Diss.--Zürich. / Bibliography: p. 143-145.

Thesis (MScEng) -- Stellenbosch University, 2003. / ENGLISH ABSTRACT: High Speed Cutting (HSC), specifically milling is a significant contemporary development in machining. The Die and Mould industry is experiencing a difficult business climate. There is competitive pressure for shorter lead times and lower prices. Companies worldwide, are under financial pressure, to meet the challenges of a globalised business environment. The conventional position of milling and Electric Discharge Machining (EDM / Erosion) is discussed with the proposal to use HSC and EDM as complementary processes. Among new developments the progress in computer infrastructure is prominent. There is also a paradigm shift that should be made from experience based process planning to modern, up to date knowledge based process planning. High Speed Cutting is now a mature process capable of acceptable process security. The examples detailed include crankshaft-forging tooling, injection moulding tooling and powder sintering tooling. A process chain is proposed for the complementary HSC / EDM process with estimated illustrative time saving over the conventional EDM dominated process. HSC will be the first process removing the bulk of the material, finishing as far as possible and with EDM finally machining the features that will be difficult or impossible with HSC. To facilitate the use of the complementary processes a decision model to determine the crossover point between HSC and EDM is proposed. The decision model is firstly presented as a flow diagram to determine whether the task is a candidate for HSC only, EDM only, or the complementary HSC / EDM process. The key parameters e.g tool H d ratio are variables. This is in order that the flow diagram may be adapted to a specific machine tool infrastructure and expertise level in a company. The second part is a HSC machining time estimation model. The time is estimated per segment roughed, semi-finished, or finish machined. The model is in an empirical form with constants that can be adapted to the practices of a specific company. It is intended that the constants also be periodically revised to reflect the development in HSC expertise that will occur during the use HSC in the company. The model is practically evaluated with a case study, including the detail steps, not included in the model. Conceptual guidelines are given for software implementation. It is concluded that HSC and EDM are suitable complementary processes. It is a necessary prerequisite to use pallets to avoid multiple set-ups. Complementary HSC and EDM is especially appropriate for the gradual deployment and skill development for HSC. HSC and complementary HSC / EDM is considered the opportunity for companies to make a major breakthrough in lead time and operating expense if the necessary pallet/fixturing equipment, CAx infrastructure and human capability is available. / AFRIKAANSE OPSOMMING: Hoe Spoed Masjinering (HSC), spesifiek frees is ‘n betekenisvolle ontwikkeling in masjinering. Die Gereedskap en Gietvorm bedryf ervaar ‘n moelike besigheidsklimaat. Daar is kompeterende druk vir korter lewertye en laer pryse. Maatskappye wereldwyd is onder finansiele druk om in die geglobaliseerde besigheidsmilieu te presteer. Die posisie van frees en Elektriese Ontladingsmasjinering (EDM / Vonkerosie) word bespreek met die voorstel om HSC en EDM as komplementere prosesse te gebruik. Onder die nuwe ontwikkelings is daar prominente vooruitgang in rekenaarinfrastruktuur. Daar is ook ‘n paradigmaverskuiwing nodig van ondervinding gebaseerde na op datum kennis gebaseerde proses beplanning. HSC is nou ‘n ontwikkelde proses met voldoende prosessekerheid. Die voorbeelde sluit krukas smee gereedskap, inspuitgiet gereedskap, en poeier-sinter persgereedskap in. ‘n Prosesketting word voorgestel vir die komplementere HSC / EDM proses met ‘n beraamde illustratiewe tydbesparing oor die konvensionele EDM gedomineerde proses. HSC sal die eerste proses wees wat die meerderheid van die materiaal verwyder en oppervlaktes so ver as moontlik afwerk, met EDM wat die finale afwerking doen en ook die masjinering wat vir moeilik haalbaar of onmoontlik is vir HSC. Om die gebruik van die komplementere prosesse te fasiliteer, word ‘n beluitnemingsmodel vir die oorgangspunt tussen HSC en EDM voorgestel. Dit word eerstens as vloeidiagram gebruik om die taak te klassifiseer vir HSC alleen, EDM alleen of vir komplementere HSC en EDM. Die sleutelparameters, bv die beitel 116 verhouding, is veranderlikes. Dit is sodat die vloeidiagram aangepas kan word by ‘n spesifieke masjienvermoe en ‘n kundigheidsvlak in ‘n maatskappy. Die tweede deel is ‘n HSC masjineringstyd model. Die tyd word beraam per segment uitgerof, afgewerk, of finaal afgewerk. Die model is in empiriese vorm met konstantes wat kan aangepas word by die praktyke van ‘n firma. Dit is die bedoeling dat die konstantes periodiek aangepas word om die ontwikkeling te weerspieel wat in die maatskappy plaasvind. Die model word prakties evalueer met ‘n gevallestudie, insluitend die detailstappe, wat nie in die modelformulering ingesluit is nie. Konseptuele riglyne word gegee vir programmatuur implementering. Die gevolgtrekking word gemaak dat HSC en EDM geskikte komplementere prosesse is. Dit is ‘n voorvereiste om pallette te gebruik om veelvuldige opstellings te vermy. Komplementere HSC / EDM is veral toepaslik om HSC geleidelik in ‘n firma te ontplooi en kundigheid te bou. Die HSC / EDM kombinasie word ook die geleentheid geag vir firmas om ‘n deurbraak te maak in lewertyd en bedryfsuitgawes as die nodige pallettoerusting, CAx infrastruktuur en menslike vermoe beskikbaar is.

Este trabalho estuda o processo de trefilação combinada do aço SAE 1045, que consiste nas etapas de pré-endireitamento com múltiplos rolos, jateamento, trefilação, corte e endireitamento por rolos, tendo como produto final barras acabadas trefiladas. Este produto final é empregado na fabricação de hastes de amortecedores para indústria automotiva. O Objetivo do estudo é de entender como são geradas e como se comportam as principais heterogeneidades mecânicas do material processado e a influência dos parâmetros do processo e das características do material na formação e modificação dessas heterogeneidades, buscando como resultado parâmetros otimizados para o processo. Foram variados no processo três parâmetros e avaliadas a interação existente entre eles. Os parâmetros modificados foram ângulo da ferramenta de trefilação (fieira), o ângulo de endireitamento e polimento por rolos cruzados (PERC) e a colocação de revestimento de carbo-nitreto de titânio (TiCN) no núcleo da ferramenta de trefilação (fieira). Foi realizada caracterização do aço, como microestrutura, composição química e microdureza. As tensões residuais superficiais das amostras foram caracterizadas utilizando o método de difração de raios-X. Após avaliação das tensões residuais superficiais, foi analisada a variação das tensões com a profundidade através do método do furo cego (hole-drilling), A classificação das inclusões foi de acordo com o método microscópico A (“piores campos”) da norma ASTM E45-97, feita através da maior severidade encontrada analisando o material aleatoriamente através de varredura com microscópio em sua superfície. Os resultados obtidos permitiram conhecer a combinação de ângulo de fieira e de endireitamento por rolos cruzados (PERC) mais favoráveis para gerar níveis baixos de tensões residuais. Além do ângulo, foi possível verificar que a geometria das zonas da ferramenta de trefilação (fieira) influência os níveis de tensões residuais após a trefilação. O núcleo da fieira com revestimento em todos os ensaios realizados apresentou menores níveis de tensões residuais, mostrando ser uma condição importante para a otimização do processo principalmente para a redução das tensões trativas após a trefilação. / This paper studies the process of cold drawing combined SAE 1045 steel, which consists of the steps with multiple pre-straightening rolls, sandblasting, drawing, cutting and straightening by rollers, with the final product finished extruded bars. This final product is used in the manufacture of rods of shock absorbers for the automotive industry. The objective of the study is to understand how they are generated and how they behave the main mechanical heterogeneities of the processed material and the influence of process parameters and material characteristics of the formation and modification of these heterogeneities, seeking as a result the optimized parameters for the process. We varied three parameters in the process and evaluated the interaction between them. The parameters were modified angle of wire drawing tool (spinneret), the angle of straightening and polishing rolls (PERC) and the placement of coating titanium carbo-nitride (TiCN) in the core of the wire drawing tool (spinneret). We performed characterization of steel, such as microstructure, chemical composition and microhardness. The surface residual stresses of the samples were characterized using the method of X-ray diffraction. After evaluation of surface residual stresses, we analyzed the variation of stress with depth by the method of blind hole (hole-drilling), Classification of inclusions was according to the microscopic method ("worst fields") of ASTM E45 -97, made more severe by analyzing the material found randomly through scanning with microscope on its surface. The results obtained allow us to know the combination of angle stringer and straightening by rollers (PERC) more favorable to generate low levels of residual stresses. In addition to the angle, we found that the geometry of the areas of wire drawing tool (spinneret) influence the levels of residual stress after wire drawing. The core of the spinneret clad in all tests had lower levels of residual stress, proving to be an important condition for the optimization of the process mainly to the reduction of tensile stress after wire drawing.

In Haushofers Roman Die Wand werden die Augen auffällig betont und der Sehvorgang ausführlich geschildert. Diese Arbeit beschäftigt sich mit den Fragen: Wie und wo wird das Augenmotiv im Roman betont? Welche Funktionen haben die vielen Schilderungen von Augen und Schauen? Und welche Themen können dadurch behandelt werden? Dies wird durch ausgewählte Szenen und Textabschnitte diskutiert. Meine kurze Präsentation von dem Motiv Augen und Schauen in der Literaturgeschichte dient in diesem Aufsatz als ein theoretischer Grund.

The topic of this diploma thesis is the motif of a Double-goer and related elements in Die Elixiere des Teufels by E. T. A. Hoffmann and The Picture of Dorian Gray by Oscar Wilde. We can divide it into 5 basic parts. The first and the second parts describe the development of the gothic novel, its main motifs and the motif of a Double-goer. The third part analyses these motifs in Die Elixiere des Teufels, whereas the fourth part has the same task in The Picture of Dorian Gray. Then, the related elements and differences in both works are pointed out in the last part.

Este trabalho estuda o processo de trefilação combinada do aço SAE 1045, que consiste nas etapas de pré-endireitamento com múltiplos rolos, jateamento, trefilação, corte e endireitamento por rolos, tendo como produto final barras acabadas trefiladas. Este produto final é empregado na fabricação de hastes de amortecedores para indústria automotiva. O Objetivo do estudo é de entender como são geradas e como se comportam as principais heterogeneidades mecânicas do material processado e a influência dos parâmetros do processo e das características do material na formação e modificação dessas heterogeneidades, buscando como resultado parâmetros otimizados para o processo. Foram variados no processo três parâmetros e avaliadas a interação existente entre eles. Os parâmetros modificados foram ângulo da ferramenta de trefilação (fieira), o ângulo de endireitamento e polimento por rolos cruzados (PERC) e a colocação de revestimento de carbo-nitreto de titânio (TiCN) no núcleo da ferramenta de trefilação (fieira). Foi realizada caracterização do aço, como microestrutura, composição química e microdureza. As tensões residuais superficiais das amostras foram caracterizadas utilizando o método de difração de raios-X. Após avaliação das tensões residuais superficiais, foi analisada a variação das tensões com a profundidade através do método do furo cego (hole-drilling), A classificação das inclusões foi de acordo com o método microscópico A (“piores campos”) da norma ASTM E45-97, feita através da maior severidade encontrada analisando o material aleatoriamente através de varredura com microscópio em sua superfície. Os resultados obtidos permitiram conhecer a combinação de ângulo de fieira e de endireitamento por rolos cruzados (PERC) mais favoráveis para gerar níveis baixos de tensões residuais. Além do ângulo, foi possível verificar que a geometria das zonas da ferramenta de trefilação (fieira) influência os níveis de tensões residuais após a trefilação. O núcleo da fieira com revestimento em todos os ensaios realizados apresentou menores níveis de tensões residuais, mostrando ser uma condição importante para a otimização do processo principalmente para a redução das tensões trativas após a trefilação. / This paper studies the process of cold drawing combined SAE 1045 steel, which consists of the steps with multiple pre-straightening rolls, sandblasting, drawing, cutting and straightening by rollers, with the final product finished extruded bars. This final product is used in the manufacture of rods of shock absorbers for the automotive industry. The objective of the study is to understand how they are generated and how they behave the main mechanical heterogeneities of the processed material and the influence of process parameters and material characteristics of the formation and modification of these heterogeneities, seeking as a result the optimized parameters for the process. We varied three parameters in the process and evaluated the interaction between them. The parameters were modified angle of wire drawing tool (spinneret), the angle of straightening and polishing rolls (PERC) and the placement of coating titanium carbo-nitride (TiCN) in the core of the wire drawing tool (spinneret). We performed characterization of steel, such as microstructure, chemical composition and microhardness. The surface residual stresses of the samples were characterized using the method of X-ray diffraction. After evaluation of surface residual stresses, we analyzed the variation of stress with depth by the method of blind hole (hole-drilling), Classification of inclusions was according to the microscopic method ("worst fields") of ASTM E45 -97, made more severe by analyzing the material found randomly through scanning with microscope on its surface. The results obtained allow us to know the combination of angle stringer and straightening by rollers (PERC) more favorable to generate low levels of residual stresses. In addition to the angle, we found that the geometry of the areas of wire drawing tool (spinneret) influence the levels of residual stress after wire drawing. The core of the spinneret clad in all tests had lower levels of residual stress, proving to be an important condition for the optimization of the process mainly to the reduction of tensile stress after wire drawing.

No description available.

Aluminium alloys have been seen a dramatic increase in transport manufacturing in past two decades. This is primarily driven by the achievement of effective weight-savings, increased vehicle fuel efficiency and reduced CO2 emissions in transport. One of the significant progresses in most recent years has been in the application of aluminium-intensive car body structure, in which the manufacturing of thin wall castings with improved ductility is one of the critical issues. High pressure die casting (HPDC) is a fast and economical near-net shape manufacturing method to produce thin wall components. Therefore the application of HPDC process to make thin wall structural components for aluminium-intensive car body structure is one of the most challenges in recent development. However, the currently available die cast aluminium alloys are unable to fulfil this requirement because of the insufficient ductility, which is essential for joining castings with sheets and extruded parts. This has become critical in further development and extensive acceptance in car manufacturing industry. Generally, the mechanical properties of die castings are determined by alloy composition, defect levels and microstructure in the castings. In the present study, the significant achievement is the development of Al-Mg-Si-Mn alloy for HPDC process to provide improved ductility in die castings in order to satisfy the requirement of mechanical properties, in particular ductility for the application in automotive body structure. Starting from the thermodynamic analysis and CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) modelling of Al-Mg-Si system for solidification and phase formation, the alloy composition was optimised using international standard tensile samples to review the effect of various alloying elements on the mechanical properties. Another achievement is the understanding of the solidification and microstructural evolution, the relationship between the microstructure and mechanical properties, and the strengthening mechanisms in the developed alloy. The solidification behaviour in the shot sleeve and in the die cavity was examined for the formation of the primary α-Al phase, eutectic Al-Mg2Si phases in the alloy. The morphology, size and size distribution of the primary α-Al phase were characterised under different solidification conditions. The growth morphology of the primary α-Al phase formed in the shot sleeve and in the die cavity was analysed using the Mullins-Sekerka instability theory and the growth rate of eutectic Al-Mg2Si phases during solidification was calculated using Jackson-Hunt theory. Still another achievement is the study of the effect of Mn and Fe on the morphology, size and distribution of various Fe-rich compounds in the Al-Mg-Si alloy produced by HPDC process. The assessment was associated with the mechanical properties of yield strength, ultimate tensile strength and elongation with different Fe and Mn contents. CALPHAD modelling of multi-component Al-Mg-Si-Mn-Fe and Al-Mg-Si-Fe systems was studied to find out the effect of Fe impurity in the Al-Mg-Si alloy. The precise accumulation of iron during HPDC using fully recycled materials was examined to predict the maximum cycles to produce castings with required mechanical properties. The strengthening mechanism and the relationship between the microstructure and mechanical properties are explored in the alloy made by secondary materials. Furthermore, the effect of nickel on the microstructure and mechanical properties of the die-cast Al-Mg-Si-Mn alloy was also studied in association with the formation of Ni-rich intermetallics during solidification in the die-cast Al-Mg-Si-Mn alloy containing different Ni contents. The final achievement is the understanding of the repeatability of die castings made by the new alloy with industrial scale components. The tensile properties of standard samples that were obtained directly from HPDC process and made by the machined die castings at different locations were further assessed for the reproducibility of casting components made by the Al-Mg-Si-Mn alloy. The distributions of yield strength, ultimate tensile strength and elongation of the tensile samples were analysed by the average values with standard deviations and by the Weibull statistical model with three parameters. The correlations between the mechanical properties and the microstructural features, porosity levels and fracture morphology were investigated for the different types of samples. It was found that three-parameter Weibull analysis was capable of analysing the reproducibility of die cast components and the scattering of tensile properties was mainly due to the presence of porosity and non-uniform microstructure in the die-castings.

The mechanical properties achieved with high performance wrought aluminium alloys are superior to cast aluminum alloys. To obtain an intricate shaped component, wrought alloys are commonly subjected to forging followed by subsequent machining operation in the automobile industry. As machining of such high strength wrought aluminium alloys adds to cost, productivity gets affected. Shortening the process by near net shaped casting would tremendously enhance productivity. However, casting of such alloys frequently encounter hot tear defect. Therefore, circumventing hot tear to successfully die cast near net shaped wrought alloy components is industrially relevant. A recent advanced casting process, namely ‘Semisolid Die casting’, is proposed as a likely solution. Hot tearing originates due to lack of liquid flow in the inter-dendritic region. To reduce hot tear susceptibility, fine and non-dendritic grain structure is targeted, amenable for processing by semisolid route. For semisolid processing an adequate freezing range for processing is required. Accordingly A6061 wrought alloy whose composition is tuned with higher silicon and magnesium content within the grade limits, is chosen for the study. With the objective of obtaining fine and non-dendritic microstructured billets, electromagnetic stirring (EMS) and cooling slope (CS) methods are employed. On conducting a parametric study with EMS, a finest possible primary α-Al grain size of about 70 μm is obtained at low stirring time at stirring current levels of 175 A and 350 A, with the addition of grain refiner. CS, on the other hand, rendered a grain of 60 μm at a slope length of 300 mm at a slope angle of 45° with grain refiner addition. Of the two methods, CS billets are chosen for subsequent induction heating. A 3-step induction heating cycle has been devised to attain a temperature of 641°C in the billet on the basis of factors including coherency point, viscosity of the slurry and solid fraction sensitivity with temperature. The billet microstructure is found to be homogenous throughout after quenching in water. The characterization of phase along primary α-Al grain boundary and its composition analysis is done by SEM and EPMA respectively, after billet casting as well as induction heating. In addition, the bulk hardness is determined in BHN. The induction heated billets are semisolid die cast to produce an engine connecting rod used in automobiles. The microstructure is characterized at various locations, and is found to consist of smooth α-Al grains in a background matrix of fine grains formed due to secondary solidification. The component hardness is found to be 66 BHN comparable with A6061 alloy under T4 heat treated condition. X-ray radiography does not confirm presence of surface hot tear, which is the normal defect associated with casting of wrought aluminium alloys. No defects are observed along the constant cross-sectional area of the connecting rod, suggesting that the processing could be suitable for semisolid extrusion.

Hoy en día las empresas se ven inmersas en un mercado totalmente exigente, en especial las del tipo manufacturero. El cliente demanda constantemente que el producto sea de altísima calidad y entregado a tiempo, lo que pone a prueba la capacidad de flexibilización de la empresa. El trabajo de título presentado a continuación tiene lugar en la empresa CMPC Tissue S.A, encargada fabricar y comercializar productos tissue (papeles higiénicos, toallas de cocina, servilletas y pañuelos de papel) en Chile y el extranjero. La planta de Talagante consta de un área de fabricación que abastece a dos áreas de producción; Conversión Doblados y Conversión Rollos. Una gran variedad de productos son fabricados en las 5 líneas de producción de Conversión Rollos. Para poder lograr esto, cada línea debe ser modificada físicamente cuando un cambio de producto o formato se presenta, paralizando la producción de ésta. El trabajo desarrollado está enfocado a disminuir el tiempo improductivo asociado a un cambio de formato. Para ello, la empresa ha decidido implementar una herramienta conocida como SMED (Single Minute Exchange of Die). Este concepto introduce la idea de que en general, cualquier cambio de máquina o inicialización de proceso debería durar no más de 10 minutos. El propósito, como estrategia de planta, es que mediante esta implementación, el tiempo que toma realizar un cambio no demore más de 30 minutos para el departamento de Conversión Rollos. Con esto se busca flexibilizar la producción de la empresa, realizando un mayor número de cambios sin que esto afecte la eficiencia de las líneas. Tras la primera implementación de SMED en la empaquetadora de la línea 200, se observó una notoria disminución en la duración de los cambios en dicho equipo. En varias ocasiones se logró bajar la barrera de los 30 minutos propuesta por la empresa, lo que propone un auspicioso futuro para el resto de las implementaciones en Conversión Rollos. Además, se comprobó que el aprendizaje obtenido tras la aplicación de la herramienta en la línea 200, sirvió para lograr una segunda implementación en la L160, mucho más rápida que la primera, alcanzando resultados igualmente satisfactorios Los resultados obtenidos permitieron la estandarización de la implementación de SMED, definiendo las actividades a realizar y los responsables de llevarlas a cabo.