Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Vita. / Bibliography: leaves 158-162. / by David V. Fitterman. / Ph.D.

No description available.

Este trabalho visou entender e avaliar a resistência mecânica da junção de chapas de aço obtidas pelo processo de União de Chapas por Conformação a Frio (UCCF). Esse processo é conhecido no meio industrial pelo termo em inglês: clinching ou press joining. O formato de união cilíndrico, também conhecido como Round, foi selecionado para unir os corpos de provas. As uniões metálicas ensaiadas foram fabricadas com aço de baixo teor de carbono sem camada superficial de proteção (170MPa de limite de escoamento). O material escolhido é de comum utilização na indústria automotiva. Duas espessuras diferentes foram avaliadas: 0,8mm e 1,2mm. Um completo procedimento foi criado para determinar os parâmetros ideais do processo UCCF baseado nos critérios de falha existentes na literatura e na experiência do fornecedor do equipamento. A união em estudo foi submetida, experimentalmente, a cargas multiaxiais com o auxílio de um dispositivo baseado no ensaio de Arcan para possibilitar uma condição de carga combinada, onde foi possível identificar graficamente o comportamento estrutural do corpo de prova em estados de carregamento que variam de tração (normal à superfície do ponto) até cisalhamento (perpendicular à superfície do ponto). Os valores de resistência mecânica encontrados foram de 1,13kN (mínimo) a 2,55kN (máximo) para as chapas de aço com espessura de 0,8mm e de 1,89kN (mínimo) e 3,18kN (máximo) para as chapas de 1,2mm. Um estudo comparativo com Solda Ponto por Resistência Elétrica (SPRE) foi realizado. A UCCF alcançou resultados de 47,68% dos valores obtidos para a SPRE para chapa com espessura de 0,8mm e 37,78% para chapas de 1,2mm. / The purposes of this work were understand and evaluate cold forming sheet metal joining of steel plates mechanical resistance. This process is well known as clinching or press joining. Round clinching element was selected to be used on all tested specimens due to its industry suitability. The metallic specimens were built on mid carbon steel without zinc coat protection (Yield Stress: 170MPa). This is a common material on automotive industry. Two different thicknesses were evaluated: 0.8mm and 1.2mm. A full procedure to determine ideal clinching parameters was created based on available literature information and clinching supplier know-how. All union technology was experimentally submitted to multiaxial loads using device based on Arcan concept. Joining mechanical behavior curves were plotted from traction (normal to element joint surface) to shear (perpendicular to element joint surface) loads. As a result, 0.8mm thickness steel plates achieved load values from 1.13kN (minimum) to 2.55kN (maximum), 1.2mm thickness steel plates achieved values from 1.89kN (minimum) e 3.18kN (maximum). A comparative study was made with Electric Resistance Spot Weld (ERSP). Clinching joining achieved results as 47.68% and 37.78% of ERSP loads for 0.8mm and 1.2mm thickness steel plates respectively.

The positive temperature coefficient of resistivity (PTCR) sensors is resistor materials that undergo a sharp change in resistivity at a designed Curie temperature due to its unique structure and chemical composition. This effect serves important control functions in a wide variety of electronic circuitry and similar applications. Conventional calcining of mixed oxides method (CMO) is used for fabricating lanthanum doped barium titanate (BaTiO3) for PTCR behaviour through solid-state-sintering route, at 1100°C, 1350°C. Two batches of samples were fabricated at low and high sintering temperatures of 1100°C, 1350°C respectively. The effect of different concentrations of donor dopant on BaTiO3 on the electrical properties of Ba(1-x)LaxTiO3 with x= 0.0005, 0.001, 0.002, 0.0025, 0.003 mol%, is investigated at low sintering temperature. The influence of lantanum doping with Al2O3+SiO2+TiO2 (AST) as sintering aids on the electrical properties of Ba(1-x)LaxTiO3 with x= 0.0005, 0.001, 0.003 mol%, is also investigated. The results of the electrical characterization for the first batch of samples showed an increase in room temperature resistance with increaisng donor concentration. Also the results of the electrical characterization for the second batch of samples also showed the same increase in room temperature resistance with increasing donor concentration. For first batch of sensors the high room temperature resistance keeps the jump small and these materials showed V-shaped NTCR-PTCR multifunctional cryogenic sensor behavior with a strong negative coefficient of resistance effect at room temperature.Where as the second batch of sensors showed few orders of magnitude rise in resistivity values. The La-doped BaTiO3 ceramics co-doped with Mn gives an enhanced PTCR effect which can be exploited for various sensor applications.

The positive temperature coefficient of resistivity (PTCR) sensors is resistor materials that undergo a sharp change in resistivity at a designed Curie temperature due to its unique structure and chemical composition. This effect serves important control functions in a wide variety of electronic circuitry and similar applications. Conventional calcining of mixed oxides method (CMO) is used for fabricating lanthanum doped barium titanate (BaTiO3) for PTCR behaviour through solid-state-sintering route, at 1100°C, 1350°C. Two batches of samples were fabricated at low and high sintering temperatures of 1100°C, 1350°C respectively. The effect of different concentrations of donor dopant on BaTiO3 on the electrical properties of Ba(1-x)LaxTiO3 with x= 0.0005, 0.001, 0.002, 0.0025, 0.003 mol%, is investigated at low sintering temperature. The influence of lantanum doping with Al2O3+SiO2+TiO2 (AST) as sintering aids on the electrical properties of Ba(1-x)LaxTiO3 with x= 0.0005, 0.001, 0.003 mol%, is also investigated. The results of the electrical characterization for the first batch of samples showed an increase in room temperature resistance with increaisng donor concentration. Also the results of the electrical characterization for the second batch of samples also showed the same increase in room temperature resistance with increasing donor concentration. For first batch of sensors the high room temperature resistance keeps the jump small and these materials showed V-shaped NTCR-PTCR multifunctional cryogenic sensor behavior with a strong negative coefficient of resistance effect at room temperature.Where as the second batch of sensors showed few orders of magnitude rise in resistivity values. The La-doped BaTiO3 ceramics co-doped with Mn gives an enhanced PTCR effect which can be exploited for various sensor applications.

A dissertation submitted to the Faculty of Engineering, Cape Peninsula University of Technology, Cape Town, in partial fulfilment of the requirements for the MTech Degree in Mechanical Engineering 2012 / Flow features provide considerable guidance for the rational selection of techniques to predict hydraulic behaviour and for suitable operating conditions for pipelines. Traditionally, water was used to transport coarse particles, and it was necessary to operate at velocities at which the flow was turbulent in order to avoid blockage. Consequently the friction losses were too high for economic operation. In addition, wear on pipes, fittings and pumps presented serious problems. Nowadays, it is well established that it is possible to operate at very high solids concentration in a heavy vehicle (carrier fluid). Similar solids throughputs may be achieved at very much lower velocities by operating in the laminar flow regime. This results not only in lower power requirement, but it also reduces wear and water consumption. In spite of these potential benefits, only a few studies dealing with the transport of coarse particles in heavy media have been reported. Since the distinction between different flow patterns is of paramount importance for modelling purposes, as equations are flow pattern dependent, and given the importance of avoiding excessive wear of pipes at low and high velocities, the present work was carried out in the context of dense or non-Newtonian carrier fluid. This project comprised analysis of existing data acquired at the Flow Process and Rheology Centre of the Cape Peninsula University of Technology. Kaolin in the range of 6% to 15% volumetric concentration was used as a carrier fluid and coarse material in the range of 10% to 30% volumetric concentration was simulated by silica sand ranging in size from 1 mm to 3 mm. For the purpose of this study flow patterns derived from resistance curves for various mixtures, particle concentrations, particle grading and flow conditions were compared with “concentration profiles” and images obtained from electrical resistance tomography (ERT). It appeared from this work that the sand concentration does not change the flow pattern but increases or reduces the pressure gradients depending on the case. The concentration of kaolin carrier can change the flow patterns from layered to homogeneous flow, inducing an increase in total pressure gradients as it increases. Flow patterns obtained from ERT compared reasonably well with those derived from pressure gradients profiles. The transition velocities from layered to heterogeneous flow obtained from both methods were similar, especially for low and moderate carrier concentrations. As the kaolin carrier concentration or as the sand concentration increased it became more difficult to distinguish the transition velocity between heterogeneous and layered flow. More work is still needed to improve the ERT instrument and its image reconstruction software.

Este trabalho visou entender e avaliar a resistência mecânica da junção de chapas de aço obtidas pelo processo de União de Chapas por Conformação a Frio (UCCF). Esse processo é conhecido no meio industrial pelo termo em inglês: clinching ou press joining. O formato de união cilíndrico, também conhecido como Round, foi selecionado para unir os corpos de provas. As uniões metálicas ensaiadas foram fabricadas com aço de baixo teor de carbono sem camada superficial de proteção (170MPa de limite de escoamento). O material escolhido é de comum utilização na indústria automotiva. Duas espessuras diferentes foram avaliadas: 0,8mm e 1,2mm. Um completo procedimento foi criado para determinar os parâmetros ideais do processo UCCF baseado nos critérios de falha existentes na literatura e na experiência do fornecedor do equipamento. A união em estudo foi submetida, experimentalmente, a cargas multiaxiais com o auxílio de um dispositivo baseado no ensaio de Arcan para possibilitar uma condição de carga combinada, onde foi possível identificar graficamente o comportamento estrutural do corpo de prova em estados de carregamento que variam de tração (normal à superfície do ponto) até cisalhamento (perpendicular à superfície do ponto). Os valores de resistência mecânica encontrados foram de 1,13kN (mínimo) a 2,55kN (máximo) para as chapas de aço com espessura de 0,8mm e de 1,89kN (mínimo) e 3,18kN (máximo) para as chapas de 1,2mm. Um estudo comparativo com Solda Ponto por Resistência Elétrica (SPRE) foi realizado. A UCCF alcançou resultados de 47,68% dos valores obtidos para a SPRE para chapa com espessura de 0,8mm e 37,78% para chapas de 1,2mm. / The purposes of this work were understand and evaluate cold forming sheet metal joining of steel plates mechanical resistance. This process is well known as clinching or press joining. Round clinching element was selected to be used on all tested specimens due to its industry suitability. The metallic specimens were built on mid carbon steel without zinc coat protection (Yield Stress: 170MPa). This is a common material on automotive industry. Two different thicknesses were evaluated: 0.8mm and 1.2mm. A full procedure to determine ideal clinching parameters was created based on available literature information and clinching supplier know-how. All union technology was experimentally submitted to multiaxial loads using device based on Arcan concept. Joining mechanical behavior curves were plotted from traction (normal to element joint surface) to shear (perpendicular to element joint surface) loads. As a result, 0.8mm thickness steel plates achieved load values from 1.13kN (minimum) to 2.55kN (maximum), 1.2mm thickness steel plates achieved values from 1.89kN (minimum) e 3.18kN (maximum). A comparative study was made with Electric Resistance Spot Weld (ERSP). Clinching joining achieved results as 47.68% and 37.78% of ERSP loads for 0.8mm and 1.2mm thickness steel plates respectively.