Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2010. / The research presented in this report focuses on Investment Casting capabilities for light metal alloys in South Africa and forms part of the Advanced Manufacturing Technology Strategy's (AMTS): Light Weight Metals flagship programme. The research is centred on the suitability of rapid prototyping (RP)/Iayer manufacturing (LM) methods to produce patterns for the investment casting of aluminium (AI), magnesium (Mg) and titanium (Ti) alloys, together known as Rapid Investment Casting. Three core RP technologies are investigated namely: Three Dimensional Printing - Drop-on-Bed from Z-corporation, Three Dimensional Printing - Drop-on- Drop from ThermoJet - 3D Systems and Selective Laser Sintering from EOS. Various RP/LM processes are discussed in detail and highlight the technologies selected in this study. A standard benchmark part, adapted from the European project framework FP6, designed and utilised in similar studies is used as the basis for the research. The Investment Casting process is discussed fully and compared to the Rapid Investment Casting, listing both the advantages and disadvantages of the above mentioned methods. In addition a special study has been conducted on investment casting of large components using layer manufactured patterns. This study not only helped to establish and validate the shrinkage value calculated for the aluminium castings but also showed substantial capability lacks in SA foundries to handle this type of components, which are by definition most often of high added value.

Orientador: Gelson Luis Adabo / Banca: Renata Garcia Fonseca / Banca: Ricardo Faria Ribeiro / Resumo: O estudo avaliou a expansão térmica dos materiais metálicos titânio c.p. (RMI Company, Ohio, EUA), Co-Cr-Mo-W (Dentaurum, Pforzhem, Alemanha) e Ni-Cr (Dentaurum, Pforzhem, Alemanha) para estimar a contração de fundição do titânio e determinou a expansão de presa e térmica dos revestimentos fosfatados Rematitan Plus (Dentaurum, Pforzhem, Alemanha), específico para titânio e Rema Exakt (Dentaurum, Pforzhiem, Alemanha) e Castorit Super C (Dentaurum, Pforzhem, Alemanha). Cada concentração de líquido especial foi variada na proporção de (100%, 75% e 50%) de água destilada, com o objetivo de determinar em que concentração de líquido e em que temperatura a somatória da expansão de presa e térmica seriam suficientes para compensar a contração estimada. Para a dilatometria dos metais padrões de cera com 14 mm de altura e 7 mm de diâmetro foram obtidos a partir de um padrão metálico, em seguida, montados em base formadora de cadinho com o conduto de alimentação e incluídos com cada revestimento na concentração de 100%. Os padrões foram incluídos e aquecidos no forno EDG (EDG - Equipamentos, São Carlos, SP). O Ti c.p. foi fundido na máquina Discovery - Plasma (EDG - Equipamentos, São Carlos, SP), e as outras ligas a fundição ocorreu em máquina de fundição centrífuga convencional. Após o polimento, os corpos de prova foram analisados e a expansão térmica foi registrada no Dilatômetro DIL 409 (Netzch) em atmosfera de ar, numa taxa de aquecimento de 10ºC/min. O Ti c.p. foi aquecido até 1550ºC, o Co-Cr-Mo-W até 1160ºC e o Ni-Cr até 1090ºC. Para a medida da expansão de presa, os revestimentos foram misturados com líquido especial e vertidos no molde de silicone (Siqmol) com cavidade de 50 mm X 10 mm X 10 mm. Uma lâmina de vidro e o apalpador (Tesa)...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study evaluated the thermal expansion of the metallic materials titanium c.p. (RMI Company, Ohio, USA), Co-Cr-Mo-W (Dentaurum, Pforzhem, Germany) and Ni-Cr-Mo (Dentaurum, Pforzhem, Germany) to estimate the casting shrinkage of titanium and determine the setting and thermal expansion of phosphate-bonded investment materials. This investment used were Rematitan Plus (Dentaurum, Pforzhem, Germany), specific for titanium, Rema Exakt (Dentaurum, Pforzhem, Germany) and Castorit Super C (Dentaurum, Pforzhem, Germany). Each concentration of special liquid/distilled/water was varied in which ratio by 100%, 75% and 50%. This aim of this study was to determine what liquid concentration and temperature the overall expansion could be enough to compensate the casting shrinkage. For the dilatometry of the metals, wax patterns (14 mm X 7 mm) were made, attached to sprue, mounted in and mounted on crucible formers and included in 100% of special liquid. The invested patterns were heated in a burnout EDG (EDE - São Carlos - Brazil). Ti c.p. was casting in the machine Discovery - Plasma (EDG - Equipments, São Carlos, SP), and the other alloys were casting in a conventional centrifugal casting machine. After polishing, the samples were analyzed and the thermal expansion was recorded in the equipment Dilatômetro DIL 409 (Netzch) in air's atmosphere, in a rate of heating of 10ºC/min. The Ti c.p. was heated up to 1550ºC, the Co-Cr-Mo-W up to 1160ºC and Ni-Cr-Mo up to 1090ºC. For measurement of the vertical setting expansion, those investments were mixed with special liquid and invested into silicone moulds of the metal pattern (50 mm x 10 mm x 10 mm). A glass plate and dial gauge were seated on the sample, and after two hours the setting expansion was measured (Se). The distance between the ends (De)...(Complete abstract, click electronic access below) / Mestre

Orientador: José Geraldo Trani Brandão / Banca: Fernando de Azevedo Silva / Banca: Paulo Cesar Ribeiro Quintairos / Resumo: Este estudo mostra as variáveis dinâmicas do processo de fundição centrífuga de cilindros de laminação, que são utilizados para realização de conformação em gaiolas de laminação. O objetivo desse estudo é analisar as principais variáveis dinâmicas do processo de fundição centrifugada de cilindros de laminação e estudar as relações entre estas variáveis. Os processos de fundição centrífuga podem ser classificados em fundição centrífuga vertical e horizontal. Para a fundição centrífuga vertical, são elaborados os envelope de carga de dois modelos de máquinas centrífugas verticais existentes na literatura, onde se consegue determinar o tipo de rolamento de apoio utilizado na máquina. Para a fundição centrífuga horizontal, são estudadas variáveis como rotação, razão G, "aspect ratio", espessura e vibração de uma amostra de aproximadamente 1.000 cilindros de ferro fundido, aço rápido e aço alto cromo. Desta amostra, verifica-se que a causa de sucateamento de parte dos cilindros não está ligada a adoção de variáveis dinâmicas incorretas no processo. Também é visto que diferentemente do alumínio, os cilindros de ferro fundido, aço rápido e aço alto cromo exigem maior rotação quanto maior a espessura da casca fundida. / Abstract: This paper shows the dynamic variable of centrifugal casting process of rolling mill rolls which are used to compress the metal in rolling mill process. The main goal is to analyze the main dynamic variable and to study its relation in the process. There are two type of centrifugal casting: horizontal and vertical. For the horizontal centrifugal casting, two load envelopes are done, being possible to determine the bearing model used on the vertical centrifugal casting machine. For the horizontal centrifugal casting, variable such as rotating, ratio G, aspect ratio, thickness and vibration are studied to a sample of 1,000 casting rolls made of casting iron, high speed steel and high chromium steel. From this sample, it is seen that the cause of scrapping is not related to incorrect adoption of dynamic variables in the process. It is also verified that differently from the aluminum, cast iron, high speed steel and high chrome steel rolls demand greater speed with the increasing the shell casting thickness. / Mestre

NKN doped samples, (100-x)NKN-xSBN (0 ≤ x ≤ 10) were produced using the conventional mixed oxide route with 0.45 wt% Fe2O3 sintering aid (xSBNF). After 20-24 hours mixing, samples were calcined at 850°C and sintered at 1100–1140°C (± 180°C/hour) for 4 hours. By XRD 4 mol% SBN was found to be the solubility limit for single phase structure. By SEM, second phases were visible when 2 ≤ x ≤ 4; their structure was subsequently shown to be tungsten bronze type (TBT). 2-4 SBNF samples were high density, over 96% theoretical. For x = 0, TC = 457°C, TO-T = 234°C, Pr = 22 μC/cm2 and EC = 16.5 kV/cm. TC was found to decrease by 14.7°C and TO-T by 9.0°C per 1 mol% addition SBN. 2SBNF was the optimal formulation in terms of microstructure and electrical properties, with average grain size 3 μm, Pr = 25 μC/cm2 and EC = 8.8 kV/cm, ρ = 4.7 kΩm and Q = 1.16 eV. This material comprised approximately 90% orthorhombic and 10% tetragonal phases coexisting. Pseudo-cubic lattice parameters are a’ = c’ = 3.947180 Å, and b’ = 3.999996 Å for orthorhombic phase; the tetragonal has a’ = c’ = 3.989798 Å, and b’ = 3.975777 Å.Synchrotron XRD studies were undertaken as a function of temperature on 99.5NKN-0.5CuO + 0.6 wt% Nb2O5 solid and powder samples. The data were Rietveld refined. The solid sample underwent two polymorphic phase transitions at 300°C and 515°C; the latter was between two tetragonal phases: lattice parameters for the tetragonal phase (300-520°C) were a’ = c’ = 4.99557 Å, and b’ = 4.0363 Å; high temperature tetragonal (>500°C) exhibited a’ = c’ = 4.9519 Å, and b’ = 4.4941 Å. The powder sample of the same formulation exhibited more, smaller transformations. It was only orthorhombic at temperatures <140°C with a’ = c’ = 4.10680 Å, and b’ = 4.02620 Å. Above 140°C both orthorhombic and tetragonal phases were present. Another significant transformation occurred at 360°C where the structural unit cell parameters changed significantly. Parameter lengths are provided. P-E data was characterised by Pr = 19.9 μC/cm2 and EC = 13.5 kV/cm. Synchrotron X-ray diffraction analysis of 94 NKN-6LiTaO3 showed that tetragonal phase was present at 20-390°C, although an orthorhombic phase was identified at 20-200°C and again at 340-390°C just before the cubic transition temperature at 390°C. This is a new observation for NKN. A new and simple method for tape casting was developed to reduce powder wastage, enabling thick films of 50 μm to be cast. The reactive templated grain growth (RTGG) method was employed to orient 95NKN-5LiNbO3 and 94NKN-6LiNbO3 samples; CuO was utilised as a sintering aid. Pre-cursor BNN and NN template particles were produced using the molten salt synthesis (MSS) method, using a salt to oxide ratio of 1:1. Resulting NN particles were 15 μm wide and 0.5 μm thick. Eight layered 6LN + 0.4 wt% tapes produced using 10 wt% template particles resulted in 210 μm thick tapes with 67% orientation when sintered at 1150°C. Resulting properties include TC = 440ºC and TO-T = 70ºC, 25 kΩ resistance and capacitance 21.6 pF.

The spray cooling system of an operating billet caster has been redesigned with the aim of reducing the formation of mid-way cracks. These cracks are caused by tensile strain which is generated at the solidification front when the surface temperature of the strand rebounds owing to a sharp reduction in surface heat extraction. The objective of the design, therefore, was to achieve a cooling system that would minimize surface temperature rebound of the strand as it passes from one cooling zone to the next. A computer program based on the explicit finite difference method has been used for the design work. The spray design was implemented on one strand of an operating continuous casting machine which produced 10.8 cm square billets. Transverse sections were cut from the test strand and sulfur printed, then compared to sulfur prints of sections taken from an adjacent strand of the same heat but with unmodified sprays. It was shown that with empirical adjustment, the redesigned spray system reduced the severity of mid-way cracks in over 80% of the heats. It was also found that the carbon content and cast structure have a profound effect on the cracking tendency, whereas, the Mn/S ratio (up to 30%) is less effective. Finally, a new design method for sprays has been proposed which may result in a better temperature distribution and may be easier to adjust to suit specific operating conditions. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

To produce cast steel crankshafts, risering and gating systems are developed. Filling and solidification simulations of the steel crankshaft rigging are carried out to confirm that the rigging developed will produce a low porosity casting. A sand mold is created with Computer-aided design software, based on the developed crankshaft and rigging. Two prototype crankshafts are cast from the sand molds, and analyzed for porosity. The porosity analysis results are compared directly to the simulated porosity, and found to be in good agreement. From the analysis of the prototype crankshaft, rigging systems for a two-on and single-throw crankshaft are developed. A new casting method for steel is developed. The counter-gravity with pressurization during solidification casting method utilizes vacuum pressure of 7.3 psia to draw liquid steel into a mold, where it is held until the inlet has solidified. Once the inlet has solidified, the vacuum pressure is released, and the pressure of the entire system is raised to 45 psia. Exothermic hot topping keeps the top of the riser liquid while the rest of the casting forms a solid shell. Therefore, the pressure only acts on the liquid metal at the top of the riser, forcing the liquid metal to feed farther into the casting. The new method is tested with simple bar castings. Analysis of cast bars shows that centerline porosity is fed by the riser when pressurized, while the gravity-filled control casting is not.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22127号 / 工博第4657号 / 新制||工||1726(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 安田 秀幸, 教授 辻 伸泰, 教授 宇田 哲也 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

NR 20140805

Footwear impression evidence is often recovered at a crime scene and is either in the form of a two dimensional and/or a three-dimensional impression. Two-dimensional impressions occur when a shoe coated with a substance such as dust, blood, or ink, leaves behind a silhouette of the sole on a surface. Three-dimensional impressions contain depth information of the sole patterns that include three-dimensional characteristics that are transferred into a substrate such as dirt, mud, or sand. From these impressions, a sufficient number of identifying characteristics can be identified and used to individualize an impression to a particular footwear on the premise that it is a practical impossibility to have two shoes with the same set of randomly acquired features. This requires the capture of unknown impressions with both photography and casting; however, there are a variety of three-dimensional capture methods that can be employed. By evaluating different materials and techniques on the basis of their permanency, elasticity, and statistical ability to acquire defined identifying characteristics, a more significant comparison of successful methods can be made based on the likelihood ratios of the average occurrence of individualizing characteristics. This provides a powerful description of resolution of one particular method and can rationalize the difference between methods through statistical analysis. This research addresses a conservative statistical model of random occurrence of individual characteristics in a defined area (sole of footwear) by using binomial coefficients to evaluate possible performance discrepancies between field collection techniques and laboratory analysis of alternate materials and methods (alginate, moulage, silicone, thixotropic plastic, polyurethane foam, polymer gypsum mix) in terms of their ability to capture identifying characteristics from impressions made by a reference footwear, and allows a comparison to contemporary forensic methods utilized in the field and laboratory analysis.

No description available.