical stress. It was shown that internal heating using a volumetric rewarming method reduces the stress to tolerable levels, even in cases involving high cooling and rewarming rates. Additionally, photoelastic experiments were performed using an in-house proprietary device known as the cryomacroscope. These photoelastic experiments allowed for the in-situ visualization of the stress field in real time. Photoelasticity experiments were used to validate a key finding from finite element analysis presented in this thesis. Finally, a new phenomenon associated with the stress history was discovered, where stresses are seen to increase during rewarming around the glass transition temperature and an explanation was proposed based on the Narayanaswamy model of glasses.
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Ismail, Ernesto Bram. "Smoothed particle hydrodynamics for nonlinear solid mechanics." Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/11888.
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Includes abstract.<br>Includes bibliographical references (leaves 115-117).<br>Smooth Particle Hydrodynamics (SPH) is one of the simplest meshless methods currently in use. The method has seen significant development and has been the germination point for many other meshless methods. The development of new meshless methods regularly uses standard SPH as a starting point, while trying to improve on issues related to consistency and stability. Despite these perceived flaws it is favoured by many researchers because of its simple structure and the ease with which it can be implemented.
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Lew, Adrian Jose Ortiz Michael. "Variational time integrators in computational solid mechanics /." Diss., Pasadena, Calif. : California Institute of Technology, 2003. http://resolver.caltech.edu/CaltechETD:etd-05262003-200254.
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Stockmann, Martin, and Jens Kretzschmar. "10th Youth Symposium on Experimental Solid Mechanics, 25th - 28th May 2011, Chemnitz University of Technology, Department of Solid Mechanics." Technische Universität Chemnitz, 2011. https://monarch.qucosa.de/id/qucosa%3A18449.
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Der Tagungsband wurde im Rahmen des 10th Youth Symposium on Experimental Solid Mechanics vom 25. bis 28. Mai 2011 an der Technischen Universität Chemnitz publiziert.
Es werden aktuelle Arbeiten von jungen Wissenschaftlern aus 11 Nationen auf dem Gebiet der experimentellen Festkörpermechanik vorgestellt. Dabei reichen die Beiträge von Material- über Bauteilprüfung bis zur Biomechanik und beleuchten eine Reihe unterschiedlicher Messmethoden und Anwendungen.<br>This proceedings were published on the occasion of the 10th Youth Symposium on Experimental Solid Mechanics from 25th to 28th May 2011 at the Chemnitz University of Technology.
It presents the current work from young researchers from 11 nations in the field of experimental solid mechanics. The contributions have a range from materials testing over components testing to biomechanics and examine a number of different measurement methods and applications.
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Valkov, Boris Ivanov. "A blurred interface formulation of The Reference Map Technique for Fluid-Solid Interactions and Fluid-Solid-Solid Interactions." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92123.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 143-144).<br>In this work we present a blurred interface method for Fluid-Solid Interactions (FSI) and multiple solids immersed in a fluid or FSSI (Fluid-Solid-Solid Interactions) based on the reference map technique as presented by Kamrin and Rycroft. I will follow the chain of thought which lead from the initial sharp interface technique to the newer blurred interface one. We will present its capabilities of doing fully-coupled simulations of a compressible Navier-Stokes fluid and highly non-linear solid undergoing large deformations all performed on a single Eulerian grid with no Lagrangian particles whatsoever. The Reference Map Technique (RMT) provides an Eulerian simulation framework allowing to compute fully coupled fluid/soft-solid interactions. However, due to the extrapolations inherent to the Ghost Fluid Method (GFM) for fluid/fluid interactions, on which the RMT is based, numerical artifacts get created in the resulting pressure and velocity fields whenever the levelset defining the interface crosses a gridpoint from the fixed cartesian grid utilized in this method. We will therefore follow the creation and propagation of these artifacts as well as analyze how the blurred technique solves or avoids these problems.<br>by Boris Ivanov Valkov.<br>S.M.
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Booth, Jonathan. "The mechanism of solid-liquid interactions." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337524.
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Mkhonta, Simiso. "Mechanics of nematic liquid-crystal networks." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21972.
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Liquid-crystal networks are a new class of materials. They combine orientational properties of a liquid-crystal fluid and elastic properties of a rubber. The coupling between the two fields leads to unique properties such as shear deformations at no or sufficiently small energy cost and large spontaneous elongations during the isotropic to nematic liquid-crystal phase transition. The conventional network in a rubber, is made of crosslinked polymers which have anisotropic and inhomogeneous microstructure. In this work, we develop a phenomenological theory to describe a liquid-crystal network with a simpler microstructure, defined by a hexagonal lattice. We study how the network field influences the thermodynamic properties of the constituent liquid crystals and in turn how liquid-crystal order influences the network elasticity. We also clarify the phenomenon of soft elasticity in terms of the geometry of a uniaxial hexagonal lattice. In addition, we also study pattern formation exhibited by a liquid-crystal network after a thermal quench from the isotropic phase into the nematic liquid-crystal phase. We also generalized our phenomenological theory to a case where internal orientational degrees of freedom are allowed to pick particular directions.<br>Les réseaux de crystaux liquides forment une nouvelle classe de matériaux. Ils combinent une orientation propre aux crystaux liquides et les propriétés élastiques des caoutchoucs. L'agencement de ces caractéristiques procure à ces matériaux des modules élastiques trés faibles et un étirement prononcé lors d'une transition de la phase isotropique vers la phase nématique. Un réseau de caoutchouc conventionnel est constitué de polyméres réticulés qui ont une microstructure inhomogène et anisotropique. Dans ce travail, nous développons une théorie phénoménologique qui décrit un réseau de crystaux liquides avec une microstructure simple à symétrie hexagonale. Nous étudions comment la densité du réseau influence les propriétés thermodynamiques des crystaux liquides et comment la symétrie cristalline contrôle l'élasticité du réseau. Nous clarifions ainsi le phénoméne de lélasticité molle lors de la contrainte uniaxiale d'un réseau hexagonal. De plus, nous décrivons l'auto-organisation spatiale présentée par le réseau de crystaux liquides lors d'une trempe qui induit la transition de la phase isotropique vers la phase nématique. Finalement, nous généralisons notre théorie pour inclure des cas où les degrés de liberté d'orientation du réseau peuvent prendre des valeurs particulières.
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Oakeshott, Robert Bernard Simon. "The statistical mechanics of powders." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359838.
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Dayani, D., A. Shokuhfar, M. R. Vaezi, and A. Zolriasatein. "Characterization and Formation Mechanism of Solid Solution in Nanocrystalline Al-5wt%Si Powders Produced by Mechanical Alloying." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35031.
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Due to advantages of mechanical alloying in comparison with liquid state processes, this process has used
a lot to synthesis nanostructured alloy. In the present study, aluminum and silicon elemental powders with
composition Al-5wt % Si were synthesized by mechanical alloying in high energy planetary ball. X-ray diffractometer and scanning electron microscopic were used to study microstructural and morphological changes of
powder particles and formation of solid solution of Al-Si during milling. Crystallite size, lattice strain and lattice parameter were determined by Scherer, Williamson–Hall and Nilson–Reley methods. Minimum crystallite size was 17.895 nm according to Scherer method and 32.644 nm according to Williamson-Hall. Solid solution of Al-Si was formed between 5 h and 30 h, due to crystallite size in nano scale and diffusion process in
mechanical alloying. In addition lattice parameter changes and XRD results prove it.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35031
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Bellis, Cédric. "Qualitative Methods for Inverse Scattering in Solid Mechanics." Phd thesis, Ecole Polytechnique X, 2010. http://pastel.archives-ouvertes.fr/pastel-00557545.
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Contexte. Les problèmes inverses, qui font l'objet de nombreuses études aujourd'hui, apparaissent dans une large gamme d'applications : imagerie et tomographie, identification de propriétés matérielles, contrôle non destructif,... L'étude présentée s'inscrit dans le cadre de ce dernier exemple. Elle a pour objet la recherche de nouvelles méthodes, numériquement rapides, permettant une identification qualitative d'objets (inclusions, cavités, fissures,...) enfouis dans des milieux élastiques linéaires, en connaissant (au moins partiellement) la réponse en surface à une sollicitation dynamique. La plupart des méthodes classiquement utilisées pour traiter ce type de problèmes sont fondées sur des algorithmes itératifs de minimisation qui requièrent un grand nombre de simulations directes. Dans le contexte considéré pour cette étude (propagation d'ondes dans des solides élastiques tridimensionnels), ces simulations sont très coûteuses numériquement. L'émergence récente de techniques permettant de sonder, numériquement, de façon non-itérative un milieu donné, a permis d'aborder ces problèmes sous un nouveau jour. Un ensemble d'études a en particulier montré, dans le cadre des hypothèses adoptées pour cette thèse, l'intérêt de méthodes telles que la Sensibilité Topologique ou le Linear Sampling, pour une détection approchée mais rapide. Objectifs de la thèse. L'étude qui est présentée ici, s'inscrit dans la perspectives du développement des deux méthodes mentionnées, dans le contexte de la mécanique des solides déformables, c'est-à-dire pour des problèmes de diffraction inverse en acoustique et en élasticité. Les différents point abordés dans ce travail sont les suivants : • Appréciation des capacités et des performances respectives des deux méthodes, en particulier lorsqu'elles sont mises en œuvre dans des codes numériques usuels, fondés par exemple sur la méthode des éléments finis. • Utilisation de ces développements pour une identification qualitative combinant géométrie et propriétés matérielles des défauts diffractants inconnus. • Extension de ces méthodes, ainsi que démonstration de leurs pertinences, pour des problèmes de diffraction inverse dans le domaine temporel ou utilisation des mesures multi-fréquentielles des champs diffractés. • Etude de quelques problèmes théoriques fondamentaux pour la justification et la mise en œuvre rigoureuse de ces méthodes. • Compréhension des liens théoriques pouvant exister entre la méthode de sensibilité topologique et la méthode de ”linear sampling”.
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Fidkowski, Piotr. "A hybrid parallel framework for computational solid mechanics." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67182.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 95-98).<br>A novel, hybrid parallel C++ framework for computational solid mechanics is developed and presented. The modular and extensible design of this framework allows it to support a wide variety of numerical schemes including discontinuous Galerkin formulations and higher order methods, multiphysics problems, hybrid meshes made of different types of elements and a number of different linear and non-linear solvers. In addition, native, seamless support is included for hardware acceleration by Graphics Processing Units (GPUs) via NVIDIA's CUDA architecture for both single GPU workstations and heterogenous clusters of GPUs. The capabilities of the framework are demonstrated through a series of sample problems, including a laser induced cylindrical shock propagation, a dynamic problem involving a micro-truss array made of millions of elements, and a tension problem involving a shape memory alloy with a multifield formulation to model the superelastic effect.<br>by Piotr Fidkowski.<br>S.M.
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Sandhu, Jaspal Singh 1977. "An active engagement pedagogy for introductory solid mechanics." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/16803.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.<br>Includes bibliographical references (p. 387-393).<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Introductory Solid Mechanics has historically been taught using the traditional methods of blackboard instruction. In the Mechanical Engineering Department, we have undertaken an initiative to comprehensively transform the pedagogy of 2.001 (Mechanics and Materials I), an undergraduate course in Solid Mechanics. This transformation represents a radical shift in the teaching paradigm, one which is best described as an active engagement model. Through discovery-based and cooperative learning, it is hoped that students will develop conceptual understanding of the course material, that students will become comfortable working in teams, that student retention of course material will improve, that students will be able to engage in independent learning, and that student satisfaction will improve. There are several components to this new pedagogy: physical desktop experiments, Web-enabled learning modules, a portable computing initiative, a new classroom, and a change in the lecture format. This thesis will describe all of these, but will focus on the development of the Web modules, the synthesis of these elements in developing the new pedagogy, and preliminary assessment of the project. The thesis is dually intended as a presentation of original research and as a working document for others who may wish to undertake a project of similar scope.<br>Jaspal Singh Sandhu.<br>S.M.
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Zafra-Camón, Guillermo. "Calculation of global properties of a multi-layered solid wood structure using Finite Element Analysis." Thesis, Uppsala universitet, Tillämpad mekanik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-298677.
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Finite Element Method (FEM) is a powerful numerical tool which, combined with the fast development of Computer Science in the lastdecades, had made possible to perform mechanical analysis of a widerange of bodies and boundary conditions. However, the complexity of some cases may turn the calculationprocess too slow and sometimes even unaffordable for most computers. This work aims to simplify an intricate system of layers withdifferent geometries and material properties by approximating itthrough a homogeneous material, with unique mechanical parameters.Besides the Finite Element analysis, a theoretical model is created, in order to understand the basis of the problem, and, as a firstapproach, check whether the assumptions made in the FEM model areacceptable or not. This work intends to make a small contribution to the understandingof the mechanical behaviour of the Vasa vessel, which will eventuallylead to the design of a new support structure for the ship. The preservation of the Vasa is a priority for the Swedish Property Board, as it is one of the main monuments of Sweden.
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Suarez-Herrera, Marco Fidel. "Reactions at solid-liquid interfaces." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301543.
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Chana, Kamaljeet S. "Statistical mechanics of itinerant-electron magnets." Thesis, Loughborough University, 1993. https://dspace.lboro.ac.uk/2134/33080.
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The transition metal iron is the archetypal magnetic material. However some aspects of its magnetic behaviour are still not fully understood. The conceptual difficulty is that, while unpaired electrons responsible for magnetism in an insulator are localised on the atomic sites, in a metal they have extended states. In iron these itinerant 3-D electrons may conspire to form well-defined local magnetic moments. In this limit one can treat metals such as iron in a similar fashion to insulators in the framework of the Heisenberg model. The local moments align at low temperatures giving rise to ferromagnetic behaviour and above the Curie temperature, Tc, misalign to destroy long range order. The correlation between the directions of the neighbouring moments in the paramagnetic phase remains a subject of controversy. Neutron scattering data would indicate that the magnetic moments are more correlated than would be expected in an insulator. This is generally referred to as magnetic short range order.
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Di, Felice Renzo. "Liquid fluidisation of binary-solid mixtures." Thesis, University College London (University of London), 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362618.
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Meske, Ralf. "Non-parametric gradient-less shape optimization in solid mechanics /." Aachen : Shaker, 2007. http://www.gbv.de/dms/ilmenau/toc/538233001.PDF.
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Dear, J. P. "The fluid mechanics of high-speed liquid/solid impact." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354324.
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Giffin, Brian Doran. "Partitioned Polytopal Finite-Element Methods for Nonlinear Solid Mechanics." Thesis, University of California, Davis, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10752138.
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<p> This work presents a novel polytopal finite-element framework that addresses the collective issues of discretization sensitivity and mesh generation for computational solid mechanics problems. The use of arbitrary polygonal and polyhedral shapes in place of canonical isoparametric elements seeks to remediate issues pertaining to meshing and mesh quality (particularly for irregularly shaped elements), while maintaining many of the desirable features of a traditional finite element method. </p><p> A general class of <i>partitioned element methods</i> (PEM) is proposed and analyzed, constituting a family of approaches for constructing piecewise polynomial approximations to harmonic shape functions on arbitrary polytopes. Such methods require a geometric partition of each element, and under certain conditions will directly yield integration consistency. Two partitioned element methods are explored in detail, including a novel approach herein referred to as the <i>discontinuous Galerkin partitioned-element method</i> (DG-PEM). An implementational framework for the DG-PEM is presented, along with a discussion of its associated numerical challenges. </p><p> The numerical precision of the PEM is explored via classical patch tests and single element tests for a representative sampling of polygonal element shapes. Solution sensitivity with respect to element shape is examined for a handful of problems, including a mesh convergence study in the nearly incompressible regime. Finally, the efficacy of the DG-PEM is assessed for a number of benchmark problems involving large deformations and nonlinear material behavior.</p><p>
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Cheung, Ronald Chak Man. "An investigation into finite volume methods for solid mechanics." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.681490.
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Research into applying finite volume methods to problems in solid mechanics is presented. The investigation has been motivated by the idea that a high-fidelity aeroelastic simulation can be made possible by extending the finite volume methods already implemented in many existing computational fluid dynamics solvers to solid mechanics. A detailed study and survey of applicable methods have been conducted to identify suitable candidates for a three-dimensional time-accurate large-deformation solid mechanics solver. A vertex-centred and a cell-centred solver were initially implemented. Upon comparison, the cell-centred solver appeared to be computationally more efficient despite suffering from a numerical issue. From this analysis, an improved formulation was subsequently developed for the cell-centred solver. In addition, a robust method for numerical gradient evaluation has been developed and incorporated to minimise errors associated with skewed cells or poorly supported cells at domain boundary. The method is based upon the Green-Gauss method, but takes advantage of a secondary numerical gradient to improve overall accuracy and reliability . The improved cell-centred solver has been shown to be accurate, robust and suitable for large deformations in a non-linear validation case against NASTRAN. High computational efficiency has also been demonstrated in OpenMP parallelisation and convergence acceleration via multigrid. The multigrid implementation has been made possible through incorporating a dual-time implicit scheme into the solver.
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Mansfield-Williams, H. D. "Mode 11 fracture mechanics in solid wood and fracture mechanics in laminated veneer lumber." Thesis, Brunel University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390815.
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Samaniego, Reyna Jose Cuauhtemoc. "Ab initio quantum mechanical approaches in solid state." Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289791.
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Wang, Wentao Ph D. Massachusetts Institute of Technology. "Solid State MEMS Resonators in Silicon." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/100152.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 191-196).<br>Two of the greatest challenges in MEMS are those of packaging and integration with CMOS technology. Development of solid state RF MEMS resonators in silicon, resonators that do not require any release etch step, eliminates the necessity for complex encapsulation methods and costly packaging. Such solid state solution could also enable direct integration into front-end-of-line (FEOL) processing in CMOS, making these devices an attractive choice for on-chip signal generation and signal processing. This thesis discusses the physics, design considerations, and process developments to build such solid state MEMS resonators in silicon, showing a series of incremental stages of the prototyping of such devices. The major challenge of building solid state MEMS resonators lies in maintaining comparable device performance relative to released ones, especially quality factor Q. Energy localization structures, such as acoustic Bragg reflectors (ABRs) are implemented for such solid state resonators to maintain high Q and suppress spurious modes. Towards the goal of high aspectratio structures that have the capability of direct CMOS integration, deep trench (DT) capacitor based MEMS resonators are studied and demonstrated. This concept enables high Q, low loss multi-GHz resonators in a simple, robust manufacturing process.<br>by Wentao Wang.<br>Ph. D.
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Lee, Won Yong S. M. Massachusetts Institute of Technology. "Modeling of solid oxide fuel cells." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38564.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.<br>Includes bibliographical references (p. 107-110).<br>A comprehensive membrane-electrode assembly (MEA) model of Solid Oxide Fuel Cell (SOFC)s is developed to investigate the effect of various design and operating conditions on the cell performance and to examine the underlying mechanisms that govern their performance. We review and compare the current modeling methodologies, and develop an one-dimensional MEA model based on a comprehensive approach that include the dusty-gas model (DGM) for gas transport in the porous electrodes, the detailed heterogeneous elementary reaction kinetics for the thermo-chemistry in the anode, and the detailed electrode kinetics for the electrochemistry at the triple-phase boundary. With regard to the DGM, we corrected the Knudsen diffusion coefficient in the previous model developed by Multidisciplinary University Research Initiative. Further, we formulate the conservation equations in the unsteady form, allowing for analyzing the response of the MEA to imposed dynamics. As for the electrochemistry model, we additionally analyzed all the possibilities of the rate-limiting reaction and proposed rate-limiting switched mechanism. Our model prediction agrees with experimental results significantly better than previous models, especially at high current density.<br>by Won Yong Lee.<br>S.M.
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Jakobsson, Håkan. "Adaptive reduction of finite element models in computational solid mechanics." Doctoral thesis, Umeå universitet, Institutionen för matematik och matematisk statistik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-43750.
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Wang, Jin. "Arbitrary Lagrangian-Eularian method and its application in solid mechanics." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0016/NQ27267.pdf.
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Ribeiro-Ayeh, Steven. "Finite element modelling of the mechanics of solid foam materials." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-154.
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Casals-Roigé, L. "Variational explicit dynamic integrators for finite element solid mechanics applications." Thesis, Swansea University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636214.
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The goal of this Thesis is the formulation of some new discrete variational integrators, in the sense of the Veselov formulation of discrete mechanics, which will be used to solve dynamic explicit solid mechanics problems with the Finite Element Method. The reason for developing algorithms with this methodology is that when developed in this manner, they preserve the linear and angular momentum, conserve the symplectic form and in addition it has been observed that possess very good energy behaviour. Firstly, a new variational algorithm will be developed in this Thesis that will permit remarkably bigger time steps in nearly incompressible applications. After a detailed development, which takes into account the fractional step method, a stability calculation will suggest that the reason for the increase of the time step can stem from the dependence of the stable time step on the sheer wave speed instead of the slower volumetric wave speed. A pressure stabilization is given for the equal order interpolation. Next an explicit variational Arbitrary Lagrangian-Eulerian formulation is exposed in detail . The equilibrium equation will suggest different possibilities for moving the nodes explicitly. The order into which the operations have to be performed to move the nodes in the material and spatial mesh will be studied giving at the end some examples. Finally a new variational error indicator is proposed, which has been obtained as the residual of the configurational equations. The convergence to zero when the mesh becomes finer and the great agreement between the residual and the more distorted zones of the mesh indicate that it can be an excellent tool to decide which nodes have to be relocated in Arbitrary Lagrangian-Eulerian computations.
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Nordsletten, David. "Fluid-solid coupling for the simulation of left ventricular mechanics." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.510199.
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Nishimura, Naoshi. "APPLICATIONS OF THE BOUNDARY INTEGRAL EQUATION METHODS TO SOLID MECHANICS." Kyoto University, 1988. http://hdl.handle.net/2433/74720.
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Giardina, Ronald Joseph Jr. "General Nonlinear-Material Elasticity in Classical One-Dimensional Solid Mechanics." ScholarWorks@UNO, 2019. https://scholarworks.uno.edu/td/2666.
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We will create a class of generalized ellipses and explore their ability to define a distance on a space and generate continuous, periodic functions. Connections between these continuous, periodic functions and the generalizations of trigonometric functions known in the literature shall be established along with connections between these generalized ellipses and some spectrahedral projections onto the plane, more specifically the well-known multifocal ellipses. The superellipse, or Lam\'{e} curve, will be a special case of the generalized ellipse. Applications of these generalized ellipses shall be explored with regards to some one-dimensional systems of classical mechanics. We will adopt the Ramberg-Osgood relation for stress and strain ubiquitous in engineering mechanics and define a general internal bending moment for which this expression, and several others, are special cases. We will then apply this general bending moment to some one-dimensional Euler beam-columns along with the continuous, periodic functions we developed with regard to the generalized ellipse. This will allow us to construct new solutions for critical buckling loads of Euler columns and deflections of beam-columns under very general engineering material requirements without some of the usual assumptions associated with the Ramberg-Osgood relation.
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Srivastava, Ankit. "Mechanics and Mechanisms of Creep and Ductile Fracture." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc283799/.
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The main aim of this dissertation is to relate measurable and hopefully controllable features of a material's microstructure to its observed failure modes to provide a basis for designing better materials. The understanding of creep in materials used at high temperatures is of prime engineering importance. Single crystal Ni-based superalloys used in turbine aerofoils of jet engines are exposed to long dwell times at very high temperatures. In contrast to current theories, creep tests on Ni-based superalloy specimens have shown size dependent creep response termed as the thickness debit effect. To investigate the mechanism of the thickness debit effect, isothermal creep tests were performed on uncoated Ni-based single crystal superalloy sheet specimens with two thicknesses and under two test conditions: a low temperature high stress condition and a high temperature low stress condition. At the high temperature, surface oxidation induced microstructural changes near the free surface forming a layered microstructure. Finite element calculations showed that this layered microstructure gave rise to local changes in the stress state. The specimens also contained nonuniform distribution of initial voids formed during the solidification and homogenization processes. The experiments showed that porosity evolution could play a significant role in the thickness debit effect. This motivated a basic mechanics study of porosity evolution in single crystals subjected to creep for a range of stress states. The study was performed using three-dimensional finite deformation finite element analysis of unit cells containing a single initially spherical void in a single crystal matrix. The materials are characterized by a rate-dependent crystal plasticity constitutive relation accounting for both primary and secondary creep. The effect of initial void spacing and creep exponent was also explored. Based on the experimental observations and results of finite element calculations a quantitative mechanistic model is proposed that can account for both bulk and surface damage effects and assess their relative roles in the observed thickness debit effect. Another set of calculations aim at relating the crack growth resistance and fracture surface morphology to material microstructure for ductile structural metals. The process that governs the ductile fracture of structural materials at room temperature is one of nucleation, growth and coalescence of micron scale voids, and involves large plastic deformations. Experimental studies have shown that fracture surfaces in a wide variety of materials and under a wide variety of loading conditions have remarkable scaling properties. For thirty years, the hope to relate the statistical characterization of fracture surfaces to a measure of a material's crack growth resistance has remained unfulfilled. Only recently has the capability been developed to calculate sufficient amounts of three dimensional ductile crack growth in heterogeneous microstructures to obtain a statistical characterization of the predicted fracture surfaces. This development has enabled the exploration of the relation of both fracture toughness and fracture surface statistics to material properties and microstructure when the fracture mechanism is one of void nucleation, growth and coalescence. The relation of both toughness and the statistical properties of fracture surfaces in calculations of heterogeneous microstructures to various microstructural features is discussed and a remarkable correlation between fracture surface roughness and fracture toughness is shown for the first time.
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Cai, Shaobiao. "3D numerical modeling of dry/wet contact mechanics for rough, multilayered elastic-plastic solid surfaces and effects of hydrophilicity/hydrophobicity during separation with applications." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1205118488.
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Wang, Hao. "Theoretical strength of solids." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42747.
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Theoretical strength of solids is defined as the ultimate strength beyond which plastic deformation, fracture, or decohesion would occur. Understanding the microscopic origin from quantum mechanics and thermoelastic formulation is of great importance to mechanical properties and engineering design of various solids. While quite a few theory models have been made in the past century by several generations of scientists, including Frankel and Born, a general and convincing framework has not been fully established. We study this issue from three respects: (1) Unify various elastic stability criteria for solids that determine an upper bound of theoretical strength; (2) with ab initio method, we test the elastic stability conditions of crystal Au. The phenomenon of bifurcation is observed: under hydrostatic expansion, the rhombohedral modulus reaches zero first of all; while under uniaxial tensile stress, the tetragonal shear modulus first reaches zero; (3) propose a nonlinear theoretical formulation of stability criterion. As an analytic method, this scheme is quite simple, in the mean time, it saves computation resource.
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Landinez, Borda Edgar Josué 1984. "Mechanical properties of HCP 4He = Propriedades mecânicas de 4He HCP." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/276927.
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Orientador: Maurice de Koning<br>Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin<br>Made available in DSpace on 2018-08-26T09:46:10Z (GMT). No. of bitstreams: 1
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Previous issue date: 2014<br>Resumo: Esta Tese aborda o problema de determinar propriedades mecânicas fundamentais de 4 He solido na fase hcp usando simulação atomística. Tais propriedades têm sido associadas à possível existência de uma fase cristalina superfluida conhecida como super-solidez. Embora experimentos sofisticados investigando propriedades mecânicas do Hélio sólido têm sido realizados, os resultados dependem da dinâmica microscópica que nem sempre é acessível experimentalmente. Desta maneira as interpretações dos experimentos ficam sujeitos a debates. Neste contexto a modelagem atomística é uma ferramenta útil para fornecer informação qualitativa e quantitativa do comportamento atomístico das propriedades mecânicas. Através de Monte Carlo de integrais de trajetória (PIMC) calculamos a resistência ideal de cisalhamento e tensão de Peierls de uma discordância screw para este sólido quântico protótipo. A resistência ideal estabelece um limite teórico superior de comportamento elástico do material. É a máxima tensão que um cristal livre de defeitos pode suportar, sem produzir uma deformação plástica. Os reultados mostram que o limite de resistência ideal é acompanhado pela nucleação homogênea de uma falha de empilhamento. A resistência ideal é anisotrçopica no plano basal, mas esta anísotropia é bem descrita pela lei de Schmid, que é baseida em conceitos clássicos. Além disso, a comparação do valor da resistência ideal com os de um conjunto grande de cristais clássicos mostra que os resultados para 4 H e estão bem descritos pelo modelo Frenkel-Orowan modificado, que também se baiseia em conceitos puramente clássicos. Em relação às propierdades de discordância, investigamos a estrutura do caroço e a tensão de Peierls para a discordância screw no plano basal. Os resultados mostram uma forte tendência de dissociação e uma tensão de Peierls da ordem e 0.4 bar e estão totalmente consistentes com o comportamento em sólidos clássicos. Assim, os resultados da Tese mostram que, mesmo em regimes de temperatura onde a fase líquida é superfluida, o ordenamento cristalino parece suprimir os efeitos quânticos resposáveis pela super-fluidez no líquido.<br>Abstract: This Thesis addresses a number of issues related to the determination of the fundamental mechanical properties of hcp 4 He. These properties have been linked to the possible existence of a superfluid crystalline phase know as supersolid. While many sophisticated experiments have investigated these properties, their results often require assumptions regarding the underlying processes on the atomic scale which are not accessible experimentally. In this way, the experimental interpretations often remain subject of debate. In this context, atomistic modeling is a useful tool that allows one to obtain both qualitative as well quantitative information about these processes. Using Path-integral Monte Carlo simulations we compute the ideal shear strength (ISS), as well as the structure and mobility parameteres for the screw dislocation for this prototypical quantum solid. The ideal shear strength represents a theoretical upper limit of the elastic response of a crystal, being defined as the maximum stress a defect-free crystal can withstand before deforming plastically. Our resuls show that the ISS limit is accompanied by the homogeneous nucleation of a stacking fault. Furthermore, the ISS on the basal plane is found to be anisotropic, although the anisotropy is well described by Schmid¿s law of resolved shear stress. In addition, comparison of the intrinsic ISS value to values of a large set of classical crystals shows that the results for 4 He are well described by the modified Frenkel-Orowan model, which is also based on purely classical concepts. Considering dislocation properties, we investigate the core structure and Peierls stress for the screw dislocation in the basal plane. The results show a strong dissociation tendency of the core and a Peierls stress of the order of 0.4 bar, consistent with the behavior of classical solids. Accordingly the results of this Thesis show that, even in the temperature regime where the liquid phase is superfluid the crystalline order seems to suppress the quantum effects for the liquid superfluidity<br>Doutorado<br>Física<br>Doutor em Ciências
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Venkatesan, Arvind. "WAVE MOTION IN ELASTIC-PLASTIC SOLIDS BY SPACE-TIME CONSERVATION ELEMENT AND SOLUTION ELEMENT METHOD." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1367581029.
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Mouille, Hervé. "Influence of strain rate and temperature upon the mechanical and fracture behavior of a simulated solid propellant /." This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07212009-040252/.
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