Poles are used as an important constituent of transmission, distribution and communication structures / highway and street lighting systems and other various structural applications. Concrete is the main production material of the pole industry. Concrete is preferred to steel and wood due not only to environmental and economic reasons but also because of its high durability to environmental effects and relatively less frequent maintenance requirements. Centrifugal casting is the most preferred way of manufacturing concrete poles. However, misapplication of the method may lead to a significant reduction in strength and durability of the poles. Segregation of concrete mixture is a frequent problem of centrifugal casting. The segregated concrete within the pole cross-section possesses different physical properties. In particular, the shrinkage tendency of the inner concrete, where the cement paste is accumulated, becomes significantly larger. Differential shrinkage of hardened concrete across the pole section gives rise to the development of internal tensile stresses, which, in turn, results in longitudinal cracking along the poles. There is a vast literature on experimental studies of parameters affecting differential shrinkage of centrifugally cast poles. This research aims to computationally investigate the differential shrinkage-induced internal stress development and cracking of concrete poles. To this end, two and three-dimensional mathematical models of the poles are constructed and finite element analyses of these models are carried out for different scenarios. The computationally obtained results that favorably agree with the existing experimental data open the possibility to improve the centrifugal manufacturing technique by using computational tools.

In this study, the aim is to investigate the stiffness, longitudinal tensile strength and circumferential tensile strength of short fiber reinforced polyester composite pipes produced by centrifugal casting production method. To achieve this aim, theoretical calculation of modulus of elasticity of pipes was done and then test program was carried out on pipe samples produced with three different resin types which were orthophthalic, isophthalic and vinyl ester resin and three different fiber types which were E glass fiber, ECR glass fiber and basalt fiber. The tests were performed according to ISO (International Organization for Standardization) standards. When resin type and fiber type effect on the fiber reinforced polyester pipe samples were evaluated, calculated elastic modulus values were in accordance with the test results. According to the experimental test data, which were used to evaluate the effect of resin type on fiber reinforced polyester pipe properties, there is not a significant difference was observed in the stiffness, longitudinal and circumferential tensile strength test results of pipes having different resin types. In other words, there was not a significant effect of resin type on the stiffness, longitudinal tensile strength and circumferential tensile strength of short fiber reinforced pipes produced by centrifugal casting method. According to the experimental test data, which were used to evaluate the effect of fiber type on the properties of fiber reinforced polyester pipe, basalt fiber reinforced pipe samples showed higher mechanical performance over E glass fiber and ECR glass fiber reinforced pipes. However, the test results of basalt reinforced polyester pipe were not as good as the individual properties of basalt fiber. Finally, by comparing the basalt fiber reinforced pipe samples having almost the same stiffness and tensile test results as E glass fiber reinforced pipe samples, the gain in fiber and resin amount were investigated. Basalt fiber reinforced pipes were slightly lighter and thinner than E glass fiber reinforced pipes. However, the decrease in the amount of the fiber and resin in basalt reinforced pipe did not result in an overall cost reduction.

In this study molecular dynamics simulation program in NVT ensemble using Velocity Verlet integration was written in order to investigate the glass forming ability of two metallic systems. The Zn-Mg system, one of the frontiers of simple metal-metal metallic glasses and Fe-B, inquiring attention due to presence of many bulk glass forming alloy systems evolved from this binary with different alloying element additions. In addition to this, atomistic calculations on the basis of ordering were carried out for both Zn-Mg and Fe-B systems. Ordering energy values are calculated using electronic theory of alloys in pseudopotential approximation and elements which increase the ordering energy between atoms were determined. The elements which increase the ordering energy most were selected as candidate elements in order to design bulk amorphous alloy systems. In the experimental branch of the study centrifugal casting experiments were done in order to see the validity of atomistic calculations. Industrial low grade ferroboron was used as the master alloy and pure element additions were performed in order to constitute selected compositions. Fe62B21Mo5W2Zr6 alloy was successfully vitrified in bulk form using nearly conventional centrifugal casting processing. Specimens produced were characterized using SEM, XRD, and DSC in order to detect the amorphous structure and also the crystalline counterpart of the structure when the cooling rate is lower. Sequential peritectic and eutectic reaction pattern was found to be important for metallic glasses which can be vitrified in bulk forms with nearly conventional solidification methods.

Les fontes de fer sont des matériaux largement utilisés dans de nombreux domaines allant de l’industrie automobile au secteur de l’énergie en passant par la fabrication des tuyaux d’adduction d’eau. Du fait de la teneur en carbone élevée de ces alliages, du graphite et/ou des carbures de fer précipitent pendant la solidification. Les propriétés finales des pièces dépendent alors de la nature de la matrice, de la présence ou non de carbures et surtout de la forme du graphite. Celui-ci peut cristalliser sous la forme de lamelles, de sphères ou de particules de formes intermédiaires. Les éléments présents à l’état de traces dans le bain de fonte liquide influencent de manière considérable la croissance du graphite et conditionnent sa forme finale. Leur moyen d’action ainsi que le mécanisme de croissance du graphite sphéroïdal sont encore un sujet de débat et cette thèse a pour objectif de contribuer à la compréhension des phénomènes mis en jeu. Les échantillons utilisés ont été élaborés selon le procédé de coulée par centrifugation, son influence sur les mécanismes étudiés est d’ailleurs au cœur de ce projet. Les différents essais et analyses réalisés prouvent que la structure des nodules observés dans les échantillons centrifugés est la même que dans le cas des pièces moulées en sable. De plus, les éléments traces montrent une action similaire lors de la solidification et pendant la croissance en phase solide durant le traitement thermique destiné à éliminer les carbures. Ces résultats suggèrent que le mécanisme de croissance du graphite sphéroïdal est le même lors de la croissance à partir du liquide ou en phase solide par décomposition des carbures. Une proposition est d’ailleurs faite pour expliquer le développement des nodules par une germination continue du graphite sur les plans de base conjuguée à une croissance selon les directions prismatiques. Un modèle mathématique associé à ce mécanisme est présenté et son application au procédé de centrifugation donne des résultats en accord avec les observations expérimentales. / Cast irons are widely used in the foundry industries for applications mainly in the automotive, energy and pipes industries. Because of the high carbon content, graphite and/or iron carbides appear during solidification. The properties of the casting depend on the nature of the matrix, the presence or not of carbides and the shape of the graphite. It can crystallise under the form of lamellae, spheroids or particles with an intermediate shape. Trace elements present in the melt strongly influence graphite growth and shape. Their action and the growth mechanism of the spheroidal graphite are still under debate and the aim of this project is to contribute to the understanding of these phenomena. The samples have been cooled by the centrifugal casting process whose influence on the studied mechanisms is the focus of this project. The different analyses that have been carried out show that the structure of the nodules is the same in centrifugated and sand mold castings. Moreover, the trace elements exhibit a similar action during solidification and solid state growth during heat-treatment for carbide dissolution. These results suggest that the growth mechanism of spheroidal graphite is the same during growth from the liquid and by solid state decomposition of carbides. A schematic is proposed to explain the growth of the nodules by a continuous nucleation on the basal surface of the graphite coupled to a growth along the prismatic directions. A mathematical model associated to this mechanism is presented and its application to the centrifugal casting process gives results in good agreement with experimental observations.

A fundição centrífuga é um importante processo de produção de tubos de ligas metálicas e de cilindros de laminação. A transferência de calor no metal durante a fundição centrífuga de tubos foi modelada matematicamente e o coeficiente de transferência de calor na interface metal-molde determinado em função do tempo utilizando a técnica da solução inversa. A solução inversa foi obtida a partir das curvas de resfriamento experimentais disponíveis na literatura para a fundição centrífuga de um tubo de ferro-fundido. O resultado da solução inversa mostrou, pela primeira vez, que o comportamento do coeficiente de transferência de calor na interface metal-molde durante a fundição centrífuga é semelhante ao da fundição estática: tem-se um valor elevado logo após o vazamento, apresentando um decréscimo exponencial com o tempo. Um modelo matemático da transferência de calor na interface metal-molde foi desenvolvido com base nos mecanismos fundamentais de transferência de calor, como a transferência por condução e radiação através do vão formado nesta interface. Para a previsão deste vão, foram considerados os efeitos da contração térmica e da deformação plástica da casca metálica solidificada. A utilização deste modelo matemático para a transferência de calor na interface metal-molde permitiu o cálculo de curvas de resfriamento em excelente aderência às curvas experimentais reportadas na literatura. / Centrifugal casting is an important process to produce metallic pipes in general and cylinders for steel rolling mills. A mathematical model was proposed for the heat transfer during solidification of centrifugally cast pipes. The heat transfer coefficient at the metal-mold interface was determined as a function of time by the inverse solution technique. The inverse solution was obtained using experimental cooling curves available in the literature for a centrifugally cast-iron pipe. The inverse solution showed, for the first time, that the behavior with time of the heat transfer coefficient at the metal-mold interface is analogous to that observed in traditional static casting processes: an initial relatively large value decreases exponentially with time. A mathematical model for the heat transfer at the metal-mold interface based on fundamental heat transfer principles was proposed. In this model, the heat conduction and radiation in the gap formed at the metal-mold interface, as well as the thermal and plastic deformation of the solid shell, were taken into account. This model, applied to predict the solidification of a cast-iron tube in the centrifugal casting process, enabled the calculation of cooling curves that are in excellent agreement with experimentally measured curves.

Intermetallic alloys gama TiAl are prospective materials of future thanks its excellent machanical qualities and low density. However this alloy clash with for wider expansion to the practice on burdensomeness production and processing. Among disavantages belongs to also her bad fluidity. The diploma work is angaged in possibilities imporing fluidity alloys TiAl by the help of centrifuge casting. Casting healthy casts was achieved in experimental part.

In recent years, bulk amorphous alloys and nanocrystalline materials have been synthesized in a number of ferrous and non-ferrous based alloys systems, which have gained some applications due to their unique physico-chemical and mechanical properties. In the last decade, Zr-based alloys with a wide supercooled liquid region and excellent glass forming ability have been discovered. These systems have promising application fields due to their mechanical properties / high tensile strength, high fracture toughness, high corrosion resistance and good machinability. In this study, the aim is to model, synthesize and characterize the Zr-based bulk amorphous alloys. Initially, theoretical study on the basis of the semi-empirical rules well known in literature and the electronic theory of alloys in pseudopotential approximation has been provided in order to predict the potential impurity elements that would lead to an increase in the GFA of the selected Zr-Ni, Zr-Fe, Zr-Co and Zr-Al based binary systems. Furthermore, thermodynamic and structural parameters were calculated for mentioned binary and their ternary systems. According to the theoretical study, Zr67Ni33 binary system was selected and its multicomponent alloys were formed by adding its potential impurity elements / Mo, W and Al. Centrifugal casting method was used to produce alloy systems. Structural characterizations were performed by DSC, XRD, SEM and EDS methods. In the near-surface regions of Zr60Ni25Mo10W5 and Zr50Ni20Al15Mo10W5 alloys, amorphous structure has been observed. Experimental studies have shown that Zr-Ni based systems with impurity elements Mo, W and Al, not widely used in literature, might be good candidates for obtaining high GFA.

The aim of this study, which was carried out in two main parts, is to investigate the glass forming ability of Fe-based systems. The first part involves the theoretical modeling to cover the requirement of a predictive model to identify the Fe-based alloy families that have high glass forming ability in the frame of atomistic and thermodynamic approach. The second part involves the experimental investigations to prove the results of the conducted theoretical modeling studies. For this purpose, in the first part, theoretical investigations were performed to identify the third alloying elements that will lead to an increase in the glass forming ability on the base of electronic theory of alloys in pseudopotential approximation for selected Fe- based systems, Fe - (B, Zr, Nb, C, W). In the experimental part, in the frame of the theoretical investigation results, one of the theoretically modeled binary system, and the third alloying elements that were predicted to lead an increase in the glass forming ability of the selected binary system, were determined. As a first step, designated compositions were synthesized by using low grade conventional Fe-B alloy as a raw material by using centrifugal casting technique and copper mold casting method. To compare the results, same compositions were also cast from the high purity elements by using the same technique and method. For the characterization of these cast specimens, DSC, XRD, SEM, EDS and metallographic examination techniques were used. Amorphous structure was successfully obtained in the thin sections of the wedge-cast samples for Fe-B-Nb and Fe-B-W ternary systems.

Principal message of this thesis is to introduce designer Pavel Pánek putting him into proper historical context and to reveal some of his unpublished designs or sketches which are hidden to the eye of wider audience. First chapter is fully devoted to the concise history of technique of pressing glass and mention is made of so called pressing ring playing important role in it. One of the sections contains in brief Pavel Pánek's biography where some moments of crucial importance are underlined. Most important part is that, which provides with account of Pánek's works that I found either interesting or crucial for the development of pressed glass. At the beginning of the description of each piece brief description of used technology is added. I am striving to emphasize Pánek's inexhaustible inventiveness and knowledge of techniques that eventually gave rise to some of his best pieces ever. It appears that in some way Pánek was to a certain extent predestined to grow into a sculptor of great providence especially for the sake of his vocational education. Due to the fact Pánek's personality faces false accusation of plagiarism and theft of foreign invention nowadays I had to include apologetic chapter in it. At the end of the thesis I conclude that Pánek, embodied one of the most experimentally -...