No description available.

Twin Screw Rheo Extrusion (TSRE) is a novel semisolid extrusion process developed at BCAST for producing simple profiles such as rods and wires of light alloys directly from melts with refined microstructures and improved mechanical properties. The process represents a shortened manufacturing route with great savings in investment, energy consumption and operation space. Research was carried out to investigate the feasibility of processing magnesium and aluminium alloys, to obtain the operations for the optimized microstructures and mechanical properties of the final product and to understand the mechanisms governing the evolution of microstructures. Experiments were conducted using an AZ91D magnesium alloy and several aluminium alloys on two specially made twin screw rheo extrusion machines and a range of conditions were tested. Results showed that the TSRE process was feasible for the AZ91D magnesium alloy and aluminium alloys, although modifications were required for processing aluminium alloys as the twin screw material used was found to react with aluminium. Analysis revealed that the extruded samples of both alloys had a uniform fine microstructure in both transversel and longitudinal directions and liquid segregation was limited, due to the application of intensive shearing during slurry making and extrusion. Low extrusion temperature was found to refine the structure and suppress the formation of the eutectic. The eutectic was easily dissolved upon heat treatment resulting in reasonable mechanical properties. Numerical analysis on thermal management was carried out and the results showed that a steady state thermal profile with a temperature gradient between the slurry feeding point and extrusion die could be established, promoting nucleation and preventing the formed solid particles from extensive growth during extrusion, which was confirmed by microstructural observations.

This thesis describes the processing and characterisation of Al-70Si alloys manufactured by gas atomised spray forming at Sandvik-Osprey (Neath, UK) and Oxford University using a newly commissioned spray forming pilot-plant facility. Spray formed Al-70Si (CE7) provides an attractive balance of thermophysical properties making it suitable for thermal management applications. Microstructural characterisation of CE7 was conducted using optical microscopy, image analysis, electron probe micro analysis (EPMA) and electron backscatter diffraction (EBSD). Microscopy revealed an interpenetrating network microstructure consisting of fine, randomly oriented polycrystalline primary Si interpenetrated by large, α-Al grains devoid of eutectic Si. Mechanical testing and thermal cycling simulated a service environment and revealed for the first time crack initiation, growth and blunting mechanisms, the effect of intermetallic phases on the bulk mechanical properties, and anisotropy effects resulting from macrosegregation of Al during solidification. A relationship between the inter-phase interface length and the fracture toughness has been proposed and methods of interface length refinement have been investigated, including chill casting and spray forming. Spray formed CE7 modified with separate additions of B, P, P+Ce and Sr have been microstructurally and mechanically characterised and compared with binary CE7. While alloy additions were effective in refining primary and eutectic Si in chill cast alloys, spray formed alloys showed little change in interface length. Particle injection of Si-Al powder was effective in refining the scale of the spray formed microstructure, and improving mechanical properties. The deleterious effect of intermetallic phases on bulk mechanical properties has been demonstrated and highlighted the importance of melt cleanliness and materials control during manufacturing.

The construction of bonds in a controlled and selective manner and the development of operationally simple, general and reliable methods to achieve these aims remains a key goal of chemical synthesis and the countless industries it impacts upon. With this in mind, the chemo-, regio- and stereoselective introduction of a number of functionalities into small molecules was investigated. Traditionally the majority of functionalisations have used precious metals; the scope of transformations that can be achieved using these catalysts is remarkable. Palladium in particular has found widespread application in new bond-forming processes and, in addition to cross-coupling reactions, palladium catalysis has been used to effect a wide variety of asymmetric reactions. This work describes investigations into the palladium-catalysed enantioselective electrophilic fluorination of azaarylacetates and amides A2 and the oxidative annulation of ferrocene derivatives A4 (Scheme A1). Both products have structural significance; heterocycles and stereogenic fluorinated centres, present in A3, are important motifs in the pharmaceutical industry, and ferrocenes are important rigid scaffolds in chiral ligands such as those in the Josiphos family e.g. A7. Scheme A1. Palladium catalysis for a) enantioselective fluorination and b) oxidative annulation Whilst a general catalyst remained elusive for the asymmetric fluorination of azaarylacetates and amides, benzoxazole-containing substrates were consistently fluorinated with excellent enantioselectivity (up to 96% ee) using palladium catalyst A1 (Scheme 1a). The oxidative annulation of ferrocene derivatives proved challenging and although the reaction was successful, the product could only be isolated in up to 24% yield (Scheme 1b). In order to determine the yield-limiting step of the reaction, mechanistic studies were conducted and palladacycle A6 was synthesised as a possible reaction intermediate. Recently there has been a shift towards the development of more sustainable, environmentally benign and economic catalyst systems and iron is quickly becoming recognised as a viable alternative owing to its high natural abundance and low toxicity. A general iron-catalysed hydrofunctionalisation procedure is described that was used to form a wide variety of carbon-carbon and carbon-heteroatom bonds (Scheme A2). Scheme A2. Iron catalysis for carbon-carbon and carbon-heteroatom bond formation With just 0.5 mol% iron catalyst, the broad scope formal hydrofunctionalisation of styrene derivatives was achieved using commercially available and bench-stable catalysts and reagents. An iron-catalysed highly regioselective hydromagnesiation gave a common benzylic Grignard reagent, which was reacted with an array of electrophiles in a highly chemo- and regioselective manner. Significantly, the products of formal hydroboration, hydrosilylation and cross-coupling reactions were obtained.

For numerical modeling and predictive analysis of warm hydroforming, better understanding of material properties (i.e. Flow curves) is required at elevated temperatures and high strains. Hydraulic bulge testing is a suitable method to obtain this information. However, analysis of the test data is not standardized as there are numerous approaches developed and adopted throughout the years. In this study, first, different approaches for hydraulic bulge analysis were compared with stepwise experiments to determine the best combination of approaches in obtaining accurate flow curves at different temperatures and strain rates. Then, three different grades of stainless steels (AISI 201, 301 and 304) were tested at various hydroforming conditions to determine the effect of pressure, temperature and strain rate on formability (i.e. cavity filling and thinning). These experimental findings were then used to be compared with predicted values from FEA. Results showed that material model works accurately in predicting the formability of materials in warm hydroforming.

The diploma thesis is focused on revision of the type collection of two similar arborescent Carboniferous lycopsids Lepidodendron lycopodioides and Lepidodendron selaginoides. Both species are often misinterpreted in the literature due to their obscure definition by Sternberg. Both species were revised morphometrically, allowing for their redefinition based on morphological characters. The emended diagnosis of both species is provided. Using of existing names of the species was solved in accordance with the International botanical code. Changes in various parametres during ontogenetic development of L. lycopodioides and L. selaginoides were described in detail by using morphometric analysis and both species were redefined. Klíčová slova: Lepidodendron lycopodioides, Lepidodendron selaginoides, pennsylvan, Intra-Sudetic Basin, Radnice Basin, morphometric analysis.

This master thesis provides an overview of the paper machine with focus on the forming section. The forming section is the first part in the paper machine where the paper pulp is injected through a head box. The paper pulp contains about 99.5% of water and 0.5% fiber. The water as content is reduced by vacuum and gravity. The problem to be studied in this project is related to external rewetting. This is water going back to the paper web from the forming fabric after the dewatering zone. The dewatering is based on vacuum slots under the forming fabric. The vacuum slots absorb water from the soaked paper pulp through the forming fabric. External rewetting causes problem, hence the paper will have a higher dry content when leaving the forming section. The paper should have as low dry content as possible in the end of the forming section. Three different forming fabrics from Albany International were chosen for the project. The structures of the forming fabrics were two different double layers and one plain weave. The performance of the fabrics was studied by 4 different methods. The methods used were 2 different wicking tests, a vacuum dewatering trial and one foulard test. Also micro tomography was done to understand the structure of each design. The main test was a foulard test where the aim was to see in what way the rewetting got affected by different pores sizes. The results showed higher water content for the paper that was on top of the forming fabric with the larger pores.

L’objectif de ces travaux de thèse est de contribuer à la compréhension d’un procédé de mise en forme composite appelé EPITHER. Il s’agit d’un procédé visant la réalisation de pièces composites massives à utilisations structurelles pour les marchés de l’automobile et de l’aéronautique. Il a été breveté en 2011 et en 2015/2016.Les trois étapes de réalisation des pièces EPITHER sont les suivantes : enroulement d’une préforme en optimisant l’anisotropie du composite en fonction des chemins d’efforts de la pièce réelle, mise en forme de la préforme par thermoformage, apport de propriétés morphologiques supplémentairesLes travaux de thèse s’orientent autour de trois axes majeurs : la mise en place d’une phase expérimentale, la compréhension des étapes de consolidation des pièces et l’influence des paramètres de mise en forme. / The objective of this work is to contribute to the comprehension of a new composite forming process which name is EPITHER. This forming process was created to produce massive composites parts used for structural applications in automotive and aeronautics industries. Two patents have been deposed in 2011 and in 2015/2016.There are three steps in the forming process EPITHER: winding a preform in order to maximize and optimize the anisotropy of the composite considering the mechanical specifications of the final part, forming the preform by a thermoforming step, add morphological properties in a last step.The Phd deals with three major research axis: setting up an experimental study, the comprehension of the consolidation steps and a study of the consolidation parameters.

O propósito deste trabalho é a modelagem experimental e estudo do controle do processo de hidroconformação de tubos. Assim, o trabalho visa o projeto e a construção de um dispositivo servo-controlado de hidroconformação de tubos com um sistema de controle digital. O trabalho compreende o projeto e a construção de um dispositivo a ser acoplado em uma prensa hidráulica, a instrumentação dos equipamentos usados e a implantação do sistema de controle automático do processo através de um computador PC e de placas de interface A/D e D/A. Os aplicativos de controle foram desenvolvidos em linguagem de alto nível no sistema operacional Windows. No projeto do aplicativo, inicialmente foram realizadas rotinas para testes do sistema em malha aberta. As demais rotinas são aquelas associadas às funções matemáticas do modelo fenomenológico do sistema de hidroconformação, aquelas destinadas ao controlador de malha fechada. O tipo de estratégia de controle a ser utilizada foi definida no decorrer do projeto e foi baseada em um modelo de processo não linear, linearizado em torno de cada ponto de operação. Para fins de obtenção do modelo nominal para o controlador, os atuadores e sensores tiveram suas dinâmicas desprezadas face a dinâmica do processo e suas curvas de processo foram levantadas experimentalmente. / This works aims is the experimental modeling of a tube hydroforming (THF) “T" branch, and de THF process automatic control study. Thus, the design and the construction of a servo-controlled hydraulic device for THF, with a automatic digital control system, is embedded in our objectives. Design and construction of device to append on a hydraulic press, implantation of the measurement equipment and implementation of the control system algorithms through a PC with I/O interface boards is necessary. Control algorithms were developed in Hi-level language for windows operating system. The application design was based on experimental initial tests performed with no feed-backing controlling mode. Routes related to phenomenological mathematical model of the THF process were validate against the literature database, and were devoted to the feed-backing controller mode. Control strategy to employ in final application was defined during the process calibration, based on the non-linear characteristics of the “T" branch THF. To obtain the final load path model sensors and cylinders had their dynamics neglected because the THF dynamic is very much higher, and had their behavior curves experimentally raised.

O processo de conformação por jateamento com granalhas (peen forming) trata da conformação de chapas ou painéis através da ação de um jato de esferas de aço que, atingindo uma de suas superfícies, torna-a convexa na face de recepção do jato e gera tensões residuais superficiais de compressão. Tornar o processo de jateamento com granalhas reprodutível e controlável é um grande objetivo a ser alcançado para que o mesmo possa ser aplicado de forma segura na indústria aeronáutica. Buscando-se estudar a viabilidade e o desenvolvimento de conhecimento da técnica de jateamento de esferas, definiu-se uma metodologia para o projeto de experimentos focalizados nos dois tópicos principais: variáveis de processo e características do material jateado. As variáveis de processo observadas foram diâmetro de granalha, velocidade de impacto, porcentagem de cobertura e pré-tensão. No material jateado, variaram-se a liga de alumínio (7050-T7451 e 7475-T7351) e espessura. As chapas de alumínio foram caracterizadas em: raio de curvatura, microestrutura, dureza, profundidade e morfologia da camada deformada e perfis de tensões residuais. Avaliou-se o efeito do processo nas características do material. Analisando-se os dados, foi possível obter equações semi-empíricas de relação entre processo e raio de curvatura através de um novo parâmetro chamado densidade de energia cinética, que engloba os parâmetros diâmetro de granalha, velocidade de impacto e espessura da chapa. Encontrou-se ainda forte relação entre energia cinética e espessura da camada deformada e profundidade da máxima tensão residual. Os dados experimentais foram utilizados para o treinamento de uma rede neural artificial, que gerou boa previsibilidade do raio de curvatura. / The peen forming process is the forming of metal sheet or panels through the action of a jet of hard spheres, hitting one of the surfaces, making it convex and causing residual compressive stresses on surface. Making the peen forming process reproducible and controllable is a major goal to its safe application in the aircraft industry. Aiming the study of the feasibility of peen forming and the development of its technical knowledge, a methodology for the design of experiments was created focusing on two main topics: process variables and the properties of the formed material. The process variables observed were shot diameter, impact velocity, percentage of coverage and pre-tension. With respect to the formed material, two aluminum alloys (7050-T7451 and 7475-T7351) and four different thicknesses were used. The aluminum plates were characterized by: radius of curvature, microstructure, hardness, depth and morphology of the deformed layer and profiles of residual stresses. The effect of the process on material was evaluated. Analyzing the data, semi-empirical equations were obtained for the relationship between process and radius of curvature through a new parameter called the density of kinetic energy, which includes the parameters shot diameter, impact velocity and plate thickness. It was also found a strong relationship between kinetic energy and thickness of the deformed layer and depth of maximum residual stress. Experimental data were used to train an artificial neural network, which generated a good predictability of the radius of curvature.