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Dissertations / Theses on the topic 'Mechanics solution'

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Published: 10 December 2022

Last updated: 28 January 2023

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1

Anderson, Todd Alan 1971. "Exact solution of finite geometry composite panels under transient surface loading." Thesis, The University of Arizona, 1995. http://hdl.handle.net/10150/278508.

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The exact three-dimensional transient solution of a multi-layer orthotropic panel subjected to transverse loading is presented. The finite geometry panel, supported by rollers, is subjected to an arbitrarily distributed surface load. Governing equations, derived from Reissner's functional, are solved by applying Fourier or Laplace transformation in time and enforcing the continuity of traction and displacement components between the adjacent layers. Material damping is incorporated into the analysis through complex material constants. The accuracy of the present analysis is established by considering a thick and thin laminate under quasi-static and transient loading, respectively. The solution of the static analysis is compared with a known exact solution and the transient analysis is compared with a finite element analysis. Transient responses of a thick laminate and a composite sandwich panel are also investigated. Material damping is found to significantly affect the transient stress and displacement fields of a laminate.

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2

Wilmott, P. "The asymptotic solution of models in theoretical mechanics." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354870.

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3

Telotte, John Charles. "Thermodynamic properties of multicomponent mixtures from the solution of groups approach to direct correlation function solution theory." Gainesville, FL, 1985. http://www.archive.org/details/thermodynamicpro00telo.

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4

Benson, D. J. A. "Finite volume solution of Stokes and Navier-Stokes equations." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302883.

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5

Korsunsky, Alexander Michael. "The solution of axisymmetric crack problems in inhomogenous media." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259844.

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6

Lee, Jong-eao John. "The inverse spectral solution, modulation theory and linearized stability analysis of N-phase, quasi-periodic solutions of the nonlinear Schrodinger equation /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu148726601122429.

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7

Hewett, Caspar Julian Mnaser. "Unconditionally stable finite difference schemes for the solution of problems in hydraulics." Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275595.

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8

Gilpin, Richard. "The numerical solution and analysis of mathematical models for bubbly two-phase flow." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289348.

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9

Malek, Alaeddin. "Numerical spectral solution of elliptic partial differential equations using domain decomposition techniques." Thesis, Cardiff University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241798.

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10

DE, FREITAS MAGALHAES GOMES RIVALLAIN Fernanda. "Influence du revêtement sur le comportement en fatigue des dalles orthotropes : Etude d'une solution en BFUP." Phd thesis, UNIVERSITE PARIS-EST, 2012. http://tel.archives-ouvertes.fr/tel-00868667.

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Les tabliers métalliques à dalle orthotrope sont sensibles au phénomène de fatigue produit par les charges des poids lourds du trafic. Ce comportement n’est pas précisément prédit avec les méthodes de l’Eurocode 3, compte tenu de la complexité des effets locaux et de la connaissance insuffisante du rôle mécanique du revêtement (diffusion des charges et participation à la flexion locale). De plus l’augmentation du trafic des camions et éventuellement celle des charges admissibles par essieu en Europe tend à rendre ce problème bien plus critique. Le renforcement de ces tabliers est donc souhaitable de façon à prolonger la durée de vie des ponts existants, et aussi augmenter la durabilité des nouveaux ponts. Le béton fibré à ultra haute performance (BFUP) a été envisagé comme nouvelle solution de revêtement, étant donné ses très performantes propriétés mécaniques et de durabilité. L’objectif de cette étude, réalisé dans le cadre du projet ANR Orthoplus, est de quantifier expérimentalement l’apport des revêtements couramment utilisés dans les structures à dalle orthotrope (ultra-mince et béton bitumineux) et valider la solution innovante en BFUP. Les essais statiques et dynamiques sur les corps d’épreuve à l’échelle 1 (2,40x4,00) m2 ont été réalisés sur la plate-forme d’essai des structures de l’IFSTTAR. Quatre corps d’épreuve ont été testés : tôle de platelage de 14 mm non revêtue et revêtue de 80 mm de béton bitumineux, tôle de 10 mm revêtue de 35 mm de BFUP et tôle de 12 mm revêtue de 35 mm de BFUP. L’influence des différents types de chargement positionnés au centre des corps d’épreuve a été analysée : plaques métalliques type Eurocode 1 et vraies roues de camion. L’étude est portée sur le détail de fatigue: liaison auget-tôle de platelage entre pièces de pont. La contrainte géométriques de fatigue est évaluée expérimentalement en utilisant deux schémas d’extrapolation linéaire des mesures de déformation réalisées à proximité du cordon de soudure du détail étudié : le schéma du rapport CECA et celui proposé par l’Institut International de Soudure. L’extrapolation est faite à partir des mesures réalisées au-dessous de la tôle de platelage (σT) et sur l’âme de l’auget (σA). Les résultats expérimentaux ont été confrontés aux modèles aux éléments finis à différents niveaux : du modèle le plus simple possible au plus complexe. A partir des contraintes de fatigue obtenues expérimentalement, nous avons calculé la durée de vie des dalles orthotropes testés à l’aide de la règle du cumul linéaire de l’endommagement (Règle de Miner). Enfin nous avons mené une étude par analyse de cycle de vie d’un pont à dalle orthotrope pour vérifier la pertinence environnementale des solutions de revêtement.

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11

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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12

Aktas, Metin. "Exact Supersymmetric Solution Of Schrodinger Equation For Some Potentials." Phd thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605819/index.pdf.

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Exact solution of the Schrö
dinger equation with some potentials is obtained. The normal and supersymmetric cases are considered. Deformed ring-shaped potential is solved in the parabolic and spherical coordinates. By taking appropriate values for the parameter q, similar results are obtained for Hulthé
n and exponential type screened potentials. Similarly, Morse, Pö
schl-Teller and Hulthé
n potentials are solved for the supersymmetric case. Supersymmetric solution of PT-/non-PT-symmetric and non-Hermitian Morse potential is also studied. The Nikiforov-Uvarov and Hamiltonian Hierarchy methods are used in the calculations. Eigenfunctions and corresponding energy eigenvalues are calculated analytically. Results are in good agreement with ones obtained before.

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13

Chan, Andrew Hin-Cheong. "A unified finite element solution to static and dynamic problems of geomechanics." Thesis, Swansea University, 1988. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624605.

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14

Coward, Andrew Charles. "The numerical solution of some fluid flow and mass transfer problems using non-orthogonal grids." Thesis, University of Exeter, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236000.

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15

Westfall, James. "Efficient and Flexible Solution Strategies for Large-Scale, Strongly Coupled Multi-Physics Analysis and Optimization Problems." Thesis, University of Colorado at Boulder, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10108692.

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Aerospace problems are characterized by strong coupling of different disciplines, such as fluid-structure interactions. There has been much research over the years on developing numerical solution methods tailored to each of the different disciplines. The classical approach to solving these strongly coupled systems is to stitch together these individual solvers by solving for one discipline and using the solution as boundary conditions for the successive disciplines. In more recent years, research has focused on numerical methods that handle solving coupled disciplines together. These methods offer the potential of better computational efficiency. These coupled solution methods range from monolithic solution strategies to decoupled partitioned strategies. This research develops a flexible finite element analysis tool which is capable of analyzing a range of aerospace problems including highly coupled incompressible fluid-structure interactions and turbulent compressible flows. The goal of this research is to access the viability of streamline-upwind Petrov-Galerkin (SUPG) finite element analysis for compressible turbulent flows. Additionally, this research uses a selection of nonlinear solution methods, linear solvers, iterative preconditioners, varying degrees of coupling, and coupling strategies to provide insight into the computational efficiency of these methods as they apply to turbulent compressible flows and incompressible fluid-structure interaction problems. The results suggest that SUPG finite element analysis for compressible flows may not be robust enough for optimization problems due to ill-conditioned matrices in the linear approximation. This research also shows that it is the degree of coupling and criticality of the coupling that drives the selection of the most efficient nonlinear and linear solution methods.

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16

Karasin, Abdulhalim. "An Improved Finite Grid Solution For Plates On Generalized Foundations." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604697/index.pdf.

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In many engineering structures transmission of vertical or horizontal forces to the foundation is a major challenge. As a first approach to model it may be assumed that the foundation behaves elastically. For generalized foundations the model assumes that at the point of contact between plate and foundation there is not only pressure but also moments caused by interaction between the springs. In this study, the exact stiffness, geometric stiffness and consistent mass matrices of the beam element on two-parameter elastic foundation are extended to solve plate problems. Some examples of circular and rectangular plates on two-parameter elastic foundation including bending, buckling and free vibration problems were solved by the finite grid solution. Comparison with known analytical solutions and other numerical solutions yields accurate results.

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17

Anderson, Frank Clayton. "A dynamic optimization solution for a complete cycle of normal gait /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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18

Polton, Richard. "Numerical grid generation and its application in the solution of a model of the Vacuum-Arc Remelting (VAR) process." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323918.

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19

Gustner, Börstell Simon, and Tobias Olsson. "Optimerad installation av hydraulslang i simuleringsmiljö : Industrial Path Solution - Cable Simulation." Thesis, Linköpings universitet, Fluida och mekatroniska system, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-139079.

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Examensarbetet som presenteras i rapporten görs på uppdrag av Specma Group AB i Göteborg. Syftet är att analysera och utvärdera den nuvarande slangdragningen på Rolls Royce vattenjet aggregat S71-4. Efter analysen ska det undersökas om det är möjligt att optimera slangdragningen. I så fall ska ett konceptförslag presenteras som fördelaktigt innefattar en förklaring till varför den teoretiska livslängden ökar för slangarna i systemet. Arbetet utfördes genom förstudier om bakomliggande hydraulikteori och kvalitativa intervjuer av personer med stor erfarenhet av hydraulik. Det utfördes också tester i Specmas testcenter där slangarnas materialkarakteristik togs fram, vilket användes för att möjliggöra simuleringar. Programvaror som används är Creo Parametric vid modellering av modellen samt Industrial Path Solution – Cable Simulator (IPS CS) vid simulering och analyser. Det gjordes också en utbildning på Fraunhofer – Chalmer Centre för att fördjupa kunskaperna om IPS CS. Under arbetets gång har det genomförts analyser och utvärderingar av slangdragningen med uppmätta verkliga parametrar. Resultatet har sedan presenterats för Rolls Royce. Det visualiserades genom filmer hur valda parametrar påverkar slangarna, vilket också sammanställdes i diagram med exakta värden. Det presenterade materialet resulterade i att två förbättringsförslag kunde göras där fokuspunkterna specificerades av Rolls Royce. De två optimeringsförslagen som arbetet har resulterat i har utgått från två olika huvudfokus. Det första förslaget fokuserade på att optimera slangarnas längder medan det andra förslaget i att reducera läckagepunkterna i systemet. Optimeringsförslagen presenterades för Rolls Royce, vilket ledde till att de valde att implementera ett av dem i framtida produktion av S71-4.

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20

Ghamasaee, Rahman 1953. "A neural network approach for the solution of Traveling Salesman and basic vehicle routing problems." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282498.

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Easy to explain and difficult to solve, the traveling salesman problem, TSP, is to find the minimum distance Hamiltonian circuit on a network of n cities. The problem cannot be solved in polynomial time, that is, the maximum number of computational steps needed to find the optimum solution grows with n faster than any power of n. Very good combinatoric solution approaches including heuristics with worst case lower bounds, exist. Neural network approaches for solving TSP have been proposed recently. In the elastic net approach, the algorithm begins from m nodes on a small circle centered on the centroid of the distribution of cities. Each node is represented by the coordinates of the related point in the plane. By successive recalculation of the position of nodes, the ring is gradually deformed, and finally it describes a tour around the cities. In another approach, the self organizing feature map, SOFM, which is based on Kohonen's idea of winner takes all, fewer than m nodes are updated at each iteration. In this dissertation I have integrated these two ideas to design a hybrid method with faster convergence to a good solution. On each iteration of the original elastic net method two nx m matrices of connection weights and inter node-city distances must be calculated. In our hybrid method this has been reduced to the calculation of one row and one column of each matrix, thus, If the computational complexity of the elastic net is O(n x m) then the complexity of the hybrid method is O(n+m). The hybrid method then is used to solve the basic vehicle routing problem, VRP, which is the problem of routing vehicles between customers so that the capacity of each vehicle is not violated. A two phase approach is used. In the first phase clusters of customers that satisfy the capacity constrain are formed by using a SOFM network, then in the second phase the above hybrid algorithm is used to solve the corresponding TSP. Our improved method is much faster than the elastic net method. Statistical comparison of the TSP tours shows no difference between the two methods. Our computational results for VRP indicate that our heuristic outperforms existing methods by producing a shorter total tour length.

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21

文國輝 and Kwok-fai Man. "Elastic solution for rectangular and circular plates on non-homogeneous soil foundation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1988. http://hub.hku.hk/bib/B31208320.

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22

Man, Kwok-fai. "Elastic solution for rectangular and circular plates on non-homogeneous soil foundation /." [Hong Kong : University of Hong Kong], 1988. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12350679.

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23

Rastkar, Siavash. "Characterization of Homogenized Mechanical Properties of Porous Ceramic Materials Based on Their Realistic Microstructure." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2478.

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The recent advances in the Materials Engineering have led to the development of new materials with customized microstructure in which the properties of its constituents and their geometric distribution have a considerable effect on determination of the macroscopic properties of the substance. Direct inclusion of the material microstructure in the analysis on a macro level is challenging since spatial meshes created for the analysis should have enough resolution to be able to accurately capture the geometry of the microstructure. In most cases this leads to a huge finite element model which requires a substantial amount of computational resources. To circumvent this limitation a number of homogenization techniques were developed. By considering a small element of the material, referred to as Representative Volume Element (RVE), homogenization methods make it possible to include the effects of a material’s microstructure on the overall properties at the macro level. However, complexity of the microstructure geometry and the necessity of satisfying periodic boundary conditions introduce additional difficulties into the analysis procedure. In this dissertation we propose a hybrid homogenization method that combines Asymptotic homogenization with MeshFree Solution Structures Method (SSM). Our approach allows realistic inclusion of complex geometry of the microstructure that can be captured from micrographs or micro CT scans. In addition to unprecedented flexibility in handling complex geometries, this method also provides a completely automatic analysis procedure. Using meshfree solution structures simplifies meshing to creating a simple cartesian grid which only needs to contain the domain. This also eliminates manual modifications which usually needs to be performed on meshes created from image data. A computational platform is developed in C++ based on meshfree/asymptotic method. In this platform also a novel meshfree solution structure is designed to provide exact satisfaction of periodic boundary conditions for boundary value problems such as homogenization. Performance of the developed platform is tested over 2D and 3D domains against previously published data and/or conventional finite element methods. After getting satisfactory results, homogenized properties are used to compute localized stress and strain distributions over inhomogeneous structures. Furthermore, effects of geometric features of pores/inclusions on homogenized mechanical properties is investigated and it is demonstrated that the developed platform could provide an automated quantitative analysis tool for studying effects of different design parameters on homogenized properties.

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24

Li, Lin. "A semi-analytical self-similar solution of a bent-over jet in crossflow /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20353029.

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25

Cosper, Lane. "Existence of a Unique Solution to a System of Equations Modeling Compressible Fluid Flow with Capillary Stress Effects." Thesis, Texas A&M University - Corpus Christi, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10790012.

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The purpose of this thesis is to prove the existence of a unique solution to a system of partial differential equations which models the flow of a compressible barotropic fluid under periodic boundary conditions. The equations come from modifying the compressible Navier-Stokes equations. The proof utilizes the method of successive approximations. We will define an iteration scheme based on solving a linearized version of the equations. Then convergence of the sequence of approximate solutions to a unique solution of the nonlinear system will be proven. The main new result of this thesis is that the density data is at a given point in the spatial domain over a time interval instead of an initial density over the entire spatial domain. Further applications of the mathematical model are fluid flow problems where the data such as concentration of a solute or temperature of the fluid is known at a given point. Future research could use boundary conditions which are not periodic.

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26

Li, Lin, and 李琳. "A semi-analytical self-similar solution of a bent-over jet in crossflow." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31221373.

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27

Tabor, Nathan Kyle. "Development of solution techniques and design guidelines for equestrian trails on public lands." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/5023.

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Thesis (M.S.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on November 6, 2007) Includes bibliographical references.

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28

Rakotoniriana, Miarana. "Contribution à l'étude du transfert en solution." Phd thesis, Ecole Polytechnique X, 2005. http://tel.archives-ouvertes.fr/tel-00113105.

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Le transfert en solution est un mécanisme de déformation des roches sédimentaires, qui se traduit par une réduction de porosité et une compaction de la roche. A de grandes profondeurs d'enfouissement (environ 3km), les minéraux des grains se dissolvent dans le fluide du contact intergranulaire, sont transportés par diffusion dans le contact vers le pore, et se déposent sur les surfaces libres des grains. Notre étude est basée sur un modèle de deux grains en contact ayant subi un début de dissolution, et modélisés par deux sphères tronquées. Le contact entre deux grains est simplement représenté par une zone limitée par deux interfaces planes, bien que cette zone soit en réalité constituée de contacts solides et de fluide libre interconnecté, structure connue sous le nom d'îles et chenaux. A cette échelle, une loi de contact phénoménologique permet de relier la vitesse de raccourcissement du grain à la force thermodynamique du transfert en solution, qui est fonction de l'énergie libre d'Helmholtz, de la contrainte normale intergranulaire, et d'un terme relatif à la diffusion. La contrainte normale intergranulaire peut être ainsi exprimée en fonction des quantités relatives à la dissolution et à la diffusion, et en fonction du taux de raccourcissement des grains. Cette contrainte intergranulaire constitue la condition aux limites sur l'interface solide/solide, du problème mécanique. La pression de fluide est la condition de chargement appliquée sur l'interface solide/pore.
Une approche analytique de la résolution de ce problème permet de comprendre que la singularité en contrainte au point de jonction entre la zone de contact et le pore, a pour origine la discontinuité du chargement, entre le chargement sur l'interface solide/solide (la contrainte normale intergranulaire), et la pression de fluide sur l'interface solide/pore. Cette singularité est retrouvée par les calculs éléments finis.
La méthode numérique permet de constater que l'approximation qui consiste à négliger l'énergielibre d'Helmholtz dans la force thermodynamique est valable pour les différentes tailles de grains considérées dans ce travail (entre 0.1mm et 2mm). On montre également que la distribution de la contrainte intergranulaire est de moins en moins parabolique lorsque le grain s'aplatit. Il en est de même lorsque la taille de grain est plus faible, donc lorsque la diffusionest le processus dominant.
La loi de fluage (approchée) qui donne la vitesse de raccourcissement du grain en fonction de la force thermodynamique (sans l'énergie d'Helmholtz) permet de constater que plus la taille de grain diminue, plus le processus de diffusion est rapide : la dissolution est dans ce cas le mécanisme qui gouverne le transfert en solution.
A une échelle plus petite, on s'intéresse à la stabilité d'une interface solide/fluide en faisantune analyse de stabilité en 3D. Le mode d'instabilité dominant est une onde dont le front est perpendiculaire à la direction de la contrainte effective de compression maximale. Les résultats de cette analyse sont cohérents avec les observations expérimentales en ce qui concerne l'orientation et la longueur d'onde de l'instabilité. La non-conformité concernant les gradients des longueurs d'ondes et le taux de croissance sont discutés.

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Xu, Yongmo. "Factors influencing reinforcement corrosion in concrete structures containing internal chloride with particular reference to chloride binding and pore solution chemistry." Thesis, London South Bank University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245131.

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30

Bokil, Shrikant A. "On Computational Modeling of Dynamic Drop-Surface Interactions During Post-Impact Spreading of Water and Aqueous Surfactant Solution." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1378195747.

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31

Max, Bertrand. "Comportement mécanique et couplage mécanique-oxydation dans l'alliage 718 : effet des éléments en solution solide." Thesis, Toulouse, INPT, 2014. http://www.theses.fr/2014INPT0063/document.

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L'alliage 718 est le superalliage le plus utilisé industriellement du fait de ses excellentes propriétés mécaniques, ainsi que de sa tenue à l'oxydation et à la corrosion dans une large gamme de températures et de modes de sollicitation. Néanmoins, cet alliage présente une sensibilité vis-àvis des phénomènes de corrosion sous contrainte et fissuration assistée par l'oxydation sous contrainte dans les gammes de température de service. Les mécanismes à l'origine de ce phénomène restent encore mal compris, cependant un lien entre le changement de mode de rupture et les domaines d'apparition d'instabilités de l'écoulement plastique est clairement établi. Au cours de cette étude nous avons étudié ce phénomène d'instabilités, effet Portevin Le Chatelier, de l'alliage 718 au cours d'essais de traction menés dans une large gamme de températures et de vitesses de déformation. Différents domaines d'instabilités ont pu être mis en évidence, dont les caractéristiques suggèrent l'interaction des dislocations avec des solutés de différentes natures : interstitiels aux plus basses températures, et substitutionnels pour les températures les plus élevées. Des essais de spectroscopie mécanique sur l'alliage 718 et des alliages de compositions voisines montrent un effet de la mobilité des atomes de molybdène au sein du matériau dans cette gamme de températures. Des essais dédiés à l'étude des phénomènes d'interaction entre plasticité et oxydation ont aussi été réalisés. Les résultats mettent en évidence un fort effet de vitesse sur les propriétés mécaniques de l'alliage 718 en atmosphère inerte et sur les caractéristiques de l'endommagement intergranulaire assisté par l'oxydation lors d'essais sous air laboratoire. La discussion engendrée par l'ensemble des résultats présentés permet d'émettre certaines hypothèses sur les couplages entre mécanismes de déformation et endommagement par l'oxydation à l'origine des phénomènes de fissuration observés
Alloy 718 is the superalloy the most widely used in industry due to its excellent mechanical properties, as well as oxidation and corrosion resistance in wide range of temperatures and solicitation modes. Nevertheless, it is a well-known fact that this alloy is sensitive to stress corrosion cracking and oxidation assisted cracking under loading in the range of temperatures met in service. Mechanisms explaining this phenomenon are not well understood: nevertheless, it is well established that a relation exists between a change in fracture mode and the apparition of plastic instabilities phenomenon. During this study, the instability phenomenon, Portevin-Le Chatelier effect, in alloy 718 was studied by tensile tests in wide ranges of temperatures and strain rates. Different domains of plastic instabilities have been evidenced. Their characteristics suggest the existence of interactions between dislocations and different types of solute elements: interstitials for lower temperatures and substitutionals for higher testing temperatures. Mechanical spectroscopy tests have been performed on alloy 718 and various alloys which composition is comparable to that of alloy 718. These tests prove the mobility of molybdenum atoms in the alloy in the studied temperature range. Specific tests have been performed to study interaction phenomenon between plasticity and oxidation. These results highlight the strong effect of plastic strain rate on both mechanical behavior and intergranular cracking in alloy 718. The subsequent discussion leads to propose hypothesis on coupling effects between deformation mechanisms and oxidation assisted embrittlement in the observed cracking processes

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32

Rawat, Naveen. "Exchange Mechanisms in Macroscopic Ordered Organic Magnetic Semiconductors." ScholarWorks @ UVM, 2015. http://scholarworks.uvm.edu/graddis/480.

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Small molecule organic semiconductors such as phthalocyanines and their derivatives represent a very interesting alternative to inorganic semiconductor materials for the development of flexible electronic devices such as organic thin field effect transistors, organic Light Emitting Diodes and photo-voltaic cells. Phthalocyanine molecules can easily accommodate a variety of metal atoms as well in the central core of the molecule, resulting in wide range of magnetic properties. Exploration of optical properties of organic crystalline semiconductors thin films is challenging due to sub-micron grain sizes and the presence of numerous structural defects, disorder and grain boundaries. However, this can be overcome by fabricating macroscopically ordered semiconductor films by solution processing. Presence of fewer grain boundaries and defects while modifying the pi orbital overlap by controlling the molecular stacking by forming macroscopic long range ordered grains, was essential in understanding the delocalization and diffusion length and its role in magnetic exchange mechanisms in this system. The origins of magnetic exchange mechanism between delocalized ligand electrons and spins in organic semiconductors has been of key interest as it underlies many complex optical and transport properties and is investigated in this thesis. The interaction between magnetic ions in organic magnetic semiconductors is quite challenging to interpret due to competing exchange mechanisms present in crystalline thin films. Better understanding of these exchange mechanisms is essential for tuning of magnetic exchange interaction to suit the need of practical magnetic storage and spintronic devices. Optical techniques such as linear dichroism, magnetic circular dichroism and magneto-photoluminescence are used and provided key understanding about the relation between excitons, spin exchange mechanisms and collective magnetic behavior of delocalized electrons in organic semiconductors. An enhancement in the collective magnetization of the crystalline thin films with strong exchange coupling between the delocalized ligand electrons and d-electrons is observed. The electronic states responsible for magnetic exchange are identified utilizing magnetic field and temperature dependent studies. Furthermore, soluble organics allowed engineering of organic analogues to diluted magnetic semiconductors (DMS) by creation of metal/metal-free Pc alloys. Optical studies provided crucial information about delocalization and diffusion lengths in these systems allowing fine tuning of this delocalization length scale and metal-metal distance. The exploration of magnetic behavior in metal/metal-free Pc alloys opens an avenue for tuning magnetic properties through an exchange similar to Ruderman-Kittel-Kasuya Yosida (RKKY) type interaction in organic magnetic semiconductors.

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33

Hiermeier, Michael [Verfasser], Wolfgang A. [Akademischer Betreuer] Wall, Wolfgang A. [Gutachter] Wall, Alexander [Gutachter] Popp, and Michael [Gutachter] Ulbrich. "Advanced Non-Linear Solution Techniques for Computational Contact Mechanics / Michael Hiermeier ; Gutachter: Wolfgang A. Wall, Alexander Popp, Michael Ulbrich ; Betreuer: Wolfgang A. Wall." München : Universitätsbibliothek der TU München, 2020. http://d-nb.info/1222161613/34.

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34

Roy, Cédric. "Étude de mélanges de cellulose dans des solutions aqueuses de soude." Phd thesis, École Nationale Supérieure des Mines de Paris, 2002. http://tel.archives-ouvertes.fr/tel-00274837.

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La mise en solution et la mise en forme de la cellulose sont deux thèmes d'exploration scientifique intense, souvent à des fins industrielles. Parmi les solvants de la cellulose connus, les solutions aqueuses de soude représentent une solution d'avenir, moins polluante. L'aspect scientifique de notre travail concernait la structure, la dissolution et la structuration de la cellulose dans des mélanges 9% soude/eau. D'abord, le diagramme de phases des solutions soude/eau a été construit. Le système soude/eau à basse température est formé d'hydrates de soude cristallins et de glace, et d'eau amorphe non cristallisable même à-60'C. La structure des mélanges cellulose/soude/eau a été proposée en fonction du type de cellulose (microcristalline et pâte de bois). Dans les deux cas, deux à trois groupes hydroxyles par unité glucopyranose sont occupés par les hydrates de soude. L'écoulement et la gélification des systèmes cellulose/soude/eau ont été étudiés. Ces mélanges ont les propriétés de suspensions. La gélification a lieu à chaque température, et elle est plus rapide quand la température est plus élevée. L'aspect industriel concernait l'étude d'un nouveau procédé de fabrication d'éponges synthétiques, par traitement de cellulose dans la soude selon un cycle temps/température complexe. L'objectif était de comprendre les phénomènes physico-chimiques qui ont lieu lors de la phase de " congélation " à -18'C, essentielle pour obtenir des produits finis avec de bonnes propriétés mécaniques. Nous avons mis en évidence une structuration importante lors des différentes étapes de fabrication, avec une gélification des mélanges à 0'C, et surtout un phénomène de séparation de phases à -18'C. Ce phénomène entraîne une cristallisation, responsable des propriétés des produits finis, et il est le " moteur " du procédé.

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35

Mishra, Shashank. "Developing Novel Computational Fluid Dynamics Technique for Incompressible Flow and Flow Path Design of Novel Centrifugal Compressor." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1460731437.

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36

Arumugam, Krishnamoorthy. "Redox chemistry of actinyl complexes in solution : a DFT study." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/redox-chemistry-of-actinyl-complexes-in-solution-a-dft-study(ff09f316-847e-498e-a046-1db7bb4c6758).html.

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The chemistry of actinides in solution is a very important aspect of the nuclear fuel cycle, especially as the energy needs of the world continue to increase. However, the radio-active nature of the actinides makes experimentation very difficult and dedicated expensive instruments are required. In addition, the disposal of radio-active waste materials requires a proper understanding of their chemistry at a molecular level. To tackle the problem, and to underpin the experimental studies, in this thesis we have studied the redox chemistry and disproportionation mechanism of actinyl complexes in solution using state-of-the art computational methods. Reduction potentials of actinyl complexes in solution have been estimated in solution using density functional theory (DFT) approaches. Solvation effects were included in the quantum chemistry calculations with the conductor like polarisable continuum model (CPCM) solvation method. First of all, we have validated our computational method by studying a variety of solute cavity definitions within the CPCM solvation model and assessed the performance of a range of DFT functionals to suitable to accurately describe the actinide chemistry in solution. Penta-valent uranyl(V) ions are unstable and readily disproportionate; in this study we have explored outer-sphere electron transfer and disproportionation mechanisms to determine the stability of these ions in solution. We have found that the process of outer-sphere disproportionation is unlikely to occur in non-aqueous solutions, such as DMSO, DMF, DCM, acetonitrile and pyridine, when the uranyl(V) ion is bound with a multi-dentate organic ligand. However, our computational results hypothesise that the presence of a trace of water in the experimental conditions can promote a disproportionation reaction by protonating the uranyl(V) ‘yl’ oxygen atoms and then the electron transfer process would proceed through either inner or outer sphere mechanism. In addition, the effect of alkali metal cations on the outer-sphere disproportionation mechanisms was also studied. Overall it has been shown that DFT can be used to accurately predict the redox properties of actinyl complexes in solution and thus contributing for an effective and efficient design of nuclear material separations, proper as well as safer radioactive waste disposal.

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MIRANDA, CARLOS A. de J. "Obtencao da tensao de clivagem e nivel de confiabilidade na determinacao da temperatura de referencia de acos ferriticos na transicao .Abordagem numerica experimental." reponame:Repositório Institucional do IPEN, 1999. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10734.

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Made available in DSpace on 2014-10-09T12:43:27Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T13:57:46Z (GMT). No. of bitstreams: 1 06630.pdf: 9701259 bytes, checksum: 3a0ddeea466df64d4d1c1cf28780f43d (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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38

Tryggeson, Henrik. "Analytical vortex solutions to Navier-Stokes equation." Doctoral thesis, Växjö universitet, Matematiska och systemtekniska institutionen, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:vxu:diva-1282.

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Fluid dynamics considers the physics of liquids and gases. This is a branch of classical physics and is totally based on Newton's laws of motion. Nevertheless, the equation of fluid motion, Navier-Stokes equation, becomes very complicated to solve even for very simple configurations. This thesis treats mainly analytical vortex solutions to Navier-Stokes equations. Vorticity is usually concentrated to smaller regions of the flow, sometimes isolated objects, called vortices. If one are able to describe vortex structures exactly, important information about the flow properties are obtained. Initially, the modeling of a conical vortex geometry is considered. The results are compared with wind-tunnel measurements, which have been analyzed in detail. The conical vortex is a very interesting phenomenaon for building engineers because it is responsible for very low pressures on buildings with flat roofs. Secondly, a suggested analytical solution to Navier-Stokes equation for internal flows is presented. This is based on physical argumentation concerning the vorticity production at solid boundaries. Also, to obtain the desired result, Navier-Stokes equation is reformulated and integrated. In addition, a model for required information of vorticity production at boundaries is proposed. The last part of the thesis concerns the examples of vortex models in 2-D and 3-D. In both cases, analysis of the Navier-Stokes equation, leads to the opportunity to construct linear solutions. The 2-D studies are, by the use of diffusive elementary vortices, describing experimentally observed vortex statistics and turbulent energy spectrums in stratified systems and in soapfilms. Finally, in the 3-D analysis, three examples of recent experimentally observed vortex objects are reproduced theoretically. First, coherent structures in a pipe flow is modeled. These vortex structures in the pipe are of interest since they appear for Re in the range where transition to turbulence is expected. The second example considers the motion in a viscous vortex ring. The model, with diffusive properties, describes the experimentally measured velocity field as well as the turbulent energy spectrum. Finally, a streched spiral vortex is analysed. A rather general vortex model that has many degrees of freedom is proposed, which also may be applied in other configurations.

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Damasceno, Marcus Vinicius Araujo. "Estudos teóricos dos efeitos de solvente no espectro eletrônico de absorção da molécula óxido mesitil." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-16032010-104730/.

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Efeitos de solventes tem sido um tema de grande interesse científco. Em particular, o estudo dos efeitos de solventes no espectro eletrônico de absorção tem sua própria motivação e complexidade. Neste trabalho, nós estudamos os efeitos da solução aquosa na estabilidade conformacional e no espectro eletrônico de absorção da molécula Óxido Mesitil (OM). Essa molécula pertence a família das cetonas ,-insaturadas e, semelhantemente aos outros membros da família, ela apresenta transições eletrônicas sensíveis ao solvente. Inicialmente, estudamos os isômeros syn e anti do OM isoladamente usando cálculos quânticos para determinar a energia livre relativa, a barreira de rotação, os momentos de dipolo e as transições eletrônicas de absorção. Nosso melhor resultado mostra que o isômero syn do OM é a conformação mais estável, por cerca de 1.3 kcal/- mol calculado com nível MP2/aug-cc-pVDZ. Com o mesmo nível de cálculo, obtivemos os momentos de dipolo de 2.80 e 3.97 D para os isômeros syn e anti respectivamente, que estão em boa concordância com os valores experimentais de 2.8 e 3.7 D. Para o espectro eletrônico de absorção, analisamos a banda mais intensa, -*, com diferentes funcionais de densidade e funções base. Obtivemos o comprimento de transição de 229 nm calculado com nível TD-B3LYP/6-311++G** para o isômero syn em muito boa concordância com o valor experimental de 231 nm medido em solução de iso-octano (solvente de baixa polaridade). Para realizar os estudos em solução, geramos estruturas supermoleculares dos isômeros do OM em solução aquosa usando simulações computacionais com o método Monte Carlo. Usamos os potenciais Lennard-Jones e Coulomb para descrever as interações intermoleculares com os parâmetros do campo de força OPLS. Verifcamos que as cargas atômicas OPLS não descrevem bem o potencial eletrostático do OM. Portanto, realizamos um processo iterativo para incluir a polarização do soluto na presença do solvente para descrever melhor as interações entre o OM e as moléculas de água. Assim, obtivemos um aumento de cerca de 80% nos momentos de dipolo dos isômeros isolados. Adicionalmente, calculamos a energia livre relativa entre os isômeros em solução aquosa usando teoria de perturbação termodinâmica. Obtivemos que o isômero anti do OM é a conformação mais estável, por cerca de 2.8 kcal/mol. Examinando os efeitos de solvente no espectro eletrônico de absorção do OM, identificamos que existem duas contribuições competindo para o deslocamento da banda -*. Uma contribuição vem da mudança conformacional syn anti do OM devido a mudança de polaridade, baixa alta, do solvente. Essa mudança conformacional provoca um deslocamento para o azul de 1210 cm-1 na transição -*. A outra contribuição vem do efeito do solvente na estrutura eletrônica do OM, que provoca um deslocamento para o vermelho de - 4460 cm-1 nessa transição. Adicionando essas duas contribuições, temos o efeito do solvente total no espectro eletrônico de absorção do OM em solução aquosa. Nosso melhor resultado é um valor médio de 248 nm obtido com 75 cálculos TD-B3LYP/6-311++G** de estruturas supermoleculares estatisticamente descorrelacionadas compostas por um anti-OM rodeado por 14 moléculas de água explícitas embebidas no campo eletrostático de 236 moléculas de água tratadas como cargas pontuais simples. Esse resultado está em muito boa concordância com o resultado experimental de 243 nm em solução aquosa. Sendo assim, este trabalho demonstra que a mudança conformacional syn anti é essencial para entender o deslocamento espectral da transição -* do OM em água.
Solvent effects have been the subject of considerable scientifc interest. In particular, the study of solvent effects in electronic absorption spectroscopy has its own motivation and complexities. In this work we study the effects of the aqueous solution in the conformational stability and the electronic absorption spectrum of the Mesityl Oxide (OM) molecule. This molecule belongs to the family of the ,-unsaturated ketones and, like other members of the family, presents sensitivity to solvent in the absorption transitions. Initially we studied the isolated syn and anti isomers of OM by performing quantum mechanical calculations to obtain the relative free energy, the rotational barrier, the dipole moments and the electronic absorption transitions. Our best result showed that the OM syn isomer is the most stable conformer, by approximately 1.3 kcal/mol calculated with the MP2/aug-cc-pVDZ level. With the same level of calculation, we obtained the dipole moments of 2.80 and 3.97 D for the syn and anti isomers respectively, which are in good agreement with the experimental values of 2.8 and 3.7 D. For the electronic absorption spectrum, we analyzed the most intense band, -*, with different density functional and basis sets. We obtained a transition wavelength of 229 nm calculated with TD-B3LYP/6-311++G** level for the syn isomer in good agreement with the experimental value of 231 nm measured in iso-octane (solvent of low polarity). For performing the in-solution studies, we generated supermolecular structures of the OM isomers in aqueous solution using computer simulations with the Monte Carlo method. We used the Lennard-Jones and Coulomb potentials to describe the intermolecular interactions with the OPLS force field parameters. We found that the OPLS atomic charges do not describe well the electrostatic potential of OM. Therefore we performed an iterative process for including the solute polarization in the presence of the solvent to better describe the interactions between the OM and the water molecules. We obtained an increase of about 80% in the dipole moments of the isolated isomers. Additionally, we calculated the relative free energy between the isomers in aqueous solution using thermodynamic perturbation theory. We found that the anti isomer is the most stable conformer in aqueous solution, by about 2.8 kcal/mol. Examining the solvent effects in the electronic absorption spectrum of OM, we found that there are two competing contributions to the -* band shift. One contribution is due to the syn anti conformational change of OM caused by the low high polarity change of the solvent. This conformational change led to a blue shift of 1210 cm-1 in the * band. The remaining contribution is due to the solvent effect in the electronic structure of OM, which led to a red shift of -4460 cm-1. Adding these two contributions, we obtained the total solvent effect in the electronic absorption spectrum of OM in aqueous solution. Our best result was an average wavelength transition of 248 nm obtained using 75 TD-B3LYP/6-311++G** quantum calculations on statistically uncorrelated supermolecular structures composed by one anti-OM surrounded by 14 explicit water molecules in the electrostatic embedding composed of 236 water molecules described as simple point charges. This result is in very good agreement with the experimental result of 243 nm in aqueous solution. Thus, this work demonstrates that the syn anti conformational change is the essential ingredient to understand the spectral shift of the - * absorption transition of OM in water.

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40

Zeng, Qiang. "Comportement poromécanique des matériaux cimentaires soumis au gel-dégel en présence de sels : modélisation et expérimentation." Phd thesis, Ecole Nationale des Ponts et Chaussées, 2011. http://tel.archives-ouvertes.fr/tel-00688191.

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Les matériaux cimentaires peuvent se détériorer grandement lorsqu'ils sont soumis à des cycles de gel/dégel avec ou sans sels de déverglaçage. Ceci peut porter atteinte à la durabilité à long terme des bétons/mortiers dans les régions aux hivers froids. Laissant de côté les processus d'endommagement et de rupture mécanique à l'oeuvre dans de tels problèmes, ce mémoire de thèse est consacré aux phénomènes physiques et thermo-mécaniques accompagnant la solidification de l'eau dans des solides poreux cohésifs, avec une attention particulière aux "propriétés matériau" issues de l'hydratation du ciment et de l'évolution de la microstructure. Ce travail reprend la poromécanique des milieux poreux partiellement gelés telle que développée par Olivier Coussy, tout en lui adjoignant une analyse de l'effet de la fin de la surfusion (en volume, hors contribution capillaire) et de la présence de sels dans le liquide saturant l'espace poreux. Nous avons mesuré la température de fin de surfusion en fonction de la concentration en sel. Ceci nous permet ensuite de calculer l'angle de contact entre la glace et les parois des pores dans le cadre classique de la nucléation hétérogène : on trouve que cet angle diminue avec la concentration en sel. Nous montrons que la dilatation instantanée consécutive à la fin de la surfusion dépend de la structure poreuse puisque cette dernière détermine la teneur en glace dans l'espace poreux. À l'aide de la distribution de tailles de pores estimée par porosimétrie par intrusion de mercure, nous estimons le degré de saturation en glace en fonction de la température et de la concentration initiale en sel via la relation de Gibbs-Thomson. Nous avons mesuré la déformation d'échantilllons de pâte de ciment saturée. L'analyse poromécanique montre que la déformation dépend de la concentration initiale en sel et de la structure poreuse des pâtes de ciment. En utilisant la même approche expérimentale sur des pâtes de ciment sèches, nous trouvons que la porosité (avec ou sans vide d'air entraîné) influence significativement le coefficient d'expansion thermique du matériau. En ce qui concerne les pâtes de ciment saturées, les mesures expérimentales et l'approche poromécanique en condition drainée ou non-drainée montrent que le degré de saturation initiale en liquide des vides d'air entraîné a un impact important sur la déformation de l'échantillon avec la température.

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41

Edrington, Sarah. "THE LIMITS & EFFECTS OF DRAW ON PROPERTIES AND MORPHOLOGY OF PAN-BASED PRECURSOR AND THE RESULTANT CARBON FIBERS." UKnowledge, 2017. http://uknowledge.uky.edu/me_etds/89.

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The process, structure, and property relationship of PAN fiber as a precursor to carbon fiber was studied. The limitations of stable spinning and property improvement associated with hot draw in solution spinning were found and quantified. Conditions were varied to generated precursor fiber up to the limit of draw, from which actual samples were collected for thermal conversion to carbon fiber. Samples of PAN and subsequent carbon fiber were characterized using tensile testing and x-ray analysis. The effects of draw on modulus and break stress, as well as the orientation of the crystalline structure of both parent precursor and resultant carbon fiber were found and related back to the quantified draw limit.

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42

Sarker, Pratik. "Dynamic Response of a Hingeless Helicopter Rotor Blade at Hovering and Forward Flights." ScholarWorks@UNO, 2018. https://scholarworks.uno.edu/td/2545.

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The helicopter possesses the unrivaled capacity for vertical takeoff and landing which has made the helicopter suitable for numerous tasks such as carrying passengers and equipment, providing air medical services, firefighting, and other military and civil tasks. The nature of the aerodynamic environment surrounding the helicopter gives rise to a significant amount of vibration to its whole body. Among different sources of vibrations, the main rotor blade is the major contributor. The dynamic characteristics of the hingeless rotor consisting of elastic blades are of particular interest because of the strongly coupled equations of motion. The elastic rotor blades are subjected to coupled flapping, lead-lag, and torsional (triply coupled) deflections. Once these deflections exceed the maximum allowable level, the structural integrity of the rotor blade is affected leading to the ultimate failure. The maximum deflection that a blade can undergo for a specific operating condition needs to be estimated. Therefore, in this study, the triply coupled free and forced response of the Bo 105 hingeless, composite helicopter rotor blade is investigated at hovering and forward flights. At first, a model of the composite cross-section of the rotor blade is proposed for which a semi-analytical procedure is developed to estimate the sectional properties. These properties are used in the mathematical model of the free vibration of the rotor blade having the proposed cross-section to solve for the natural frequencies and the mode shapes. The aerodynamic loadings from the strip theory are used to estimate the time-varying forced response of the rotor blade for hovering and forward flights. The large flapping and inflow angles are introduced in the mathematical model of the forward flight and the corresponding nonlinear mathematical model requires a numerical solution technique. Therefore, a generalization of the method of lines is performed to develop a robust numerical solution in terms of time-varying deflections and velocities. The effect of the unsteady aerodynamics at the forward flight is included in the mathematical model to estimate the corresponding dynamic response. Both the analytical and the numerical models are validated by finite element results and the convergence study for the free vibration is performed.

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43

Schuler, Thomas. "Influence des amas lacunes-solutés sur le vieillissement des solutions solides de Fer-α." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112170/document.

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La compréhension et la maîtrise des mécanismes qui pilotent le vieillissement des aciers en présence d’une sursaturation de lacunes est un défi dans de nombreux domaines industriels, et particulièrement dans le cas des réacteurs nucléaires. Ces aciers contiennent invariablement des solutés interstitiels en tant qu’éléments d’alliage ou impuretés, et des lacunes (V) qui sont des défauts structuraux d’équilibre. Nous avons choisi le système Fe-V –X (X = C, N ou O) comme matériau modèle d’un acier ferritique. Au sein de ce système, des amas lacunes-solutés interstitiels sont susceptibles de se former car, malgré les concentrations très faibles de leurs constituants, ces amas présentent une énergie de liaison importante. Dans cette étude, nous avons tout d’abord cherché à calculer les propriétés intrinsèques d’équilibre de ces amas traités individuellement, à la fois leur propriétés thermodynamiques (énergie libre de liaison) et cinétiques (mobilité, taux de dissociation, ainsi que leur lien avec une description continue de la diffusion). Cette caractérisation effectuée à l’échelle atomique a ensuite permis de mettre en évidence différents effets de ces amas sur un système macroscopique contenant simultanément différents types d’amas : augmentation des limites de solubilité des solutés et de la concentration totale des lacunes en solution solide, couplage de flux entre lacunes et solutés, accélération des cinétiques de précipitation des solutés et dissolution des précipités par une stabilisation de la solution solide par les lacunes. Ces résultats ont été obtenus grâce au développement et/ou à l’extension de méthodes analytiques de physique statistique qui décrivent les constituants de ces amas et leurs interactions à l’échelle atomique. Enfin, nous nous sommes également intéressés aux cavités dans le fer-α, dont l’étude nécessite une approche différente de celle des petits amas. Entre autres, nous avons étudié les effets d’un réseau discret sur la forme d’équilibre d’une cavité, et décrit différents mécanismes d’évolution de ces objets à l’échelle atomique
Understanding and monitoring the aging of steels under vacancy supersaturation is a challenge of great practical interest for many industrial groups, and most of all for those related to nuclear energy. These steels always contain interstitial solutes, either as alloying elements or as impurities, and vacancies (V) that are equilibrium structural defects of materials. We have chosen the Fe-V -X system (X = C, N or O) as a model system for ferritic steels. Vacancy-solute clusters are likely to form in such systems because, despite the very low concentrations of their components, these cluster show very high attractive bonding. First of all, we have been working on the computation of intrinsic equilibrium properties of individual clusters, both thermodynamic (free binding energies) and kinetic (mobilities, dissociation coefficients, and their relationship with continuum diffusion) properties. Thanks to this atomic-scale characterization procedure, we have been able to highlight various effects of these clusters on a macroscopic system containing different cluster types : increase of solute solubility limits and total vacancy concentrations, flux couplings between interstitial solutes and vacancies, acceleration of solute precipitation kinetics and precipitate dissolution by solid solution stabilization due to vacancies. These results would not have been obtained without the development and/or extension of analytical methods in statistical physics which are able to describe cluster’s components and their interactions at the atomic scale. Finally, we have also been working on cavities in α-iron, the study of which requires a different approach. Our study highlights the impact of the atomic discrete lattice on the equilibrium shape of cavities, and describes various kinetic mechanisms of these objects at the atomic scale

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下田, 昌利, Masatoshi Shimoda, 秀幸畔上, Hideyuki Azegami, 俊明桜井, and Toshiaki Sakurai. "複数荷重を考慮した線形弾性体の多目的形状最適化(平均コンプライアンス最小化問題を例として)." 日本機械学会, 1995. http://hdl.handle.net/2237/7241.

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45

SHIMODA, Masatoshi, Hideyuki AZEGAMI, and Toshiaki SAKURAI. "Multiobjective Shape Optimization of Linear Elastic Structures Considering Multiple Loading Conditions (Dealing with Mean Compliance Minimization problems)." 日本機械学会, 1996. http://hdl.handle.net/2237/12155.

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46

Guillon, Emmanuel. "Durabilité des matériaux cimentaires : modélisation de l'influence des équilibres physico-chimiques sur la microstructure et les propriétés mécaniques résiduelles." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2004. http://tel.archives-ouvertes.fr/tel-00133395.

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Les performances des matériaux de construction à matrice cimentaire proviennent principalement du ciment hydraté. Grâce à l'expérimentation et à la modélisation ces matériaux ont pu être adaptés à certains environnements chimiquement agressifs. Nous proposons une nouvelle approche basée sur les transports réactifs, applicable à tout solution agressive externe. L'évolution des minéraux de la matrice cimentaire, par dissolutions ou précipitations, est mise en relation avec celle de la solution interstitielle, elle même reliée aux échanges ioniques avec l'extérieur. Les dégradations chimiques modifient la microstructure du matériau, qui est modélisée par des images digitalisées. Notre approche a été validée sur trois matériaux différents, dans trois environnements distincts. Un modèle mécanique aux éléments-finis, complémentaire, caractérise l'évolution du module de Young résiduel du matériau dégradé en utilisant la représentation digitalisée de la microstructure.

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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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48

Olchitzky, Estelle. "Couplage hydromécanique et perméabilité d'une argile gonflante non saturée sous sollicitations hydriques et thermiques." Phd thesis, Marne-la-vallée, ENPC, 2002. https://pastel.archives-ouvertes.fr/tel-00005692.

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Dasht, Bozorg Amin. "Mechanical developmentfor a softrobotics solution." Thesis, KTH, Maskinkonstruktion (Inst.), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-187475.

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Bioservo Technology AB är ett företag som etablerades i Sverige 2006 . Företaget sammarbetar med läkare och sjukhus för att utveckla produkter för att hjälpa de som har svaga muskler.Det här examensarbete, som gjordes på Biservo Tecknology AB i Stockholm, är en del av projektet Iron Arm, som börjades 2014. Syftet med Iron Arm projektet är att assistera äldre som lider av nedsatt muskelstyrka och därmed har svårt att lyfta armen. I detta examensarbete konstrueras en aktuator som ger extra kraft för att lyfta armen och underlätta vardagsarbeten, som att kamma håret, äta mat, laga mat och att ta på sig ytterkläder.
Nowadays, the human ability to utilize the technology has increased. One of the most important branches of technology in human service is Robotics, which helps humans to perform their daily work.This thesis is a part of a big project (Iron Arm) that was done at the Bioservo Technology AB in Kista-Stockholm. Bioservo exerts its effort to use SEM™ (Soft Extra Muscle) technology to build the new products. The aim of this thesis work was to design an effective mechanical actuator that will complete the former prototype built by Bioservo through another master thesis work done by John Ekblom in 2014. The thesis also describes how a mechanical actuator can be used in a device (robotic arm) to provide extra force and to assist someone who has weak arm lifting muscles. A big challenge for this device is to have a low weight because the user should wear the device and carry it during the entire day.

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Chilcott, Mark David. "Mechanics of non-Newtonian fluids." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329946.

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