Tesis: "Thermal and thermomechanical simulation"

1

Nogales, Tenorio Sergio. "Numerical simulation of the thermal and thermomechanical behaviour of metal matrix composites /". Düsseldorf : VDI-Verl, 2008. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=017035682&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

2

Jia, Yabo. "Numerical simulation of steady states associated with thermomechanical processes". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEE007.

Texto completo

Resumen

De nombreux procédés de fabrication thermomécanique comme le laminage, le soudage ou encore l’usinage mettent en jeu soit des sollicitations mobiles par rapport à la matière fixe, soit de la matière mobile par rapport à des sollicitations fixes. Dans tous les cas, après un régime transitoire en général assez court, les champs thermiques, métallurgiques et mécaniques associés à ces procédés atteignent un état stationnaire. La recherche de ces états stationnaires à l’aide de la méthode des éléments finis classique nécessite de mettre en œuvre des modèles complexes et couteux où les sollicitations se déplacent par rapport à la matière (ou l’inverse). La recherche directe des états stationnaires a fait l’objet de nombreux travaux de recherche ces trente dernières années. Des méthodes sont aujourd’hui disponibles et pour certaines sont proposées dans des codes de calcul du commerce. Ainsi, une option de calcul dite repère mobile proposée par différents auteurs est disponible dans le logiciel SYSWELD. Cette méthode permet de calculer les états thermique, métallurgique et mécanique stationnaires associés à un procédé de soudage, en résolvant un problème de diffusion-convection en thermique et en intégrant, en mécanique, les équations constitutives du comportement du matériau le long des lignes de courant. Si cette méthode a été utilisée avec succès dans de nombreuses applications, elle présente néanmoins quelques limitations. Ainsi le maillage doit être structuré et la convergence des calculs est en général assez lente. Nous proposons dans cette thèse de résoudre le problème mécanique dans un repère lié aux sollicitations, en nous appuyant sur une méthode de calcul par éléments finis reposant sur l’intégration nodale et la technique SCNI (Stabilized Conforming Numerical Integration). Cette méthode permet l’utilisation de maillages en tétraèdres (ou triangles en 2D) sans rencontrer de problème de verrouillage volumique résultant de l’incompressibilité plastique associée au critère de plasticité de von Mises. Plutôt que de rechercher directement l’état stationnaire, l’idée générale est ici de construire l’état stationnaire à partir d’une analyse transitoire en faisant entrer pas à pas la matière par l’amont et en la faisant sortir par l’aval d’un maillage fixe par rapport aux sollicitations et de taille limitée. L’état stationnaire n’est donc atteint qu’au bout d’un certain temps d’analyse. Après une introduction générale (Chapitre 1) et un état de l’art sur les méthodes existantes (Chapitre 2), nous présentons une approche de simulation du mouvement de matière dans le cadre de la méthode des éléments finis classique sur un problème de soudage (Chapitre 3). Nous y proposons également des conditions aux limites thermiques pertinentes pour calculer directement la distribution de températures en régime stationnaire. La méthode des éléments finis reposant sur l’intégration nodale est ensuite décrite au Chapitre 4. Les avantages et inconvénients de la méthode sont discutés. La méthode est validée sur une application en grandes déformations élastoplastiques, un problème de flexion et une simulation thermomécanique de soudage. La méthode des éléments finis reposant sur l’intégration nodale est alors développée pour prendre en compte un mouvement de matière (Chapitre 5). Trois types de mouvement sont considérés : en translation, circulaire et en hélice. Différentes méthodes de transport de champ sont abordées et discutées ainsi que le couplage thermomécanique. Des perspectives à ce travail sont proposées au Chapitre 6. Les perspectives envisagées visent d’une part à améliorer la méthode proposée et d’autre part, à développer la méthode pour simuler d’autres procédés. Une première application de la méthode à la simulation de la coupe orthogonale y est présentée
In the numerous thermomechanical manufacturing processes such as rolling, welding, or even machining involve either moving loads with respect to the fixed material or moving material with respect to fixed loads. In all cases, after a transient regime which is generally quite short, the thermal, metallurgical, and mechanical fields associated with these processes reach a steady state. The search for these stationary states using the classical finite element method requires the implementation of complex and expensive models where the loads move with respect to the material (or vice versa). The steady-state simulation in one increment has been the subject of much researches over the past thirty years. Methods are now available and some are integrated into calculation codes commercial. Thus, a so-called Moving Reference Frame method proposed by various authors is available in the SYSWELD software. This method makes it possible to calculate the steady-state of thermal, metallurgical, and mechanical states associated with a welding process, by solving a thermal diffusion-convection problem in thermal-metallurgy and by integrating, in mechanics, the constitutive equations of the material along the streamline. Moreover, this method has been used successfully in many applications, it nevertheless has some limitations. Thus the mesh must be structured and the convergence of computations is generally quite slow. In this thesis, we propose to solve the mechanical problem in a frame linked to the solicitations, by relying on a finite element calculation method based on nodal integration and the SCNI (Stabilized Conforming Numerical Integration) technique. This method allows the use of tetrahedron meshes (or 2D triangles) without encountering a locking problem resulting from the plastic incompressibility associated with the von Mises plasticity criterion. Rather than directly calculating the steady-state, the general idea here is to construct the steady-state from a transient analysis by bringing material step by step upstream and by making it exit downstream of a fixed mesh related to the solicitations and of the limited mesh size. The steady-state is therefore only achieved after certain steps of analysis. Apart from a general introduction (Chapter 1) and a state of the art on the existing methods (Chapter 2), we present an approach of simulation of the movement of material within the framework of the classical finite element method on a welding problem (Chapter 3). We also provide relevant thermal boundary conditions for directly calculating the steady-state of temperature distribution. The finite element method based on the nodal integration technique is then described in Chapter 4. The advantages and disadvantages of the method are discussed. The nodal-integration-based finite element is validated by comparing its simulation results with classical finite element methods in large elastoplastic strains, a bending problem, and a thermomechanical simulation of welding. The nodal-integration-based finite element is then developed and applied to simulate material motion (Chapter 5). Three types of movement are considered: translational, circular, and helical. Different methods of field transport are approached and discussed as well as thermomechanical coupling. Perspectives for this work are presented in Chapter 6. The envisaged perspectives aim, on the one hand, to improve the proposed method and on the other hand, to develop the method to simulate other processes. A first application of the material motion method to the simulation of the orthogonal cut is presented there

Los estilos APA, Harvard, Vancouver, ISO, etc.

3

Pimenta, Paulo Vicente de Cassia Lima. "Thermomechanical simulation of continuous casting process using element based finite-volume method". Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=13684.

Texto completo

Resumen

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior
The continuous casting technique in the last four decades has been large used for to production of semi-finished steel. The heat transfer is major mechanism and it occurs in various steps during the continuous casting. The quality of steel is directly related to the way the heat transfer occur because the thermal variations produce mechanical loads as well as contact forces which are generated through the rollers and shake of the mold. Such factors may cause defects such as fractures or cracks in the final product if the resulting stresses and strains exceed critical values. The technique must be improved in order to reduce the appearance of defects and the production time. For this a good understanding of physical phenomena involved during the solidification process is critical. The focus of this work is to apply the EbFVM (Element based Finite-Volume Method) approach to study the effects of linear tensions unidirectionally coupled with the temperature applied to continuous casting of the steel 1013D (0,3% of carbon) In the simulations we adopted some simplifications such as the Plane Strain and isotropic material. We also neglected the body forces contact with the rollers the liquid pressure on the walls of the steel ingot (ferrostatic pressure) and the convective effect. However despite of the simplifications adopted this work provides quantitative informations on the linear tensions accumulation that point out to areas of possible of cracks formations
A tÃcnica de lingotamento contÃnuo nas Ãltimas quatro dÃcadas Ã cada vez mais utilizada na produÃÃo de aÃo semiacabado. A transferÃncia de calor Ã o principal mecanismo dominante e ocorre em todas as etapas do processo. A qualidade do aÃo no lingotamento estÃ diretamente relacionada Ã forma que ocorrem as trocas de calor pois as variaÃÃes tÃrmicas produzem carregamentos mecÃnicos assim como as forÃas de contato as quais sÃo geradas por intermÃdio dos rolos e da oscilaÃÃo do molde. Tais fatores podem causar defeitos como fraturas ou trincas no produto final caso as tensÃes e deformaÃÃes resultantes excedam valores crÃticos. O aprimoramento da tÃcnica tem a finalidade de evitar o surgimento de defeitos e reduzir o tempo de produÃÃo. Para isso Ã fundamental uma boa compreensÃo dos fenÃmenos fÃsicos envolvidos ao longo do processo de solidificaÃÃo. O foco deste trabalho Ã aplicar a abordagem do EbFVM (Element based Finite-Volume Method) no estudo dos efeitos das tensÃes lineares acopladas unidirecionalmente com a temperatura aplicado ao lingotamento contÃnuo do aÃo 1013D (0,3% de carbono) Nas simulaÃÃes adotou-se algumas simplificaÃÃes com o estado plano de tensÃes e isotropia do material. Descartando-se as forÃas de corpo o contato com os rolos a pressÃo do aÃo lÃquido nas paredes do lingote (pressÃo ferrostÃtica) e o efeito convectivo. Contudo apesar das simplificaÃÃes adotadas este trabalho traz informaÃÃes quantitativas quanto a formaÃÃo do acÃmulo das tensÃes lineares que apontam para regiÃes de possÃveis formaÃÃes de trincas

Los estilos APA, Harvard, Vancouver, ISO, etc.

4

Rombo, Oskar. "Software Benchmark and Material Selection in an Exhaust Manifold : Thermo-mechanical fatigue simulation of an exhaust manifold in AVL Fire M". Thesis, Karlstads universitet, Institutionen för ingenjörsvetenskap och fysik (from 2013), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-68662.

Texto completo

Resumen

Today, there is a great focus on downsizing the engines, this means that the engines are made smaller in size but retain the same power. This in combination with the drive to increase the power of the engines has led to the engine components being exposed to high thermal loads. Today’s engines also use very high cylinder pressure. The high thermal loads in combination with the high cylinder pressure have led to that the engine components are often very close to their material limits, so close that damage is common. This places high requirements on the materials, which makes the material selection a critical part of the engineering process.The main focus in this thesis work has been to develop and investigate a FEM model that can be used to quickly evaluate materials in an exhaust manifold that is exposed to thermo-mechanical fatigue (TMF). The model was then used to verify a material selection made for an existing exhaust manifold. One of AVL’s own software programs has also been evaluated, to see if it is a viable alternative to ABAQUS when preforming TMF simulations.The material selection made in this master thesis had the restriction that the exhaust manifold should not fail due to low cycle fatigue (LCF) when exposed to TMF. The goal has been to minimize the mass of the exhaust manifold by selecting a strong material with low density. The reason for this is because today there is a big focus on energy efficient cars with low emission levels. The simplest way to achieve this is to minimize the mass of the vehicle.The simulations conducted in this work has been performed in two different software’s, ABAQUS and AVL Fire M. In AVL Fire M flow simulations and steady-state heat transfer simulations have been performed. In ABAQUS, steady-state and transient heat transfer simulations and stress-strain simulations have been performed.The material selection process showed that Inconel 601 is the most suitable material for an exhaust manifold exposed to TMF. The simulations using Inconel 601 showed that this material will not fail due to LCF.The FEM model that was developed in this thesis was a lot faster compared to the existing TMF model used at AVL.CPU time for the existing model: 14 days 13 hours 14 minutes and 30 seconds (Core time).CPU time for the model developed in this thesis: 1 day 6 hours 37 minutes and 49 seconds (Core time).Two alternative models have been proposed for TMF simulations, one that uses the model developed in this thesis and one that is a combination of the existing model and the model developed in this work.

Los estilos APA, Harvard, Vancouver, ISO, etc.

5

Sahli, Mehdi. "Simulation and modelling of thermal and mechanical behaviour of silicon photovoltaic panels under nominal and real-time conditions". Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAD036.

Texto completo

Resumen

Le travail présenté dans cette thèse porte sur le développement d’un modèle multi-physique numérique, destiné à étudier le comportement optique, électrique et thermique d’un module photovoltaïque. Le comportement optique a été évalué en utilisant des chaines de Markov. Le comportement électrique est obtenu pour les panneaux en Silicium à l’aide d’une méthode d’optimisation numérique. Le comportement thermique est développé en 1D sur l’épaisseur du module, et le modèle multi-physique a été faiblement couplé sous MATLAB. Le comportement sous des conditions nominales d’opération a été validé en utilisant les données déclarées par les constructeurs. Ce modèle a été utilisé pour effectuer une étude paramétrique sur l’effet des irradiances solaires en régime permanent. Le modèle a été validé pour des conditions d’utilisations réelles en comparant avec des mesures expérimentales de température et de puissance électrique. Une étude thermomécanique en 2D sous ABAQUS/CAE et se basant sur le modèle multi-physique a été effectué en conditions nominales d’opération, ainsi qu’en cycle de fatigue selon la norme 61215 pour prédire les contraintes qui sont imposées sur le panneau dans les deux cas mentionnés précédemment
The work presented in this thesis deals with the development of a numerical multi-physics model, designed to study the optical, electrical and thermal behaviour of a photovoltaic module. The optical behaviour was evaluated using stochastic modelling based on Markov chains, whereas the electrical behaviour was drawn specifically for Silicon based photovoltaic panels using numerical optimization methods. The thermal behaviour was developed in 1D over the thickness of the module, and the multi-physics module was weakly coupled in MATLAB. The behaviour of commercial panels under nominal operation conditions was validated using data declared by the manufacturers. This model was used to perform a parametric study on the effect of solar irradiances in steady state. It was also validated for real use conditions by comparing it to experimental temperature and electrical power output. A thermomechanical study in 2D in ABAQUS/CAE based in the multi-physics model was carried out in nominal operating conditions, as well as in fatigue thermal cycling according to the IEC 61215 Standard to predict the stresses that are imposed on the panel

Los estilos APA, Harvard, Vancouver, ISO, etc.

6

Feng, Wei. "Caractérisation expérimentale et simulation physique des mécanismes de dégradation des interconnexions sans plomb dans les technologies d’assemblage a trés forte densite d’intégration « boitier sur boitier »". Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14014/document.

Texto completo

Resumen

Les assemblages PoP pour « Package on Package » permettent d’augmenter fortement la densité d’intégration des circuits et systèmes microélectroniques, par superposition de plusieurs éléments semi-conducteurs actifs. Les interconnexions internes de ces systèmes sont alors soumises à des contraintes jamais atteintes. Nous avons pu identifier, caractériser, modéliser et simuler les mécanismes de défaillance potentiels propres à ces assemblages, et leur évolution : • Les gauchissements dans la phase d’assemblage du « PoP » et ses contraintes thermomécaniques sont plus importants que ceux de chacun des composants individuels. Un modèle analytique original a été construit et mis en ligne afin d’évaluer a priori ce gauchissement. • Les comportements hygroscopiques et hygromécaniques sont simulés et mesurés par une approche originale. L’assemblage « PoP » absorbe plus d’humidité que la somme des deux composants individuels, mais son gauchissement hygromécanique et ses contraintes hygromécaniques sont moins élevées. • Deux types d’essais de vieillissement accéléré sont réalisés pour étudier la fiabilité du « PoP » assemblé sur circuit imprimé : des cycles thermiques et des tests sous fort courant et température élevée. Dans ces deux types d’essais, l’assemblage d’un composant « top » sur un autre composant « bottom » pour former un PoP augmente les risques de défaillances. • L’évolution de la microstructure selon le type de vieillissement est comparée par des analyses physiques et physico-chimiques. Les fissures sont toujours situées dans l’interface substrat/billes, qui correspond aux zones critiques prédites par les simulations
The assemblies PoP (Package on Package) can greatly increase the integration density of microelectronic circuits and systems, by vertically combining discrete semiconductor elements. The interconnections of these systems suffer the stresses never reached before. We were able to identify, characterize, model and simulate the potential failure mechanisms of these assemblies and their evolution: • The warpage in the assembly phase and thermomechanical stress of "PoP" are more serious than the individual components. An original analytical model has been built and put online for pre-estimating this warpage. • The hygroscopic and hygromechanical behaviors are simulated and measured by an original method. The assembly "PoP" absorbs more moisture than the sum of the individual components, but its hygromechanical warpage and stress are smaller. • Two types of accelerated aging tests are performed to study the reliability of "PoP" at the board level: the thermal cycling and the testing under current and temperature. In both types of tests, assembly a component "top" on another component "bottom" to form a “PoP” increases the risk of failure. • The microstructure evolution depending on the type of aging is compared by the physical and physico-chemical analysis. The cracks are always located in the interface substrate/balls, which corresponds to the critical areas predicted by the simulations

Los estilos APA, Harvard, Vancouver, ISO, etc.

7

Guzman, Maldonado Eduardo. "Modélisation et simulation de la mise en forme des composites préimprégnés à matrice thermoplastiques et fibres continues". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI015/document.

Texto completo

Resumen

Les matériaux composites sont largement employés dans le domaine aérospatial grâce à leurs excellentes propriétés mécaniques, leur résistance aux chocs et à la fatigue, tout en restant plus légers que les matériaux conventionnels. Au cours des dernières années, l'industrie automobile a montré un intérêt croissant pour les procédés de fabrication et de transformation de matériaux composites à matrice thermoplastiques. Cela favorisé par le développement et l'optimisation des procèdes de mise en forme tels que le thermostampage, en vue de la réduction de temps de cycle. La modélisation et la simulation de ce procédé sont des étapes importantes pour la prédiction des propriétés mécaniques et de la faisabilité technique des pièces à géométrie complexe. Elles permettent d'optimiser les paramètres de fabrication et du procédé lui-même. À cette fin, ce travail propose une approche pour la simulation de la mise en forme des matériaux composites préimprégnés thermoplastiques. Un modèle viscohyperélastique avec une dépendance à la température a été proposé dans l'objectif de décrire le comportement du composite thermoplastique à l'état fondu. Et permets de faire des simulations de mise en forme à différentes températures. Au cours cette simulation, des calculs thermiques et mécaniques sont effectués de manière séquentielle afin d'actualiser les propriétés mécaniques avec l'évolution du champ température. L'identification des propriétés thermiques sont obtenues par homogénéisation à partir des analyses au niveau mésoscopique du matériau. La comparaison de la simulation avec le thermoformage expérimental d'une pièce représentative de l'industrie automobile analyse la pertinence de l'approche proposée
Pre-impregnated thermoplastic composites are widely used in the aerospace industry for their excellent mechanical properties, impact resistance and fatigue strength all at lower density than other common materials. In recent years, the automotive industry has shown increasing interest in the manufacturing processes of thermoplastic-matrix composites materials, especially in thermoforming techniques for their rapid cycle times and the possible use of pre-existing equipment. An important step in the prediction of the mechanical properties and technical feasibility of parts with complex geometry is the use of modelling and numerical simulations of these forming processes which can also be capitalized to optimize manufacturing practices.This work offers an approach to the simulation of thermoplastic prepreg composites forming. The proposed model is based on convolution integrals defined under the principles of irreversible thermodynamics and within a hyperelastic framework. The simulation of thermoplastic prepreg forming is achieved by alternate thermal and mechanical analyses. The thermal properties are obtained from a mesoscopic analysis and a homogenization procedure. The comparison of the simulation with an experimental thermoforming of a part representative of automotive applications shows the efficiency of the approach

Los estilos APA, Harvard, Vancouver, ISO, etc.

8

Mostallino, Roberto. "Développement de diodes laser émettant à 975nm de très forte puissance, rendement à la prise élevé et stabilisées en longueur d’onde pour pompage de fibres dopées et réalisation de lasers à fibre". Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0132/document.

Texto completo

Resumen

Cette thèse CIFRE adresse le développement de diodes laser, émettant à 975nm, de très forte puissance, rendement à la prise élevé, et stabilisées en longueur d’onde pour pompage de fibres dopées Er/Yb et réalisation de lasers à fibre. La thèse a été développée dans le cadre d’un partenariat étroit entre le Laboratoire IMS, le GIE III-V Lab, principal fondeur français de composants à semiconducteurs III-V pour des applications électroniques et photoniques, et THALES Research & Technology à Palaiseau en région parisienne. Un travail en profondeur de caractérisation et d’analyse a porté sur les aspects thermiques qui contribuent, en particulier,à limiter les niveaux de puissance optique de sortie. Dans ce cadre, nous avons réalisé un ensemble de caractérisations complémentaires au GIE III-V lab et à l’IMS nous permettant d’envisager des solutions correctives d’optimisation technologique portant en particulier sur la profondeur de gravure définissant la largeur de la zone d’émission et la nature du substrat dissipateur. Ces solutions ont été proposées à partir de modélisations physiques mises en oeuvre avec un simulateur dédié, propriété de III-V Lab et de simulations par éléments finis thermiques et thermomécaniques (approche multiphysique) de la structure microassemblée définitive. Ces travaux se sont prolongés par la fabrication et la caractérisation électro-optique et thermique de plusieurs structures verticales : LOC (Large Optical Cavity), SLOC (Super Large OpticalCavity) et AOC (Asymetrical Optical Cavity). Les diodes laser de type LOC et SLOC sont stabilisées en longueur d’onde en intégrant un réseau de Bragg (DFB). Une puissance optique de 8W avec une efficacité de 60% a été obtenue ; ce qui permet de situer ces travaux à l’état de l’art international notamment vis-à-vis de ceux publiés par l’Institut Ferdinand-Braun.L’originalité des travaux menés dans cette thèse nous a permis d’avoir accès à une bourse du Cluster européen « Laserlab » (The Integrated Initiative of European Laser Research Infrastructures), pour conduire des campagnes d’expérimentation à l’Institut Max Born à Berlin dans le groupe du Dr J.W. Tomm. Les travaux ont porté sur la caractérisation thermique de ces diodes laser de forte puissance émettant à 975nm, à double hétérostructure symétrique et asymétrique (SLOC et AOC), en utilisant des techniques complémentaires (microphotoluminescence,photoluminescence résolue en temps, spectroscopie de photocourant et mesures L-I pulsées) et permettant d’évaluer le type de contraintes résiduelles apportées par les étapes de report de la diode Laser ainsi que la cinétique de dégradation catastrophique de type COD
This PhD addresses the development of high-power laser diodes emitting at 975nm withhigh efficiency and wavelength stabilized using a Bragg grating. This thesis was conducted in the framework of a close partnership between IMS Laboratory, the GIE III-V lab, who is themain French founder of III-V semiconductor devices for electronic and photonic applications,and THALES Research & Technology in Palaiseau. An in-depth characterization and analysiswork has addressed thermal aspects that contribute, in particular, to limit the optical outputpower of a laser diode. In such a context, we have carried out a set of complementary characterizations both at III-V lab and IMS allowing us to provide some corrective solutionsfor technological optimization concerning the etching depth of the grooves that defines the emitting stripe of the laser diode and the nature of the submount acting as a thermocompensator.These solutions have been proposed from optical modelling implemented with a dedicated simulator, property of III-V lab, and thermal and thermomechanical (multiphysics approach) finite element simulations of the overall microassembled structure. All this work has resulted in the fabrication as well as electro-optical and thermal characterizations of three vertical structures namely LOC (Large Optical Cavity), SLOC (Super Large Optical Cavity)and AOC (Asymmetrical Optical Cavity). The LOC and SLOC vertical structures have been processed with a Fabry-Perot cavity and also including a Bragg grating (DFB architecture) while the AOC one was only fabricated with a Fabry-Perot cavity. State-of-the-art results aredemonstrated since in particular an optical power of 8W with an efficiency of 60% has been obtained that can be compared to those recently published by the Ferdinand-Braun Institute.The originality of the work carried out in this PhD has allowed us to receive a grant from the European Laserlab Cluster (The Integrated Initiative of the European Laser Research Infrastructures), to conduct dedicated experiments at the Max-Born Institute (Berlin) in thegroup of Dr. J.W. Tomm. The work aimed to characterize mechanical strain of the laser diode induced by the soldering process. Two vertical structures (SLOC and AOC) were investigated using complementary techniques (microphotoluminescence, time-resolved photoluminescence,photocurrent spectroscopy and pulsed L-I measurements), allowing to quantify the level of residual stress provided by the laser diode mounting process as well as the kinetics of the catastrophic degradation process (COD)

Los estilos APA, Harvard, Vancouver, ISO, etc.

9

Barth, Nicolas. "Sur la modélisation et la simulation du comportement mécanique endommageable de verres borosilicatés sous sollicitation thermique". Thesis, Strasbourg, 2013. http://www.theses.fr/2013STRAD016/document.

Texto completo

Resumen

On étudie le comportement thermomécanique de colis de déchets vitrifiés par modélisation multi- physiques. Les colis sont réalisés avec un conteneur en acier inoxydable dans lequel est coulé un verre borosilicaté. Pour le verre, la méthode des éléments finis est employée pour les calculs thermiques, la relaxation structurale du volume massique, le comportement viscoélastique et l’endommagement. Ces lois consécutives modélisent l’influence de la sollicitation thermique initiale. La relaxation structurale du verre, issue du modèle TNM-KAHR, permet la prise en compte d’effets fondamentaux quant à la transition vitreuse, en fonction des traitements thermiques expérimentaux et simulés. Lorsque le verre dépasse localement une criticité du champ de contrainte, on procède au couplage du calcul de structure viscoélastique, pour le verre solide en relaxation,avec la mécanique de l’endommagement qui réactualise la rigidité et les contraintes en mode I et en mode II. On applique cette méthodologie complète de simulation à l’issue des adaptations nécessaires au cas de blocs de verre massifs en solidification. Ces modèles permettent alors l’obtention de surfaces de fracturation quantifiées, dans le verre, à partir de l’énergie dissipée par le modèle d’endommagement
We study the thermomechanical behavior of vitrified waste packages by multiphysics modeling. The packages are manufactured by the cast of borosilicate glass into stainless steel canisters. The finite element method is used for the thermal computations.In the glass, the finite element analysis is also used to compute the specific volume evolution and the viscoelastic behavior, due to the structural relaxation of glass, as well as the simulation of the damage behavior. These consecutive behavior laws model theinfluence of the initial thermal response. Glass structural relaxation is computed using the TNM-KAHRmodel, which allows us to take into account fundamental phenomena of the glass transition, depending on the results of experimental and simulated thermal treatments. For the solid glass within this relaxation process, the stress may locally increase beyond critical values. The viscoelastic structure simulation is then coupled with continuum damage mechanics where stresses and stiffness are updated in mode I and mode II. We apply this simulation protocol after adopting conditions relative to the case of these manufactured bulky solidifying glass casts. The models then allow us to quantify the cracking surfaces inside the glass fromthe energy dissipated within the damagemodel

Los estilos APA, Harvard, Vancouver, ISO, etc.

10

Salmon, Fabien. "Simulation aéro-thermo-mécanique des effets du feu sur les parois d'un milieu confiné : application à l'étude des thermo-altérations de la grotte Chauvet-Pont d'Arc". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0041/document.

Texto completo

Resumen

En 1994, la découverte de la grotte Chauvet-Pont d'Arc (Ardèche, France) révéla des marquesthermiques, d'origine anthropique, uniques au monde. Elles sont les témoins de feux préhistoriqueseffectués dans la partie profonde de la cavité. La datation par thermoluminescence des chauffes estcohérente avec la première période de fréquentation humaine il y a entre 37 000 et 33 500 ans. Lesarchéologues ont identifié deux types de thermo-altérations : des changements de couleur et desécaillages. Les changements de couleur résultent de réactions chimiques s'opérant à hautetempérature dans le calcaire, rendant la roche rouge ou grise. Des essais ex situ ont montré que lacouleur rouge survient après une chauffe de 10 minutes à 250oC tandis qu'une température minimumde 350oC est nécessaire pour la couleur grise. Le phénomène d'écaillage provient de fortes contraintesmécaniques dans la roche causées par la dilatation thermique et des processus thermo-hydriques. Deplus, des particules de suie recouvrent encore une partie des parois dans les zones altérées. À partirde ces indices, l'objectif de la thèse est de caractériser les feux de la Galerie des Mégacéros qui sesitue dans la partie profonde de la grotte. L'estimation des quantités de bois, du nombre de feux etde la capacité à alimenter les foyers pourrait aider les archéologues à faire des hypothèses sur lafonction de ces feux.Pour des raisons de conservation, seule la simulation peut reproduire des feux dans la géométrie de lagrotte sans nécessiter sa reconstitution. Cette étude consiste à construire une modélisation numériquede feux confinés et des impacts thermiques résultants. Un couplage fluide-structure est donc développéà partir de deux logiciels open source : OpenFOAM et Cast3m. Le premier effectue la simulation descénarios de feux grâce au module FireFOAM. Le second réalise les calculs thermo-mécaniques dansle massif. Afin d'étendre le champ d'application initial de FireFOAM, des modèles numériques ontété implémentés dans le code. Ceux-ci concernent le dépôt de suie, l'évaluation des risques, lacorrection des mesures par thermocouple et une condition limite en température. De plus, quelquesexigences de modélisation améliorant la qualité des résultats sont détaillées dans le manuscrit. Lemodèle ainsi développé est validé sur des feux expérimentaux exécutés dans une ancienne carrière decalcaire dont les dimensions sont proches de celles de la Galerie des Mégacéros. Du pin sylvestre, quicorrespond à l'essence dont sont issus les échantillons de charbon analysés de la grotte, est utilisécomme combustible. La combustion aboutit à des thermo-altérations analogues à celles observéesdans la grotte Chauvet-Pont d'Arc. Des écaillages et des changements de couleur se sont produits auplafond et aux parois de la carrière. La comparaison avec la simulation est effectuée à partir desmesures de températures, de vitesses ainsi que de concentrations de gaz et de particules.Le modèle numérique est ensuite appliqué à la simulation de feux dans la géométrie de la Galerie desMégacéros. Toutes les zones altérées de cette galerie sont traitées et les scénarios qui ont pu se produiresont précisés. Ces travaux fournissent ainsi une vue d'ensemble de la localisation et de l'intensité desfeux dans cette partie de la grotte. De plus, l'adéquation avec les conditions de vie est indiquée pourles feux les plus puissants. Ces informations pourraient aider les archéologues dans la compréhensiondes fonctions de ces feux
In 1994, the discovery of the Chauvet-Pont d'Arc cave (Ardèche, France) revealed singularanthropogenic thermal marks on walls. They are the witnesses of high intensity prehistorical firescarried out deep in the cavity. The thermoluminescence evaluation of the heating ages is consistentwith the earlier period of human occupation between 37,000 and 33,500 years ago. The archaeologistsidentified two kinds of thermo-alterations : colour changes and spallings. The colour changes resultfrom high-temperature chemical reactions in limestone, turning rock red or grey. Ex situ tests showedthat red colour happens after heating at 250oC for ten minutes while at least 350oC is necessary forgrey. Spalling stems from high stresses in rock due to restrained thermal expansion and thermohydricprocesses. In addition, part of the walls near thermo-altérations is still covered with soot. From theseclues, this investigation aims to characterize the fires of the Megaloceros Gallery which is located inthe deep part of the cave. Estimating the amounts of wood, the fires number and the ability tosupply the hearths could help make assumptions about the function of these fires.For the sake of conservation, only simulation can reproduce fires in the cave geometry withoutrequiring any reconstruction. This study is to set up a numerical modelling of fires in confinedgeometries and the induced thermal impacts on walls. A fluid-structure coupling is then developedfrom two free open source codes : OpenFOAM and Cast3m. The former manages the simulation offire scenarios through the FireFOAM tool. The latter handles the thermo-mechanical calculations inthe rock mass. To extend the initial scope of FireFOAM, some numerical models have beenimplemented in the code. This relates to soot deposit, danger assessment, thermocouple correctionand a thermal boundary condition. In addition, some modelling requirements improving the qualityof the results are detailed in the manuscript. The advanced model is then validated on experimentalfires in a former limestone quarry which has dimensions close to the Megaloceros Gallery ones. Thesame fuel (pinus sylvestris) as the one identified in the cave is burnt. The combustion led to similarthermo-alterations as those observed in the Chauvet-Pont d'Arc cave. Spallings and colour changesoccurred on the ceiling and walls of the quarry. The comparison with simulation is carried out thanksto the measurement of temperatures, velocities, soot deposits, gases and particles concentrations.The numerical model is then applied to the simulation of fires in the Megaloceros Gallery geometry.All the impacted areas of this gallery are considered and the scenarios that may have occurred arespecified. This investigation then provides an overview of the fires locations and intensities in thispart of the cave. Moreover, the compatibility with living conditions is indicated for the most powerfulfires. These information could help for archaeologists in the understanding of the functions of these fires

Los estilos APA, Harvard, Vancouver, ISO, etc.

11

Sardo, Lucas. "Modélisation et simulation numérique de la thermomécanique des écoulements dans les co-malaxeurs". Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEM044/document.

Texto completo

Resumen

L’objectif de ce travail a été de modéliser les écoulements de polymères dans les co-malaxeurs de type BUSS. Le co-malaxeur est une extrudeuse particulière utilisée comme une boite noire depuis des dizaines d’années par des industriels. Sur le fourreau sont fixés des doigts de malaxage et la vis principale dispose d’interruptions de filets et oscille pour permettre le passage des doigts de malaxage dans les différents chenaux. Cet outil est utilisé pour gélifier du PVC ou disperser des charges dans des matrices polymères. Ce travail de thèse répond donc à un besoin industriel puisque, actuellement, mettre au point un produit nécessite de nombreuses heures d’essais coûteux.Un modèle thermomécanique instationnaire en deux dimensions fondé sur les approximations d’Hele-Shaw a été développé. La discrétisation du domaine du co-malaxeur a été faite par éléments finis. La résolution numérique s’effectue par éléments finis et éléments finis stabilisés par SUPG. La modélisation nous permet d’obtenir en tout point du domaine de calcul la pression, les vecteurs débits, les vitesses de cisaillement, la viscosité et la température.Les résultats issus des simulations nous permettent d’obtenir des ordres de grandeur de pressions et températures et des indices de mélange pour différentes conditions procédés. Une comparaison entre les résultats issus de la modélisation et des essais expérimentaux montre que, dans les zones remplies, le modèle donne des résultats satisfaisants
The aim of this study was to model molten polymers flow in BUSS type co-kneaders. The BUSS co-kneader is a particular single-screw extruder. It is composed of a rotating screw like standard single screw extruders, but with interrupted flights and mixing pins fixed to the barrel. The screw has also an axial reciprocal movement. It has been used for decades in industry for its mixing capacities, specifically for PVC gelification or polymer compounding with fibres, additives or carbon black. This work is therefore answering to nowadays industrial needs, as developing new products is expensive and time consuming.A 2D time-dependent thermomechanical model based on Hele Shaw approximations was developed and the co-kneader domain was discretized by finite elements. The numerical problem was solved by finite elements and SUPG stabilized finite elements. This model provides, at every point of the calculation domain, the pressure, throughput vectors, shear rates, viscosity as well as temperature.Simulation results provide pressure and temperature orders of magnitude, as well as information on polymer mixing depending on process parameters. A comparison between the model and experimental trials shows a satisfactory agreement in the filled zones

Los estilos APA, Harvard, Vancouver, ISO, etc.

12

Kakou, Luc Arnaud N'Doua. "Mesures et modélisations multi-physiques des dispositifs GaN pour la co-intégration SiP en technologie FOWLP". Electronic Thesis or Diss., Limoges, 2024. http://www.theses.fr/2024LIMO0123.

Texto completo

Resumen

Cette thèse, en lien avec le projet SMART3 du plan nano 2022, a pour but d’évaluer et de développer de nouvelles technologies de packaging 2D et 3D pour répondre à l’intégration hétérogène de différentes technologies de semi-conducteurs (GaN, AsGa, Si, …) afin de concevoir des systèmes entièrement intégrés appelés « System in Package ». La technologie utilisée est du type FO-WLP (Fan Out Wafer Level Packaging). Les défis d’intégration avec cette technologie nécessitent le plus souvent une approche multiphysique et un co-design circuits boitier pour permettre d’allier performances et fiabilité. Mon travail s’est focalisé sur les aspects thermiques et thermomécaniques de certains véhicules de test du projet et sur la comparaison avec des mesures thermiques et thermomécaniques. Les aspects multi-échelles ont également été abordés puisque nous avons par exemple effectué l’analyse thermique d’un dispositif en partant du transistor, en passant par le SiP et le SiP monté sur un PCB. D’un point de de vue thermomécanique, nous nous sommes intéressés au calcul de la déformation « warpage » dans les SiP. Nous avons comparé avec succès mesures et simulations sur le véhicule de test RIC 4X4
The aim of this thesis, which is linked to the SMART3 project of the nano 2022 plan, is to evaluate and develop new 2D and 3D packaging technologies to address the heterogeneous integration of different semiconductor technologies (GaN, GaAs, Si, ...) in order to design fully integrated systems known as ‘System in Package’. The technology used is FO-WLP (Fan Out Wafer Level Packaging). The challenges with this technology require a multiphysics approach and, very often, the co-design of the circuits with the package to combine performance and reliability. My work focused on the thermal and thermomechanical aspects of some test vehicles of the project and on their comparison with thermal and thermomechanical measurements. Multi-scale aspects were also addressed, as we carried out the thermal analysis of a device starting from the transistor, passing through the SiP and the SiP mounted on a PCB. From a thermomechanical point of view, we were interested in the calculation of warpage deformation in SiP. We have successfully compared measurement and simulation on the RIC 4x4 test vehicle

Los estilos APA, Harvard, Vancouver, ISO, etc.

13

Rodovalho, Francielle da Silva. "Simulação numérica de blocos e prismas de alvenaria em situação de incêndio". Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-27082018-123952/.

Texto completo

Resumen

A alvenaria estrutural é um sistema construtivo muito antigo no qual as paredes exercem função estrutural além da função de vedação. Este sistema construtivo é muito utilizado no Brasil, entretanto, poucas pesquisas foram realizadas sobre o seu comportamento em situação de incêndio e o país ainda não possui métodos normativos de dimensionamento de alvenaria estrutural em situação de incêndio. Assim, o objetivo deste trabalho foi verificar o desempenho da alvenaria estrutural com blocos de concreto submetida a elevadas temperaturas através da simulação de prismas. No software Abaqus foram simulados o comportamento do bloco e prisma sujeitos à compressão em temperatura ambiente e do prisma em situação de incêndio com diferentes condições de contorno. O comportamento do bloco e prisma sujeitos à compressão e em temperatura ambiente foi validado até a carga última. As elevações de temperatura das faces não expostas ao fogo ficaram bem representadas por meio das simulações térmicas. A perda de resistência dos materiais foi adotada conforme a literatura técnica nas simulações termomecânicas. Através do que foi analisado no trabalho observou-se que os prismas se comportam bem quanto ao isolamento térmico em situação de incêndio, principalmente aquele com revestimento em argamassa nas duas faces. Quanto ao critério de resistência mecânica os resultados numéricos não foram validados com experimentais, entretanto, foi possível representar a deterioração térmica dos materiais.
The structural masonry is a very old building system in which the walls have structural and partition function. The use of this building system is widely spread in Brazil, however, few research programs were carried out on their behavior under fire situation and the country has not yet developed standard normative methods for designing structural masonry subject to fire. Thus the purpose of this research was to verify the performance of concrete blockwork structural masonry submitted to high temperatures through the simulation of prisms. In the Abaqus software the behavior of block and prism subjected to compression at room temperature and of the prism under fire situation with different boundary conditions were simulated. The compression of the block and prism at room temperature was validated until ultimate loads. The temperature rises of the non-exposed faces were well represented through thermal simulations. The material\'s resistance loss was adopted according to the technical literature in the thermomechanical simulations. Based on the analyzed examples it was observed that the prisms behave well regarding the thermal insulation under fire situation, mainly when having mortar coating on both sides. Regarding the mechanical resistance criterion, the numeric results were not validated with experimental ones, however, it was possible to represent the thermal deterioration of the materials.

Los estilos APA, Harvard, Vancouver, ISO, etc.

14

Thompson, Joseph Andrew. "Thermomechanical behaviour of plasma-sprayed thermal barrier coatings". Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621757.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

15

Theodore, Fred. "Préformage de monocristaux de saphir optique : optimisation de la croissance hors fissuration par simulation numérique du problème thermomécanique". Grenoble INPG, 1998. http://www.theses.fr/1998INPG0100.

Texto completo

Resumen

Le preformage de monocristaux designe des methodes d'elaboration de geometries speciales au plus pres des cotes fonctionnelles. Nees de la necessite de controler le diametre des boules czochralski, ces techniques ont evolue jusqu'a concevoir le tirage au travers de filieres alimentees par des canaux capillaires. Applique au saphir, le preformage pose des problemes de qualite cristalline, de rupture fragile au cours de la croissance, et de respect des tolerances dimensionnelles. Des cristaux sont elabores par croissance capillaire classique et par une technique originale de preformage local dont on effectue la mise au point pour le tirage de tubes, de plaques, de cones, d'hemispheres, etc. Les pieces sont ensuite caracterisees pour verifier qu'elles conservent les proprietes optiques, notamment dans l'infrarouge, et les proprietes mecaniques des monocristaux massifs. Une grande part du travail realise consiste en la simulation numerique des conditions de croissance a haute temperature (t > 2000 c). Le calcul des echanges thermiques dans le four de tirage permet d'etablir les lois de regulation validees experimentalement. Un modele de comportement thermo-elasto-viscoplastique du saphir est mis en place et valide par la simulation d'essais mecaniques rapportes dans la litterature. La modelisation du comportement thermomecanique pendant la croissance donne ensuite une evolution fiable des contraintes dans le cristal et de la degradation de la qualite microstructurale par multiplication de dislocations. Elle est egalement appliquee a l'etude de conditions particulieres de tirage non realisees experimentalement. Enfin, ces calculs qui integrent toute l'histoire de la solidification determinent des criteres de compatibilite pour la croissance sans fissuration.

Los estilos APA, Harvard, Vancouver, ISO, etc.

16

Du, Yong. "Thermomechanical stress studies for advanced copper metallization and integration". Access restricted to users with UT Austin EID Full text (PDF) UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3031046.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

17

Neumann, Rudolf [Verfasser]. "Two-Scale Thermomechanical Simulation of Hot Stamping / Rudolf Neumann". Karlsruhe : KIT Scientific Publishing, 2017. http://www.ksp.kit.edu.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

18

Sharma, Bed P. "Effect of sonication on thermal, mechanical, and thermomechanical properties of epoxy resin /". Available to subscribers only, 2009. http://proquest.umi.com/pqdweb?did=1966551531&sid=3&Fmt=2&clientId=1509&RQT=309&VName=PQD.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

19

Sharma, Bed Prasad. "Effect of sonication on thermal, mechanical, and thermomechanical properties of epoxy resin". OpenSIUC, 2009. https://opensiuc.lib.siu.edu/theses/113.

Texto completo

Resumen

Epoxy resin is an important engineering material in many industries such as electronics, automotive, aerospace, etc not only because it is an excellent adhesive but also because the materials based on it provide outstanding mechanical, thermal, and electrical properties. Epoxy resin has been proved to be an excellent matrix material for the nanocomposites when including another phase such as inorganic nanofillers. The properties of a nanocomposite material, in general, are a hybrid between the properties of matrix material and the nanofillers. In this sense, the thermal, mechanical, and electrical properties of a nanocomposite may be affected by the corresponding properties of matrix material. When the sonication is used to disperse the nanofillers in the polymer matrix, with the dispersal of the nanofillers, there comes some modification in the matrix as well and it finally affects the properties of nanocomposites. In this regard, we attempted to study the thermal, mechanical, and dynamic properties of EPON 862 epoxy resin where ultrasonic processing was taken as the effect causing variable. Uncured epoxy was subjected to thermal behavior studies before and after ultrasonic treatment and the cured epoxies with amine hardener EPICURE 3223 (diethylenetriamine) after sonications were tested for mechanical and dynamic properties. We monitored the ultrasonic processing effect in fictive temperature, enthalpy, and specific heat capacity using differential scanning calorimetry. Fictive temperature decreased whereas enthalpy and specific heat capacity were found to increase with the increased ultrasonic processing time. Cured epoxy rectangular solid strips were used to study the mechanical and dynamic properties. Flexural strength at 3% strain value measured with Dillon universal testing machine under 3-point bending method was found to degrade with the ultrasonic processing. The storage modulus and damping properties were studied for the two samples sonicated for 60 minutes and 120 minutes. Our study showed that the 60 minutes sonicated sample has higher damping or loss modulus than 120 minutes sonicated sample.

Los estilos APA, Harvard, Vancouver, ISO, etc.

20

Trojanowski, Albin S. "Thermomechanical properties of polymers at high rates of strain". Thesis, University of Oxford, 1997. http://ora.ox.ac.uk/objects/uuid:a2c20a83-094d-4293-8c5f-665640c1ce5a.

Texto completo

Resumen

-1 were achieved when testing specimens and this rate was obtained using a split Hopkinson pressure bar. A substantial number of preliminary tests were conducted in order to obtain a suitable specimen size which was then used in the temperature measurement process. Quasistatic, intermediate and high strain-rate tests were performed; the last utilised the radiometer for temperature measurement. An Eyring plot was constructed from which fundamental values for activation volumes and enthalpies were obtained. Full descriptions of the testing techniques used have been included and a brief photoelastic analysis has been carried out on a partially deformed specimen which shows molecular alignment.

Los estilos APA, Harvard, Vancouver, ISO, etc.

21

Cowan, Richard Scott. "Development of tribological design strategies based on a thermomechanical wear transition model". Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17976.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

22

Goupee, Andrew. "Methodology for the Thermomechanical Simulation and Optimization of Functionally Graded Materials". Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/GoupeeA2005.pdf.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

23

Balboa, lópez Hector. "Simulation of thermomechanical properties of U-PuO2 nuclear fuel under irradiation". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX108/document.

Texto completo

Resumen

L’objectif de cette thèse a été d’utiliser une approche numérique pour étudier l’impact des dommages d'irradiation sur la microstructure du combustible nucléaire composé d'un mélange d’oxyde de plutonium et d’uranium (MOX). Cette approche, réalisée à l'échelle atomique, repose sur l'utilisation de potentiels empiriques développés dans la littérature pour l'oxyde mixte $(U,Pu)O_2$ dans l’approximation des interactions d’ions rigides.Une première étape a été une analyse critique des propriétés structurales, thermodynamiques et mécaniques prédites par 5 potentiels de la littérature. Les calculs de dynamique moléculaire ont été réalisés à l'aide du code LAMMPS, sur l'ensemble de la gamme de composition de $UO_2$ à $PuO_2$ et à des températures comprises entre 300 K et le point de fusion. Nous montrons que les potentiels les plus satisfaisants sont ceux développés par Cooper et Potashnikov. Ces deux potentiels reproduisent correctement la stabilité thermodynamique des phases ainsi que l'évolution en température des paramètres de maille et de la chaleur spécifique. Cependant le comportement mécanique des oxydes est différent selon le potentiel choisi. Tout d'abord, on note que les constantes élastiques et le facteur d'anisotropie obtenus par le potentiel Cooper sont plus fidèles aux recommandations de la littérature. Ensuite, nous montons que la propagation d'une fracture induit une transformation de phase en pointe de fissure avec le potentiel de Cooper alors qu'une fissuration fragile est observée avec le potentiel Potashnikov.Une seconde étape a été l'étude des dommages d'irradiation dans les oxydes mixtes en se limitant à l'utilisation des deux potentiels de Cooper et de Potashnikov. Des calculs de dynamique moléculaire de cascades de déplacement ont été réalisés à différentes énergies, température et compositions en plutonium. Ensuite, afin d'évaluer les dommages d'irradiation sur des temps plus longs que ceux accessibles en dynamique moléculaire, la méthode d’accumulation de défauts a été utilisée. Pour les deux potentiels, l’évolution des dommages primaires avec l’augmentation de la dose suit globalement les mêmes étapes que celles trouvées précédemment dans $UO_2$. Tout d’abord, les défauts ponctuels sont créés. Par la suite, ils se regroupent et forment de petites boucles de Frank, qui après se transforment en dislocations parfaites. Cependant, la cinétique de la recombinaison de défauts ponctuels est significativement plus lente avec le potentiel de Cooper ce qui conduit à la création de petites régions désordonnées pour les cascades d'énergie élevée. L’effet de la teneur en plutonium est analysé. Nous montrons en particulier que la densité de dislocations crée diminue lorsque la teneur en plutonium augmente.Bien que la dynamique moléculaire a été décrite comme un microscope moléculaire en raison de sa capacité à décrire avec précision des systèmes atomiques, elle présente un inconvénient majeur, celui lié aux temps de l’ordre de la femto-seconde nécessaires pour résoudre les vibrations atomiques. Cela limite le temps total de simulation approximativement quelques nanosecondes. Afin de stimuler les processus, tels que la diffusion de cations, un autre outil de calcul est nécessaire. Les techniques de Monte Carlo (KMC) atomiques peuvent simuler de plus longtemps que la dynamique moléculaire . Cependant, pour que KMC fonctionne avec précision, il est nécessaire de connaître a priori tous les mécanismes de transition entre les états possibles. Pour cette raison, la method de Monte Carlo cinétique adaptative (aKMC) est choisie pour surmonter ces limitations. Cette méthode détermine les états de transition disponibles pendant la simulation. De cette manière, elle entraîne le système dans des états imprévus via des mécanismes complexes. La puissance de cet outil s'est révélée efficace pour découvrir la recombinaison de cations sur de plus longues périodes de temps que la DM
The objective of this doctoral research is to use a numerical approach to study the impact of irradiation damage on the microstructure of the mixed uranium-plutonium oxide fuel (MOX). This numerical approach comprises mainly the use of Molecular Dynamics (MD) using empirical potential. Several empirical potentials for $(U,Pu)O_2$ can be found in the literature. The results of these potentials can exhibit significant differences. For this reason an extensive assessment of the main empirical potential found in the literature had to be performed.Five empirical interatomic potentials were assessed in the approximation of rigid ions and pair interactions for the $(U_{1-y},Pu_y)O_2$ solid solution. Simulations were carried out on the structural, thermodynamics and mechanical properties over the full range of plutonium composition, meaning from pure $UO_2$ to pure $PuO_2$ and for temperatures ranging from 300 K up to the melting point. The best results are obtained by potentials referred as Cooper and Potashnikov. The first one reproduces more accurately recommendations for the thermodynamics and mechanical properties exhibiting ductile-like behaviour during crack propagation, whereas the second one gives brittle behaviour at low temperature.From our results from the empirical potentials assessment, we can move to the radiation damage using only two potentials (Cooper and Potashnikov). In order to know the main source of defect during irradiation, MD displacement cascades were simulated. This revealed the damage created due to varying projectile energies. In addition, the Frenkel pair accumulation method was chosen to investigate the dose effect. This method circumvents the highly computing time demanding accumulation of displacement cascade by directly creating their final states, i.e. mainly point defects. Overall, results obtained with both potentials show the same trend. However, kinetics of point defect recombination are significantly slower with Cooper potential implying creation of small disordered region with high energy displacement cascades. The evolution of the primary damage with increasing dose follows the same steps as those found previously in pure $UO_2$. First, point defects are created. Subsequently, they cluster and form small Frank loops, which in turn transform and grow into unfaulted loops. We demonstrate also that increasing temperatures accelerate the production of dislocations shifting their creation to lower doses. The effect of the plutonium content is also evidenced, especially with Cooper potential. It shows that the dislocation density decreases when the plutonium content increases.Although, MD has been described as a molecular microscope due to its ability to discribe accuratily systems of atoms, it has a large drawback that is the short time steps of the order of femto-seconds needed to resolve the atomic vibrations. This limits the time typically few microsecond. In order to invetigate processess, such as, cation diffusion and rare-event annihilation of defects after cascaces, another computational tool is required. Atomistic or object kinetic Monte Carlo (KMC) techniques can run for longer timescales than MD. However, for KMC to work accurately, all of the possible inter-state transition mechanisms and their associated rates need to be known a priori. For this reason, the adaptive kinetic Monte Carlo (AKMC) is chosen to overcome these limitations. This method determines the available transition states during simulation. In this way, it takes the system into unforeseen states via complex mechanisms. The power and range of this tool proved to be efficient to discover cation Frenkel pair recombination over a longer periods of time than MD

Los estilos APA, Harvard, Vancouver, ISO, etc.

24

Arqam, Mohammad. "Thermomechanical analysis of compact high-performance electric swashplate compressor". Thesis, Griffith University, 2021. http://hdl.handle.net/10072/410159.

Texto completo

Resumen

This PhD is sponsored by industry and is part of a project to develop and manufacture smart electric compressor for mobile refrigeration and air conditioning applications on commercial and heavy vehicles including industrial machinery. Compact electric compressors are of great value for the future due to the growth of the electric vehicle market. Recent advancements in the field of mobile air conditioning and refrigeration have witnessed extensive use of the swashplate compressor due to its compact structure, continuous operation, small size, light weight and better thermal comfort inside the vehicle. The design of the swashplate compressor is complex so that it requires considerable contributions from different fields of engineering viz. engineering mechanics, heat transfer and fluid dynamics. The estimate of compressor performance through modelling and experiments at the early stages of design and development serves as a useful tool for the designer. The input power, torque, in-cylinder gas pressure and temperature, flow through valves, and volumetric efficiency are important parameters to characterize the compressor performance. In this thesis, a set of practical thermomechanical models are derived and validated against experiments. An ideal gas based analytical model is developed for a 10 cylinder swashplate compressor with a view to predict its performance in terms of shaft torque and mass flow rate for a given rotational speed requiring minimal computational effort to run. Three sub-models are developed to account for the piston and swashplate kinematics and dynamics through deriving expressions for piston displacement as an explicit function of angle of rotation of swashplate and interactions between forces and moments. The compression process model is formulated to predict in-cylinder temperatures and pressures during one revolution of the swashplate together with refrigerant mass flow rate in and out of the compressor. A complete time-varying model is then developed by combining above three sub-models. Results are obtained in terms of compressor torque and volumetric efficiency and agree well with experiments. Considering the importance of refrigerant flow through reed valves affecting compressor performance, a real-gas, restricted-flow valve model is also developed and compared with the ideal-gas, ideal-valve model. Real gas properties of R134a are evaluated using NIST standard reference database. A minor-loss discharge coefficient approach is used to determine the refrigerant flow rate through reed valves. The model predicts the discharge temperature, refrigerant mass flow rate and volumetric efficiency accurately as a function of rotational speed. The effect of real gas properties, heat transfer to and from the compressor wall during compression and expansion and the valve model are analyzed. The suction side valve model is found to have the largest influence on the compressor performance as a function of rpm whereas heat transfer model has the least. The key contribution of this study is in assembling a practical combination of models that is capable of capturing the essential physics without being overly complex. To the authors’ knowledge this is the first swashplate study that shows clearly the cyclic variation in thermo-physical properties. The literature shows the dynamic characteristics of the compressor are well connected with the start-up transients of the swashplate mechanism and the suction and discharge pressures. To evaluate this, an experimentally validated transient swashplate compressor model is developed including mass moment of inertia of the pistons and swashplate to evaluate the motor torque loading during compressor start-up. The effects of essential parameters such as moment of inertia, bearing torque, viscous resistance to the piston motion, suction and discharge pressures on the compressor performance are presented. The actual start-up behavior is tracked using a high-speed data logger capturing phase currents for the BLDC motor, instantaneous power and rotational speed. The suction and discharge pressures are found to have the largest influence on the starting torque whereas rotational mass moment of inertia has the least. The original contribution of this work is in deriving a transient swashplate compressor model that includes the mass moment of inertia of the swashplate mechanism and clarifying the relative importance of line pressures, viscous losses and bearing resistance on the start-up torque. Since minimizing the size of the compact Brushless DC (BLDC) motor driving the compressor is important, it is worth optimizing the cooling performance of the electric motor. An experimentally validated computational fluid dynamics (CFD) model is developed to investigate the thermal performance of an air-cooled Brushless Direct Current (BLDC) motor driving swashplate compressor. Different fin arrangements on the motor housing are analysed including small protrusions on the fin surface. The findings show greater enhancements can be achieved by adding an extra fin in the cooling flow passage rather than through the inclusion of grooved walls. Thermographs of the motor housing are found to be in close agreement with the model predictions. The key achievement of this thermal investigation is in demonstrating air-cooling is a practical and effective alternative to refrigerant cooling of compact high performance electric swashplate compressors for mobile refrigeration and air conditioning applications. The effect of thermal resistance between the windings and stator core of an air-cooled Brushless DC motor is also investigated. Measurements are found to be in close agreement with predictions. The numerical simulations suggest significant benefits of injecting encapsulation material in the stator core to enhance heat transmission from windings to the surrounding electrical steel. To confirm this, an experimental investigation is carried out by adding thermal resin to the winding slots on 2.5 kW and 4 kW brushless DC motors. The findings show that the potting material can reduce the temperature of the windings by 10 °C to 20 °C for electrical power inputs of 2.4 kW to 3.8 kW. The winding temperature is also found to be sensitive to the winding arrangement in the stator slot. With tighter, more compact windings also leading to significant temperature reductions.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
Full Text

Los estilos APA, Harvard, Vancouver, ISO, etc.

25

Meinshausen, Lutz [Verfasser]. "Modeling the SAC microstructure evolution under thermal, thermomechanical and electrical constraints / Lutz Meinshausen". Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2014. http://d-nb.info/1067587780/34.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

26

Shayed, M. A., R. D. Hund y Ch Cherif. "Effect of thermal-resistant polymeric coatings on thermomechanical and topographical properties of glass fiber". Sage, 2015. https://tud.qucosa.de/id/qucosa%3A35611.

Texto completo

Resumen

Thermal-resistant coatings, based on polysilazane and polysiloxane polymers, were applied onto the glass fiber rovings with the dip-coating method. The coated glass fibers were characterized by performing different experiments to evaluate the effect of coatings on thermomechanical and topographical properties of glass fiber. The effect of temperature on the mechanical properties of the coated rovings were studied and compared with the uncoated rovings. Thermogravimetric analysis was carried out to investigate the thermal stability of coated samples. Scanning electron microscopy and energy-dispersive X-ray analyses were performed to evaluate the surface topographical characteristics of the glass fiber rovings. These analyses showed the changes in surface morphological properties due to modification of glass fiber by coating treatment. The results of tensile testing indicated that thermal-resistant coatings enhanced up to 60% tensile strength and 20% stiffness of uncoated glass fiber roving. Thermomechanical study up to 500°C revealed that polysiloxane coating on glass fiber showed better performance than polysilazane polymeric coating.

Los estilos APA, Harvard, Vancouver, ISO, etc.

27

Calcaterra, Jeffrey Ronald. "Life prediction evaluation and damage mechanism identification for SCS-6/Timetal 21S composites subjected to thermomechanical fatigue". Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/12548.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

28

Agarwal, Anshul. "Thermal adaptive implicit reservoir simulation /". May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

29

Nallathambi, Ashok Kumar [Verfasser], Eckehard [Akademischer Betreuer] Specht y Albrecht [Akademischer Betreuer] Bertram. "Thermomechanical simulation of direct chill casting / Ashok Kumar Nallathambi ; Eckehard Specht, Albrecht Bertram". Magdeburg : Universitätsbibliothek, 2010. http://d-nb.info/1151571539/34.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

30

Ahmer, Zeeshan. "An investigation on thermomechanical behaviour of a tool steel X38CrMoV5". Paris, ENMP, 2011. http://www.theses.fr/2011ENMP0075.

Texto completo

Resumen

L'acier X38CrMoV5-47HRC est principalement utilisé dans les outillages de mise en forme à chaud. L'outil devrait comprendre haute résistance à la fatigue ainsi que la dureté élevée de défier les chocs thermiques et mécaniques. Surface de l'outil est principalement ruinés par le processus cyclique et progressive des conditions de température éphémère i. E. Fatigue non-isotherme. Les lois de comportement appropriées sont donc nécessaires pour prédire le comportement du matériau dans des conditions non-isothermes. Cette thèse représente une contribution à prédire le comportement mécanique de X38CrMoV5-47HRC par des simulations numériques en utilisant des modèles de comportement. Évaluation de la robustesse et les limites d'un modèle de type Chaboche thermoelastoviscoplastic est effectuée sous plusieurs conditions d'essai différentes à partir de plusieurs essais uni axiaux (LCF et TMF) et les conditions de charge complexes avec une gamme de température variable transitoires et d'amplitude variable de déformation mécanique. Après la caractérisation du modèle dans ces conditions, ses paramètres ont été ré-identifiés dans le but de mettre à jour le modèle pour travailler dans des conditions de chargement complexes. Sans perdre de vue les limites du modèle, de nouvelles orientations sont également examinées dans le but d'améliorer le modèle en termes de son application dans des conditions sévères
Hot work tool steel X38CrMoV5-47HRC is mainly used in industrial manufacturing processes such as high pressure die casting, hot Forging, stamping and rolling etc. The tools should comprise high fatigue strength as well as high toughness to defy thermal and mechanical shocks. The tool's Surface is principally ruined by the cyclic and progressive process under ephemeral temperature i. E. The process of non-isothermal fatigue. The appropriate constitutive laws are therefore required to predict the behaviour of material under non-isothermal conditions. This thesis depicts a contribution to predict the mechanical behaviour of X38CrMoV5-47HRC by numerical simulations using constitutive behaviour models. Assessment of the robustness and limitations of a Chaboche type thermoelastoviscoplastic model is carried out under several different test conditions starting from several uniaxial tests (LCF and TMF) to complex loading conditions with variable transient temperature range and variable amplitude of mechanical strain. After characterization of the model under the said conditions, its parameters have been re-identified in order to update the model to work under complex loading conditions. Keeping in view the model's limitations, further directions are also discussed in order to improve the model in terms of its application under severe loading conditions

Los estilos APA, Harvard, Vancouver, ISO, etc.

31

Hegde, Shashikant. "Enhance thermomechanical reliability of microsystems packaging through new base substrate and dielectric materials". Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/17141.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

32

Gennick, Kendall. "Finite element modeling and simulation of thermomechanical processing of particle reinforced metal matrix composites". Monterey, California. Naval Postgraduate School, 1997. http://hdl.handle.net/10945/8410.

Texto completo

Resumen

Approved for public release; distribution is unlimited
During the consolidation phase, reinforcement particles of Metal Matrix Composites (MMC's) tend to be non uniformly distributed. The result is that the material properties of the composite materials are not as good as those originally desired. Through large amounts of straining, homogeneity can be achieved. Finite element models of MMC's undergoing different thermomechanical processes (TMP's) to true strains of approximately 1.2 were generated. The models consist of particle clusters within the particle-depleted matrix. The particle clusters were modeled by either a smeared model in which the particles refine the grains in the cluster, or a discrete model of the particles within clusters. The smeared and discrete models qualitatively agreed with each other. The results suggest that the best TMP to reach a state of reinforcement particle homogeneity was a hot worked, low strain rate TMP

Los estilos APA, Harvard, Vancouver, ISO, etc.

33

Rolseth, Anton y Anton Gustafsson. "Implementation of thermomechanical laser welding simulation : Predicting displacements of fusing A AISI304 T-JOINT". Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-19946.

Texto completo

Resumen

Laser welding is an advanced joining technique with the capability to form deep, narrow, and precise welds. Numerical models are used to simulate the process in attempts of predicting distortions and stresses in the material. This is done to reduce physical testing, optimize processes and enable integrated product- and process development. The Virtual Manufacturing Process research group at University of Skövde wishes to increase their knowledge on modeling options of thermomechanical simulations to grant local industries these benefits. A numerical model for the laser welding process was developed in ABAQUS. This was done by examining the macrograph structure of a simple weld and applied to a stainless-steel T-joint welding application. The macrograph data was used to calibrate a mathematical heat source model. User subroutine DFLUX was used to enable movement of the heat source and element activation was used to simulate the fusion of the two parts. A T-joint welding experiment was carried out to measure deflection and the result was compared to numerical simulations. Different combinations of heat source models, coupling type and element activation was compared in relation to predicting the deflection. Computational time and modeling complexity for the techniques was also considered.The results showed that a 3D Gaussian heat source model will imitate the keyhole weld achieved superior to the compared 2D model. The 3D model provides greater flexibility since it enables combinations of any geometrical bodies. It was shown that element activation has a significant contribution on part stiffness and thus resulting distortions. To implement element activation a fully coupled analysis is required. The deflection of the fully coupled 3D simulation with element activation showed a 9% deviance in deflection compared with experiments.

Los estilos APA, Harvard, Vancouver, ISO, etc.

34

Mouiya, Mossaab. "Thermomechanical properties of refractory materials, influence of the diffuse microcracking". Electronic Thesis or Diss., Limoges, 2024. http://www.theses.fr/2024LIMO0066.

Texto completo

Resumen

Les matériaux réfractaires sont largement utilisés dans les applications à haute température mais ne sont pas toujours enclins à résister aux chocs thermiques sévères. Pour résoudre ce problème, une microstructure incorporant des microfissures préexistantes est une solution bien connue pour améliorer la résistance aux chocs thermiques. Néanmoins, une telle microstructure endommagée nécessite une meilleure compréhension pour optimiser son design sans compromettre l'intégrité du matériau. Dans un tel contexte, le Titanate d'Aluminium (Al₂TiO₅, AT) présentant une forte anisotropie de dilatation thermique, constitue un système modèle idéal pour créer un réseau de microfissures adapté afin d'améliorer la flexibilité et le comportement à la rupture. Cette thèse étudie les propriétés thermomécaniques des matériaux réfractaires développés à base d'AT, comprenant des céramiques polycristallines et des composites alumine/AT, en mettant l'accent sur les relations entre la microstructure et les propriétés macroscopiques. Dans le cas de ces deux matériaux, les microfissures préexistantes jouent un rôle clé sur le module de Young, le comportement de dilatation thermique, la réponse contrainte-déformation en traction, l'énergie de rupture et donc la résistance aux chocs thermiques. Un effet d’hystérésis significatif sur le module de Young et l’expansion thermique en fonction de la température témoigne des mécanismes de fermeture-réouverture de microfissures. Des essais de traction uniaxiale ont mis en évidence des lois de comportement non linéaires, impactant l'énergie de rupture et la résistance aux chocs thermiques. En particulier, des essais de traction incrémentale à 850 °C ont montré des comportements antagonistes à la montée ou à la descente en température du fait de l’histoire thermique. Les composites (alumine/AT) avec des 0 à 10 % d’inclusions présentent des microfissures diffuses dues à un différentiel d’expansion thermique. Ils présentent un module de Young réduit, des lois de comportement fortement non linéaires et une déformation à la rupture plus élevée à température ambiante. Les essais de choc thermique effectués par le dispositif innovant ATHORNA pour tous les matériaux à base d'AT étudiés ont confirmé leur résilience sous gradient thermique élevé. Ces résultats fournissent des informations précieuses pour le design de futurs matériaux réfractaires avancés présentant une résistance aux chocs thermiques améliorée
Refractory materials are widely used in high-temperature applications but are not always prone to resist severe thermal shock. To address this problem, microstructure incorporating pre-existing microcracks are already well known to improve thermal shock resistance. Nevertheless, such damaged microstructure needs a better understanding to optimize their design without compromising material integrity. In such context, Aluminum Titanate (Al₂TiO₅, AT) exhibiting a great thermal expansion anisotropy, constitutes an ideal model system for creating a tailored microcracks network in order to improve flexibility and fracture behavior. This thesis investigates the thermomechanical properties of developed AT-based refractory materials, including polycrystalline AT and alumina/AT composites, with emphasis on the relationship between microstructure and macroscopic properties. In both materials, pre-existing microcracks play a key role on Young's modulus, thermal expansion behavior, tensile stress-strain response, fracture energy, and thus thermal shock resistance. A significant hysteretic effect on Young's modulus and thermal expansion as a function of temperature indicates microcracks closure-reopening mechanisms. Uniaxial tensile tests revealed nonlinear stress-strain laws, impacting fracture energy and thermal shock resistance. In particular, incremental tensile tests at 850 °C showed contrasting behaviors during heating and cooling, attributed to thermal history. Composite materials with AT inclusions (0 - 10 wt.%) embedded in an alumina matrix exhibit diffuse microcracking due to thermal expansion mismatch. These composites exhibited reduced Young's modulus, highly nonlinear stress-strain laws, and higher strain to rupture at room temperature. Thermal shock tests performed by the innovative ATHORNA device for all studied AT-based materials confirmed their resilience under high thermal gradients. These findings provide valuable insights for the design of future advanced refractory materials with improved thermal shock resistance

Los estilos APA, Harvard, Vancouver, ISO, etc.

35

Streiff, Matthias Streiff Matthias. "Opto-electro-thermal VCSEL device simulation /". [S.l.] : [s.n.], 2004. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=15464.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

36

B, M. Shiva Kumar y kathiravan Ramanujam. "Thermal Simulation of Hybrid Drive System". Thesis, Linköpings universitet, Fluida och mekatroniska system, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-71695.

Texto completo

Resumen

Safety, performance and driving comforts are given high importance while developing modern day cars. All-Wheel Drive vehicles are exactly designed to fulfill such requirements. In modern times, human concern towards depleting fossil fuels and cognizance of ecological issues have led to new innovations in the field of Automotive engineering. One such outcome of the above process is the birth of electrical hybrid vehicles. The product under investigation is a combination of all wheel drive and hybrid system. A superior fuel economy can be achieved using hybrid system and optimized vehicle dynamic forces are accomplished by torque vectoring action which in turn provides All-Wheel Drive capabilities. Heat generation is inevitable whenever there is a conversion of energy from one form into another. In this master thesis investigation, a thermal simulation model for the product is built using 1D simulation tool AMESim and validation is done against the vehicle driving test data. AMESim tool was chosen for its proven track record related to vehicle thermal management. The vehicle CAN data are handled in MATLAB. In a nutshell, Simulation model accounts for heat generation sources, oil flow paths, power loss modeling and heat transfer phenomena. The final simulation model should be able to predict the transient temperature evolution in the rear drive when the speed and torque of motor is supplied as input. This simulation model can efficiently predict temperature patterns at various locations such as casing, motor inner parts as well as coolant at different places. Various driving cases were tried as input including harsh (high torque, low speed) ones. Simulation models like this helps Engineers in trying out new cooling strategies. Flow path optimization, flow rate, convection area, coolant pump controlling etc are the few variables worth mentioning in this regard.

Los estilos APA, Harvard, Vancouver, ISO, etc.

37

Fux, Volker. "Thermal simulation of ventilated PV-facades". Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/7852.

Texto completo

Resumen

The application of double glazed facades, especially in administration buildings is becoming more and more popular. Aside from the architectural aspects, the energetic consequences with respect to the building into which it is integrated have been discussed much over the past few years. In order to quantify the energy balance of such facades, the heat transfer rate between the inner facade layers and the gap temperature are important factors and constitute the core of this thesis. In contrast to experimental estimations of heat transfer rates, which are measured using heat flux sensors, in this study the energy balance within the facade was determined primarily by means of computational fluid dynamics (CFD). For the purpose of verifying the CFD results, simulation results were assessed through comparison with experimental flow data obtained using particle image velocimetry (PIV). Comparison of CFD simulations and PIV measurements showed good agreement for different symmetric and asymmetric plate temperatures as well as for different forced flow rates. A new Nusselt correlation was developed, which was derived from a CFD parameter study. The suggested correlation includes plate distances which vary from 0.05 to 0.5m, surface temperatures from -10 to 60 degrees C, inlet temperatures from -10 to 30 degrees C and Reynolds numbers (Red) between 500 and 6500. In order to estimate the thermal behaviour of a ventilated facade at an early stage of building planning, a transient simulation program was developed which is able to calculate the dynamic energy balance that occurs in a double facade. To facilitate integration of the calculation method into the commercial building simulation program TRNSYS 15, a new Type (Type 111) was written. This Type 111 can be used to connect an arbitrary facade construction to the existed building model Type56. Comparisons between calculated results from the developed model and measurements on real facades(a hybrid, mechanically-ventilated PV fagade and a naturally-ventilated, double glazed facade) provided sufficiently good agreement. The total energy rate through a window (g-value), estimated by the special g-value test rig at the Stuttgart University of Applied Sciences could also be reproduced accurately using the developed program.

Los estilos APA, Harvard, Vancouver, ISO, etc.

38

Wang, Zhimao. "Experimental Study and Modelling of Thermomechanical Features and Heterogeneity of the Cr203-NiCr Systems". Thesis, Troyes, 2021. http://www.theses.fr/2021TROY0020.

Texto completo

Resumen

Les contraintes résiduelles ont été déterminées dans le métal et l'oxyde pour différents systèmes oxyde/métal. La détermination expérimentale des contraintes dans la couche d'oxyde a été réalisée in-situ lors de chargements thermiques à haute température grâce à la diffraction de rayons X synchrotron en mode réflexion. En comparant les contraintes en fonction du temps avec la solution numérique, au sens des moindres carrés, le paramètre de fluage pour l'oxyde (Jox) et le paramètre de contrainte de croissance pour l'oxyde (Dox) ont été optimisés. Les mesures de contraintes dans le substrat à température ambiante ont été réalisées par diffraction de rayons X synchrotron en mode transmission. La plus grande partie de la distribution des contraintes est comprise entre 0 MPa et 500 MPa et elle montre un gradient de distribution, qui se trouve dans la zone proche de l'interface. Pour le modèle thermomécanique complet, il a été proposé de simuler par modélisation numérique dans ABAQUS. Le résultat de ces simulations est comparé aux observations expérimentales, ce qui montre une bonne concordance pour les contraintes notamment en fonction du temps pour la couche d'oxyde
Residual stresses have been determined both in metal and oxide in different oxide/metal systems. Measurements and analyses of stress in the oxide layer have been especially performed in-situ during thermal loadings at high temperature thanks to synchrotron X-ray diffraction in reflexion mode. By comparing the stresses as a function of time with the numerical solution, in the least squares sense, the creep parameter for the oxide (Jox) and the growth stress parameter for the oxide (Dox) were optimized. Stress measurements in the substrate at room temperature were performed by synchrotron X-ray diffraction in transmission mode. Most of the stress distribution is between 0 MPa and 500 MPa and it shows a gradient distribution, which is in the area near the interface. For this “full” thermomechanical model, it has been also proposed to perform simulations with a numerical approach using ABAQUS. The result of these simulations is compared to the experimental observations, which shows a good agreement for the stresses especially as a function of time for the oxide layer

Los estilos APA, Harvard, Vancouver, ISO, etc.

39

Luo, Haoming. "High frequency thermomechanical study of heterogeneous materials with interfaces". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI130.

Texto completo

Resumen

Le transfert de chaleur est intimement lié à la propagation du son (transfert acoustique) dans les matériaux, par exemple dans les isolants et les semi-conducteurs, les principaux vecteurs d’énergie sont des phonons acoustiques. Le concept de présence d’interfaces a été largement exploité pour manipuler efficacement les phonons des longueurs d’onde macroscopiques aux longueurs d’onde nanométriques. Les derniers correspondent aux fréquences en régime THz, qui sont responsables du transport thermique à température ambiante. Dans cette thèse, la méthode des éléments finis est utilisée pour effectuer des analyses transitoires de la propagation des paquets d’ondes dans différents milieux à 2D. Elle est commencée par une étude paramétrique de l’atténuation des paquets d’ondes dans un système élastique semi-infini avec des interfaces circulaires périodiques. Trois paramètres clés sont étudiés, notamment le contraste de rigidité, la densité d’interface et la longueur d’onde des phonons. Différents régimes de transfert (propagatif, diffusif et localisé) sont identifiés, qui permettent d’identifier la contribution des phonons à la conductivité thermique. Outre les interfaces circulaires, la réponse mécanique et l’atténuation acoustique pour différents types d’interfaces sont également étudiées, telles que l’inclusion de forme dendritique, l’inclusion d’Eshelby, et les matériaux poreux avec des pores ordonnés / désordonnés. Afin d’étendre l’étude aux matériaux amorphes, j’ai également considéré un milieu hétérogène avec des rigidités aléatoires réparties dans l’espace selon une distribution gaussienne basée sur la théorie de l’élasticité de cisaillement hétérogène des verres. Enfin et surtout, deux versions de lois de comportement viscoélastiques sont proposées pour prendre en compte l’atténuation intrinsèque des phonons dépendant de la fréquence dans les verres, dans le but qu’un milieu visqueux homogène puisse reproduire cette atténuation intrinsèque. La simulation par éléments finis confirme qu’un modèle continu peut suivre strictement l’atténuation atomistique (G) avec une loi de comportement viscoélastique linéaire macroscopique bien calibrée. Par rapport aux données expérimentales de a-SiO2, notre deuxième loi de comportement reproduit qualitativement et quantitativement les trois régimes d’atténuation acoustique en fonction de la fréquence : successivement Γ ∝ ω^2,ω^4,ω^2
Heat transfer is actually intimately related to the sound propagation (acoustic transfer) in materials, as in insulators and semi-conductors the main heat carriers are acoustic phonons. The concept of the presence of interfaces has been largely exploited for efficiently manipulating phonons from long-wavelength to nanometric wavelengths, i.e., frequencies in THz regime, responsible for thermal transport at room temperature. In this thesis, the finite element method is used to perform transient analysis of wavepacket propagation in different mediums. I started with a parametric study of attenuation of acoustic wave-packets in a 2D semi-infinite elastic system with periodic circular interfaces. Three key parameters are investigated, including rigidity contrast, interface density and phonon wavelength. Different energy transfer regimes (propagative, diffusive, and localized) are identified allowing to understand the phonon contribution to thermal transport. Besides the circular interfaces, mechanical response and acoustic attenuation for different types of interfaces are also investigated, such as Eshelby’s inclusion, dendritic shape inclusion and porous materials with ordered/disordered holes. In order to extend the study to amorphous materials, I also considered a heterogeneous medium with random rigidities distributed in space according to a Gaussian distribution based on the theory of heterogeneous shear elasticity of glasses. Finally yet importantly, viscoelastic constitutive laws are proposed to take into account the frequency-dependent intrinsic phonon attenuation in glasses, with the aim of reproducing such intrinsic attenuation using a homogeneous viscous medium. Finite element simulation confirms that a continuum model may strictly follow the atomistic attenuation (G) for a well-calibrated macroscopic linear viscoelastic constitutive law. Compared with the experimental data in a-SiO2, our second constitutive law reproduces qualitatively and quantitatively the three regimes of acoustic attenuation versus frequency : successively Γ∝ω^2,ω^4,ω^2

Los estilos APA, Harvard, Vancouver, ISO, etc.

40

Li, Zhenhua. "Modeling and Simulation of Autonomous Thermal Soaring with Horizon Simulation Framework". DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/442.

Texto completo

Resumen

A thermal is a column of warm rising air triggered by differential heating on the ground. In recent studies UAVs were programmed to exploit this free atmospheric energy from thermals to improve their range and endurance. Researchers had successfully flown UAVs autonomously with thermal soaring method. Most research involved some form of flight simulation. Improvements to the aircraft and thermal models for simulation purpose would enable researchers to better design their UAVs and explore any potential flaws in their designs. An aircraft simulation with a thermal environment was created in Horizon Simulation Framework, a modeling and verification framework that was developed by Cal Poly Space Technologies and Applied Research laboratory. The objective of this study is to enhance the fidelity of existing modeling and simulation methods on autonomous thermal soaring, and to advance and demonstrate the capabilities of Horizon Simulation Framework through such implementation. The geometry of a small remote controlled glider was used in this simulation. Aerodynamic prediction programs DATCOM+ and AVL were used to obtained stability and control derivatives for this glider. The induced roll effect caused by the asymmetric vertical velocity distribution of a thermal was included in the aerodynamic roll moment calculation. The autonomous guidance algorithm for the glider included a turn logic which would determine the correct turn direction for the glider when a thermal is detected. The thermal model developed in this thesis included the capabilities to vary the time dependent location, height, radius, and vertical velocity characteristics of naturally occurring thermals.

Los estilos APA, Harvard, Vancouver, ISO, etc.

41

Bajracharya, Susan. "Computer simulation of thermal behavior of atriums". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq20864.pdf.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

42

Georges, Cédric. "Improvement of the mechanical properties of TRIP-assisted multiphase steels by application of innovative thermal or thermomechanical processes". Université catholique de Louvain, 2008. http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-08232008-100716/.

Texto completo

Resumen

For ecological reasons, the current main challenge of the automotive industry is to reduce the fuel consumption of vehicles and then emissions of greenhouse gas. In this context, steelmakers and automotive manufacturers decided for some years now to join their efforts to promote the development and use of advanced high strength steels such as TRIP steels. A combination of high strength and large elongation is obtained thanks to the TRansformation Induced Plasticity (TRIP) effect. However, improvement of the mechanical properties is still possible, especially by the refinement of the matrix. In this work, two main ways were followed in order to reach improved properties. The classical way consisting of the annealing of cold-rolled samples and an innovative way consisting of obtaining the desired microstructure by direct hot rolling of the samples. In the classical way, this refinement can be obtained by acting on the chemical composition (with such alloying elements like Cu and Nb). It was observed that complete recrystallisation of the ferrite matrix is quite impossible in presence of Cu precipitates. In addition, if the ferrite recrystallisation is not completed before reaching the eutectoid temperature, the recrystallisation will be slowed down by a large way. An innovative heat treatment consisting in keeping the copper in solid solution in the high-Cu steel was developed. Therefore, ferrite recrystallises quite easily and very fine ferrite grains (~1µm) were obtained. In the innovative way, the effects of hot-rolling conditions on TRIP-assisted multiphase steels are of major importance for industrial practice and could open new dimensions for the TRIP steels (i.e. thanks to precipitation mechanisms leading to additive strengthening). Impressive mechanical properties (true stress at maximum load of 1500 MPa and true strain at uniform elongation of 0.22) were obtained with a relatively easy thermomechanical process, the role played by Nb being essential.

Los estilos APA, Harvard, Vancouver, ISO, etc.

43

Menezes, Alexandre Jorge Rocha. "Analysis of the behavior of concrete thermomechanical of low resistance in low ages". Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=16161.

Texto completo

Resumen

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior
Great works of infrastructure such as hydroelectric plants require, in it building, large concrete volumes classified as mass concrete structures. These works of power generation are strategic and fundamental for the development of a nation. However, during construction and throughout its life they may have pathological manifestations that compromise its stability. One of the most common problems in this type of structure is cracking caused by heat generated due to the exothermic reaction of cement hydration. Therefore, we had to analyze the thermal behavior of concrete, concrete with similar consistency and resistance like the concrete utilized in construction dam, and analyze how the type of cement utilized and its contents affects these parameters. In addition, we studied the evolution of compressive strength and dynamic modulus of elasticity as the cement hydrates. Finally, we compared the thermal performance of concretes produced with the results obtained from a commercial software. To carry out the experiment, concrete blocks were produced of 1,5mÂ with cements CP II E 32 RS and CP IV 32 with consumption 241,2 kg/mÂ and 330,0 kg/mÂ for thermal analysis, besides cylindrical specimens for the remaining analyzes. The results showed that the thermal behavior of concrete has a small dependence on the type of cement, however the cement content affects too much this behavior, and the cement CP IV 32 showed higher thermal variations. It was also observed that the development of compressive strength is strongly dependent on the cement content, but it has low dependency on the type of cement. Computer modeling presented satisfactory results when it was compared to results of the thermal evolution blocks.
As grandes obras de infraestrutura como as centrais hidroelÃtricas requerem na sua construÃÃo grandes volumes de concreto, sendo classificadas como estruturas de concreto massa. Essas obras de geraÃÃo de energia sÃo estratÃgicas e fundamentais para o desenvolvimento de uma naÃÃo. Entretanto, durante sua construÃÃo e ao longo de sua vida Ãtil estas podem apresentar manifestaÃÃes patolÃgicas que comprometem sua estabilidade. Um dos problemas mais comuns nesse tipo de estrutura Ã a fissuraÃÃo causada pela energia tÃrmica gerada devido Ã reaÃÃo exotÃrmica de hidrataÃÃo do cimento. Diante disso, buscou-se analisar como se dÃ o comportamento tÃrmico de concretos utilizados para a construÃÃo de corpo de barragem, alÃm de analisar como o tipo de cimento utilizado e o seu teor afetam a variaÃÃo de temperatura da massa de concreto e os problemas causados por essa variaÃÃo. Buscou-se ainda analisar a evoluÃÃo da resistÃncia Ã compressÃo e do mÃdulo de elasticidade dinÃmico Ã medida que o cimento se hidratava. Por fim, comparou-se o comportamento tÃrmico dos concretos produzidos com os resultados obtidos por meio de um software comercial. Para a realizaÃÃo da parte experimental produziu-se blocos de concretos de 1,5 metros cÃbicos com cimentos CP II-E 32 RS e CP IV 32 com consumo de 241,2 kg/mÂ e 330,0 kg/mÂ para anÃlise tÃrmica, alÃm da moldagem de corpos de prova cilÃndricos para as demais anÃlises. Os resultados apontaram que o comportamento tÃrmico do concreto apresenta uma pequena dependÃncia do tipo de cimento. Entretanto, o teor de cimento afeta fortemente esse comportamento, sendo o cimento CP IV 32 o que apresentou maiores variaÃÃes tÃrmicas. Observou-se tambÃm que a evoluÃÃo da resistÃncia Ã compressÃo Ã fortemente dependente da quantidade de cimento, mas apresenta baixa dependÃncia do tipo de cimento. A modelagem computacional apresentou resultados satisfatÃrios quando comparado aos resultados da evoluÃÃo tÃrmica dos blocos produzidos.

Los estilos APA, Harvard, Vancouver, ISO, etc.

44

Somarathne, Shini. "Dynamic thermal modelling using CFD". Thesis, Brunel University, 2003. http://bura.brunel.ac.uk/handle/2438/5523.

Texto completo

Resumen

Buildings expend vast quantities of energy, which has a detrimental impact on the environment. Buildings systems are often oversized to cope with possible extreme environmental conditions. Building simulation provides an opportunity to improve building thermal design, but the available tools are typically used in combination in order to overcome their individual deficiencies. Two such tools, often used in tandem are computational fluid dynamics (CFD) and dynamic thermal modelling (DTM). DTM provides a coarse analysis, by considering external and internal thermal conditions over a building (including its fabric) over time. CFD is usually used to provide steady state analysis. Boundary conditions typically in the form of surface temperatures are manually input from DTM into CFD. CFD can model buildings dynamically, but is not commonly used, since solving for hugely different time constants of solid and air pose significant limitations, due to data generated and time consumed. A technique is developed in this study to tackle these limitations. There are two main strands to the research. DTM techniques had to be incorporated into CFD, starting from first principles of modelling heat transfer through solid materials. These were developed into employing the use of functions such as the 'freeze flow' function (FEF) and the 'boundary freeze' function (BFF) in combination with a time-varying grid schedule to model solids and air simultaneously. The FFF pauses the solution of all governing equations of fluid flow, except temperature. The BFF can be applied to solid boundaries to lock their temperatures whilst all other equations are solved. After extensive research the established DTM-CFD Procedure eventually used the FEF and BFF with transient periods and steady state updates, respectively. The second strand of research involved the application of the DTM-CFD Procedure to a typical office space over a period of 24-hours. Through inter-model comparisons with a fully transient simulation, the DTM-CFD Procedure proved to be capable of providing dynamic thermal simulations 16.4% more efficiently than a typical CFD code and more accurately than a typical DTM code. Additional research is recommended for the further improvement of the DTM-CFD Procedure.

Los estilos APA, Harvard, Vancouver, ISO, etc.

45

Williams, Sharlene Renee. "Influence of Electrostatic Interactions and Hydrogen Bonding on the Thermal and Mechanical Properties of Step-Growth Polymers". Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/29397.

Texto completo

Resumen

Current research efforts have focused on the synthesis of novel, segmented, cross-linked networks and thermoplastics for emerging technologies. Tailoring macromolecular structures for improved mechanical performance can be accomplished through a variety of synthetic strategies using step-growth polymerization. The synthesis and characterization of novel Michael addition networks, ionene families, and ion-containing polyurethanes are described, with the underlying theme of fundamentally investigating the structure-property relationships of novel, segmented macromolecular architectures. In addition, it was discovered that both covalent and electrostatic crosslinking play an important role in the mechanical properties of all types of polymers described herein. Novel cross-linked networks were synthesized using quantitative base-catalyzed Michael chemistry with acetoacetate and acrylate functionalities. These novel synthetic strategies offer unique thermo-mechanical performance due to the formation of a multiphase morphology. In order to fundamentally elucidate the factors that influence the kinetics of the Michael addition reaction a detailed analyses of model compounds were conducted in the presence of an in-situ IR spectrometer to optimize reaction conditions using statistical design of experiments. Networks were then prepared based on these optimized conditions. The mechanical performance was evaluated as a function of molecular weight between crosslink points. Furthermore, the incorporation of hydrogen bonding within the monomer structure enhanced mechanical performance. The changes in morphological, thermal, and mechanical properties evaluated using dynamic mechanical analysis (DMA) and tensile behavior are described. In addition, the use of preformed urethane segments provides a safer method for incorporating hydrogen bonding functional groups into macromolecules. In order to compare the thermomechanical and morphological properties of ion-containing polyurethanes to non-charged polyurethanes, poly(tetramethylene oxide)-based polyurethanes containing either a novel phosphonium diol or 1,4-butanediol chain extenders were prepared using a prepolymer method. The novel phosphonium polyurethane was more crystalline, and it was presumed that hydrogen bonding in the non-charged polyurethane restricted polymer mobility, and reduced PTMO crystallinity, and hydrogen bonding interactions were significantly reduced due to the presence of phosphonium cations. These results correlated well with mechanical property analysis. The phase separation and ionic aggregation were demonstrated via wide-angle X-ray scattering, small-angle X-ray scattering, scanning transmission electron microscopy, and energy-dispersive X-ray spectroscopy during STEM imaging, as described herein. In addition, a novel polyurethane containing imidazolium cations in the hard segment was synthesized and behaved very similarly to the phosphonium cation-containing polyurethane. Ammonium ionenes, which contain quaternary nitrogen in the macromolecular repeating unit, have many potential uses in biomedical applications. They offer interesting coulombic properties, and the charge density is easily controlled through synthetic design. This property makes ionenes ideal polyelectrolyte models to investigate the influence of ionic aggregation on many physical properties. Ammonium ionenes were prepared via the Menshutkin reaction from 1,12-dibromododecane and 1,12-bis(N,N-dimethylamino)dodecane. The absolute molecular weights were determined for the first time using an on-line multi-angle laser light scattering (MALLS) in aqueous size exclusion chromatography (SEC). Tensile testing and DMA were used to establish structure-property relationships between molecular weight and mechanical properties for a series of 12,12-ammonium ionenes. Furthermore, degradation studies in the presence of base support the possibility for water-soluble coatings with excellent mechanical durability that are amenable to triggered depolymerization. A novel synthetic strategy was utilized to prepare chain extended 12,12-ammonium ionenes containing cinnamate functional groups. In the presence of UV light, the polymers chain extended, and the resulting ionenes possessed enhanced thermomechanical properties and increased molecular weight. In addition, the novel synthesis of imidazolium ionenes was demonstrated, and the charge density was tuned for appropriate applications using either low molecular weight segments or oligomeric precursors. The change in charge density had a profound role in imidazolium ionene thermal and mechanical behavior.
Ph. D.

Los estilos APA, Harvard, Vancouver, ISO, etc.

46

Samadov, Hidayat. "Analyzing Reservoir Thermal Behavior By Using Thermal Simulation Model (sector Model In Stars)". Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613336/index.pdf.

Texto completo

Resumen

It is observed that the flowing bottom-hole temperature (FBHT) changes as a result of production, injection or shutting the well down. Variations in temperature mainly occur due to geothermal gradient, injected fluid temperature, frictional heating and the Joule-Thomson effect. The latter is the change of temperature because of expansion or compression of a fluid in a flow process involving no heat transfer or work. CMG STARS thermal simulation sector model developed in this study was used to analyze FBHT changes and understand the reasons. Twenty three main and five additional cases that were developed by using this model were simulated and relation of BHT with other parameters was investigated. Indeed the response of temperature to the change of some parameters such as bottom-hole pressure and gas-oil ratio was detected and correlation was tried to set between these elements. Observations showed that generally FBHT increases when GOR decreases and/or flowing bottom-hole pressure (FBHP) increases. This information allows estimating daily gas-oil ratios from continuously measured BHT. Results of simulation were compared with a real case and almost the same responses were seen. The increase in temperature after the start of water and gas injection or due to stopping of neighboring production wells indicated interwell communications. Additional cases were run to determine whether there are BHT changes when initial temperature was kept constant throughout the reservoir. Different iteration numbers and refined grids were used during these runs to analyze iteration errors
however no significant changes were observed due to iteration number differences and refined grids. These latter cases showed clearly that variations of temperature don&rsquo
t occur only due to geothermal gradient, but also pressure and saturation changes. On the whole, BHT can be used to get data ranging from daily gas-oil ratios to interwell connection if analyzed correctly.

Los estilos APA, Harvard, Vancouver, ISO, etc.

47

Tao, Jiyue y Asnaf Aziz. "Simulation of thermal stresses in a disc brake". Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-19163.

Texto completo

Resumen

The heat flux produced from the friction between a disc and pad system leads to a high temperature which causes thermal stresses in the disc and after a number of repeated braking cycles, cracks might be initiated. The finite element analysis (FEA) is performed to determine the temperatures profile in the disc and to analyze the stresses for the repeated braking, which could be used to calculate the fatigue life of a disc.Sequentially coupled approach is used for thermo-mechanical problem and the problem is divided into two parts, heat analysis and thermal stress analysis. The heat analysis is obtained by including frictional heat and adopting an Eulerian approach. The heat analysis is conducted by using Abaqus and the toolbox developed by Niclas Strömberg. The thermal stress analysis, which is the main focus of this thesis, is followed using Abaqus. The plasticity theory as background for stress analysis is discussed in detail. The rate independent elasto-plastic plasticity is used in the stress analysis. Temperature independent material properties are considered throughout the thesis work.Isotropic, kinematic and combined hardening models are analyzed for simple 2D academic models for different types of cyclic loads. A benchmark disc and pad model, which is less complicated than the real disc-pad model, is also studied. The linear kinematic hardening model with rate independent elastic-plastic plasticity is used for benchmark and real disc-pad model. The results of the benchmark model and the real model are observed to be similar in terms of plasticity theory.

Los estilos APA, Harvard, Vancouver, ISO, etc.

48

Gu, Xiaozheng. "Computer simulation of microvascular exchange after thermal injury". Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26703.

Texto completo

Resumen

A computer model is developed to study the fluid and protein redistribution after thermal injuries in rats. This model is derived by including the burned skin as a fourth compartment in the microvascular exchange model developed by Bert et al. [6]. The pathological changes that occur after thermal injuries are introduced into the burn model as perturbations. The simulations of short-term and long-term responses were then made in this four compartment (burn) model for two cases: 10% and 40% percent surface area burns. Appropriate ranges of the perturbations were estimated based on the available information in the literature. The perturbations for the 10% burn include: the plasma leak coefficient in the injured skin, the tissue pressure in the injured skin, the fluid exchange coefficients in the injured skin, the arterial capillary pressure in the injured skin and the lymph flow characteristics in the injured skin. The perturbations for the 40% burn include the perturbations for the 10% burn plus the plasma leak coefficients in the intact tissues, the fluid exchange coefficients in the intact tissues and the lymph flow characteristics in the intact tissues. The dynamic responses of the system using these perturbations were plotted. Comparisons between the simulation predictions and the experimental data were characterized in terms of sum-of-squares of differences between simulation results and experimental data. Compared to the limited amount of data available in the literature, the burn model describes microvascular exchange after thermal injuries reasonably well. The work in this thesis could easily be extended to account for fluid resuscitation following a thermal injury in rats and, it is hoped that this approach might eventually be applied to the resuscitation management of burn patients.
Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate

Los estilos APA, Harvard, Vancouver, ISO, etc.

49

Yeandel, Stephen. "Atomistic simulation of thermal transport in oxide nanomaterials". Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687351.

Texto completo

Resumen

The aim of this work has been to use atomistic computer simulation methods to calculate the thermal conductivity and investigate factors that will modify the behaviour when applied to three different oxide materials: MgO, SiO2 and SrTiO3. These were chosen as they represent distinct classes of materials and are substrates for thermoelectric devices, where one of the primary goals is to tailor the system to reduce the thermal conductivity. Chapter 1 introduces thermoelectric concepts, gives a background of the theory and a review of various important thermoelectric materials. In Chapter 2 an overview of the interatomic interactions is presented along with details on the implementation of these interactions in a simulation of a 3D periodic crystal. Chapter 3 outlines the importance of phonon processes in crystals and several approaches to the calculation of thermal conductivity are presented. MgO results are given in Chapter 4. Both the Green-Kubo and Boltzmann transport equation (BTE) methods of calculating thermal conductivity were used. The effect on thermal conductivity of two different grain boundary systems are then compared and finally extended to MgO nanostructures, thus identifying the role of surfaces and complex nanostructure architectures on thermal conductivity. In Chapter 5 two different materials with the formula unit SiO2 are considered. The two materials are quartz and silicalite which show interesting negative thermal expansion behaviour which may impact upon the thermal transport within the material. Chapter 6 presents results on the promising thermoelectric material STO. Once again the results from both Green-Kubo and BTE calculations are compared. Grain boundaries are also studied and the effect of inter-boundary distance and boundary type on the thermal conductivity is explored. Finally, a nanostructured STO system (assembled nanocubes) with promising thermoelectric applications is studied. Chapter 7 outlines the conclusions made from this work and suggests areas for future study.

Los estilos APA, Harvard, Vancouver, ISO, etc.

50

Reichl, John Vincent. "Inverter Dynamic Electro-Thermal Simulation with Experimental Verification". Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/36100.

Texto completo

Resumen

A full electro-thermal simulation of a three-phase space-vector-modulated (SVM) inverter is performed and validated with measurements. Electrical parameters are extracted over temperature for the insulated gate bipolar transistor (IGBT) and diode electro-thermal models. A thermal network methodology that includes thermal coupling between devices is applied to a six-pack module package containing multiple IGBT and diode chips. The electro-thermal device models and six-pack module thermal model are used to simulate SVM inverter operation at several power levels. Good agreement between model and measurement is obtained for steady state operation of the three-phase inverter. In addition, transient heating of a single IGBT in the six-pack module is modeled and validated, yielding good agreement.
Master of Science

Los estilos APA, Harvard, Vancouver, ISO, etc.

Tesis sobre el tema "Thermal and thermomechanical simulation"

Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros