Дисертації з теми "Solidification structure"
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Flood, S. C. "Factors affecting the grain structure during solidification." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355749.
Повний текст джерелаWalters, Morgan C. "Solidification and structure formation in soft-core fluids." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/27342.
Повний текст джерелаHashemi-Ahmady, M. "Solidification, structure and mechanical properties of A357 aluminium alloy." Thesis, University of Southampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381127.
Повний текст джерелаGiron, Gilles. "Structure de solidification des aciers rapides en refusion continue." Grenoble INPG, 1993. http://www.theses.fr/1993INPG0141.
Повний текст джерелаCunha, M. A. da. "Structure and magnetic properties of Si-Fe ribbons produced by rapid solidification." Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383371.
Повний текст джерелаGarda, Brahim. "Essais de coulabilité en fonderie : aspects thermiques, hydrodynamiques et structure de solidification." Grenoble INPG, 1993. http://www.theses.fr/1993INPG0166.
Повний текст джерелаHeringer, Ferreira Romulo Adolfo. "Modélisation de la solidification de gouttes atomisées." Vandoeuvre-les-Nancy, INPL, 2004. http://www.theses.fr/2004INPL093N.
Повний текст джерелаIt's well known that, from the structural point of view, the parts formed by powder metallurgy processes are quite homogeneous on a macroscopic scale (of the product). Does it go in the same way on the scale of the particles which compose these parts? In this work we present results of local measurements of the species composition made on atomized Al-Cu droplets. This analysis shows a non-uniform distribution of alloy compounds in the observed sections of the droplets. A numerical model was proposed for the solidification of a spherical droplet subject to convection. The solidification starts with an imposed undercooling at the center of the droplet and progresses spherically towards its external surface. Volume average of the energy and solute balances was taken for each phase. The numerical solution of these equations allowed to evaluate the distributions of the enthalpy, temperature, phase fractions, and solute composition in the droplet. Results are presented for a droplet of Al 10%mass Cu, and nucleation undercooling of 0, 30 and 60 °C. The model predicts the solute segregation in the droplet. It predicts also a systematic remelting of the supersaturated solid structures, which can be related with fragmentation and possible grain refining
Lehmann, Peter. "Controle de la solidification par effet Seebeck." Grenoble INPG, 1996. http://www.theses.fr/1996INPG0098.
Повний текст джерелаAlbert, Virginie. "Macroségrégations et mouvement des cristaux équiaxes lors de la solidification d'alliages." Vandoeuvre-les-Nancy, INPL, 1998. http://www.theses.fr/1998INPL037N.
Повний текст джерелаBen, Hamouda Haithem. "Modélisation et simulation de la structure de solidification dans les superalliages base-nickel : application AM1." Thesis, Paris, ENMP, 2012. http://www.theses.fr/2012ENMP0040/document.
Повний текст джерелаAM1 is a nickel-based superalloy that Snecma relies on to elaborate single crystal turbine blades having complex geometry and high resistance to extreme conditions of temperature and pressure. However, controlling heat flux during solidification process is difficult because of many reasons such as the complex geometry, the way of clustering parts and the superalloy solidification kinetics. Consequently, stray grain nucleation can occur in the undercooling liquid. Therefore, it is important to precisely identify critical undercooled zones during solidification. To do this, a new coupling algorithm is integrated in Procast software through its CAFE module. This coupling considers liquid→solid transformation in solving thermal problem. Thus, predicted recalescence during stray grain nucleation can be observed. Enthalpy→temperature conversion is based on tabulated solidification paths depending on cooling rate computed at each Finite Element node. Solidification paths are calculated using a new microsegregation model based on total mass and solute mass conservation equations over a representative volume element. It includes both finite diffusion in phases and growth kinetics for multicomponent alloys. It is also coupled with a thermodynamic software for equilibrium computation. The microsegregation model fits experimental data provided by quenching tests on AM1 superalloy
Pineau, Adrian. "Modélisation 3D de structures de grains par une approche automate cellulaire. Application à la compétition de croissance dendritique et à la cristallisation du silicium polycristallin." Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEM042.
Повний текст джерелаGrains structures obtained during solidification processes strongly influence the properties of technical products. It is specially the case for cast parts in metallic alloys, or for silicon photovoltaic cells. The CA-FE (Cellular Automaton - Finite Elements) method aims to model grain structure evolution during solidification at a macroscopic scale, but also requires approximations at smaller scales. In this work, two distinct studies are proposed. First, CA simulations of growth competition among columnar dendritic grains are carried out for a succinonitrile-0.4 wt% acetone alloy. This is achieved by computing the grain goundary orientation during directional solidification. Comparisons are subsequently conducted with recent phase field results derived under the same conditions. An excellent agreement is found with phase field simulations results within arange of intermediate cell size centered around the maximum step between primary stationary dendrite tips of the two competing grains. The Esaka configuration, corresponding to a dendritic growth competition for a succinonitrile-1.3 wt% acetone alloy, is also studied. Polycristalline silicon growth was investigated within the ANR CrySaLID project. The CA method was enriched to allow facets growth and grains in twin relationship modeling. These developements use a geometrical approach based on in situ and ex situ experimental observations. The resulting numerical model was applied to experimental configurations and good qualitative and quantitative agreements were found. Simulations over a cubic and centimetric domain were lastly conducted. It was found that facets growth and twin nucleations strongly modify the grains structure compared to a dendritic microstructrure
Carozzani, Tommy. "Développement d'un modèle 3D Automate Cellulaire-Éléments Finis (CAFE) parallèle pour la prédiction de structures de grains lors de la solidification d'alliages métalliques." Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 2012. http://pastel.archives-ouvertes.fr/pastel-00803282.
Повний текст джерелаDai, Huijuan. "A study of solidification structure evolution during investment casting of Ni-based superalloy for aero-engine turbine blades." Thesis, University of Leicester, 2009. http://hdl.handle.net/2381/4551.
Повний текст джерелаPrins, Heinrich Johann. "The effect of autogenous gas tungsten arc welding parameters on the solidification structure of two ferritic stainless steels." Diss., University of Pretoria, 2019. http://hdl.handle.net/2263/79303.
Повний текст джерелаDissertation (MEng)--University of Pretoria, 2019.
Metallurgical Engineering
MEng
Unrestricted
Regados, Ygor Amadeo Sartori. "Modelo matemático para previsão da macrossegregação durante a solidificação com zona pastosa ou interface sólido-líquido plana." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-03052018-090007/.
Повний текст джерелаMacrosegregation is a source of serious problems in castings, but it can be a useful tool in metallurgical refining processes such as those employed in the production of high-purity silicon. It is often a result of convective liquid flow either at planar solidification or when a mushy zone is present, while diffusive solute transport is effective at controlled directional solidification with planar interfaces. Ingot solidification modeling at macroscopic scale is currently divided in models assuming a mushy zone is always present and planar interfaceassuming models, thus requiring prior knowledge of interface morphology. A mathematical model for macrosegregation resulting from diffusion and convection during solidification with planar interface or mushy zone was presented and implemented. Diffusive transport was evaluated numerically, revealing a transition from planar to mushy-zone solidification conforming to classical stability criterions, with an initial refined zone that grew even after a mushy zone developed and the inefficacy of macrodiffusion-induced macrosegregation at higher growth velocities shown. Convection showed stabilizing effect for planar solid-liquid interface by reducing the solute-undercooled layer and increased macrosegregation, with a tendency towards Scheil model. Silicon experiments publicly available were compared with the present model, confirming the experimentally-observed stabilizing effect and proving the key role of diffusion at macrosegregation formation on these systems. The model was evaluated with experiments made in a Bridgman-type furnace with an Al-1% Cu alloy with increasing growth velocities to study interface stability and macrosegregation with or without liquid stirring. Results indicate a planar growth region followed by a cellular interface one after the second velocity change, as identified by metallographical testing. Critical growth velocities for classical criterions were estimated after the experiments and were smaller than the evaluated ones.
Xavier, Rodrigo Yokoyama [UNESP]. "Influência da deformação plástica no tratamento térmico de homogeneização de um aço ferramenta para trabalho a frio." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/148843.
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O nível de qualidade de peças produzidas a partir de grandes lingotes está intimamente relacionado à qualidade dos lingotes em si. Dentre os diversos defeitos inerentes ao processo de solidificação, destacam-se as microssegregações de elementos de liga, que causam uma deterioração nas propriedades do produto final. Uma maneira de reduzir o dano causado pela microssegregação é através do Tratamento Térmico de Homogeneização, este por sua vez demanda elevados tempos de processo, elevando custos e tempos de fabricação. Uma das formas de reduzir os tempos de homogeneização, uma vez que este apresenta caráter difusional, é através da redução do espaçamento interdendrítico. Neste trabalho foi analisada a influência da deformação plástica como forma de reduzir o espaçamento entre dendritas no tratamento térmico de homogeneização. Para tal fim, utilizou-se um lingote fundido em aço ferramenta de composição química similar ao AISI A2. As amostras foram retiradas do núcleo do lingote no estado bruto de solidificação e sofreram deformações de 0,6 e 1,3 através do processo de laminação a quente, sendo temperadas em água na sequência. Após laminadas as amostras passaram por um tratamento térmico de homogeneização na temperatura de 1200°C por 8h ou 16h e foram novamente temperadas em água. As análises foram feitas através de Microscopia Óptica, Dureza Vickers, Difratometria de Raios-X e Microscopia Eletrônica de Varredura. Foi observado em todas as amostras a presença de microrechupes, e uma microestrutura composta predominantemente por dendritas oriundas da solidificação, identificadas pela fase martensítica, envoltas por uma matriz formada de austenita retida, contendo carbonetos e sulfetos. Com a deformação plástica foi possível quebrar a estrutura dendrítica a aproximar as regiões segregadas das não segregadas. O tratamento térmico por um tempo de 8h não foi suficiente para homogeneizar a microestrutura e reduzir as microssegregações, independentemente do estado de deformação das amostras. O tratamento térmico por 16h apresentou os melhores resultados em relação à homogeneidade química, sendo tanto melhor o resultado quanto maior a deformação imposta às amostras.
The quality of pieces produced from large ingots is closely related to the quality of ingots itself. Among the various defects inherent to the solidification process, there is the microsegregation of alloying elements, causing a deterioration in the properties of the final product. One way to reduce the damage caused by microsegregation is through the homogenization heat treatment, this in turn demands long time of process, increasing costs and lead-times for manufacture. One way to reduce the homogenization time, since it has a diffusive character, is by reducing the interdendritic spacing. In this study was analyzed the influence of plastic deformation as a mean to reduce the spacing between dendrites in the homogenization heat treatment. For this purpose it was used a cast ingot of chemical composition similar to the AISI A2 tool steel. Samples were cut from the ingot center in the as-cast state and suffered deformations of 0.6 and 1.3 through the hot rolling process and quenched in water in the sequence. After rolling the samples passed through a homogenization heat treatment at a temperature of 1200°C for 8h and 16h and again were quenched in water. Analyses were performed by Optical Microscopy, Vickers Hardness, X-Ray Diffractometry and Scanning Electron Microscopy. It was observed in all samples the presence of microcavities, and a microstructure consisting predominantly by solidifications dendrites identified by a martensitic phase, involved by a retained austenite matrix containing carbides and sulfides. The plastic deformation broke the dendritic structure, and approached the segregated regions to the non-segregated regions. The heat treatment for 8h was not sufficient to homogenize the microstructure and reduce the microsegregation, independently of the deformation state of the samples. The heat treatment for 16h presented the best results in relation to the chemical homogeneity, and the better the result as the greater the deformation imposed on the samples.
Chen, Shijia. "Modélisation tridimensionnelle Automate Cellulaire - Éléments Finis (CAFE) pour la simulation du développement des structures de grains dans les procédés de soudage GTAW / GMAW." Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 2014. http://pastel.archives-ouvertes.fr/pastel-01038028.
Повний текст джерелаPerrut, Mikaël. "Etude expérimentale par observation in situ de la dynamique non-linéaire des fronts de solidification directionnelle eutectiques fibreux de l'alliage transparent succinonitrile-camphre." Paris 6, 2007. https://tel.archives-ouvertes.fr/tel-00492990.
Повний текст джерелаWe present an experimental investigation of the dynamics of _brous non-faceted eutectic directional-solidi_cation structures in semi-bulk samples. A transparent succinonitrile-d,camphor alloy is used. The whole structure is followed in real time using a new optical setup, which permits to observe the growth front in oblique view with a micronic resolution. The symmetry of the _brous structure is basically hexagonal. We show that a residual curvature of the isotherms causes a constant stretching of the structure, and leads to a permanent regime near the upper stability threshold (branching instability). Defects are continually generated by the branching. We also show that the lower stability threshold (_bers elimination) coincides with the Eckhaus instability threshold, as measured in thin-sample experiments. We also studied other instabilities of the _brous structure (oscillation, ovalization)
Greenlee, Alison S. "Development of a melting and directional solidification process for improving the grain structure and electronic properties of a silicon wafer." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/69781.
Повний текст джерелаCataloged from PDF version of thesis.
Includes bibliographical references (p. 57).
A manufacturing process that produces high quality, inexpensive kerfless silicon wafers for photovoltaic cells is highly desirable. The process herein described was developed to melt and directionally solidify fine-grained silicon wafers at accelerated feed rates for improved electronic properties. The proposed process encapsulates a fine grained silicon wafer which is then sandwiched between two substrates with a specialized release layer. This stack is then zonemelted and recrystallized in a novel zone-melting furnace. The innovations herein described pertain to the design of a novel radiation furnace, the substrate selection, and the process parameters required to repeatedly yields planar wafers, with several centimeter sized grains, and a low dislocation density of10⁴4 cm -² . Specifically, the phenomena that govern the thickness profile of the wafer were examined, and process modifications were made to yield a planar wafer with a +/- 15 tm thickness range over 85% of a 6" wafer. Furthermore, a relationship between the thermal characteristics of the zonemelting furnace, the process feed rate, and the relative grain size were derived. This relationship was used to design and characterize a novel, zone-melting radiation furnace that can solidify a silicon wafer with ~10 solidification angle at 60 mm/min. Additionally, preferential nucleation sites that reduce the likelihood of large grains were identified and experimentally minimized by biasing the wafer to cool preferentially from one side. Finally, mechanisms to create dislocations were identified and minimized. This included minimizing the number of stress concentrations in the wafer and reducing the thermal resistance between the wafer and its supporting conductive substrate.
by Alison S. Greenlee.
S.M.
Morel, Constance. "Etude de l'obtention par voie de fusion et solidification controlées des poudres de manganite de lanthane et de strontium pour application dans les couches de cathode de piles à combustible de type SOFC." Thesis, Orléans, 2010. http://www.theses.fr/2010ORLE2002/document.
Повний текст джерелаOur study concerns lanthanum and strontium manganites (LSM) synthesized by means of fusion in an aerodynamiclevitation furnace. This process consists in melting compacted samples with lasers, which enables to achievetemperatures as high as 2500°C while avoiding any pollution due to the crucible. The microstructure of the fusedproducts was characterized by XRD and investigated by SEM. Their chemical composition was determined by EDXanalyses and their O-stoichiometry by TGA.The study allowed us to define the conditions demanded in order to get a material exhibiting the LSM composition andthe purely perovskite structure. We evidenced the critical parameters, shew how they affect the final phases andproposed a mechanism for the crystallisation of these phases from a melt with the composition La1-xSrxMnO3±δ.To characterise our products from a mechanical point of view, an original method was used, based on the correlation ofimages recorded during an indirect tensile splitting test. Data on the elastic properties of the fused LSM were collectedand the effects on the mechanical strength of different dopants added on the B-site (Ga, Nb, Mg, 5 and 10%) werecompared
Appolaire, Benoît. "Prise en compte du mouvement des cristaux equiaxes dans la modélisation de la solidification des lingots d'acier coules en fonderie." Vandoeuvre-les-Nancy, INPL, 1999. http://www.theses.fr/1999INPL023N.
Повний текст джерелаRiberi-Béridot, Thècle. "In situ characterization by X-ray synchrotron imaging of the solidification of silicon for the photovoltaic applications : control of the grain structure and interaction with the defects and the impurities." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0412/document.
Повний текст джерелаDuring this thesis, we studied in situ the solidification of silicon with X-synchrotron imaging. The two techniques used during solidification are radiography and Bragg diffraction and they allow characterizing: dynamic growth mechanisms, growth kinetics, grain nucleation and competition, lattice deformation and dislocation related strain fields. These observations are combined with ex situ characterizations to study the crystallographic orientation, the deformations of the crystal lattice as well as the concentrations of light impurities such as carbon and oxygen. The complementarity of these techniques makes it possible to study and to better understand: the physical phenomena related to the formation of the final grain structure. Results concerning the growth kinetics of the solid-liquid interface and of the {111} facets, the establishment of the grain structure, the importance of twinning, the effect of light impurities, the strain field related to growth and grain competition and dislocations are discussed in the manuscript
Perrut, Mikael. "Etude expérimentale par observation in-situ de la dynamique non-linéaire des fronts de solidification directionnelle eutectiques fibreux de l'alliage transparent succinonitrile-camphre." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2007. http://tel.archives-ouvertes.fr/tel-00492990.
Повний текст джерелаBarrat, Jean-Louis. "Structure et cristallisation de liquides simples et de mélanges." Paris 6, 1987. http://www.theses.fr/1987PA066249.
Повний текст джерелаMangelinck-Noël, Nathalie. "Dynamique de la formation de la structure de grains dans les alliages métalliques et dans le silicium multi-cristallin pour les applications photovoltaïques." Habilitation à diriger des recherches, Aix-Marseille Université, 2013. http://tel.archives-ouvertes.fr/tel-00945414.
Повний текст джерелаBonvalot-Dubois, Béatrice. "Contribution à l'étude de la structure des interfaces et de la réduction chimique de matériaux composites (eutectiques orientés) à base d'oxydes NiO, CoO et MnO." Paris 11, 1988. http://www.theses.fr/1988PA112379.
Повний текст джерелаChenoufi, Adel. "Structure et comportement thermodynamique des alliages métastables Ni-Ag et Al-Mn." Rouen, 1988. http://www.theses.fr/1988ROUES015.
Повний текст джерелаBouville, Florian. "Self-assembly of anisotropic particles driven by ice growth : Mechanisms, applications and bioinspiration." Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0155/document.
Повний текст джерелаSelf-assembly phenomena are of prime interest in materials science, because they fill the gap between assembly of macrostructure and processing of nanomaterials. Self-assembly is based on the spontaneous organization of individual small constituents into patterns and structures. Controlling the spatial arrangement can possibly improve materials properties by maximizing its response in a given direction. Furthermore, particular types of spatial arrangement, such as found in natural structures, can even induce new properties. During the past three years, we have used ice templating process to trigger the assembly of platelet-shaped particles to replicate the hierarchical structure of nacre. Control over this technique allowed structural customization at different length-scales: local orientation of the platelets, ice crystal long range order, and the control if the interfaces between the platelets. This hierarchical process has set the ground for the creation of a new fully mineral nacre-like alumina. The local platelet self-assembly triggered by ice growth was investigated by Discrete Element Modelling which provided new insight into the dynamic phenomenon responsible for the particles alignment. Synchrotron X-ray tomography was used to validated the model results. The different architecture observed in the final samples are not the result of a percolation threshold, as one could expect, but is instead a consequence of the delicate balance between pushing and engulfment at the solidification front. The local alignment of platelets can be beneficial for the functional and structural characteristics of composites and relevant aspects for two potential applications were investigated: the thermal properties of the hexagonal boron nitride/silicon rubber composites and the mechanical properties of macroporous alumina. Further adaptation of the process allowed for long range ordering of the ice crystals (up to the centimeter scale). Different tools have also been developed in order to characterize the response of composites as a function of the architecture at the level of the macropores and particle organisation. Once those two levels of alignment were achieved, the addition of a glassy phase and nanoparticles to the grain boundaries of the platelets introduces, just like in nacre, interfaces capable of deflect and even stopping crack propagation
Calonne, Virginie. "Propagation de fissure par fatigue dans les aciers austeno-ferritiques moulés : influence de la microstructure, du vieillissement et de la température d'essai." Phd thesis, École Nationale Supérieure des Mines de Paris, 2001. http://tel.archives-ouvertes.fr/tel-00005649.
Повний текст джерелаL'objectif de ce travail est d'étudier les vitesses et les mécanismes de propagation de fissure par fatigue en fonction du vieillissement et de la température d'essai (20°C/320°C). Pour cela, deux aciers moulés (30 % de ferrite) sont testés. Dans le but de mieux comprendre le rôle joué par l'orientation cristallographique des phases dans le mécanisme de propagation, la microstructure du matériau est étudiée par diffraction des électrons rétrodiffusés (ESBD) et par Trempe en Solidification Dirigée. Des éprouvettes sont également prélevées de telle sorte que la fissure se propage au travers de structures de solidification équiaxes et basaltiques. Microstructure, propriétés mécaniques en fatigue / fissuration et mécanismes sont alors reliés. Pour la gamme de delta K balayée, la fissure avance sans chemin préférentiel par une rupture successive des lattes de chacune de phases. Le plan macroscopique de fissuration, déterminé par ESBD, est imposé par l'orientation cristallographique du grain ferritique. Ainsi, selon la structure de solidification, des fissures secondaires peuvent apparaître ce qui influe sur les vitesses de propagation.
La fermeture de fissure, mesurée afin d'estimer les vitesses de propagation intrinsèques au matériau, diminue avec le vieillissement ce qui s'explique par l'accroissement de la composante cinématique du comportement plastique cyclique. La pente de la droite de Paris déterminée à partir de vitesses intrinsèques augmente avec le vieillissement. Le domaine de vitesse peut alors être séparé en deux parties : celle pour laquelle les vitesses sont plus faibles dans le matériau non vieilli et celle pour laquelle la tendance est inversée.
Wittwer, Oliver Marc. "Solidification of xenon: Instabilities leading to complex structures /." Zürich : ETH, 2006. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16643.
Повний текст джерелаNakada, Masayuki. "Modification of solidification structures by pulse electric discharging." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/14853.
Повний текст джерелаAbbas, Fatima. "Modélisation et simulation numérique de la déformation et la rupture de la plaque d'athérosclérose dans les artères." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMLH05/document.
Повний текст джерелаThis thesis is devoted to the mathematical modeling of the blood flow in stenosed arteries due to atherosclerosis. Atherosclerosis is a complex vascular disease characterized by the build up of a plaque leading to the narrowing of the artery. It is responsible for heart attacks and strokes. Regardless of the many risk factors that have been identified- cholesterol and lipids, pressure, unhealthy diet and obesity- only mechanical and hemodynamic factors can give a precise cause of this disease. In the first part of the thesis, we introduce the three dimensional mathematical model describing the blood-wall setting. The model consists of coupling the dynamics of the blood flow given by the Navier-Stokes equations formulated in the Arbitrary Lagrangian Eulerian (ALE) framework with the elastodynamic equations describing the elasticity of the arterial wall considered as a hyperelastic material modeled by the non-linear Saint Venant-Kirchhoff model as a fluid-structure interaction (FSI) system. Theoretically, we prove local in time existence and uniqueness of solution for this system when the fluid is assumed to be an incompressible Newtonian homogeneous fluid and the structure is described by the quasi-incompressible non-linear Saint Venant-Kirchhoff model. Results are established relying on the key tool; the fixed point theorem. The second part is devoted for the numerical analysis of the FSI model. The blood is considered to be a non-Newtonian fluid whose behavior and rheological properties are described by Carreau model, while the arterial wall is a homogeneous incompressible material described by the quasi-static elastodynamic equations. Simulations are performed in the two dimensional space R^2 using the finite element method (FEM) software FreeFem++. We focus on investigating the pattern of the viscosity, the speed and the maximum shear stress. Further, we aim to locate the recirculation zones which are formed as a consequence of the existence of the stenosis. Based on these results we proceed to detect the solidification zone where the blood transits from liquid state to a jelly-like material. Next, we specify the solidified blood to be a linear elastic material that obeys Hooke's law and which is subjected to an external surface force representing the stress exerted by the blood on the solidification zone. Numerical results concerning the solidified blood are obtained by solving the linear elasticity equations using FreeFem++. Mainly, we analyze the deformation of this zone as well as the wall shear stress. These analyzed results will allow us to give our hypothesis to derive a rupture model
Cruz, Kleber Augustin Sabat da. "Microestrutura de solidificação, resistencias mecanica e ao desgaste de ligas Al-Sn e Al-Si." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265102.
Повний текст джерелаTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: A procura por relações funcionais correlacionando parâmetros microestruturais e o comportamento mecânico de ligas metálicas é fundamental para a pré-programação do produto final. O presente estudo pretende contribuir para o entendimento sobre a influência dos parâmetros microestruturais na resistência ao desgaste e nas propriedades mecânicas de ligas de dois sistemas binários: AI-Sn e AI-Si. Tais ligas são bastante usadas em aplicações de engenharia, tais como mancais e camisas de cilindro de motores de combustão, respectivamente. Apesar do grande uso das ligas do sistema AI-Sn como material tribológico, são escassos os estudos sobre o desenvolvimento microestrutural destas ligas na literatura. Neste estudo, quatro ligas hipoeutéticas do sistema AI-Sn e três ligas hipoeutéticas do sistema AI-Si foram submetidas a solidificação unidirecional, na direção vertical e sentido ascendente, sob condições transitórias de fluxo de calor. Os espaçamentos dendríticos primários (À1) e secundários (À2) foram medidos nas direçõe.s transversal e longitudinal dos lingotes, respectivamente, e correlacionados com as variáveis térmicas que atuaram durante a solidificação. Uma abordagem teórico-experimental foi desenvolvida para determinar quantitativamente_as variáveis térmicas, tais como: coeficiente de transferência de calor na interface metal/molde, velocidade de deslocamento da isoterma liquidus, gradientes térmicos, taxa de resfriamento e tempo local de solidificação. Este estudo também aborda a influência do teor de soluto nos espaçamentos dendríticos das ligas estudadas. Os dados experimentais obtidos, concementes à solidificação das ligas AI-Sn, são comparados com modelos de crescimento dendrítico existentes na literatura. O comportamento mecânico das ligas AI-Sn e AI-Si foi analisado por meio de ensaios de tração e de desgaste. O ensaio de desgaste utilizado foi o ensaio de micro-abrasão por esfera rotativa fixa, sob condições a seco (sem óleo lubrificante ou solução abrasiva). As amostras submetidas aos ensaios de desgaste foram retiradas na direção transversal dos lingotes. A condição a seco foi adotada para impedir a interferência de elementos interfaciais na resposta da microestrutura com relação ao desgaste mecânico. O volume de desgaste é o parâmetro quantificador da resistência ao desgaste e, são obtidas equações que correlacionam o volume de desgaste com espaçamentos dendríticos, levando em consideração o tempo de ensaio, que está relacionado com a distância de deslizamento.
Abstract: The search for relationships between microstructural parameters and mechanical behavior of alloys is fundamental for the pre-programming of final properties of as-cast components. The present study aims to contribute to the understanding about the influence of microstructural parameters on the wear resistance and mechanical properties of alloys of two binary systems: Al-Sn and AI-Si. Such alloys are widely used in engineering applications, especially as bearing components such as journal bearings and cylinder liners, respectively. Despite the wide use of Al-Sn alloys as bearing materiaIs studies on the microstructural development of such alloys are rare.. In the present study, four Al-Sn and three AI-Si hypoeutectic alloys were directionally solidified under upward unsteady state heat flow conditions. The primary (1,,1) and secondary (Â.2) dendrite arm spacings were measured along the castings length and correlated with transient solidification thermal variables. A combined theoretical and experimental approach has been used to quantitatively determine such thermal variables, i.e., transient metaVmold heat transfer coefficients, tip growth rates, thermal gradients, tip cooling rates and local solidifÍcation time. This study also focuses on the dependence of dendrite arm spacings on the alloy solute content. Furthermore, the experimental data conceming the solidification of AI -Sn alloys are compared with the main predictive dendritic models from the literature. The mechanical behaviors ofthe AI-Sn and AlSi alloys were analyzed by wear and tensile tests. Micro-abrasive wear tests under dry sliding conditions and by using a fixed rotating sphere were applied to transversal samples collected along the casting. The dry condition is adopted to prevent effects of interfacial elements such as abrasive slurry or lubricant oil on the microstructural response during the tests. The wear volume was used to evaluate the wear resistance. Afterwards, equations correlating the wear volume and the dendritic arm spacing have been proposed taking into account the influence of time (sliding distance).
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica
Odložil, Jan. "Tuhnutí odlitků ve skořepinových formách při odlévání ve vakuu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228718.
Повний текст джерелаMosbah, Salem. "Modélisation multi échelle des structures de grains et des ségrégations dans les alliages métalliques." Phd thesis, École Nationale Supérieure des Mines de Paris, 2008. http://tel.archives-ouvertes.fr/tel-00349885.
Повний текст джерелаJay, Pascal. "Solidification de fontes blanches au vanadium en coulée centrifuge : étude structurale et modélisation." Grenoble INPG, 1991. http://www.theses.fr/1991INPG0020.
Повний текст джерелаAnn, Hee-Sung. "Solidification study and improved structural integrity of electroslag welds. /." Full text open access at:, 1987. http://content.ohsu.edu/u?/etd,145.
Повний текст джерелаBedel, Marie. "Étude de la formation des structures de solidification et des macroségrégations en coulée semi-continue d'aluminium." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0013/document.
Повний текст джерелаDuring solidification of metallic alloy, heterogeneities of solute composition and microstructure size appear. Mathematical models are valuable tools in the understanding and the control of the formation of these heterogeneities, which are incompatible with industrial requirements. Worldwide, SOLID is the only solidification model that simultaneously accounts for inoculation, the growth and motion of grains, natural convection and solidification shrinkage. The aim of this thesis is to improve the modelling of the coupling of nucleation and grain growth in this model. The solute diffusion, which controls the grain growth, is modelled by a diffusion length that takes into account both the motion of the solid-liquid interface and the convection of the liquid. At the microscopic scale, a third phase is added in order to improve the prediction of the growth of grains, particularly of the development of their morphology. The model can quantitatively predict the competition between the nucleation on inoculant particles and the grain growth at the microscopic scale. The model is applied to solidification of a static ingot and to direct chill casting in order to study the inoculation-growth coupling at the macroscopic scale. At this scale, the transport of the grains, of inoculant particles and of solute are all considered and are fully coupled. Comparisons of the model predictions to experimental measurements show the fundamental role of the transport of inoculants and of grains in the formation of the heterogeneities. The consideration of the development of dendritic grain morphologies considerably influences the predictions, even when their final morphology is globular
Gandin, Charles-André. "Modélisation stochastique de la solidification : formation de structures de grains dendritiques /." [S.l.] : [s.n.], 1995. http://library.epfl.ch/theses/?nr=1322.
Повний текст джерелаHeyvaert, Laurent. "Modélisation de la formation des structures et des microporosités durant la solidification d'alliages d'aluminium." Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0265/document.
Повний текст джерелаThis thesis is part of the project PRINCIPIA (PRocédés INdustriels de Coulée Innovants Pour l'Industrie Aéronautique) of the ANR MATEPRO (MATériaux Et PROcédés pour des produits performants). The goal of this project is the promotion of new aluminum-copper-lithium alloys for the aeronautic industry in order to propose an alternative to composite materials. Unfortunately, these alloys are highly sensitive to the appearance of porosity during the alloy creation process. It is due to a high hydrogen solubility and oxidation. Inside this project, my work was to establish a porosity model at the scale of the ingot. Porosity starts to develop during the solidification process due to a lower solubility of hydrogen in the solid phase. Hydrogen content in liquid phase increases by segregation and leads to pores' nucleation. Thus, it is necessary to take into account solidification for porosity-modeling purposes. It is even more important because the alloys' local composition alters the pores' growth and the microstructure modifies the chemical equilibrium by pinching effect.After a first part dedicated to general improvement of knowledge about transport phenomena in DC casting, the porosity formation model was developed based on model found in literature. The model was able to reproduce the inhomogeneity experimentally observed in an aluminum-magnesium ingot. This profile is explained by the hydrogen diffusion time which limits the pore growth. The pore density is critical for the growth limitation by hydrogen diffusion. Depending on the density, the growth switch from a non limited to a limited growth
Coudon, Florent. "Comportement mécanique du superalliage base nickel à solidification dirigée DS200+Hf." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEM062/document.
Повний текст джерелаVarious studies were aimed at developing crystal plasticity models to account for the anisotropic mechanical behaviour of single crystals. Directionally solidified (DS) materials can be modeled using such approaches, taking into account the underlying crystallographic structure. It requires the knowledge of the position, shape and crystallographic orientations of grains. To prevent heavy microstructure analyses, other models have to be developed for industrial calculations, using homogenization theory or considering a batch of synthetic pieces calculated using Crystal Plasticity Finite Elements Method (CPFEM). The aim of this thesis is to bring computational tools to carry out the two types of modeling for industrial applications. First of all, a crystal plasticity model for one grain of DS200+Hf is defined ranging from room temperature to 1200°C. Some scale transition rules, using full-field or mean-field approaches, are studied first in the theoretical case of a representative volume element (RVE) and then on tri-dimensional structures in order to access overall and local responses. For the RVE responses, micromechanical models are compared with a reference produced by CPFEM for various loadings. Moreover, the mechanical behaviour of a DS200+Hf cruciform specimen is studied. Biaxial tests with digital image correlation allow us to check the model predictions. These results raise questions about the modeling of oligogranular structures (i.e. with a small number of grains): should it be accepted that the local scale must be explicitly meshed, or, despite the fact that scale separability is not ensured, can we consider that the homogenized model still produces reliable results?
Mazet, Thierry. "Etude des structures de solidification et des ségrégations dans les lingots d'acier." Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL107N.
Повний текст джерелаBillotte, Thomas. "Caractérisation et modélisation des structures de solidification en soudage TIG d’alliages austénitiques." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0084/document.
Повний текст джерелаToday, industrials want to upgrade their welding numerical simulation knowledge’s in order to be able to guarantee the welded structure integrity. Solidification is the main step of welding process. As soon as the grain selection in welded region is well reproduced by simulation software, mechanical properties and nondestructive test response can be deduced. This work tries to find thermometallurgical phenomena in order to describe the microstructures formation during welding. These mechanisms are used for validating a new solidification model which realizes a thermal calcul post-treatment with a cellular automaton (CAFE_WELD). In this aim, welding experiences were done and characterized with EBSD. These analyses allow following the grain selection into the weld. The refusion effect is clearly seen in the case of multi-pass weld. These results are completed by the fine solidification characterizations on filler metal employed in welding experiences. In this way, the model implementation can be done in order to do numerical simulation of the same experiences. The comparisons between real and numerical experiences show that the physical laws taken into account in CAFE_WELD model are not sufficient to reproduce the microstructural properties occurring in welding
Mašková, Lenka. "Řízená krystalizace odlitků z hliníkových slitin ve skořepinových formách." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-228994.
Повний текст джерелаGennesson, Marvin. "Étude expérimentale de la mise en place des structures de solidification dans les lingots d'acier." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0278/document.
Повний текст джерелаImproving the solidification of large industrial steel ingots remains a scientific challenge. During casting chemical heterogeneities (macrosegregation), sometimes in the scale of meters, can arise. Solid grain motion is one phenomena responsible for macrosegregation. Inoculation allows the number, size and morphology of these grains to be modified through additions to the liquid metal. In this work 42CrMo4 and 34Cr4 grade steel ingots of several sizes were modified with potential inoculants. Characterization techniques (2D and 3D) were developed to compare dendritic solidification structures before and after inoculation. The first series of small ingots (50 g) showed grain refinement for powder additions with a low lattice misfit between the inoculant and solidifying melt, and a coarsening effect when ferrocerium was added. The best inoculant candidates (TiN, CeO2, Si3N4 powders and cerium ferroalloy) were tested in medium sized ingots, after which the cerium addition was tested with a 6,2 t industrial ingot. Cerium is responsible for coarsening the grain size in all sizes of cast ingots investigated. This is likely due to a modification of the solid/liquid and liquid/mold interfacial energy along with the replacement of existing sites with cerium inclusions which are not active during nucleation
Jazayeri-Gharehbagh, Ali. "The effects of Si and V additions on the structures and properties of rapidly solidified Ti₃Al." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339932.
Повний текст джерелаFARIA, JUNIOR RUBENS N. de. "The Structures and properties of Pr/Nd-Fe-B-(Cu) permanent magnets and alloys." reponame:Repositório Institucional do IPEN, 1993. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10359.
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Thesis (Ph.D)
IPEN/T
University of Birmingham, Birmingham, England
Boubeker, Rabia. "La formation des structures équiaxes : mouvement des grains, croissance-refusion, conséquences sur les macroségrégations." Vandoeuvre-les-Nancy, INPL, 2004. http://docnum.univ-lorraine.fr/public/INPL_T_2004_BOUBEKER_R.pdf.
Повний текст джерелаIn order to improve the predictions ofheterogeneitiesof composition observed on steel ingots at the end of solidification, a numerical study which takes into account the movement and the growth of equiaxed grains has been realized. After a bibliographic part related to the formation of the equiaxed grains, a diphasic approach has been adopted to describe the growth and the remelting of globular grains moving in the liquid bulk. This numerical study was implemented in the computer code SOLill. The movement of the grains has been described in a first part with the assumption that the grains move at the same speed than that of the liquid phase. The results obtained. " showed the influence of the movement and growth-remelting of the grains on solidification, especially in the evolution of the superheated zones. Then, we have taken into account the own movement of the grains which differs from that of the liquid phase. Ln this case, a solid fraction of coherence beyond which grains are imposed to be fixed has been introduced. This study showed that the final macrosegregation is strongly dependent on this fraction of coherency and on the flux density of fragments. Finally, we have demonstrated that it was possible to adjust the input data of the model in order to get a good agreement between the numerical and the experimental results
Hamri, Bachir. "Etude de la modification des structures de solidification à l'aide d'un brasseur électromagnétique." Doctoral thesis, Universite Libre de Bruxelles, 1998. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/215138.
Повний текст джерелаSferdjella, Sabrina. "Étude de l'effet des mouvements de convection sur les structures de solidification et ségrégations de l'alliage d'aluminium 5182." Vandoeuvre-les-Nancy, INPL, 2004. http://www.theses.fr/2004INPL078N.
Повний текст джерелаIn order to understand the influence of convection on the formation of solidification structures and segregations in 5182 Aluminium alloy, billets of this alloy were cast at Centre de Recherche de Voreppe (ALCAN-Péchiney). The billets were 76 mm in diameter and cast in a semi-continuous system. The mould was inserted into an inductor generating an electromagnetic field which permits the stirring of the melt. The stirring was applied either in the direction of the natural convection, or in the reverse direction. Four intensities were used. The effect of grain refining and superheat was also studied. The billets obtained were refined or not, cast with high superheat (35°C - 40°C) or low superheat (15 - 30°C), and were stirred directly or inversely with the four stirring intensities, applied successively during the casting. The results showed that the different parameters used have some influence on the temperature profiles, on the billet structure and on the microsegregation profiles. In the case of stirred and non refined billets, it was observed that the temperature profiles present an isothermal plateau around the liquidus temperature. In the case of stirred and refined billets, the isothermal plateau was at 2. 5°C of undercooling. This plateau was associated with the transport and growth of the solid. The observations of the billet structure show the presence of bands of columnar grains alternated with bands of equiaxed grains, in the case of stirred and non grain refined billets. These bands were explained using a GV diagram, considering the growing time of the columnar and equiaxed grains, and the transport time of the equiaxed grains. In the case of grain refined billets, the structure observed is formed of dendritic and/or globulitic grains. It was observed that the extent of globulitic grains increased when the stirring intensity increased ; it was also observed that the grain size decreased when the stirring increased even with grain refined billets. Results show a decrease of grain size with low superheat. The microsegregation profiles show an influence of the stirring via the structure of the billet. It was observed that for the dendritic structure, the microsegregation profiles present a negative curvature which becomes positive when the extent of the globulitic grains increases