Tesis: "Processus de solidification"

1

Droux, Jean-Jacques. "Simulation numérique bidimensionnelle et tridimensionnelle de processus de solidification /". [S.l.] : [s.n.], 1991. http://library.epfl.ch/theses/?nr=901.

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2

Lamazouade, André. "Modélisation du processus de croissance cristalline de Bridgman par une méthode enthalpique". Aix-Marseille 2, 2000. http://www.theses.fr/2000AIX22049.

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3

Dalmazzone-Jolivet, Christine. "Impact de la surfusion sur le processus de solidification dans une opération de prilling". Compiègne, 1992. http://www.theses.fr/1992COMPD551.

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L'objet de cette étude était de mettre en évidence l'influence des paramètres liés à la surfusion sur la solidification des produits organiques. Le procédé industriel de solidification auquel nous nous sommes intéressés est le prilling, dont le dimensionnement est très dépendant de la surfusion des produits que l'on souhaite mettre en forme par cette opération. Notre travail a comporté trois étapes principales : - Une étude préliminaire des conditions de solidification de différents produits organiques par Analyse Enthalpique Différentielle ; - Une étude plus approfondie de la surfusion d'un produit organique particulier présentant un important degré de surfusion. Ce travail a porté notamment sur l'influence de différents paramètres tels que volumes de l'échantillon, vitesse de refroidissement, surchauffe, temps, cycles de fusion / solidification, sur le degré de surfusion. Cette étude a été complétée par la détermination de la vitesse linéaire de solidification du produit en fonction du degré de surfusion ; - Une modélisation du processus de solidification, dans le cadre de l'opération de prilling, prenant en compte le paramètre surfusion. L'ensemble de ces travaux a permis de montrer l'extrême complexité du processus de solidification et l'importance de la prise en compte du paramètre surfusion pour le dimensionnement des procédés de solidification.

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4

Hachani, Lakhdar. "Etude de l'influence de la convection naturelle et forcée sur le processus de la solidification : cas d'un alliage métallique binaire". Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00949060.

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Ce travail se situé dans la perspective d'un contrôle de la structure de solidification des alliages métalliques sous l'effet de la convection naturelle et forcée afin d'améliorer à terme la maîtrise des microstructures de solidification grâce à un brassage électromagnétique efficace permettant d'avoir une homogénéisation du bain liquide qui par la suite peut améliorer la microstructure finale de l'alliage. La possibilité retenue dans ce travail est de réaliser ce brassage sans contact avec la solution liquide (alliage sous fusion) et sans pollution par d'autres éléments en utilisant un brassage par la force de Lorentz. L'objet de la thèse comporte une étude théorique à la fois expérimentale basée sur une installation expérimentale particulièrement documentée et instrumentée, développée au laboratoire SIMAP/EPM à Grenoble, nommée AFRODITE. Ce dispositif expérimental permet de fournir des données de quantitatives et qualitatives sur le processus de solidification des alliages métalliques. Ces données sont nécessaires à la contribution aux études menées sur la solidification des alliages métallique et enrichir la base des donnée des modèles numériques développés pour prédire les défauts liés à la solidification. L'alliage choisi dans notre travail est l'étain-plomb, vue sa basse température de fusion. Les expériences envisagées visent à étudier l'effet de deux modes de configuration dynamique sur la solidification de l'alliage Sn-Pb: la convection thermosolutale avec la variation de deux paramètres essentiels (la vitesse de refroidissement et la différence de température expérimentale) et la convection forcée par l'utilisation de plusieurs modes de brassage électromagnétique. Cette étude s'intéresse en particulier à la caractérisation des macrostructures et les défauts liés à la macroségrégation. L'originalité de l'étude vise à mesurer in situ les températures instantanées. Ceci nous a permis d'évaluer l'évolution du transfert thermique due à la convection naturelle/forcée, ainsi que leurs influence sur le processus de la solidification sous différents aspects. L'analyse post-mortem de l'alliage métallique, fournit la structure de solidification et la distribution des ségrégations à différentes échelles (mésoscopique et macroscopique).

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5

Yaghi, Mohammed. "Phase Field Modeling of Water Solidification : A Port-Hamiltonian Approach". Electronic Thesis or Diss., Lyon 1, 2024. http://www.theses.fr/2024LYO10198.

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Cette thèse présente une étude sur la modélisation, la formulation par le formalisme des Systèmes Hamiltoniens à ports et la discrétisation des processus de solidification dont l'interface est supposée diffuse et est modélisée par l'approche des champs de phase. Ses travaux traitent en détail de la solidification de l'eau dans le contexte de fournir des modèles numériques adaptés à la simulation, à la conception et au contrôle de procédés de purification de l'eau. Le premier chapitre rappelle d'abord de manière synthétique les modèles physiques de systèmes biphasique et de leur interface. Il présente ensuite en détail l'approche des champs de phase pour la modélisation des interfaces diffuses ainsi que le modèle thermodynamique du système biphasique. Puis il rappelle le modèle dynamique de la solidification d'une espèce, en particulier de l'eau, comme un système de deux équations d'évolution, l'équation d'Allen-Cahn et l'équation de bilan d'énergie. Ces modèles sont basés sur les propriétés thermodynamiques employant l'entropie totale comme potentiel thermodynamique. Dans le deuxième chapitre, après le rappel de la définition de systèmes hamiltoniens dissipatifs à port frontière, on rappelle que l'on peut formuler l'équation d'Allen-Cahn ainsi que le modèle de solidification complet sous cette forme, en augmentant les variables d'état avec le gradient de la variable de champ de phase. Puis l'on montre que les relations thermodynamiques issues des données sont exprimées en termes de variables intensives et mènent à une formulation hamiltonienne à port implicite. Le dernier chapitre se concentre sur la discrétisation préservant la structure du processus de solidification en utilisant la Méthode des Éléments Finis Partitionnés. Cela garantit que le modèle discrétisé conserve des propriétés clés telles que la conservation de l'énergie et la passivité. Le chapitre développe les formulations faibles, les projections et les hamiltoniens discrets pour l'équation de la chaleur et l'équation d'Allen-Cahn, puis développe la discrétisation du modèle de solidification complet. La principale contribution de ce chapitre réside dans la méthodologie de discrétisation appliquée au modèle Port Hamiltonien implicite du processus de solidification en utilisant l'entropie comme fonction génératrice. Globalement, cette thèse propose une approche pour la modélisation, la simulation et le contrôle des processus de solidification en utilisant le cadre Hamiltoniens à ports. Les résultats posent une base complète pour de futures recherches et développements dans les systèmes à paramètres distribués avec interfaces mobiles, en particulier pour les applications en ingénierie environnementale et chimique
This thesis presents a study on modeling, formulating, and discretizing solidification processes using the Port Hamiltonian framework combined with the phase field approach. The goal is to provide numerical models suitable for simulating, designing, and controlling such processes. It addresses the challenges of representing and controlling phase change phenomena in distributed parameter models with moving interfaces, with a particular focus on the solidification of pure water. The work has been motivated by the development of green processes for water purification technologies such as cyclic melt and crystallization of water, which offer a low-energy solution while minimizing the use of hazardous materials. The first chapter recalls briefly the physical models of multiphase systems and the description of the interface between the phases, in terms of thin or diffuse interfaces. It presents the phase field theory and the associated thermodynamical models of the multiphase systems. Finally, it expresses the dynamics of solidification processes as a coupled system of evolution equations consisting of the Allen-Cahn equation and energy balance equations. A main contribution of this chapter consists in a comprehensive presentation of solidification using the entropy functional approach within the phase field framework. In the second chapter, the Port Hamiltonian formulation of the dynamics of solidification processes using the phase field approach is developed. This chapter introduces Boundary Port Hamiltonian Systems and shows how an extension of the state space to the gradient of the phase field variable leads to a Port Hamiltonian formulation of the solidification model. The model is written in such a way that it utilizes the available thermodynamic data for liquid water and ice, allowing for a detailed and physically-based modeling, leading to an implicit Boundary Port Hamiltonian model. The final chapter focuses on the structure-preserving discretization of the solidification process using the Partitioned Finite Element Method. This ensures that the discretized model retains the Port Hamiltonian structure and, in turn, the key properties such as energy conservation and passivity. The chapter covers weak formulations, projections, and discrete Hamiltonians for the heat equation and the Allen-Cahn equation, leading to the spatial discretization of the solidification model. The principal contribution of this chapter lies in the discretization methodology applied to the implicit Port Hamiltonian model of the solidification process using entropy as the generating function. Overall, this thesis provides structured models of solidification processes using the Port Hamiltonian framework, providing a foundation for their physics-based simulation and control and for future research and development in distributed parameter systems with moving interfaces, particularly for environmental and chemical engineering applications

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6

Hassan, Hamdy Abo Ali. "Etude et optimisation des transferts de chaleur en injection moulage : analyse de leur influence sur les propriétés finales". Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13956.

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Les plastiques sont typiquement des polymères de grand poids moléculaire. Ils peuvent contenir des autres substances pour améliorer leurs performances et/ou pour réduire les prix. L'industrie plastique est l'une des industries qui a la croissance la plus rapide du monde : de nombreux produits de la vie quotidienne contiennent l'utilisation du produit plastique. Il y a différents procédés pour la mise en forme des polymères (soufflage, moulage par soufflage, moulage par compression, moulage par transfert, extrusion, moulage par injection) pour lesquels les matériaux utilisés, la qualité et la forme du produit fabriqué varient. En particulier, la demande des pièces moulées par injection augmente chaque année. Cela vient du fait que le moulage par injection est identifié comme une des techniques de fabrication les plus efficaces et économiques pour produire des pièces en plastique de formes précises et complexes. Il y a trois étapes significatives dans le processus : premièrement, on remplit la cavité avec le polymère fondu à une température et à une pression d'injection élévées (étape de remplissage et bien remplissage). Deuxièmement la chaleur de la pièce en polymère est évacuée par le système de refroidissement (étape de refroidissement). Troisièmement, après que la partie solidifiée a été éjectée, le moule est fermé et le prochain cycle d'injection commence (étape d'éjection)
Plastics are typically polymers of high molecular weight, and may contain other substances to improve performance and/or reduce costs. Plastic industry is one of the world?s fastest growing industries; almost every product that is used in daily life involves the usage of plastic. There are different methods for polymer processing (thermoforming, blow molding, compression molding of polymers, transfer molding of polymers, extrusion of polymers, injection molding of polymers, etc.) which differ by the method of fabrications, the used materials, the quality of the product and the form of the final product. Demand for injection molded parts continues to increase every year because plastic injection molding process is well known as the most efficient manufacturing techniques for economically producing precise plastic parts and complex geometry at low cost and a large quantity. The plastic injection molding process is a cyclic process where polymer is injected into a mold cavity, and solidifies to form a plastic part. There are three significant stages in each cycle. The first stage is filling the cavity with hot polymer melt at high injection pressure and temperature (filling and post-filling stage). It is followed by cooling the injected polymer material until the material is completely solidified (cooling stage), finally the solidified part is ejected (ejection stage)

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7

Mehrabi, M. Reza. "Modeling transport processes in directional solidification". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11999.

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8

Leung, Winnie C. M. "Thermomechanical analyses of metal solidification processes". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/42561.

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9

Gao, Fuquan. "Molten microdrop deposition and solidification processes". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11622.

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10

Chakraborty, Suman. "Studies On Momentum, Heat And Mass Transfer In Binary Alloy Solidification Processes". Thesis, Indian Institute of Science, 2001. https://etd.iisc.ac.in/handle/2005/287.

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The primary focus of the present work is the development of macro-models for numerical simulation of binary alloy solidification processes, consistent with microscopic phase-change considerations, with a particular emphasis on capturing the effects of non-equilibrium species redistribution on overall macrosegregation behaviour. As a first step, a generalised macroscopic framework is developed for mathematical modelling of the process. The complete set of equivalent single-phase governing equations (mass, momentum, energy and species conservation) are solved following a pressure-based Finite Volume Method according to the SIMPLER algorithm. An algorithm is also developed for the prescription of the coupling between temperature and the melt-fraction. Based on the above unified approach of solidification modelling, a macroscopic numerical model is devised that is capable of capturing the interaction between the double-diffusive convective field and a localised fluid flow on account of solutal undercooling during non-equilibrium solidification of binary alloys. Numerical simulations are performed for the case of two-dimensional transient solidification of Pb-Sn alloys, and the simulation results are also compared with the corresponding experimental results quoted in the literature. It is observed that non-equilibrium effects on account of solutal undercooling result in an enhanced macrosegregation. Next, the model is extended to capture the effects of dendritic arm coarsening on the macroscopic transport phenomena occurring during a binary alloy solidification process. The numerical results are first tested against experimental results quoted in the literature, corresponding to the solidification of an Al-Cu alloy in a bottom-cooled cavity. It is concluded that dendritic arm coarsening leads to an increased effective permeability of the mushy region as well as an enhanced eutectic fraction of the solidified ingot. Consequently, an enhanced macrosegregation can be predicted as compared to that dictated by shrinkage-induced fluid flow alone. For an order-of-magnitude assessment of predictions from the numerical models, a systematic approach is subsequently developed for scaling analysis of momentum, heat and species conservation equations pertaining to the case of solidification of a binary mixture. A characteristic velocity scale inside the mushy region is derived, in terms of the morphological parameters of the two-phase region. A subsequent analysis of the energy equation results in an estimation of the solid layer thickness. It is also shown from scaling principles that non-equilibrium effects result in an enhanced macro-segregation compared to the case of an equilibrium model For the sake of assessment of the scaling analysis, the predictions are validated against computational results corresponding to the simulation of a full set of governing equations, thus confirming the trends suggested by the scale analysis. In order to analytically investigate certain limiting cases of unidirectional alloy solidification, a fully analytical solution technique is established for the solution of unidirectional, conduction-dominated, alloy solidification problems. The results are tested for the problem of solidification of an ammonium chloride-water solution, and are compared with those from existing analytical models as well as with the corresponding results from a fully numerical simulation. The effects of different microscopic models on solidification behaviour are illustrated, and transients in temperature and heat flux distribution are also analysed. An excellent agreement between the present solutions and results from the computational simulation can be observed. The generalised numerical model is subsequently utilised to investigate the effects of laminar double-diffusive Rayleigh-Benard convection on directional solidification of binary fluids, when cooled and solidified from the top. A series of experiments is also performed with ammonium chloride-water solutions of hypoeutectic and hypereutectic composition, so as to facilitate comparisons with numerical predictions. While excellent agreements can be obtained for the first case, the second case results in a peculiar situation, where crystals nucleated on the inner roof of the cavity start descending through the bulk fluid, and finally settle down at the bottom of the cavity in the form of a sedimented solid layer. An eutectic solidification front subsequently progresses from the top surface vertically downwards, and eventually meets the heap of solid crystals collected on the floor of the cavity. However, comparison of experimental observations with corresponding numerical results from the present model is not possible under this situation, since the associated transport process involves a complex combination of a number of closely interconnected physical mechanisms, many of which are yet to be resolved. Subsequent to the development of the mathematical model and experimental arrangements for macroscopic transport processes during an alloy solidification process, some of the important modes of double-diffusive instability are analytically investigated, as a binary alloy of any specified initial composition is directionally solidified from the top. By employing a close-formed solution technique, the critical liquid layer heights corresponding to the onset of direct mode of instability are identified, corresponding two a binary alloy with three different initial compositions. In order to simulate turbulent transport during non-equilibrium solidification processes of binary alloys, a modified k-8 model is subsequently developed. Particular emphasis is given for appropriate modelling of turbulence parameters, so that the model merges with single-phase turbulence closure equations in the pure liquid region in a smooth manner. Laboratory experiments are performed using an ammonium chloride-water solution that is solidified by cooling from the top of a rectangular cavity. A good agreement between numerical and experimental results is observed. Finally, in order to study the effects of three-dimensionality in fluid flow on overall macrosegregation behaviour, the interaction between double-diffusive convection and non-equilibrium solidification of a binary mixture in a cubic enclosure (cooled from a side) is numerically investigated using a three-dimensional transient mathematical model. Investigations are carried out for two separate model systems, one corresponding to a typical metal-ally analogue system and other corresponding to an actual metal-alloy system. As a result of three-dimensional convective flow-patterns, a significant solute macrosegregation is observed in the transverse sections of the cavity, which cannot be captured by two-dimensional simulations.

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11

Chakraborty, Suman. "Studies On Momentum, Heat And Mass Transfer In Binary Alloy Solidification Processes". Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/287.

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The primary focus of the present work is the development of macro-models for numerical simulation of binary alloy solidification processes, consistent with microscopic phase-change considerations, with a particular emphasis on capturing the effects of non-equilibrium species redistribution on overall macrosegregation behaviour. As a first step, a generalised macroscopic framework is developed for mathematical modelling of the process. The complete set of equivalent single-phase governing equations (mass, momentum, energy and species conservation) are solved following a pressure-based Finite Volume Method according to the SIMPLER algorithm. An algorithm is also developed for the prescription of the coupling between temperature and the melt-fraction. Based on the above unified approach of solidification modelling, a macroscopic numerical model is devised that is capable of capturing the interaction between the double-diffusive convective field and a localised fluid flow on account of solutal undercooling during non-equilibrium solidification of binary alloys. Numerical simulations are performed for the case of two-dimensional transient solidification of Pb-Sn alloys, and the simulation results are also compared with the corresponding experimental results quoted in the literature. It is observed that non-equilibrium effects on account of solutal undercooling result in an enhanced macrosegregation. Next, the model is extended to capture the effects of dendritic arm coarsening on the macroscopic transport phenomena occurring during a binary alloy solidification process. The numerical results are first tested against experimental results quoted in the literature, corresponding to the solidification of an Al-Cu alloy in a bottom-cooled cavity. It is concluded that dendritic arm coarsening leads to an increased effective permeability of the mushy region as well as an enhanced eutectic fraction of the solidified ingot. Consequently, an enhanced macrosegregation can be predicted as compared to that dictated by shrinkage-induced fluid flow alone. For an order-of-magnitude assessment of predictions from the numerical models, a systematic approach is subsequently developed for scaling analysis of momentum, heat and species conservation equations pertaining to the case of solidification of a binary mixture. A characteristic velocity scale inside the mushy region is derived, in terms of the morphological parameters of the two-phase region. A subsequent analysis of the energy equation results in an estimation of the solid layer thickness. It is also shown from scaling principles that non-equilibrium effects result in an enhanced macro-segregation compared to the case of an equilibrium model For the sake of assessment of the scaling analysis, the predictions are validated against computational results corresponding to the simulation of a full set of governing equations, thus confirming the trends suggested by the scale analysis. In order to analytically investigate certain limiting cases of unidirectional alloy solidification, a fully analytical solution technique is established for the solution of unidirectional, conduction-dominated, alloy solidification problems. The results are tested for the problem of solidification of an ammonium chloride-water solution, and are compared with those from existing analytical models as well as with the corresponding results from a fully numerical simulation. The effects of different microscopic models on solidification behaviour are illustrated, and transients in temperature and heat flux distribution are also analysed. An excellent agreement between the present solutions and results from the computational simulation can be observed. The generalised numerical model is subsequently utilised to investigate the effects of laminar double-diffusive Rayleigh-Benard convection on directional solidification of binary fluids, when cooled and solidified from the top. A series of experiments is also performed with ammonium chloride-water solutions of hypoeutectic and hypereutectic composition, so as to facilitate comparisons with numerical predictions. While excellent agreements can be obtained for the first case, the second case results in a peculiar situation, where crystals nucleated on the inner roof of the cavity start descending through the bulk fluid, and finally settle down at the bottom of the cavity in the form of a sedimented solid layer. An eutectic solidification front subsequently progresses from the top surface vertically downwards, and eventually meets the heap of solid crystals collected on the floor of the cavity. However, comparison of experimental observations with corresponding numerical results from the present model is not possible under this situation, since the associated transport process involves a complex combination of a number of closely interconnected physical mechanisms, many of which are yet to be resolved. Subsequent to the development of the mathematical model and experimental arrangements for macroscopic transport processes during an alloy solidification process, some of the important modes of double-diffusive instability are analytically investigated, as a binary alloy of any specified initial composition is directionally solidified from the top. By employing a close-formed solution technique, the critical liquid layer heights corresponding to the onset of direct mode of instability are identified, corresponding two a binary alloy with three different initial compositions. In order to simulate turbulent transport during non-equilibrium solidification processes of binary alloys, a modified k-8 model is subsequently developed. Particular emphasis is given for appropriate modelling of turbulence parameters, so that the model merges with single-phase turbulence closure equations in the pure liquid region in a smooth manner. Laboratory experiments are performed using an ammonium chloride-water solution that is solidified by cooling from the top of a rectangular cavity. A good agreement between numerical and experimental results is observed. Finally, in order to study the effects of three-dimensionality in fluid flow on overall macrosegregation behaviour, the interaction between double-diffusive convection and non-equilibrium solidification of a binary mixture in a cubic enclosure (cooled from a side) is numerically investigated using a three-dimensional transient mathematical model. Investigations are carried out for two separate model systems, one corresponding to a typical metal-ally analogue system and other corresponding to an actual metal-alloy system. As a result of three-dimensional convective flow-patterns, a significant solute macrosegregation is observed in the transverse sections of the cavity, which cannot be captured by two-dimensional simulations.

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12

Hoadley, Andrew Forbes Alexander. "Modelling of heat flow in batch solidification processes". Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278260.

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13

Tropsa, Vlado. "Predicting residual stresses due to solidification in cast plastic plates". Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271561.

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14

Messiaen, Laure. "Recherche de paramètres morphologiques influents pour la prévision des caractéristiques mécaniques d'un acier austénoferritique". Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 1997. http://tel.archives-ouvertes.fr/tel-00817970.

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Les aciers inoxydables austénoferritiques sont couramment utilisés dans l'industrie (nucléaire en particulier) pour leurs bonnes propriétés, notamment mécaniques. Cependant ces aciers sont susceptibles de "vieillir" en cours d'utilisation à des températures élevées. Comme ces propriétés (résilience, ténacité) sont souvent très dispersées et se dégradent lors du vieillissement, on cherche à les prévoir avec la plus grande précision possible. Pour ce faire on propose d'expliquer une partie de la dispersion observée sur la résilience par des paramètres mesurables, liés à la morphologie biphasée et bipercolée particulièrement complexe de ces aciers. Cette morphologie est d'abord caractérisée à partir de l'observation d'images en 2D et de la reconstitution d'une image en 3D. Parallèlement on précise la genèse de cette microstructure. Au vu des observations et analyses précédentes, les outils classiques de la morphologie mathématique peuvent être utilisés pour quantifier par analyse d'image cette structure et proposer des variables pertinentes. En utilisant un modèle paramétrique pour décrire le comportement de la résilience , on montre l'influence d'un paramètre morphologique -la finesse de la microstructure- sur cette dernière. Dans le cas des produits très vieillis -le plus important en pratique-, le manque de données disponibles ne permet pas de proposer un modèle de résilience qui tienne compte de cette variable morphologique. Un modèle mathématique de la structure 3D du matériau est enfin proposé: une chaîne de Markov homogène de processus spatiaux 3D dont l'évolution dans le temps mime la solidification. La morphologie de la microstructure est ainsi résumée à 8 paramètres. Ce modèle est susceptible d'être couplé avec un modèle de résilience pour élargir ses possibilités de prévision. Il pourrait également être utilisé pour servir de base à des modélisations ultérieures de l'endommagement et de la rupture de matériaux biphasés.

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15

Huang, Ying. "Treatment of PCB-contaminated soil by stabilization and solidification processes". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ39663.pdf.

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16

Pagalthivarthi, Krishnan V. "Thermosolutal convection and related transport processes in binary alloy solidification". Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/18245.

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17

Sharpe, Michael Anthony. "On convection and stability of some welding and solidification processes". Thesis, University of Southampton, 2000. https://eprints.soton.ac.uk/50624/.

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In this thesis a variety of problems are considered, the first of which is associated with the welding process. Experiments indicate that the shape of a weld pool is influenced by convection in the liquid metal. In recent years it has been shown that this convection is crucially affected by the Marangoni (or thermocapillary) force. Recently Craine and Belgrove ([30], [7]) have developed a two-dimensional, axisymmetric model which includes the Marangoni force on the free surface of a semi-infinite region of liquid steel when a point source of current and heat is incident on the free surface. An asymptotic solution to this problem is obtained in this thesis, and the surface tension gradient with respect to temperature, dj/dT, a parameter which is crucial to the magnitude of the Marangoni force, is found to affect every coefficient in the leading and first order asymptotic expansions. In various theoretical and experimental models purely poloidal flow bifurcates to a rotating flow. To investigate this possibility for our flow a linear stability analysis is performed on a numerically obtained poloidal solution for the flow and temperature distribution in a hemisphere (a model first derived in [7]). For the azimuthal stability mode m = 0 the equation governing the linear stability of the rotating motion is found to decouple from the corresponding poloidal equations. The poloidal and azimuthal stability equations both become unstable at different critical currents dependent on the sign and magnitude of d^/dT. An investigation of the eigenvectors indicates the onset of instability near to the point source. For the upper modes instability occurs only when m = 1 and in a very small region of parameter space. In the second part of this thesis a freezing sphere problem with flow is used to compare a sharp interface Stefan model and a diffuse interface phase-field model. Firstly a Stefan model that includes a disparity between the density of the solid and liquid phases is derived and solved numerically. This model is compared with a recent phase-field model with flow, derived by Anderson et al. in [2]. In this thesis the one-dimensional isotropic version of Anderson's model is obtained in spherical polar coordinates and using certain simplifications when the dimensionless thickness of the interface £5 is vanishingly small a leading order asymptotic expression reproduces the Stefan model with flow. The phase-field model is subsequently modified and solved numerically, and the results are compared with the sharp interface model. Close agreement is observed between these models when es < 0.01.

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18

Chen, Yin-Heng. "Study of solidification, shrinkage and natural convection in casting processes /". The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487676847114631.

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19

Chow, Peter M. Y. "Control volume unstructured mesh procedure for convection-diffusion solidification processes". Thesis, University of Greenwich, 1993. http://gala.gre.ac.uk/6133/.

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The research work presented herein addresses the unstructured mesh problem in finite volume (FV) or control volume (CV) method used in numerical simulations. The modelling work conducted is in context of solidification for casting processes. The control volume-unstructured mesh (CV-UM) method can be categorised into two approaches, a vertex-centred and a cell-centred approach. The classification of the approach is based on the relationship between the control volume and the unstructured mesh. The vertex-centred is naturally unstructured and has been used successfully in fluid flow and heat transfer calculations. The cell-centred on the other hand has always been associated with structured (quadrilateral) meshes, this has been extended to handle unstructured mesh in the current work and is called the irregular control volume (ICV) method. Both approaches have been studied for solidification by conduction only, using several standard phase change test cases and one with experimental data from the casting industry. The result of this work is reported and their suitability for solidification addressed. For the ICV method, the extension to solve the full convective-diffusive solidification was undertaken, these are primarily the fluid flow and energy equations solved using the well known SIMPLE algorithm. One spin-off from the ICV is the appearance of "highorder cell" control volumes, control volumes with more than the standard four cell faces in two-dimensions. The high-order cell technique is exhibiting the same characteristics as high-order schemes used in standard CV method, when applied to standard CFD test cases. The one current drawback for the technique is the generation of these high-ordercells, currently no fully- or semi-automatic mesh generation is available. This prevented further study of the technique and used in the solidification test cases, where in one, experimental data is available for the phase change fronts. This was carried Out using quadrilateral meshes, but solved using the unstructured approach of the ICV. The predicted solution is in qualitative agreement with experiment. The second convective-diffusive solidification problem is the first to demonstrate the CV-UM integrated framework by solving two major casting components simultaneously, the solidification (the work undertaken in this research) and the residual stress for deformation. This is still an on going research work, where refinement and validation are required and further integration of casting processes, such as mould filling, are necessary to complete the various stages of the shape casting process. This kind of integrated simulation requires huge amount of computations, it will take days for traditional scalar computers to do one prediction. Vector and parallel machines offer ways in which to bring down the computing times to a level that is in hours instead of days. To utilise machines with vector and parallel capability efficiently, the algorithm of the model process need to be mapped onto such architectures for it to take full advantage of the computing powers. The solidification algorithm in threedimensions has been vectorised and a speed-up of five is possible. This was part of a collective study into mapping algorithms Onto vector and parallel computers, where it emerged that the ideal computing architecture is a network of processors each with its own vector capabilities.

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20

Maffettone, Roberta. "Stabilization/solidification processes for the treatment of contaminated soil and waste". Doctoral thesis, Universita degli studi di Salerno, 2015. http://hdl.handle.net/10556/1753.

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2013-2014
Recovering industrial waste and contaminated soil is one of the main objectives in environmental management. Nowadays in Italy, landfilling is responsible for up to 40% of total soil contamination and up to 50% of the used remediation techniques involves excavation and disposal. On the other hand, the European Legislation has set key drivers to improve waste management, as setting recycling targets and limiting the use of landfilling with its rising cost. In this scenario, new technologies to reduce the toxicity of contaminated soil and hazardous waste before their disposal or to reuse them as aggregates are of great interest. Stabilisation/solidification (S/S) is a treatment for wastes and soils which mainly uses cementitious or pozzolanic binders to produce a solid monolith that incorporates the contaminants. This process is particularly effective on heavy-metals contaminated soils. Other additives/fillers can also be used during a pre-treatment phase to amend adverse chemical and physical characteristics, e.g. high moisture content. Alternative methods to treat contaminated waste and soil exploited the application of accelerated carbonation to cement-based S/S. This process can improve the characteristics of the stabilized products in terms of leaching, strengths or pH. Accelerated carbonation (ACT) is an enhanced form of natural carbonation that has been developed during the last years at industrial scale for the treatment of contaminated soil and industrial wastes. Accelerated carbonation induces a rapid reaction exposing the mineral or the reactive waste to a controlled atmosphere containing CO2 and promotes rapid hardening of the product. The resultant precipitation of calcium carbonate reduces the porosity of the material, and leads to further changes at the microstructure, aiding the retention of contaminants and improving the mechanical properties. The pH is also lowered with the result of reduced solubility of many heavy metals. Waste can be formed into aggregate by agglomeration. If the two processes are combined, it is feasible to produce hardened aggregate. The final product can be reused as aggregate in engineering fill or in concrete production. The aim of the research project conducted during the Ph.D. programme is the development of an innovative approach for the enhancing of stabilization/solidification treatment of contaminated soils and wastes. The research aimed at the identification of innovative formulation using cement and thermal wastes for heavy-metals contaminated soil treatment and at the investigation of the effect of the accelerated carbonation applied to cement-based stabilization/solidification. Tests of cement-based stabilization/solidification using Portland cement and the effect of accelerated carbonation on metals mobility were investigated on artificial heavy-metals contaminated soil at the Sanitary Environmental Engineering Division (SEED) at the University of Salerno. The process was assessed with further investigations on soil washing residues blended with thermal ashes and cement for the production of lightweight recycled aggregate. This part was conducted within the LLP Erasmus Placement Programme at the Centre for Contaminated Land Remediation (CCLR) of the University of Greenwich (UK). The process investigated entailed the mixing of soil washing residues with paper incineration ashes, reactive to carbon dioxide, or sewage sludge ashes followed by accelerated carbonation to produce the aggregate. Portland cement was used as the binder, which also has an ability to combine with CO2. The effect of accelerated carbonation on the cemented contaminated soil was evaluated by mineralogical and structural properties. Chemical stability was measured by leaching of heavy metals from the raw materials and the final products. The aggregates produced showed comparable strength to commercially lightweight aggregates. Accelerated carbonation increased the strength and the density of the aggregate compared to the hydrated one. Heavy metals leaching were substantially unaffected by carbonation, apart for copper and barium. Further investigation tested the aggregates for using in lightweight concrete block and for green roofing. The use of a synthetic CO2 flue gas lead to a capture of the carbon dioxide leading to a “low carbon” product. The study showed the applicability of the process for manufacturing lightweight aggregates from soil washing residues and ashes by enhanced cement based S/S as a good alternative for a wide range of civil engineering applications. The effect of accelerated carbonation has to be further explained. Future investigations are needed to enhance the process based on the variability of the wastes. Other waste and alternative carbon dioxide reactive fillers can be considered to be treated by the process. [edited by author]
XIII n.s.

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21

Ahmad, Nasir. "Numerical simulation of transport processes in multicomponent systems related to solidification problems /". [S.l.] : [s.n.], 1995. http://library.epfl.ch/theses/?nr=1349.

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Kapellakis, Iosif Emmanouil. "Olive mill wastewater management and treatment through soil, aquatic and solidification processes". Thesis, Glasgow Caledonian University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422022.

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23

Juang, Shueiwan Henry. "Finite element analysis of flow and solidification: application to die casting processes". The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1244133006.

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Juang, Shuei-wan Henry. "Finite element analysis of flow and solidification : application to die casting processes /". Connect to resource, 1991. http://rave.ohiolink.edu/etdc/view.cgi?acc%5Fnum=osu1244133006.

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25

Xu, Rui. "Control of heat and fluid flow in solidification processes by an inverse method". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0026/MQ52088.pdf.

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Zhang, Shaojie. "Numerical simulation of mechanical interactions between liquid and solid phase in solidification processes". Thesis, Université Paris sciences et lettres, 2020. https://pastel.archives-ouvertes.fr/tel-02897918.

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La maîtrise des phénomènes de macroségrégation et des défauts liés à la déformation est le principal enjeu des processus de solidification. La modélisation numérique apporte une réponse aux besoins industriels pour maîtriser ces défauts. L'un des problèmes les plus critiques et essentiels est le calcul simultané de l'écoulement du fluide dans les régions liquides et de l'évolution contrainte-déformation dans les régions déjà solidifiées. Dans ce but spécifique, un algorithme de solution partitionnée est développé pour modéliser à la fois les processus de coulée en lingots et de coulée continue: l'écoulement de liquide induit par convection naturelle ou étape de remplissage, le retrait de solidification, la déformation thermiquement induite de la phase solide. Sur la base des deux champs de vitesse - solide et liquide résultant de cette résolution couplée, la résolution du transport des espèces chimiques (macroségrégation) est réalisée
Control of macrosegregation phenomena and deformation related defects is the main issue in solidification processes. Numerical modeling provides an answer to industrial needs to master these defects. One of the most critical and essential issues is the concurrent computation of fluid flow in the bulk liquid and stress-strain evolution in the already solidified regions. For this specific purpose, a partitioned solution algorithm is developed to model both ingot casting and continuous casting processes. Liquid flow induced by natural convection or filling step, solidification shrinkage and thermally induced deformation of the solid phase. On the basis of the resulting liquid and solid velocity fields, the transport of chemical species (macrosegregation) is achieved

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27

Ranganathan, Sathees. "Rapid solidification behaviour of Fe and Al based alloys". Doctoral thesis, KTH, Materialvetenskap, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11325.

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Rapid solidification experiment on Fe-Cr-Mo-Mn-Si-C alloy was performed to investigate metastable phases formed during the solidification. A wide range of cooling rate was used to analyse the sample from melt spinning technique (~107 K/s) to water quenching method (~102 K/s). A single phase featureless structure was obtaind initially in the melt spinning experiment for 77Fe-8Cr-6Mn-5Si-4C alloy. Reduction of C and addition of Mo led to form a complete featureless structure for 2.85 mm rod for 72.8Fe-8Cr-5Mo-6Mn-5Si-3.2C. Subsequent investigation of influence of Mo, Cr and Mn on the single phase featureless structure concludes that 7.5 mm thick complete featureless phase could be formed at 63.8Fe-15Cr-7Mo-6Mn-5Si-3.2C alloy composition. In a separate attempt, powder samples of 40 μm dia. size complete featureless powders were produced for three slightly different compostions for the same alloy system. Characterisation of the featureless phases reveals that it could be a single phase metastable structure of ε phase or austenitic solid solution with high amount of alloying element dissolved in it. Subsequent heat treatment of this featureless phase of the rod and the powder at different temperatures formed bainitic ferrite with fine carbides dispersed in the austenitic matrix. Hardness values measured on featureless phase found to have influenced by the alloying element specially Mo, Cr and Mn. In an attempet to improve clean melting condition to extend the featureless phase and to form amorphous, an elliptic short arc lamp vaccum furnace was designed with 10 kW lamp power. Around 30 g of iron based alloy system was melted and cast as a 7 mm rod sample in a copper mould. Design details of new mirror and the lamp furnace are presented. In a separate study, influence of the melt temperature on Al-Y and Al-Si alloys were investigated by levitaion casting in a silver mould at around 2000 K/s cooling rate. Plate like structure of Al8Y3 primary phase was observed at low melt temperature with small percentage of peritectic transformation of Al8Y3 and liquid melt into Al9Y2. A pre-dentritic star like crystal of Al3Y was observed in a fine eutectic matrix at very high melt temperature. Amount and number of primary Si crystals formed in a unit area during the solidification increases as the melt temperature increases.
QC 20100805

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28

Kirkpatrick, Timothy. "The kinetics of tin solidification in lead-free solder joints". Diss., Online access via UMI:, 2006.

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29

Kinyanjui, Robert. "Thermal processes and solidification kinetics of evolution of the microstructure of Sn-xAg-yCu solder alloys". Diss., Online access via UMI:, 2005.

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Thesis (Ph. D.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Multidisciplinary Program in Materials Science and Engineering, 2005.
Includes bibliographical references.

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30

Mondragon, Camacho Ricardo. "Non-physical enthalpy method for phase change modelling in the solidification process". Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/nonphysical-enthalpy-method-for-phase-change-modelling-in-the-solidification-process(2ab7597c-eaaa-44d8-abb8-0bf49e413c76).html.

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This research is concerned with the development of a mathematical approach for energy and mass transport in solidification modelling involving a control volume (CV) technique and finite element method (FEM) and incorporating non-physical variables in its solution. The former technique is used to determine an equivalent capacitance to describe energy transport whilst the latter technique provides temperatures over the material domain. The numerical solution of the transport equations is achieved by the introduction of two concepts, i.e. weighted transport equations and non-physical variables. The main aim is to establish equivalent transport equations that allow exact temporal integration and describe the behaviour of non-physical variables to replace the original governing transport equations. The variables defined are non-physical in the sense that they are dependent on the velocity of the moving CV. This dependence is a consequence of constructing transport equations that do not include flux integrals. The form of the transport equations facilitate the construction of a FEM formulation that is applicable to heat and mass transport problems and caters for singularities arising from phase-change, which can prove difficult to model. However, applying the non-physical enthalpy method (NEM) any singularity involved in the solidification process is precisely identified and annihilated.

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31

Kotadia, Hirenkumar R. "Solidification behaviour of Al-Sn-Cu immiscible alloys and Al-Si cast alloys processed under intensive shearing". Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4517.

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Alloy castings are usually solidified with a coarse columnar grain structure under normal casting conditions unless the mode of the solidification is carefully controlled. It is desirable for the grain structure to be fine and equiaxed to improve their mechanical performance as finished castings. It is possible to develop a fine and equiaxed grain structure either by increasing the number of nucleation sites or by grain multiplication. Immiscible alloys with a microstructure in which a soft phase is dispersed homogeneously in a hard matrix have significant potential applications in advanced bearing systems, especially for the automotive industry. Despite considerable efforts made worldwide, including extensive space experiments, no casting techniques so far can produce the desired immiscible microstructure of alloys. Experimental results on Al-Sn-Cu immiscible alloys have confirmed that intensive shearing using melt conditioning by an advanced shearing technology (MCAST) unit, is an effective way to achieve a fine and uniform dispersion of the soft phase without macro-demixing, and that such a dispersed microstructure can be further refined in alloys with precipitation of the primary Al phase prior to the demixing reaction. In addition, it was found that melt shearing at 200 rpm for 60 s will be adequate to produce a fine and uniform dispersion of the Sn phase, and that a higher shearing speed and prolonged shearing time can only achieve further minor refinement. A study of Al-Si hypoeutectic and hypereutectic alloys presents the effects of the processing temperature and intensive shearing on the microstructural and mechanical properties which have been investigated systematically. Attempts have been made to explain the solidification mechanism with intensive melt shearing. The sheared melt was cast into tensile test samples by high pressure die caster (HPDC) to examine the microstructures and mechanical properties. The experimental results reveal that significant grain refinement and uniformity of grains was achieved by the intensive shearing and also a considerable increase in mechanical properties with pouring temperature by changing intermetallic particles morphology, the position of defect band and reduced microscopic defects.

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32

Dias, Antonio Carlos Pires. "Solidificação de ligas euteticas livres de Pb para soldagem : parametros termicos e microestrutura". [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264429.

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Orientadores: Amauri Garcia, Noe Cheung
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: As ligas de solda à base de estanho apresentam excelente fluidez e temperaturas de trabalho ideais para a união de componentes eletrônicos. A solda com ligas do sistema estanho chumbo é a mais comum para soldas em eletrônica. Entretanto, há muitas preocupações com o uso do chumbo, devido aos diversos efeitos adversos na saúde humana e contaminação do meio ambiente. Por essas razões, na maioria dos países o chumbo já é condenado e proibido de ser incorporado em diversos produtos. Neste sentido, a indústria eletrônica está de olho em soldas livres de chumbo que possam substituir a clássica solda estanho-chumbo. É objetivo deste trabalho analisar a solidificação de ligas eutéticas dos sistemas Sn-Ag e Sn-Cu, que são duas ligas com potencial de substituição. Foram desenvolvidos experimentos para determinar a influência do acabamento superficial da chapa molde nos parâmetros térmicos de solidificação durante a solidificação direcional ascendente em regime transitório de extração de calor de ligas eutéticas Sn-Pb, Sn-Cu e Sn-Ag. Foram utilizados dois tipos de acabamentos superficiais na chapa molde: lixado e ranhurado, para investigar as condições de afinidade metal/substrato. Foi desenvolvida uma abordagem teórico-experimental para determinar quantitativamente as variáveis térmicas, tais como: coeficiente de transferência de calor global (hg) e velocidade de deslocamento da frente de solidificação. As micro estruturas de solidificação foram caracterizadas e os espaçamentos dendríticos secundários (?2) foram medidos na direção longitudinal dos lingotes, e correlacionados com as variáveis térmicas que atuaram durante a solidificação.
Abstract: Tin based alloys for welding applications have excellent fluidity and adequate temperature working range to join electronic components. The most used tin alloys for welding is the eutectic Sn-Pb alloy. However, there are some concerns about lead, due to hazardous effects to health and to environment. Due to theses reasons, many countries condemn and prohibit the use of lead in several products. In this sense, the electronic industries are looking for lead-free solder alloys with a view to replace the traditional Sn-Pb eutectic alloy. The aim of this work is to analyze the solidification of Sn-Ag and Sn-Cu eutectic alloys which are potential alloys candidates to replace the eutectic Sn-Pb alloy. Experiments were conducted to determine the influence of the mold wall roughness on the thermal solidification parameters during the upward unsteady-state directional solidification of eutectic Sn-Pb, Sn-Cu and Sn-Ag alloys. Two different kinds of surface mold finishing, sanded and grooved, were used in order to analyze metal/substrate affinity. A combined theoretical and experimental approach has been used to quantitatively determine such thermal variables, i.e., transient global heat transfer coefficient (hg) and solidification growth rates. The microstructures have been characterized and the secondary (?2) dendrite arm spacings were measured along the castings length and correlated to transient solidification thermal variables.
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

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33

Narra, Sneha Prabha. "Melt Pool Geometry and Microstructure Control Across Alloys in Metal Based Additive Manufacturing Processes". Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/914.

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There is growing interest in using additive manufacturing for various alloy systems and industrial applications. However, existing process development and part qualification techniques, both involve extensive experimentation-based procedures which are expensive and time-consuming. Recent developments in understanding the process control show promise toward the efforts to address these challenges. The current research uses the process mapping approach to achieve control of melt pool geometry and microstructure in different alloy systems, in addition to location specific control of microstructure in an additively manufactured part. Specifically, results demonstrate three levels of microstructure control, starting with the prior beta grain size control in Ti-6Al-4V, followed by cell (solidification structure) spacing control in AlSi10Mg, and ending with texture control in Inconel 718. Additionally, a prediction framework has been presented, that can be used to enable a preliminary understanding of melt pool geometry for different materials and process conditions with minimal experimentation. Overall, the work presented in this thesis has the potential to reduce the process development and part qualification time, enabling the wider adoption and use of additive manufacturing in industry.

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34

Kotova, Yulia. "Entwicklung und Implementierung von Programmmodulen zur Simulation gießtechnischer Prozesse". Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2010. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-39300.

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In Rahmen dieser Arbeit wurde ein Simulationsprogramm für Gießprozesse weiterentwickelt. Zunächst wurden die Richtigkeit der mathematischen Lösung und die Sensibilität der Software bestätigt. Dazu wurde ein Vergleich der berechneten mit den experimentellen Werten durchgeführt. Zur Messung der Wanddicke des erstarrenden Gussteils wurde eine neue Methode zur Visualisierung der Berechnungsergebnisse erarbeitet. Anhand zweier Beispiele zur Berechnung eines dünnwandigen, komplizierten Al-Gussteils und eines exothermischen Speisers wurde eine korrekte Nutzung neuer Gießtechnologien aufgezeigt. Das Simulationssystem wurde speziell für das Stranggießen modifiziert. Die neu entwickelten Berechnungsalgorithmen sowie die Visualisierungsmöglichkeiten erlauben eine exakte Modellierung des Strangabzuges in der Gießmaschine. Auch in diesem Falle liefert der Vergleich zwischen den durchgeführten Berechnungen und den erzielten Versuchswerten die Richtigkeit und Exaktheit der neu eingesetzten Methode.

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35

Gockel, Joy E. "Integrated Control of Solidification Microstructure and Melt Pool Dimensions In Additive Manufacturing Of Ti - 6Al - 4V". Research Showcase @ CMU, 2014. http://repository.cmu.edu/dissertations/374.

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Additive manufacturing (AM) offers reduced material waste and energy usage, as well as an increase in precision. Direct metal AM is used not only for prototyping, but to produce final production parts in the aerospace, medical, automotive and other industries. Process mapping is an approach that represents process outcomes in terms of process input variables. Solidification microstructure process maps are developed for single bead and thin wall deposits of Ti-6Al-4V via an electron beam wire feed and electron beam powder bed AM process. Process variable combinations yielding constant beta grain size and morphology are identified. Comparison with the process maps for melt pool geometry shows that by maintaining a constant melt pool cross sectional area, a constant grain size will also be achieved. Additionally, the grain morphology boundaries are similar to curves of constant melt pool aspect ratio. Experimental results are presented to support the numerical predictions and identify a proportional size scaling between beta grain widths and melt pool widths. Results demonstrate that in situ, indirect control of solidification microstructure is possible through direct melt pool dimension control. The ability to control solidification microstructure can greatly accelerate AM process qualification potentially allow for tailored microstructure to the desired application.

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36

Kuchi, Satish C. "Effect of Finite Geometry on Solidification Microstructure in Beam-Based Fabrication of Thin Wall Structures". Wright State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=wright1253252782.

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Cante, Manuel Venceslau. "Solidificação transitoria, microestrutura e propriedades de ligas Al-Ni". [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265081.

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Orientador: Amauri Garcia
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: O desenvolvimento de microestruturas otimizadas durante o processo de solidificação são de fundamental importância nas propriedades e desempenho de produtos acabados baseados em ligas metálicas. Neste estudo é analisada a cinética envolvida no processo de solidificação, seus efeitos nos parâmetros macro e microestruturais e a sua conseqüente influência nas propriedades mecânicas. Com esse intuito, ligas hipoeutéticas do sistema binário são estudadas Al-Ni por meio de experimentos de solidificação vertical ascendente sob regime transitório de condução de calor. Os espaçamentos dendríticos primários (?1) e secundários(?2) foram medidos ao longo de todos os lingotes para cada uma das ligas analisadas e correlacionados com as variáveis térmicas de solidificação. Uma abordagem teórico-experimental é utilizada na determinação quantitativa de tais variáveis térmicas: 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. Os dados experimentais referentes à solidificação das ligas são confrontados com os principais modelos teóricos de crescimento dendrítico da literatura. Este estudo aborda, também, a influência do teor de soluto nos espaçamentos dendríticos para as ligas estudadas. Do ponto de vista macroestrutural, verifica-se que a transição colunar/equiaxial (TCE) ocorre para ligas hipoeutéticas Al-Ni para uma taxa crítica de resfriamento de 0,16 K/s. Por ensaios de tração as propriedades mecânicas das ligas do sistema Al-Ni são correlacionadas com parâmetros da micro-estrutura dendrítica resultante do processo de solidificação. Verifica-se que os limites de escoamento e de resistência à tração crescem com o aumento da concentração de soluto e decrescem com o aumento dos espaçamentos dendríticos, ?1 e ?2. O alongamento específico, por outro lado, mostra-se independente da composição e do arranjo dendrítico. Para a liga Al-5%Ni foi também realizado um estudo de solidificação rápida por refusão da superfície a laser para análise das variações microestruturais e de dureza entre as áreas não tratadas e tratadas superficialmente.
Abstract: The development of optimized microstructures during the solidification stage of processing is of fundamental importance to the mechanical properties and to the performance of finished products of metallic alloys. In this study the kinetics of solidification and its effects on macro and microstructural parameters, as well as the consequent influence on the final mechanical properties are analyzed. Hypoeutectic Al-Ni alloys are studied by upward unidirectional solidification experiments under transient heat flow conditions. Primary (?1) and secondary (?2) dendrite arm spacings are measured along the castings for all alloys analyzed and correlated with transient solidification thermal variables. A combined theoretical/ experimental approach is used to quantitatively determine such thermal variables, i.e., transient metal/mold heat transfer coefficients, tip growth rates, thermal gradients, tip cooling rates and local solidification time. The experimental data concerning the Al-Ni alloys solidification are compared to the main predictive dendritic models from the literature and the dependence of dendrite arm spacing on the alloy solute content is also analyzed. From the macrostructural point of view, it is found that the CET occurs for a critical value of cooling rate of about 0.16 K/s for hypoeutectic Al-Ni alloys.With a view to correlate mechanical properties to dendrite arm spacings, tensile testings were carried out. It is found that the ultimate tensile strength and the yield strength increase with increasing alloy solute content and with decreasing primary and secondary dendrite arm spacings. In contrast, the elongation is found to be independent of both alloy composition and dendritic arrangement. For the Al 5%Ni alloy a rapid solidification study is carried out by using laser surface remelting in order to permit microstructural and microhardness variations throughout the resulting treated and untreated zones, to be analysed.
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica

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38

Belsito, Danielle L. "Application of Computational Thermodynamic and Solidification Kinetics to Cold Sprayable Powder Alloy Design". Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-dissertations/28.

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Military aircraft that require high maneuverability, durability, ballistic protection, reparability, and energy efficiency require structural alloys with low density, high toughness, and high strength. Also, repairs to these aircraft demand a production process that has the flexibility to be relatively in-situ with the same high-performance output. Materials produced by the cold spray process, a thermo-mechanical powder consolidation technique, meet many of the requirements. In accordance with President Obamaâ€™s 2011 Materials Genome Initiative, the focus of this effort is to design customized aluminum alloy powders which exploit the unique behavior and properties of the materials created by the cold spray process. Analytical and computational models are used to customize microchemistry, thermal conditioning, and solidification behavior of the powders by predicting equilibrium and non-equilibrium microstructure and resulting materials properties and performance. Thermodynamic, kinetic, and solidification models are used, including commercial software packages Thermo-Calc, Pandatâ„¢, and JMatProÂ®, and TC-PRISMA. Predicted powder properties can be used as input into a cold spray process impact model to determine the consolidated materialsâ€™ properties. Mechanical properties of powder particles are predicted as a function of powder particle diameter and are compared to experimental results.

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39

Moj, Lukas [Verfasser]. "A two-scale, two-phase model for the numerical simulation of thermal driven solidification processes during casting and forming of metallic materials / Lukas Moj". Aachen : Shaker, 2017. http://d-nb.info/1149268972/34.

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Mercader, Célia. "Filage continu de fibres de nanotubes de carbone : de la solidification aux propriétés finales". Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14095/document.

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Ce travail de thèse concerne l'étude du filage et des propriétés de fibres composites à base denanotubes de carbone. Les propriétés mécaniques des fibres en cours de solidification et enmouvement dans un bain de coagulation sont évaluées afin d'étudier l'influence de différentsparamètres physico-chimiques impliqués dans leur fabrication. Ces fibres, combinant despropriétés mécaniques et électriques prometteuses, peuvent être obtenues de façon continuegrâce au développement d'un nouveau procédé de filage. Elles présentent de plus un effetoriginal de mémoire de température dont l'origine est étudiée dans cette thèse. Ces fibres sontpotentiellement utiles pour diverses applications: des matériaux à haute absorption d'énergiemécanique à des textiles conducteurs fonctionnels
This thesis deals with the study the wet-spinning process for the production of carbonnanotube composite fibers and their properties. We have characterized the mechanicalproperties of the fibers during their solidification as they circulate along the pipe of thespinning line. The study of the influence of various chemical parameters allowed us todevelop a new process for the continuous and scalable production of these fibers, whichexhibit unique mechanical and electrical properties. Moreover, they show an original effect oftemperature memory. The origin of this phenomenon is investigated in this work. These fiberscould be used for various applications such as high energy absorption materials or functionalconductive textile

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41

Sheridan, Luke Charles. "An Adapted Approach to ProcessMapping Across Alloy Systems and Additive Manufacturing Processes". Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1471861921.

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42

Yang, Ming. "Numerical Modeling of Aluminum Sampling Process". Thesis, KTH, Materialvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-241102.

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Castings of aluminum alloys are widely used in the automotive and aerospace industries since they play a significant role in improving the performance and fuel efficiency. In aluminum industries, sampling is the most common method to evaluate the inclusion levels which is a key indicator for the quality of the aluminum alloys. Since how the filling process and solidification process will influence the inclusion characteristics during the sampling procedure is of great importance, the objectives of this work is to create a the two-phase flow model to simulate the filling process and solidification process, as well as calculate the particles movement in the whole sampling procedure. Computational Fluid Dynamics (CFD) modeling was used and this work was performed in the software ANSYS FLUENT. A numerical two dimensional (2D) axisymmetric model was built to simulate the sampling procedure with the assumption that the filling could be done along the main axis automatically. First, the initial solidification during the filling was taken into account without particle injection. The realizable k − ε turbulence model was used to model the effects of the turbulence. Several simulations with different inlet filling rate, different initial filling temperature and different inlet diameter was calculated to see the influence on the solidification behavior. Then, the whole sampling system was modeled with particle injection. The Discrete Phase Model (DPM) was used to simulate the particle motion in the melt and the focus was on the influence of the initial solidification on the inclusion distributions. Finally, the optimal sampling position inside the aluminum sampler mold was calculated.
Gjutningar av aluminiumlegeringar används ofta inom bil-, och flygindustrin eftersom de spelar en viktig roll för att förbättra prestanda och bränsleeffektivitet. Inom aluminiumindustrin är provtagning den vanligaste metoden att utvärdera mängden inneslutningar i smältan, vilket är en nyckelindikator för kvaliteten på aluminiumlegeringarna. Eftersom både fyllnads- och stelningsprocessen kommer att påverka inneslutningskarakteristiken är provtagningsproceduren av stor betydelse. Syftet med detta arbete är att skapa en två-fasflödesmodell för att simulera fyllnings-, och stelningsprocessen, samt att beräkna partikelrörelserna under provtagningsförfarandet. Computational Fluid Dynamics (CFD) modellering användes och arbetet har utfördes med mjukvaran ANSYS FLUENT. En numerisk tvådimensionell (2D) axisymmetrisk modell byggdes för att simulera provtagningsproceduren med antagandet att påfyllningen kan göras automatiskt längs huvudaxeln. Till att börja med betraktades det första stelnandet under fyllningen utan partikelinjektion. En antagen k - ε turbulensmodell användes för att modellera effekten av turbulens. Flera simuleringar med olika inloppshastighet, påfyllningstemperatur och inloppsdiametrar beräknades för att se påverkan på stelningsbeteendet. Därefter modellerades hela provtagningsmodellen med partikelinjektion. En Diskret Fasmodell (DPM) användes för att simulera partikelrörelsen i smältan och fokus var inverkan av det initiala stelnandet på inneslutningsfördelningen. Slutligen beräknades den optimala provtagningspositionen inuti aluminiumprovformen.

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43

LEGRAND, BEATRICE. "Texturation par solidification sous champ magnetique d'alliages samarium-cobalt. Application a l'elaboration d'aimants permanents massifs". Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10237.

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La solidification d'un alliage liquide en presence d'un champ magnetique statique est une methode originale permettant d'elaborer des materiaux polycristallins orientes. D'excellents resultats de texturation sont obtenus experimentalement avec des composes samarium-cobalt, sous la forme d'alliages binaires comme le smco#5 ou substitues sm(co, cu, fe, zr)#z (z variant de 5 a 8,34), dans des conditions de solidification tres diverses (en creuset froid inductif, en creuset refractaire, par coulee). Grace a un champ magnetique de quelques tesla, les echantillons sont orientes cristallographiquement ; leur direction de facile aimantation est parallele a celle du champ applique pendant la solidification. Un taux d'orientation optimal des echantillons solidifies sous champ, en creuset froid inductif, est obtenu des 3 tesla. L'analyse de l'evolution des taux d'orientation en fonction du champ applique et les mesures de la susceptibilite paramagnetique des alliages aux temperatures de fusion et de solidification permettent d'estimer un volume des cristallites anisotropes, presentes dans le liquide, qui s'orientent a la solidification. Ce volume est de l'ordre de 10#-#3 micron#3. L'orientation par solidification sous champ est appliquee a l'elaboration d'aimants permanents de la famille des sm#2co#1#7. Des champs coercitifs de 30 koe (2390 ka/m) et des densites d'energie magnetique superieures a 20 mgoe (160 kj/m#3) sont obtenus avec des aimants massifs et anisotropes. Ces performances sont tout a fait comparables a celles des materiaux frittes commercialises actuellement. Le procede ouvre donc la voie a une nouvelle methode d'elaboration d'aimants permanents qui peut s'averer etre une alternative aux techniques de metallurgie des poudres utilisees industriellement

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44

Scuracchio, Bruno Geoffroy. "Influência dos elementos de liga no intervalo de solidificação do aço inoxidável martensítico CA6NM". Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-10032009-215046/.

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Foi investigada a influência de elementos de liga como o Cromo, o Níquel, o Carbono e o Nitrogênio no intervalo de solidificação de um aço inoxidável martensítico fundido do tipo CA6NM. Este tipo de aço, utilizado na fundição de peças de grande porte, é bastante utilizado pela sua ótima resistência ao impacto, e boas propriedades contra corrosão em meio aquoso. Além disso, este aço possui ótima fundibilidade, tendo como principal característica seu reduzido intervalo de solidificação, o que torna diminutos os defeitos relacionados a este fenômeno. Resultados obtidos por cálculos termodinâmicos utilizando-se o Thermo-calc sugeriram forte dependência deste parâmetro em relação ao teor de Carbono (0,018%C a 0,044%C), com o intervalo de solidificação variando de 25°C a 43°C no intervalo de composições definidos pela norma como aceitáveis para a liga. Os outros elementos de liga analisados, segundo os cálculos termodinâmicos, não demonstraram influência significativa dentro das faixas toleradas pela norma. Foram fundidas 13 amostras com as composições químicas simuladas no Thermo-calc, e seus intervalos de solidificação foram investigados por análise térmica diferencial (DTA) e calorimetria exploratória diferencial (DSC). Contrariando os resultados do Thermo-calc, a influência do Carbono não foi comprovada, não havendo variação do intervalo de solidificação entre as amostras. Para confirmar os resultados de análise térmica, as amostras desta técnica foram analisadas por metalografia, não sendo observado qualquer tipo de reação no material ensaiado (descarbonetação, oxidação, etc).
The influence of alloying elements like Chromium, Nickel, Carbon and Nitrogen on the solidification interval on a CA6NM martensitic stainless steel casting was investigated. This steel class, mainly used on large castings, applies due to the fact that it has very good impact resistance, and satisfactory corrosion properties. Besides that, this stainless steel class has excellent castability, having as an important characteristic its reduced solidification interval, diminishing the tendency for solidification defects. The results obtained by thermodynamic calculations using Thermo-calc package have suggested a strong influence of the Carbon content on the solidification interval (25°C a 43°C) when the carbon content is varied within the range allowed by the alloy standard (0,018%C to 0,044%C). Other alloying elements, according to the thermodynamic calculations, have no influence over the solidification interval. Thirteen samples were cast based on the simulated chemical compositions and their solidification interval was investigated by differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Contrary to the thermodynamic calculations, no influence of Carbon was observed on the solidification interval. In order to confirm the thermal analysis results, metallographic tests were performed on the DTA samples, with no observation of any unusual reaction on them, like oxidation or decarburizing.

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45

Ericsson, Ola. "An Experimental Study of Liquid Steel Sampling". Licentiate thesis, Stockholm : Skolan för industriell teknik och management, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10518.

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Alves, Luiz Henrique Dias [UNESP]. "Utilização do método de Taguchi na modelagem e otimização de vazios relacionados à solidificação em processo de fundição de aço ABNT 1030". Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/106431.

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O grande número de variáveis envolvidas no processo de fundição de aço o torna muito susceptível a ocorrência de defeitos relacionados à solidificação como rechupes e poros, que elevam o custo de fabricação devido ao sucateamento e retrabalho de peças. Explorando oportunidades neste cenário, esta Tese de Doutorado, desenvolvida dentro do ambiente industrial de uma fundição de aço propõe um modelo matemático capaz de predizer a combinação de níveis de variáveis de processo que minimizam a ocorrência de rechupes e poros relacionados à solidificação em peças fundidas em aço ABNT 1030, moldadas em areia com aglomerante químico e vazamento por gravidade. Empregou-se, no desenvolvimento do trabalho o Planejamento Estatístico de Experimentos com fatorial fracionado na fase exploratória e o método de Taguchi para validação final e desenvolvimento do Modelo matemático. Na fase de validação, utilizou-se um arranjo ortogonal L16 com quatro réplicas. Na fase exploratória, avaliou-se o volume de defeito em uma peça de produção normal da fundição. Na fase de validação, desenvolveram-se corpos de prova em forma de cubo, vazados sem alimentação. Depois de produzidos, os corpos de prova passavam por ensaio de ultrassom para identificação e localização do defeito e corte de serra, para posterior medição do volume do defeito. O sistema de medição foi validado por meio de um estudo de Análise do Sistema de Medição – MSA GR&R. Os resultados dos experimentos mostraram uma grande diferença entre a contração teórica prevista na literatura de 5,5% para o aço estudado para 2% determinado experimentalmente. As variáveis que mais influenciaram no tamanho do defeito foram: o percentual de carbono queimado no processo de elaboração do aço, percentual de alumínio na liga, percentual de óxido de ferro na areia de moldagem e a interação entre...
The number of variables involved in the steel foundry process makes it susceptible to the occurrence of defects related to the solidification, like shrinkages and pores. This charge the foundries scrap and rework costs. Exploring the opportunities at this context, this Thesis, developed inside an industrial environment of a steel foundry, purposes a mathematic model capable to predict the combination of levels of variables that minimizes the occurrence of shrinkage and pores in carbon steel cast parts, through no-bake sand molding and gravity pouring processes. Statistical Design of Experiments with fractional and factorial at the screening step and Taguchi Method for the final validation and development of the mathematic model were used. A L16 orthogonal array with four replicates was used in the validation step. The defect volume inside a regular cast part was evaluated in the screening step. In the validation step, cube form specimens were designed, poured without feeders and ultrasound tested to bound the defect then saw cut to measure the defect’s volume. In order to the validation of the measurement system, a MSA – Measurement Systems Analysis and Gauge R & R - Gauge Repeatability and Reproducibility were used. The experiments results shown a considerable difference between the theoretical expected contraction, 5.5%, and the 2% experimentally determined. The variables that influenced the defect size the most were: the carbon drop in the steel making, the Aluminum content of the alloy, the Black Iron Oxide content of the molding sand and the interaction between the pouring temperature and the carbon drop. The mathematic model was validated by experiments, which showed a good performance in the prediction of defects.

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Santos, Newton Silva. "Simulação fisica e numerica do processo de lingotamento continuo rotativo". [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264712.

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Orientador: Amauri Garcia
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: O presente trabalho descreve o desenvolvimento de um simulador físico estático do processo de lingotamento contínuo rotativo, como parte de uma metodologia experimental auxiliada por um modelo matemático para a determinação de coeficientes transitórios globais de transferência de calor metal/molde ao longo da solidificação. Através desta metodologia, investigou-se a influência da formação do gap de ar entre as paredes do molde e o metal, na cinética total do processo. O simulador fisico foi construído na mesma escala do processo industrial e constitui-se de um trecho de um equipamento de lingotamento contínuo rotativo Properzi. O simulador é equipado com um sistema de refrigeração à água por bicos pulverizadores, canal de vazamento e termopares acoplados a um sistema de aquisição de dados, onde foram realizados experimentos com ligas utilizadas na indústria de condutores elétricos de alumínio. Para a determinação dos coeficientes transitórios de transferência de calor, após o mapeamento experimental das temperaturas, empregou-se o método de comparação teórico-experimental de perfis térmicos (método IHCP) através de um modelo numérico baseado na técnica de diferenças finitas, aplicada em um volume de controle do sistema experimental. Os resultados obtidos demonstraram consistência da metodologia, permitindo a caracterização destes coeficientes e com isso a possibilidade de se prever a evolução da solidificação em processos industriais
Abstract: The present study describes the development of a static experimental set-up representing the solidification system of a Rotary Continuous Caster, as part of a metholology, which connected to a numerical model permits to determine transient global metal/mold heat transfer coefficients along solidification. By using this methodology the influence of air gap formation between mold walls and metal surface on process kinetics has been investigated . The static simulator has the same escale of an industrial caster and is constituted of a Properzi copper wheel sector, equipped with a spray cooling system, a pouring system and a thermocouple arrangement connected to a data aquisition system. Experiments were performed using aluminum alloys of the electrical conductors industry. The heat transfer coefficients were obtained by using a method base don com pari sons of numerically calculated and experimental thermal profiles (lHCP method). The used numerical model is based on a finite difference technique and applied on a control volume from the experimental system. The results have shown that the used methodology is consistent, permitting the characterization of metal/mold heat transfer coefficients and as a consequence, to predict the solidification evolution in industrial processes
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

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48

Bertelli, Felipe. "Simulação numérica e análise experimental do tratamento superficial por refusão a laser de uma liga Al-Fe". [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264533.

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Orientadores: Amauri Garcia, Noé Cheung
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Neste trabalho, o software ANSYS, baseado no Método dos Elementos Finitos, é adaptado para a simulação tridimensional do fluxo de calor no processo de refusão superficial a laser. A análise numérica é validada com resultados simulados por outros modelos existentes na literatura para casos de refusão superficial a laser de alumínio puro e com resultados simulados e experimentais de uma liga Al-5%Ni. Ensaios experimentais próprios foram realizados em amostras de uma liga Al-1,5%Fe, utilizando um laser à fibra dopado com Itérbio, com potência máxima disponível de 2 kW. Para efeito comparativo, as trilhas foram feitas variando-se valores de velocidade de deslocamento do feixe laser para um mesmo valor de potência. Observou-se que a microestrutura tanto do substrato quanto da zona tratada apresentou morfologia tipicamente celular. As microestruturas resultantes dos tratamentos a laser foram analisadas através de microscopia eletrônica de varredura, sendo observados espaçamentos celulares extremamente refinados na área tratada a laser refletindo no aumento significativo da dureza confirmado por ensaios de microdureza Vickers. Uma técnica de dissolução parcial das amostras tratadas a laser foi aplicada para evidenciar os intermetálicos no substrato e na região tratada a laser, mostrando a modificação da redistribuição dos intermetálicos no interior da poça fundida e dando indicações de aumento da resistência à corrosão na região tratada
Abstract: In this work, the software ANSYS, based on the Finite Element Method, is adapted to simulate the three-dimensional heat flux during the laser remelting surface treatment. The numerical analysis is validated against theoretical results furnished by other models from the literature for laser surface remelting of aluminum and against theoretical and experimental results of Al-5wt%Ni alloy samples. Laser remelting experiments with Al-1,5%wtFe samples have been carried out by using a 2kW Yb fiber laser. For comparative effects, the laser tracks were performed with different laser beam velocities for a fixed value of power. It was observed that both the substrate and the treated region had a typical cellular morphology. The microstructures resulting from the laser treatment were analyzed by using electron scanning microscopy and very refined cell spacing has been observed, which can induce a significant hardness increase confirmed by Vickers microhardness tests. A partial dissolution technique has been performed to foreground the intermetallics at the substrate and at the laser treated zone, showing the intermetallics redistribution inside the molten pool and giving indications of increased corrosion resistance on the treated region
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

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49

Alves, Luiz Henrique Dias. "Utilização do método de Taguchi na modelagem e otimização de vazios relacionados à solidificação em processo de fundição de aço ABNT 1030 /". Guaratinguetá : [s.n.], 2009. http://hdl.handle.net/11449/106431.

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Resumo: O grande número de variáveis envolvidas no processo de fundição de aço o torna muito susceptível a ocorrência de defeitos relacionados à solidificação como rechupes e poros, que elevam o custo de fabricação devido ao sucateamento e retrabalho de peças. Explorando oportunidades neste cenário, esta Tese de Doutorado, desenvolvida dentro do ambiente industrial de uma fundição de aço propõe um modelo matemático capaz de predizer a combinação de níveis de variáveis de processo que minimizam a ocorrência de rechupes e poros relacionados à solidificação em peças fundidas em aço ABNT 1030, moldadas em areia com aglomerante químico e vazamento por gravidade. Empregou-se, no desenvolvimento do trabalho o Planejamento Estatístico de Experimentos com fatorial fracionado na fase exploratória e o método de Taguchi para validação final e desenvolvimento do Modelo matemático. Na fase de validação, utilizou-se um arranjo ortogonal L16 com quatro réplicas. Na fase exploratória, avaliou-se o volume de defeito em uma peça de produção normal da fundição. Na fase de validação, desenvolveram-se corpos de prova em forma de cubo, vazados sem alimentação. Depois de produzidos, os corpos de prova passavam por ensaio de ultrassom para identificação e localização do defeito e corte de serra, para posterior medição do volume do defeito. O sistema de medição foi validado por meio de um estudo de Análise do Sistema de Medição - MSA GR&R. Os resultados dos experimentos mostraram uma grande diferença entre a contração teórica prevista na literatura de 5,5% para o aço estudado para 2% determinado experimentalmente. As variáveis que mais influenciaram no tamanho do defeito foram: o percentual de carbono queimado no processo de elaboração do aço, percentual de alumínio na liga, percentual de óxido de ferro na areia de moldagem e a interação entre... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The number of variables involved in the steel foundry process makes it susceptible to the occurrence of defects related to the solidification, like shrinkages and pores. This charge the foundries scrap and rework costs. Exploring the opportunities at this context, this Thesis, developed inside an industrial environment of a steel foundry, purposes a mathematic model capable to predict the combination of levels of variables that minimizes the occurrence of shrinkage and pores in carbon steel cast parts, through no-bake sand molding and gravity pouring processes. Statistical Design of Experiments with fractional and factorial at the screening step and Taguchi Method for the final validation and development of the mathematic model were used. A L16 orthogonal array with four replicates was used in the validation step. The defect volume inside a regular cast part was evaluated in the screening step. In the validation step, cube form specimens were designed, poured without feeders and ultrasound tested to bound the defect then saw cut to measure the defect's volume. In order to the validation of the measurement system, a MSA - Measurement Systems Analysis and Gauge R & R - Gauge Repeatability and Reproducibility were used. The experiments results shown a considerable difference between the theoretical expected contraction, 5.5%, and the 2% experimentally determined. The variables that influenced the defect size the most were: the carbon drop in the steel making, the Aluminum content of the alloy, the Black Iron Oxide content of the molding sand and the interaction between the pouring temperature and the carbon drop. The mathematic model was validated by experiments, which showed a good performance in the prediction of defects.
Orientador: Messias Borges Silva
Coorientador: Fernando Augusto Silva Marins
Banca: Antonio Fernando Branco Costa
Banca: Marcela Aparecida Guerreiro Machado
Banca: Amiton Sinatora
Banca: Rosinei Batista Ribeiro
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Djurdja, Kerkez. "Potencijal upotrebe piritne izgoretine u tretmanu otpadnih voda i mogućnost njene dalje sanacije primenom imobilizacionih agenasa". Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2014. https://www.cris.uns.ac.rs/record.jsf?recordId=89491&source=NDLTD&language=en.

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Predmet izučavanja ove disertacije bio je ispitivanje mogućnosti korišćenja piritne izgoretine u tretmanu otpadnih voda tekstilne industrije kao i dalji tretman mulja nastalog nakon ovog procesa. Naime, nakon iskorišćenja ovog otpada u Fenton procesima, iskorišćena piritna izgoretina u najvećem procentu čini mulj koji zaostaje nakon tretmana. Kako se piritna ruda još u procesu proizvodnje sumporne kiseline koristi neprečišćena, zaostali mulj koji je potencijalno toksičan i ne može se direktno odlagati bez prethodnog tretmana. Stoga, primenjena je tehnika stabilizacija i solidifikacija (S/S) uz korišćenje portland cementa, kalcijum-oksida, prirodnog zeolita, letećeg pepela, kaolinita, bentonita i autohtone gline za imobilizaciju metala. Istraživanja u ovoj disertaciji vršena su u dve faze. Prva faza imala je za cilj optimizaciju operativnih uslova Fenton tretmana pri kojima se postiže najviši stepen obezbojavanja i mineralizacije ispitivanih efluenata. Takođe ispitivanje je uključilo i karakterizaciju nastalih efluenata kako bi se procenila efikasnost primenjenog, i mogućnost daljeg tretmana. Druga faza uključivala je karakterizaciju nastalog mulja nakon tretmana obojenih efluenata i njegov tretman solidifikacijom i stabilizacijom. Vršeno je određivanje efikasnosti primenjenih imobilizacionih agenasa u S/S tretmanu i dominantnog mehanizma izluživanja metala koji opisuju njihov transport iz dobijenih solidifikata. Primenjeni su i modifikovani testovi izluživanja sa ciljem što bolje simulacije realnih uslova. Rezultati dobijeni simulacijom uslova će dalje omogućiti modelovanje ponašanja metala u smislu dugoročnog "izluživanja" iz tretiranog otpada kao i procenu najefikasnijih agenasa za imobilizaciju različitih metala u ovom tipu otpada. TakoĎe primenjeni su testovi izluživanja sa jednom ekstrakcijom kako bi se osiguralo slaganje rezultata sa maksimalno dozvoljenim koncentracijama aktuelnih pravilnika. Na osnovu dobijenih rezultata zaključeno je da se piritna izgoretina može uspešno koristiti kao izvor katalitičkog gvožđa u Fenton tretmanima obojenih efluenata i može se smatrati efektivnom metodom predtretmana za nebiodegradabilne otpadne vode, čineći ih pogodnijim za konvencionalni biološki tretman. Takođe u drugoj fazi istraživanja, na osnovu dobijenih rezultata, zaključeno je da je mulj tertian sa navedenim imobilizacionim agensima uspešno solidifikovan i stabilizovan materijal. Optimalane su smeše koje kao jedan od imobilizacionih agenasa sadrže leteći pepeo, prevashodno u kombinaciji sa cementom i krečom. Dobijeni podaci su neprocenjivi sa aspekta ekonomski i ekološki prihvatljivog upravljanja opasnim industrijskim otpadom.
This work is concerned with exploring the possibility of using pyrite cinders in the treatment of textile industry effluents and further treatment of sludge generated after this process. Namely, after the utilization of this waste in Fenton processes slag that remains after treatment is mostly composed of used pyrite cinder. As the pyrite ore, in the production of sulfuric acid, is used untreated, sludge that remains is potentially toxic and cannot be disposed directly without treatment. Therefore, the stabilization and solidification (S/S) technique with the usage of portland cement, calcium oxide, zeolite, fly ash, kaolinite, bentonite and native clay was used for metal immobilization. The research in this dissertation was carried out in two phases. The first phase aimed to optimize the operational conditions of Fenton treatment in which the highest degree of decolourization and mineralization was achieved in tested effluents. Also the research has included the characterization of generated effluents in order to evaluate the effectiveness of the treatment applied, and the possibility of further treatment. The second phase involved the characterization of the generated sludge after the treatment of effluents that contained dyes and its treatment with solidification and stabilization technique. The determination of used immobilization agents effectiveness was Conducted to determine the efficacy of immobilization agents in S / S treatment and the dominant mechanism of leaching of metals that describe their transport from the received solidificate . Were applied and modified leaching tests with the aim of better simulation of real conditions. The results obtained by condition simulation will enable the modeling of behavior of metals in terms of long-term leaching period from the treated sludge and assess the most effective agents for the immobilization of various metals in this type of waste. Also, single-extraction leaching tests were applied to ensure the accordance of obtained results with the maximum permissible concentrations of current regulations. Based on these results, it was concluded that the pyrite cinders can be successfully used as a source of catalytic iron in Fenton treatment of effluents containing dyes, and can be considered an effective pretreatment method for non-biodegradable waste waters, making them amenable to conventional biological treatment. Also in the second phase, based on the results obtained, it was concluded that the sludge treated with aforementioned immobilization agents represents a successfully solidified and stabilized material. The optimal mixtures are those that contain fly ash as one of the used immobilization agents, primarily in combination with cement and lime. The obtained data are invaluable in terms of economic and environmentally sound management of hazardous industrial waste.

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