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Orientador: Newton de Oliveira Pinto Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-07T09:19:10Z (GMT). No. of bitstreams: 1 Carmona_TiagoGarcia_M.pdf: 1542541 bytes, checksum: 8f386834340021978bc83fc4da322af0 (MD5) Previous issue date: 2006 / Resumo: O uso de estruturas cilíndricas para armazenamento de líquidos e materiais granulares apresenta-se como uma eficiente solução, pois sob a ação da pressão interna desenvolvem-se predominantemente esforços de tração (esforços circunferenciais) nas paredes da estrutura. A obtenção dos esforços oriundos da pressão interna é apresentada de forma superficial nos primeiros capítulos do presente trabalho. A ocorrência de manifestações patológicas nestas estruturas muitas vezes está relacionada com o efeito de flexão na parede decorrente da ação de um gradiente térmico pela armazenagem de produtos a elevadas temperaturas. Para a análise deste efeito, são revisados conceitos de termodinâmica aplicados ao problema específico dos tanques. A consideração do efeito térmico é primeiramente apresentada segundo uma abordagem clássica com a seção não fissurada. Em seguida é apresentada uma formulação pouco difundida no meio técnico, onde a consideração da fissuração da seção de concreto armado modifica substancialmente o problema. É mostrado que o gradiente térmico não é capaz de produzir o estado limite último da seção, porém possui influência decisiva no controle da fissuração. Os conceitos teóricos são ilustrados pela apresentação de estudo de caso, onde após as análises decidiu-se pelo reforço com cabos externos protendidos não aderentes / Abstract: The use of cylindrical structures for storage of liquid and granular materials is an efficient solution of engineering, because under the action of the internal pressure, the wall develops preferentially tension forces (circumferential forces) in the structure walls. The first chapters of this work presents briefly how to obtain the internal forces caused by the pressure of the stored materials. Sometimes the occurrence of damages in cylindrical storage structures is related with a thermal gradient that generates bending effects in structures that store products at high temperature. For the analysis of this effect, concepts of thermodynamic are revised and applied for the case of tanks. The consideration of the thermal effect is first presented using a classic approach that takes in account a non-cracked section. After that it is present a not well known formulation, where the consideration of cracks in the reinforced concrete sections, bring great changes to the problem. It is shown that the thermal gradient is not able to produce an ultimate limit-state, but can have decisive influence in crack control. The theoretical concepts are illustrated with a case, where after the analysis, it was decided to reinforce the structure with external tendons / Mestrado / Estruturas / Mestre em Engenharia Civil

Over the past fifty years, many states have recognized the benefits of making precast, prestressed multi-girder bridges continuous by connecting the girders with a continuity diaphragm. Although there is widespread agreement on the benefits of continuous construction, there has not been as much agreement on either the methods used for design of these systems or the details used for the continuity connections. To aid designers in choosing the most appropriate method, an analytical and experimental study was undertaken at Virginia Tech. Analyses were done to compare the differences in the predicted continuity moments for different design methods and assumptions over a range of commonly used systems of Precast Concrete Bulb Tee (PCBT) girders and cast-in-place slabs. The results of the analyses were used to develop three continuity connection details for testing during the experimental study. Three different continuity connections were tested using full depth PCBT 45 in. deep girders made continuous with a 6 ft wide slab. The bottom of the ends of the girders were made continuous with the continuity connection by extending prestressing strands for one test and extending 180 degree bent bars for the other test. Both connections adequately resisted service, cyclic, and ultimate loads. But, the test with the extended bars remained stiffer during cyclic loading and is recommended for use. A third test was performed on a system using only a slab cast across the top of the girders. Two primary cracks formed above the ends of the girders at the joint during service testing, after which no significant increase in damage took place. Results from the analytical study indicate that the predicted positive thermal restraint moments may be significant, similar in magnitude to the actual positive cracking moment capacities. Results from the experimental study indicate that restraint moments develop early due to thermal expansion of the deck during curing and subsequent differential shrinkage; however, the magnitudes of the early age restraint moments are much less than conventional analyses predict. / Ph. D.

Thermal barrier coatings have been widely used to provide thermal protection to components in the hot section of gas turbines. This research focuses on two influencing factors on coating behavior: thermal gradient and cyclic oxidation. The delamination mechanics under thermal gradient is analyzed, taking thermally grown oxide into consideration. Coatings experience thermal gradients at different stages during actual service flight. One is due to engine power shut down when landing and the other due to internal cooling of the substrate. Thermally grown oxide (TGO) also acts as a critical factor in delamination mechanics. The induced stress gradient and corresponding energy release rate for interface delamination and shallower delamination are presented. Mechanism maps that explain the criteria for preventing delamination from developing and propagating are established. Three cooling trajectories are envisaged to analyze the variation in the possibility of delamination. Multilayer coatings used in components of the hot section of aero turbine engines also experience cyclic temperature variation during flight cycles. As experiment conditions vary and coating performance is improved, the time required to run through the test of coating failure can be both time-consuming and prohibitive. Therefore, protocols providing prediction of quantified coating behavior are in demand to shorten life-time tests. Curves of mass change are obtained from quantifying scale growth and loss by different models such as Cyclic Oxidation Spall Program (COSP). A modification is made by combining COSP and a mechanic based model to obtain critical parameters for lifetime prediction from short time experiment. The time for coatings to reach peak temperature during cycling is discovered to influence prominently on modeling results. Predictions for several coating compositions and cycling conditions are consistent with the data from the existing experiments of the coating system.

Laser lithography has been implemented in many ways to pattern polymeric materials. By using a tightly focused laser beam we can induce sharp thermal gradients, exceeding 1,500,000 °C/cm, onto the surface of a thin polymer film. The temperature dependence of the surface tension in such a thermal field gives rise to a flow of material away from the center of the beam focus driven by the Marangoni or thermocapillary effect. The evolution of a film irradiated by a focused laser can be, in a general sense, predicted by a presented hydrodynamic model, which is based on simple fluid mechanics. However, the details of the individual evolution profiles show a more complicated behaviour. It has been shown that this complex behaviour can be explained by considering the optical interference effects of the thin polymer coating. An optical feedback control routine has been developed to compensate for the interference effect by monitoring and maintaining a constant absorbed laser power. This ensures that the temperature gradient that drives the lithography process is consistent during operation. Additional studies involving high laser power effects, different material systems and other thin film phenomena have revealed an interesting assortment of novel behaviours. The extension of these behaviours to the lithography process lead towards the development of applications in microfabriation and microfluidic devices. / Thesis / Master of Applied Science (MASc)

Small scale renewable energy harvesting is an attractive solution to the growing need for power in remote technological applications. For this purpose, localized thermal gradients on-chip—created via radiative cooling—could be exploited to produce microscale renewable heat engines running on environmental heat. This could allow self-powering in small scale portable applications, thus reducing the need for non-renewable sources of electricity and hazardous batteries. In this work, we demonstrate the creation of a local thermal gradient on-chip by radiative cooling of a 90 nm thick freestanding silicon nitride nanomechanical resonator integrated on a silicon substrate at ambient temperature. The reduction in temperature of the thin film is inferred by tracking its mechanical resonance frequency, under high vacuum, using an optical fiber interferometer. Experiments were conducted on 15 different days during fall and summer months, resulting in successful radiative cooling in each case. Maximum temperature drops of 9.3 K and 7.1 K are demonstrated during the day and night, respectively, in close correspondence with our heat transfer model. Future improvements to the experimental setup could enhance the temperature reduction to 48 K for the same membrane, while emissivity engineering potentially yields a maximum theoretical cooling of 67 K with an ideal emitter. This thesis first elaborates a literature review on the field of radiative cooling, along with a theoretical review of relevant thermal radiation concepts. Then, a heat transfer model of the radiative cooling experiment is detailed, followed by the experimental method, apparatus, and procedures. Finally, the experimental and theoretical results are presented, along with future work and concluding remarks.

An electrolytic cell was designed, built, and tested with several proof-of-concept experiments in which Zircaloy material was charged with hydrogen in order to generate zirconium hydride formations. The Electrolytic Charging with Hydrogen and a Thermal Gradient (ECH-TG) system has the ability to generate static 20°C to 120°C temperatures for a H2SO4 and H2O bath for isothermal experiment conditions. This system was designed to accommodate a molten salt bath in future experiments to achieve higher isothermal temperatures. Additionally, the design accommodates a cartridge heater, which when placed on the inside of the sample tube, can be set at temperatures up to 350 °C and create a thermal gradient across the sample. Finally, a custom LABVIEW VI, L2.vi, was developed to control components and record data during experimentation. This program, along with web cameras and the commercial StirPC software package, enables remote operation for extended periods of time with only minor maintenance during an experiment. While proving the concept for this design, 19 experiments where performed, which form the basis for a future parametric study. Initial results indicate formations of zirconium hydrides which formed rim structures between 8.690 +/- 0.982 μm and 12.365 +/- 0.635 μm thick. These electrolytically produced rims were compared with hydrides formed under a previous vapor diffusion experiment via Scanning Electron Microscope (SEM) imaging and Energy dispersive X-ray Spectroscopy (EDS) analysis. While the existing vapor diffusion method formed gradients of zirconium hydride, it failed to produce the gradient in the correct direction and also failed to create a hydride rim. The successful use of the ECH-TG system to create said rim, and some of the methods used to direct that rim to the OD of the tube can be used for future work with the vapor diffusion method in order to create zirconium hydrides of the correct geometry. The procedures and apparatus created for this project represent a reliable method for creating zirconium hydride rim structures.

Em um incêndio, pilares de aço inseridos em paredes apresentam uma resposta termoestrutural diferente daqueles isolados, de modo que a compartimentação oferece um aumento de sua resistência ao fogo. Poucos estudos foram desenvolvidos até o presente momento para avaliar o desempenho de pilares em contato com paredes, sendo que aqueles já realizados apresentaram respostas que ainda deixam dúvidas sobre esses elementos. Diante disso, este trabalho propõe analisar, em contexto numérico, o comportamento de pilares de aço isolados e inseridos em paredes sujeitos à ação térmica, a partir do uso do código computacional ABAQUS versão 6.14. A modelagem termoestrutural, considerando a parede somente como elemento de compartimentação, promoveu resultados pouco consistentes, o que leva a concluir que a alvenaria influencia na resposta estrutural de pilares em situação de incêndio. Por essa razão, ao inserir molas que controlam o deslocamento axial das paredes na modelagem numérica, os resultados alcançados passaram a ser mais representativos. Análises complementares a respeito da influência do fator de carga e do nível de rigidez axial e rotacional na resistência ao fogo dos pilares também foram realizadas. Para todos os modelos, constatou-se a influência negativa do fator de carga quando aumentado. Quanto à restrição axial, foi verificado que sua presença possui maior influência na resistência ao fogo em comparação com sua intensidade, uma vez que a elevação desse parâmetro não afetou o tempo crítico dos pilares, para a maior parte dos casos analisados. Em relação à rigidez rotacional, ela se mostrou favorável para a resistência ao fogo. Além do mais, a pesquisa contou com uma avaliação do método simplificado da ABNT NBR 14323:2013 para cálculo da evolução da temperatura em perfis de aço. Concluiu-se que ele apresenta melhores resultados para os pilares com aquecimento uniforme na seção transversal. Por essa razão, foi proposta uma nova metodologia de cálculo de temperatura para pilares em contato com paredes, validada por meio de testes numéricos. / In a fire situation, steel columns embedded on walls demonstrate a different thermo- structural response from those isolated, so that the subdivision offers an increase of its fire resistance. Few studies have been developed in order to evaluate the performance of columns in contact with walls, and those already performed showed results that still leave doubts about these elements. Therefore, this work proposes to analyze, in a numerical context, the behavior of isolated and embedded on walls steel columns in fire using the software ABAQUS 6.14 as a modeling tool. The thermo-structural modeling, considering the wall only as a compartmentation element, has presented poor results, which leads to the conclusion that the masonry has influence on the structural response of columns subjected to fire situation. For this reason, when inserting springs in order to control the axial displacement of the walls in numerical modeling, the obtained results were satisfactory. Further analyzes in respect of the load factor influence and the level of axial and rotational stiffness on the fire resistance of columns were also performed. For all the models, it was verified a negative influence of the load factor when increased. However, when it comes to the axial restriction, it was verified that its presence had more influence in the fire resistance of the structural element despite of its intensity, once the increase of this parameter did not affect the critical time of the columns, for most cases analyzed. In respect to rotational stiffness, it was proven favorable to the fire resistance. In addition, this research employed the simplified method presented in the ABNT NBR 14323: 2013 to calculate the temperature evolution in steel profiles. It was concluded that it presents good results only for the columns with uniform heating in the cross section. For this reason, a new methodology to calculate the temperature of columns in contact with wall was proposed, validated by numerical tests.

Thermally cycling a thin plate of nickel-based superalloy with an intense in-plane thermal gradient, or hot spot, produces thermally induced crack growth not represented by classic thermo-mechanical fatigue (TMF). With the max hot spot temperature at 1093 C (2000 F) of a 1.5 mm thick, 82.55 mm diameter circular plate of B-1900+Hf, annular buckling and bending stresses result during each thermal cycle which drive the crack initiation and propagation. A finite element analysis (FEA) model, using ANSYS 7.1, has been developed which models the buckling and as well as represents the stress intensity at simulated crack lengths upon cool down of each thermal cycle. The model approximates the out-of-plane response at heat-up within 5% error and a difference in the final displacement of 0.185 mm after twelve thermal cycles. Using published da/dN vs. Keff data, the number of cycles needed to grow the crack to the experimental arrest distance is modeled within 1 mm. The number of cycles to this point is within 5 out of 462 in comparison to the experimental test.

Protein crystallization is significant in both biotechnology and biomedical applications. In biotechnology, crystallization is essential for determining the structure of both native and synthesized therapeutically important proteins. It can also be used as a final purification step and as a stable form for protein storage. With regard to biomedical systems, protein crystallization appears to be involved in the development and manifestation of certain human diseases. In particular, there exists evidence that L-rich ferritin crystals are involved in Hereditary Hyperferritinemia Cataract Syndrome (HHCS). In the current research a microbatch crystallization apparatus has been introduced that enables (1) multiple batch crystallization experiments at various temperatures and solution conditions in parallel and (2) quantitative monitoring of crystal growth without disturbing the progress of an experiment for observation. The primary application of the apparatus is, but not limited to, screening of protein crystallization conditions, although the system can also be used for other macromolecular and small-molecule crystallization experiments. Multiwell microbatch experiments demonstrated the dependence of apoferritin crystal growth kinetics and final crystal size on temperature and cadmium concentration. Although the solubility of apoferritin might be independent of temperature, the results of this study show that the crystal growth kinetics are affected by temperature, profoundly under some conditions. For apoferritin under near physiological conditions the solution thermodynamics in the form of the second virial coefficient have proofed to be a valuable predictor for the crystallization outcome. Furthermore, the significance of the elevated level of some divalent cations in cataractous lenses has been studied both in dilute solutions and under crystallization conditions and cadmium seems to be sole menace in apoferritin condensation.