Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references (leaves 116-124). Also available in electronic version.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xvi, 222 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 219-222).

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In the production of parts for direct industrial application and for developing research purposes, it is of utmost importance to understand the defects associated with the material system. In this work, the microstructural and mechanical properties of 316L Stainless Steel deposits and cast Aluminum A356 and Magnesium AZ91 alloys are investigated. The study first examines the design of efficient gating systems utilizing the Electromagnetic Pump Green Sand system to produce vertically cast A356 plates. A series of numerical simulations were developed for each of the four gating designs in order to compare modeling results with actual castings. The method of four-point bend (FPB) testing was used to obtain information about the effect of oxide entrainment on the mechanical properties of the parts, and from this data, a two-parameter Weibull statistical analysis was performed in order to quantify specimen failure rate for each of the configurations. Metallographic analysis was carried out using optical microscopy, and fractography using Scanning Electron Microscopy (SEM). In keeping with light alloys focus, the determination of superior casting processes for AZ91 alloys is also studied. Passenger car control arms were cast by Indirect Squeeze Cast, Low Pressure Permanent Mold, T-Mag, and Ablation processes. The microstructure, grain size, porosity distribution, and defect analyses were obtained with optical microscopy and the ImageAnalyzer program. The mechanical behavior was characterized from the FPB and tensile tests. The four casting processes were evaluated in terms of reliability again using a Weibull analysis of the ultimate bending strength determined from the FPB test samples. Metallographic analysis was performed on these samples, revealing noticeable microstructural differences between them, with some even showing possible evidence of oxide films. Lastly, the study of process parameters such as beam and laser current, translation speed, and wire feed and deposition rate associated with 316L stainless steel deposits produced by both Laser Engineered Net Shaping and Electron Beam Freeform Fabrication becomes the research objective. Tensile tests, optical microscopy, and SEM were used to determine mechanical properties, characterize solidification grain structure, porosity, secondary dendrite arm spacing, and possible modes of failure.

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Orientador: Kamal Abdel Radi Ismail / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-23T08:47:57Z (GMT). No. of bitstreams: 1 SousaFilho_LourivalMatosde_D.pdf: 17246436 bytes, checksum: 4f99e2f233216584c3570917e55b69c6 (MD5) Previous issue date: 2013 / Resumo: O processo de solidificação de um material de mudança de fase ao redor de um tubo curvo resfriado é estudado numericamente com vistas à aplicação em sistemas de armazenamento de calor latente. A influência da convecção natural na fase líquida foi levada em consideração. O modelo matemático foi formulado em termos das variáveis primitivas, sendo este bidimensional e transiente. O método dos volumes finitos foi empregado para discretizar o sistema de equações diferenciais que governam o fenômeno físico, resultando em um sistema de equações algébricas lineares. Para fixar e tornar regular a frente de solidificação que se desloca ao longo do tempo, foi aplicada a técnica de transformação de coordenadas. O tratamento do termo transiente foi discretizado em uma formulação implícita para as equações da conservação, enquanto, a equação do balanço de energia na fronteira sólido-líquido, foi obtida explicitamente. Os resultados numéricos da frente de solidificação obtidos pelo presente modelo foram comparados com os resultados disponível na literatura, apresentando uma boa concordância. Resultados para alguns parâmetros fundamentais no dimensionamento de sistemas térmicos também foram obtidos e discutidos neste estudo. Os resultados mostram que os parâmetros como temperatura da parede, temperatura inicial do PCM líquido e razão de curvatura tem influencia significativa sobre a posição da interface, velocidade da interface, massa solidificada e tempo completo da solidificação / Abstract: The solidification process of a phase change material around a curved tube is cooled numerically investigated in order to apply to systems of latent heat storage. The effect of natural convection in the liquid phase was taken into account. The mathematical model was formulated in terms of the primitive variables, and this two-dimensional transient. The finite volume method was used to discretize the system of differential equations that govern the physical phenomenon, resulting in a system of linear algebraic equations. To fix and become regular solidification front which moves along the time technique was used to transform coordinates. The treatment of the transient term was discretized in implicit formulation for the equations of conservation, while the equation of energy balance in the solid-liquid boundary was obtained explicitly. The numerical results of the solidification front obtained by this model were compared with results available in the literature, showing good agreement. Results for some key parameters in the design of thermal systems were also obtained and discussed in this study. The results show that parameters like wall temperature, initial temperature of the liquid PCM and curvature ratio has a significant influence on the position of the interface, interface speed, mass, solidified and completed solidification time / Doutorado / Termica e Fluidos / Doutor em Engenharia Mecânica

The primary focus of the present work is to model the entire casting process from filling stage to complete solidification. The model takes into consideration any phase change taking place during the filling process. An implicit volume of fluid (VOF) based algorithm has been employed for simulating free surface flows during the filling process and the model for solidification is based on a fixed-grid enthalpy-based control volume approach. Solidification modelling is coupled with VOF through User Defined Functions (UDF) developed in commercial fluid dynamics (CFD) code FLUENT 6.3.26. The developed model is applied for the simultaneous filling and solidification of pure metals and binary alloy systems to study the effects of filling process on the solidification characteristics, evolution of mushy zone and the final macrosegregation pattern in the casting. The numerical results of the present analysis are compared with the conventional analysis assuming the initial conditions to be a completely filled mould cavity with uniform temperature, solute concentration and quiescent melt inside the cavity. The effects of process parameters, namely the degree of superheat, cooling temperature and filling velocity etc. are also investigated. Results show significant differences on the evolution of mushy zone and macrosegregation between the present analysis and the conventional analysis. The application of present model to simulate three dimensional sand casting is also demonstrated. The three dimensional competetive effect of filling generated residual flow and the buoyancy-induced convective flow pattern cause significant difference in macrosegregation pattern in casting.