1000 resultados para Reforço à flexão
Resumo:
Ceramics materials have good properties including chemical stability, high hardness and wear resistance. Moreover, due to its fragility, can suffer failure under relatively low levels of tension. Actually zirconia is the material of choice in metal free dental prostheses used in dentistry due its inertia in physiological environment, good bending strength, hardness and fracture toughness. The alumina and mixed tungsten and titanium carbides additions, acting as reinforcement elements in the zirconia matrix, have as their main objective the improvement of mechanical properties of this material. In this work, samples of zirconia, zirconia with 30% wt of alumina and zirconia with 30% wt mixed carbides were analyzed. The samples were sintered by uniaxial hot pressing on 30 MPa pressure, for 1 hour in an argon atmosphere. They were physically characterized by porosity and density measurements, and mechanically by 3-points bending strength and Vickers microhardness. The X-ray diffraction was used for the phase identifications and microstructure was examined by scanning electron microscopy (SEM). The addition of mixed carbides as reinforcement elements in zirconia matrix provides improvements in all properties analyzed in this work. The alumina addition has dropped the zirconia strength, although it caused improvement in other properties
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This research is about the use of the coconuts endocarp (nucifera linn) and the waste of derivatives of wood and furniture as raw material to technological use. In that sense, the lignocellulosic waste is used for manufacture of homogeneous wood sheet agglomerate (LHWS) and lignocellulosic load which take part of a polymeric composite with fiber glass E (GFRP-WC). In the manufacturing of the homogeneous wood sheet agglomerate (LHWS), it was used mamonas resin as waste s agglutinating element. The plates were taken up in a hydraulic press engine, heated, with temperature control, where they were manufactured for different percentage of waste wood and coconuts nucfera linn. Physical tests were conducted to determine the absorption of water, density, damp grade (in two hours and twenty-four hours), swelling thickness (in two hours and twenty-four hours), and mechanical tests to evaluate the parallel tensile strength (internal stick) and bending and the static (steady) flexural. The physical tests results indicate that the LHWS can be classified as bonded wood plate of high-density and with highly water resistant. In the mechanical tests it was possible to establish that LHWS presents different characteristics when submitted to uniaxial tensile and to the static (steady) flexural, since brittle and elasticity module had a variation according to the amount of dry endocarp used to manufacture each trace of LHWS. The GFRP-WC was industrially manufactured by a hand-lay-up process where the fiber glass E was used as reinforcement the lignocellulsics waste as load. The matrix was made with ortofitalic unsaturated polyester resin. Physical and mechanical tests were performed in presence of saturated humidity and dry. The results indicated good performance of the GFRP-WC, as traction as in flexion in three points. The presence of water influenced the modules obtained in the flexural and tensile but there were no significant alteration in the properties analyzed. As for the fracture, the analysis showed that the effects are more harmful in the presence of damp, under the action of loading tested, but despite this, the fracture was well defined starting in the external parts and spreading to the internal regions when one when it reaches the hybrid load
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The clay mineral attapulgite is a group of hormitas, which has its structures formed by microchannels, which give superior technological properties classified the industrial clays, clays of this group has a very versatile range of applications, ranging from the drilling fluid for wells oil has applications in the pharmaceutical industry. Such properties can be improved by activating acid and / or thermal activation. The attapulgite when activated can improve by up to 5-8 times some of its properties. The clay was characterized by X-ray diffraction, fluorescence, thermogravimetric analysis, differential thermal analysis, scanning electron microscopy and transmission electron microscopy before and after chemical activation. It can be seen through the results the efficiency of chemical treatment, which modified the clay without damaging its structure, as well as production of polymer matrix composites with particles dispersed atapugita
Resumo:
As teorias e polticas de desenvolvimento regional sofreram grandes alteraes nas duas ltimas dcadas. Os factores que impulsionam o crescimento econmico sustentado j no se relacionam apenas com o capital fsico, nem sequer com o capital humano regional. As novas condies de competitividade enfatizam a importncia do capital social, normas e regras sociais, formais ou informais que promovem a compreenso recproca e a confiana mtuas entre os agentes da economia da regio. Este artigo demonstra a forma como as instituies de uma regio se podem organizar em torno dos processos de reestruturao produtiva e encorajar as empresas na regio a adoptar normas, expectativas, valores, atitudes e prticas comuns, em suma, uma cultura comum de inovao reforada pelo processo de aprendizagem social. A aco poltica dinamizada pela autarquia da Covilh no projecto ReADAPT, a aco da Associao Nacional dos Industriais de Lanifcios ao promover as condies que sustentam e levam ao aparecimento de redes ou agrupamentos de empresas com actividades relacionadas nas reas de maior potencial de desenvolvimento da regio, e o estabelecimento de relaes entre essas redes e as restantes instituies (centros de formao, universidade, sindicatos, etc.) constituem o chamado Sistema Regional de Inovao deste territrio. Num contexto de depresso econmica sectorial e regional, o papel da ANIL e das restantes entidades parceiras assumiu-se como de animadores e facilitadores do desenvolvimento. A aprendizagem e a reflexão institucional conseguidas contriburam tambm para o que ANIL e as restantes entidades parceiras e o sector pblico com o qual interagem, tenham adquirido uma nova capacidade de inovao estratgica. Neste contexto, instituies de carcter regional/local assumem-se como um elemento essencial na construo de racionalidades e no condicionamento de comportamentos reflexivos e de cooperao, indicando os caminhos possveis a seguir aos restantes actores da regio. Em suma, as dinmicas de associao entre actores regionais so um ingrediente fundamental na receita para o desenvolvimento das regies, no sentido em que podem ajudar outros a ajudar-se na criao de significados, na construo de capacidade para agir e no suporte construo de redes atravs das quais os agentes econmicos e sociais podem colaborar em benefcio comum.
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The research and development of wind turbine blades are essential to keep pace with worldwide growth in the renewable energy sector. Although currently blades are typically produced using glass fiber reinforced composite materials, the tendency for larger size blades, particularly for offshore applications, has increased the interest on carbon fiber reinforced composites because of the potential for increased stiffness and weight reduction. In this study a model of blade designed for large generators (5 MW) was studied on a small scale. A numerical simulation was performed to determine the aerodynamic loading using a Computational Fluid Dynamics (CFD) software. Two blades were then designed and manufactured using epoxy matrix composites: one reinforced with glass fibers and the other with carbon fibers. For the structural calculations, maximum stress failure criterion was adopted. The blades were manufactured by Vacuum Assisted Resin Transfer Molding (VARTM), typical for this type of component. A weight comparison of the two blades was performed and the weight of the carbon fiber blade was approximately 45% of the weight of the fiberglass reinforced blade. Static bending tests were carried out on the blades for various percentages of the design load and deflections measurements were compared with the values obtained from finite element simulations. A good agreement was observed between the measured and calculated deflections. In summary, the results of this study confirm that the low density combined with high mechanical properties of carbon fibers are particularly attractive for the production of large size wind turbine blades
Resumo:
The gradual replacement of conventional materials by the ones called composite materials is becoming a concern about the response of these composites against adverse environmental conditions, such as ultraviolet radiation, high temperature and moist. Also the search for new composite using natural fibers or a blend of it with synthetic fibers as reinforcement has been studied. In this sense, this research begins with a thorough study of microstructural characterization of licuri fiber, as a proposal of alternative reinforcement to polymeric composites. Thus, a study about the development of two composite laminates was done. The first one, involving only the fiber of licuri and the second comprising a hybrid composite based of fiber glass E and the fiber of licuri, in order to know the performance of the fiber when of fiber across the hybridization process. The laminates were made in the form of plates using the tereftlica ortho-polyester resin as matrix. The composite laminate made only by licuri fiber had two reinforcing fabric layers of unidirectional licuri and the hybrid composite had two reinforcing layers of unidirectional licuri fabric and three layers of fiber short glass-E mat. Finally, both laminates was exposed to aging acceleration in order to study the influence of environmental degradation involving the mechanical properties and fracture characteristics thereof. Regarding the mechanical properties of composites, these were determined through uniaxial tensile tests, uniaxial compression and three bending points for both laminates in original state, and uniaxial tensile tests and three bending points after accelerated aging. As regards the study of structural degradation due to aging of the laminates, it was carried out based on microscopic analysis and microstructure, as well as measuring weight loss. The characteristics of the fracture was performed by macroscopic and microscopic (optical and SEM) analysis. In general, the laminated composites based on fiber licuri showed some advantages in their responses to environmental aging. These advantages are observed in the behavior related to stiffness as well as the microstructural degradation and photo-oxidation processes. However, the structural integrity of this laminate was more affected in case the action of uniaxial tensile loads, where it was noted a lower rate of withholding his last resistance property
Resumo:
The use of gypsum, one of the oldest building materials for the construction industry in the country has been experiencing a significant and steady growth, due to its low cost and some of its properties that confer comparative advantage over other binder materials. Its use comprises various applications including the coating of walls and the production of internal seals and linings. Moreover, the fibers are being increasingly incorporated into arrays fragile in an attempt to improve the properties of the composite by reducing the number of cracks, the opening of the same and its propagation velocity. Other properties, depending on the function of the component material or construction, among these thermal and acoustic performances, are of great importance in the context of buildings and could be improved, that is, having better performance with this embodiment. Conduct a comparative study of physico-mechanical, thermal and acoustic composite gypsum incorporating dry coconut fiber, in the form of blanket, constituted the main objective of this work. Improving the thermal and acoustic performances of precast gypsum, used for lining and internal vertical fences of buildings, was the purpose of development of these composites. To evaluate the effect of fiber content on the properties of the composites were used to manufacture the composite layer with different thicknesses. The composites were fabricated in the form of plates with dimensions of 500x500x24mm. To facilitate the comparative study of the properties were also made with material gypsum boards only. We then determined the physico-mechanical, thermal and acoustical plaster and composites. The results indicated that the composites were significant gains in relation to thermal performance and also acoustic, in certain frequency range, increasing the thickness of the blanket. Concerning other physical-mechanical properties, the results showed that although the compressive strength was lower than for the composite did not occur after a fracture catastrophic failure. The same trend was observed with regard to resistance to bending, since the composites have not suffered sudden rupture and still continued after the load supporting point of maximum load
Resumo:
Existe uma crescente preocupao com a sustentabilidade e com o impacto ambiental da atividade da construo que, desde o incio do sc. XXI, com o avano exponencial da nanotecnologia e do estudo das nanopartculas (para incorporao em argamassas e betes), tem vindo a ser atendida de uma forma inovadora. As nanopartculas, quando substituindo pequenas percentagens da massa de cimento, conferem caractersticas melhoradas s misturas: resistncia, durabilidade, entre outras. Os potenciais benefcios no beto so variados e esto, genericamente, identificados. Todavia, existem ainda algumas lacunas (e.g. estudos que incluam ensaios estruturais). Tendo este aspeto em conta, foi formado um consrcio entre a empresa Smart Inovation, Lda e o Instituto Superior de Engenharia de Coimbra por forma a conduzir uma investigao com o intuito de estudar o efeito da incorporao das nanopartculas em argamassas e betes. Inserindo-se a presente dissertao no mbito desse projeto de investigao, decidiu-se estudar o comportamento de vigas de beto incorporando nanopartculas (ou nanobeto) quando sujeitas a esforos de corte e de flexão, comparando-o com o de betes de referncia. Foram, ento, realizados dois tipos de ensaios, para as mesmas misturas (que incluem betes simples, com nanopartculas, com fibras e com nanopartculas e fibras em conjunto): (i) ao corte em que se submeteram oito vigas, simplesmente apoiadas, aplicao de uma carga concentrada a 0,85 m do apoio mais afastado; (ii) flexão em que se submeteram tambm oito vigas, simplesmente apoiadas, aplicao de uma carga concentrada a meio vo. Com base nos dados recolhidos durante os ensaios experimentais, estudou-se: a relao carga-deslocamento, os valores tericos e experimentais do esforo transverso e do momento, a curvatura, a rigidez, a fendilhao e o tipo de rotura. Da anlise de resultados, foi possvel observar que o comportamento estrutural de vigas de beto incorporando nanopartculas no evidencia, de forma clara, as previses dos ensaios de caracterizao dos betes. Porm, verificou-se que existe alguma potencialidade da incorporao das nanopartculas (principalmente as nanopartculas de Al2O3) beneficiarem a resistncia ao corte e flexão. Foi ainda possvel observar que a interao entre nanopartculas e fibras de ao induz efeitos negativos na resistncia ao corte e a resistncia flexão
Resumo:
J se passaram algumas dcadas desde que o beto o principal material de construo que ergue cidades e estruturas nas civilizaes contemporneas. Num passado no muito longnquo, a rea da durabilidade, manuteno e preveno das estruturas de beto no foi vista como prioridade, chegando a ser negligenciada, por consequncia hoje existem graves problemas nalgumas construes de beto. Por outro lado, devido ao excedente de construo habitacional em Portugal e , a atual conjuntura econmica/financeira que a Europa atravessa, o setor da construo tem sofrido um abrandamento acentuado. A conscincia e postura de sustentabilidade das novas geraes e entidades competentes, acentuou a necessidade de preservar, reparar e reforar muito do patrimnio no parque habitacional portugus e europeu. O projeto de interveno numa estrutura nunca abordada da mesma maneira, no existem duas estruturas iguais, e h particularidades neste tipo de projetos que no existem num projeto de uma estrutura nova. Para intervir numa estrutura j construda necessrio um conhecimento abrangente em vrias temticas, tais como: regulamentao, mtodos de avaliao de segurana, definio das caractersticas mecnicas dos materiais, tcnicas de reparao e reforço, metodologias de diagnostico e interveno, comportamento estrutural, etc. Atualmente existe muita informao acerca da temtica de reparao e reforço de estruturas de beto armado, no entanto h ainda alguma falta de documentao onde a informao aparece de forma integral e objetiva. Consideando o apresentado anteriormente, tentou-se compilar informao sobre os principais assuntos que interessam a um projeto de reparao/reforço de estruturas de beto armado, nomeadamente as normas e legislao aplicvel, exemplos de metodologias de inspeo e interveno, os principais ensaios em laboratrio e in situ para caracterizao dos materiais, principais tcnicas de reparao/reforço. Sobre este tpico e a ttulo de exemplo, aprofundou-se com mais detalhe as consideraes relativas ao dimensionamento com reforço com FRPs.
Resumo:
The objective of reservoir engineering is to manage fields of oil production in order to maximize the production of hydrocarbons according to economic and physical restrictions. The deciding of a production strategy is a complex activity involving several variables in the process. Thus, a smart system, which assists in the optimization of the options for developing of the field, is very useful in day-to-day of reservoir engineers. This paper proposes the development of an intelligent system to aid decision making, regarding the optimization of strategies of production in oil fields. The intelligence of this system will be implemented through the use of the technique of reinforcement learning, which is presented as a powerful tool in problems of multi-stage decision. The proposed system will allow the specialist to obtain, in time, a great alternative (or near-optimal) for the development of an oil field known
Resumo:
Tese (mestrado)Universidade de Braslia, Faculdade de Tecnologia, Departamento de Engenharia Mecnica, 2016.
Rigidez do papelo ondulado: comparao entre resultados experimentais e os obtidos por clculo analtico
Resumo:
Cardboard packing for horticultural products has as main function to protect them. The design of a cardboard packing request the knowledge of the bending stiffens which is depending on the modulus of elasticity. The objective of this work was to calculate the cardboard modulus of elasticity from data obtained in laboratory using physical characterization test, with different methods, and comparing the results with the values obtained experimentally. Ten samples of each cardboard selected for this study were tested in the paper fabrication direction and in its transverse direction. The papers liner and medium resistance to the traction, used to calculate the bending stiffness, was determined in a universal machine test. To obtaining of the bending stiffens the four points test was accomplished. Expressive variations among the methods from which the modulus of elasticity is obtained were observed and that influence the bending stiffness of the structure. The stiffness values obtained experimentally were always greater than the values obtained from analytical method. This difference can be attributed to two factors, the production processes that assurance a larger rigidity than the components separately and the addition of the adhesive layer that is not taken in consideration in the analytic calculations.
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The durability of the cellulose-cement composites is a decisive factor to introduce such material in the market. Polymers have been used in concrete and mortar production to increase its durability. The goal of this work was the physical and mechanical characterization of cellulose-cement composites modified by a polymer and the subsequent durability evaluation. The work also evaluated the dispersion of acrylic polymer in composites made of Pinus caribaea residues. The physical properties observed were water absorption by immersion and bulk density. Rupture modulus and toughness were determined by flexural test. The specimens were obtained from pads, produced by pressing and wet curing. Samples were subjected to accelerated aging tests by repeated wetting and drying cycles and hot-water bath and natural aging. The scanning electron microscopy (SEM) allowed verifying the fiber and composite characteristics along the time. For the composite range analyzed, it was observed the polymer improved the mechanical properties of composites besides a significant decreasing in water absorption. The use of polymer improved the performance of vegetable fiber-cement composites when compared to the conventional mortar, due to water absorption decreasing.
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The rice husk and its ash are abundant and renewable and can be used to obtain alternative building materials. An increase in the consumption of such waste could help minimize the environmental problems from their improper disposal. This study aimed to evaluate the use of ashes as a cargo mineral (filler). However, the rice husk chemically interferes in the conduct of the based cement mixtures. Thus, different mixes cement-rice husk with and without the addition of ash were evaluated in order to highlight the influence of its components (husk; ash), which could otherwise be excluded or be underestimated. Cylindrical samples (test of simple compression and traction by diametrical compression) and samples extracted from manufactured pressed board (test of bending and parallel compression to the surface), were used to evaluate the behavior of different mixtures of components (rice hush; RHA - rice husk ahs). The results of the mechanical tests showed, in general, there is not a statistical difference between the mixtures, which are associated with the chemical suppressive effect of the rice husk ash. The mixture of rice husk of 10 mm, with an addition of 35% of the rice husk ash, is notable for allowing the highest consumption of rice husk and rice husk ash, to reduce 25% the consumption of cement and to allow the storage (without emissions to the atmosphere), around 1.9 ton of CO2 per ton of cement consumed, thus contributing to the reduction of CO2 emissions, which can stimulate rural constructions under an ecological point of view.
Resumo:
INTRODUCTION: Armies from all over the world acknowledge the importance of good physical fitness for the performance of military duties. The Military Exercise Training (MET) attempts to provide assistance to this search for better physical fitness and performance. OBJECTIVE: To verifying the effect on the body composition and physical performance of the students at ESPCEX (Military School for Preparation of Army Cadets) after 13 weeks of MET. METHODS: The sample was formed by 287 male students from the ESPCEX, whose average age was 18.33 1.26. Such students accomplished a boarding school routine, having defined schedules, meals and activities from which they were only released during the weekends. The MET was accomplished five days a week and it comprised both aerobic and resistance training. Measurement of body mass, height, skinfold (triceps, abdominal and suprailiac) was accomplished during pre and post training periods, and the following tests were performed: 12-minutes-run, oblique sit up, arm push up and pull up. Fat percentage, fat-free body mass and fat body mass were calculated using the anthropometric data based on the Guedes 3 skinfold protocol. RESULTS: Significant reduction in fat body mass, fat percentage and in triceptal and abdominal skinfold, as well as increase in suprailiac skinfold and fat-free body mass was observed when anthropometric and body composition data were compared, during the initial and the final periods of training. Significant improvement also occurred in all prformed physical tests, in which better performance was achieved. CONCLUSION: The acquired data suggest that performance of MET 5 days a week brought significantly improved body composition as well as physical performance
