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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

Framtagning av beräkningsmall för rullaxlar / Calculation model for reel shafts

Karlsson, Axel January 2015 (has links)
Möjligheter att förbättra Hofpartner ABs beräkningsmall för rullaxlar har undersökts. Undersökningen har fokuserat på användarvänlighet, ekonomi samt hållfasthet. Målet var att göra mallen mer lättanvänd. Nuvarande mall undersöks med resultat att den är väldigt svår att följa samt att dess värden inte överensstämmer särskilt bra med verkligheten i de flesta avseenden. Arbetet koncentreras därmed på att identifiera de existerande problemen och att åtgärda dem. Mallens funktioner utvärderas och beslut fattas om att reducera mallen till att endast hantera information som regelbundet används av företaget. Genom att minska mängden data ses möjligheter att göra mallen enklare att följa och mer lättanvänd med mindre krav på förkunskaper. Nya formler för hållfasthetsberäkningar framställs och implementeras i en nyskapad mall. Formlerna kontrolleras med analyser i FEM. Analyserna visar att de nya beräkningarna ger resultat närmare verkligheten. Kostnadsberäkningarna har konstruerats som en grund till Hofpartner att bygga vidare på. Formler är implementerade men en undersökning av företagets produktion krävs för att uppnå korrekta resultat. Undersökningen behöver utföras för att kartlägga tidsåtgång för företagets produktion, arbetet har endast lett till uppskattningar. Om undersökningen utförs har Hofpartner möjlighet att åstadkomma mycket rimliga resultat i mallen. / In this project the possibilities to improve Hofpartner AB's calculation model for reel shafts has been investigated. The investigation has focused on user friendliness, economy and strength calculations. The goal was to make the model easier to use. An investigation of the current model shows that it is difficult to follow the calculations and that the results in most cases are not particularly accurate. Thus the work is focused on identifying the existing problems and improving on them. Several of the functions in the model are removed and the model now only handles information that are used with some regularity. By reducing the amount of data covered by the model possibilities is seen to simplify usage and to reduce the amount of necessary prior knowledge. New formulas for the strength calculations are presented and implemented in a new model. The formulas are verified by analysis with FEM. The analysis shows that the model is providing results close to the real values. The economical calculations are constructed as a basis for Hofpartner to continue developing. The necessary formulas are implemented but an investigation of the company's production process is necessary to achieve correct results. The newly constructed model mostly contains estimates of costs related to production time and material. If these estimates are updated with correct values Hofpartner has the possibility to achieve very reasonable results in their model.
162

Long-Term Deflection Of One-Way Concrete Slab Strips Containing Steel And GFRP Reinforcement

Darabi, Mohammadali 14 September 2011 (has links)
Fibre reinforced polymers (FRP’s) are considered an alternative to steel reinforcement in concrete structures because of their noncorrosive nature and nonmagnetic properties. FRP materials are, however, brittle and have a lower stiffness compared to steel. The latter property can lead to deflection and crack control problems in FRP-reinforced concrete flexural members under service loads. A considerable amount of information is available for short-term deflection of FRP-reinforced concrete members, but data on long-term deflections are scarce. This study presents the results of monotonic (short-term) and sustained (long-term) loading tests of 12 concrete shallow beams reinforced with either steel or glass FRP (GFRP) bars. The short-term load-deflection responses of the members are evaluated using existing deflection prediction models (Branson’s and Bischoff’s), and the long-term deflection results (monitored over a period of one year) are used to evaluate the existing ACI code and CSA standard approaches for estimating long-term deflection. The GFRP-reinforced concrete beams exhibited greater amounts of both immediate deflection (under sustained load) and long-term deflections over time, than the steel-reinforced concrete beams. The long-term deflections of both the steel- and GFRP-reinforced concrete beams are overestimated when using the ACI and CSA approaches. Although ACI Committee 440 recommends use of lower values of the long-term deflection multiplier for GFRP-reinforced concrete beams, results obtained from this study suggest that the same longterm multiplier values may be used for GFRP- and steel-reinforced concrete beams loaded at between 115 to 157 days of concrete age.
163

Polymer NdFeB Hard Magnetic Scanner for Biomedical Scanning Applications

Pallapa Venkataram, Manu Gopal January 2014 (has links)
Micromirror scanners are the most significant of the micro-optical actuator elements with applications in portable digital displays, automotive head-up displays, barcode scanners, optical switches and scanning optical devices in the health care arena for external scanning diagnostics and in vivo scanning diagnostics. Recent development in microscanning technology has seen a shift from conventional electrostatic actuation to electromagnetic actuation mechanisms with major advantages in the ability to produce large scan angles with low voltages, remote actuation, the absence of the pull-in failure mode and the acceptable electrical safety compared to their electrostatic counterparts. Although attempts have been made to employ silicon substrate based MEMS deposition techniques for magnetic materials, the quality and performance of the magnets are poor compared to commercial magnets. In this project, we have developed novel low-cost single and dual-axis polymer hard magnetic micromirror scanners with large scan angles and low power consumption by employing the hybrid fabrication technique of squeegee coating to combine the flexibility of polydimethylsiloxane (PDMS) and the superior magnetic performance of fine particle isotropic NdFeB micropowders. PCB coils produce the Lorentz force required to actuate the mirror for scanning applications. The problem of high surface roughness, low radius of curvature and the magnetic field interaction between the gimbal frame and the mirror have been solved by a part PDMS-part composite fabrication process. Optimum magnetic, electrical and time dependent parameters have been characterized for the high performance operating conditions of the micromirror scanner. The experimental results have been demonstrated to verify the large scan angle actuation of the micromirror scanners at low power consumption.
164

Design and Analysis of a Shock Absorber with a Variable Moment of Inertia Flywheel for Passive Vehicle Suspension

Xu, Tongyi 05 November 2013 (has links)
Conventional vehicle suspensions consist of a spring and a damper, while mass is rarely used. A mass, if properly used, can also create a damping-like effect. However, a mass has only one terminal which makes it difficult to be incorporated into a suspension. In order to use a mass to achieve the damping-like effect, a two-terminal mass (TTM) has to be designed. However, most of the reported TTMs are of fixed moment of inertia (TTM-CMI), which limits the further improvement of the suspension performance and responsiveness to changes in environment and driving conditions. In this study, a TTM-based vibration absorber with variable moment of inertia (TTM-VMI) is proposed. The main component of the proposed TTM absorber contains a hydraulic-driven flywheel with sliders. The moment of inertia changes with the positions of the sliders in response to the driving conditions. The performance of the proposed TTM-VMI absorber has been analyzed via dynamics modeling and simulation and further examined by experiments. The analysis results indicate that the TTM-VMI absorber outperforms the TTM-CMI design in terms of body displacement; and ride comfort, tire grip and suspension deflection for zero and impulse inputs with comparable performance for sinusoidal input.
165

Stability analysis of mobile boom cranes

Rauch, Andreas 08 August 2008 (has links)
Mobile boom cranes are used throughout the world to perform important and dangerous manipulation tasks. Given their mobility, these types of cranes can quickly be moved into position. Generally, their base is then fixed and stabilized before they start lifting heavy materials. The usefulness of these cranes can be greatly improved if they can utilize their mobile base during the lifting and transferring phases of operation. This ability greatly expands the workspace by combining base motion with the rotation, lifting, and luffing motions. Of course, the cranes lose some stability margin when a payload is attached. The stability is further degraded when the payload swings. This Master's Thesis presents a stability study of such cranes. As a first step, a static stability analysis of a boom crane is conducted in order to provide basic insights into the effects of the payload weight and crane configuration. Then, a semi-dynamic method is used to take the payload swing into account. As a final step, the results of a dynamic stability analysis obtained by using a multi-body simulation of the boom crane are compared to the outcomes of the previous approaches. This provides conclusions for the practical application of stability analysis. A control method that limits payload swing, and thereby improves stability, is also presented.
166

Um procedimento de retroanálise para pavimentos flexíveis baseado na teoria do ponto inerte e em modelagem matemática / A backcalculation procedure for flexible pavements based on inertial point theory and in mathematical modeling

José Miguel Belucio Pereira 07 May 2007 (has links)
Apresenta-se um processo de retroanálise de pavimentos flexíveis baseado na teoria do ponto inerte para a retroanálise do subleito, readaptado para bacias de deflexões teóricas obtidas com o carregamento para o ensaio com a viga Benkelman. Além da retroanálise do subleito, foi desenvolvido um modelo matemático fatorial para a obtenção do módulo resiliente equivalente das camadas presentes sobre o subleito, consideradas como uma única, denominada camada equivalente. Para a readaptação da teoria do ponto inerte e elaboração do modelo fatorial foram utilizados bancos de dados de bacias deflectométricas teóricas geradas pelo programa ELSYM5. Avaliou-se o erro na retroanálise do subleito e da camada equivalente para o processo proposto mediante comparações com outras metodologias semelhantes de retroanálise. A teoria do ponto inerte proporciona o desenvolvimento de um algoritmo simples, convergente e de resposta única para retroanálise de subleito de pavimentos flexíveis, minimizando a influência da experiência do engenheiro na resposta do problema. O procedimento de retroanálise elaborado nesta pesquisa caracteriza-se por simplicidade, sendo de uso adequado, entre outros, para avaliações em nível de rede. / A backcalculation procedure for flexible pavements is introduced based on inertial point theory for subgrade backcalculation readapted to theoretical deflection basins obtained with the load to Benkelman beam test. Beside subgrade backcalculation, it was developed a factorial mathematical model to obtain equivalent resilient modulus from the layers presents upon subgrade, considered as unique and denominated equivalent layer. To the readaptation of inertial point theory and preparing of factorial model were used theoretical deflection bowls data base generated by ELSYM5 program. The subgrade and equivalent layer modulus backcalculation were evaluated to the proposed process through others similar backcalculation methodologies. The inertial point theory provides the development of simple algorithms, convergent and with unique solution for flexible pavements subgrade backcalculation minimizing the influence of engineer experience in the problem answer. The backcalculation procedure developed in this research is characterized by simplicity being of suitable use at network evaluation level among others.
167

Avaliação e diagnóstico de vias urbanas expressas de Manaus: condições estruturais e funcionais

Pinto Filho, Washington Luiz 29 November 2013 (has links)
Submitted by Geyciane Santos (geyciane_thamires@hotmail.com) on 2015-09-30T14:23:40Z No. of bitstreams: 1 Dissertação - Washington Luiz Pinto Filho.pdf: 8211076 bytes, checksum: 5b0146ee71fe71f4ffea30a9fca0f822 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-10-02T20:44:54Z (GMT) No. of bitstreams: 1 Dissertação - Washington Luiz Pinto Filho.pdf: 8211076 bytes, checksum: 5b0146ee71fe71f4ffea30a9fca0f822 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-10-06T19:53:40Z (GMT) No. of bitstreams: 1 Dissertação - Washington Luiz Pinto Filho.pdf: 8211076 bytes, checksum: 5b0146ee71fe71f4ffea30a9fca0f822 (MD5) / Made available in DSpace on 2015-10-06T19:53:40Z (GMT). No. of bitstreams: 1 Dissertação - Washington Luiz Pinto Filho.pdf: 8211076 bytes, checksum: 5b0146ee71fe71f4ffea30a9fca0f822 (MD5) Previous issue date: 2013-11-29 / Não informada / The city of Manaus has the highest average growth rates of the fleet, according to the DENATRAN. Over the past 10 years, the fleet of cars rose from 124,840 (2003) to 297,473 cars (2013) and 3,179 buses (2003) to 7,398 buses (2013). This equates to a 138% increase. Moreover, although, according to DENATRAN in 2003, Manaus was 220,816 vehicles. In 2013, Manaus already has 551,455 registered vehicles in its municipal fleet, which equates to an increase of almost 150%. As a result of this growth, the city roads are presented with its ability to flow and dead, visually, with their decks completely deformed. In this sense, we tried to carry this research, a structural evaluation of pavements of the main streets of the town (Av. Constantino Nery, Avenida Djalma Batista, Recife Av, Av and Av Efigênio Sales Paraíba), employing the technique FWD (Falling Weight Deflectometer) in the diagnosis of the pavement structures of these pathways. The results showed that the structures of those decks still have the condition to withstand the demands of traffic load applied to them, since their structural quality obtained by the mentioned technique, presented in good condition, according to the floors they presented deflections smaller than the allowed maximum, and radii of curvature much greater than 100 m. In addition, analysis was performed of the safety of the coating with respect to tire-pavement grip, which presented values for microtexture and macrotexture well outside the ranges recommended by the standards. / A cidade de Manaus apresenta uma das maiores taxas de crescimento médio da frota de veículos, segundo dados do DENATRAN. Nos últimos 10 anos, a frota de automóveis aumentou de 124.840 (2003) para 297.473 automóveis (2013) e 3.179 ônibus (2003) para 7.398 ônibus (2013). Isto equivale a um aumento de 138 %. Ademais, ainda, segundo o DENATRAN, em 2003, Manaus tinha 220.816 veículos. Em 2013, Manaus já possui 551.455 veículos registrados na sua frota municipal, o que equivale a um aumento de quase 150 %. Como consequência deste crescimento, as vias da cidade apresentam-se com sua capacidade de fluxo inoperante e, visualmente, com seus pavimentos totalmente deformados. Neste sentido, procurou-se realizar, nesta pesquisa, uma avaliação estrutural dos pavimentos das principais vias da cidade (Av. Constantino Nery, Av. Djalma Batista, Av. Recife, Av. Paraíba e Av. Efigênio Sales), empregando a técnica FWD (Falling Weight Deflectometer) no diagnóstico das estruturas dos pavimentos das referidas vias. Os resultados obtidos mostraram que as estruturas daqueles pavimentos ainda apresentam a condição de suportar as solicitações de carga de tráfego a elas aplicadas, visto que sua qualidade estrutural, obtida pela técnica mencionada, apresentou-se em boas condições, em função dos pavimentos terem apresentado deflexões máximas inferiores às admissíveis, bem como raios de curvatura muito superiores a 100 m. Como complemento à análise estrutural, realizou-se análise das condições funcionais do revestimento com relação à aderência pneu-pavimento, a qual apresentou valores para microtextura e macrotextura bem fora dos intervalos recomendados pelas normas.
168

Novas aplicações de técnicas fototérmicas para o estudo de interfaces. / New applications of photothermal techniques for studying interfaces.

Marcos Eduardo Sedra Gugliotti 06 December 2001 (has links)
Este trabalho apresenta o desenvolvimento de novas instrumentações baseadas em efeitos fototérmicos para o estudo de interfaces sólido-líquido e líquido-gás, incluindo no último caso o efeito de surfactantes. O trabalho está dividido em capítulos, cada um enfocando o desenvolvimento e/ou aplicação de uma nova técnica. O Capítulo I apresenta uma introdução aos fenômenos fototérmicos e desecreve a construção de instrumentos clássicos de Lente Térmica (LT) nas configurações de simples e duplo feixe. Interfaces sólido-líquido foram estudadas nos capítulos II-IV usando variações da instrumentação clássica de LT. Um novo sinal fototérmico foi caracterizado, indicando a formação de uma lente térmica invertida na interface. Experimentos de varredura-z na configuração por reflexão foram usados para determinar a mudança no índice de refração da interface próximo ao ângulo crítico, e uma metodologia similar foi utilizada para a medida da difusividade térmica de amostras opacas. Nos capítulos V-VII, a deformação de superfícies líquidas foi estudada pelo efeito Marangoni induzido por laser e pela geração de ondas capilares. A transferência de calor pela interface líquido-gás foi monitorada por Deflexão Fototérmica Transversal. Em todos os casos, a influência de surfactantes foi estudada pela formação de uma monocamada na superfície dos líquidos. Observou-se que uma pequena quantidade de surfactante é capaz de cessar a movimentação de líquidos induzida por gradientes de tensão superficial e aumentar significativamente a transferência de calor pela interface. Os resultados indicam uma correlação entre as transições de fase das monocamadas e a atenuação da deformação superficial bem como o aumento na transferência de calor. Finalmente, o capítulo VIII apresenta uma coleção de trabalhos que derivaram dos estudos relacionados com as instrumentações desenvolvidas. / This work presents the development of new instrumentations based on photothermal phenomena to study solid-liquid and liquid-gas interfaces, including in the latter the effect of surfactants. The work is divided into chapters, each one focusing on the development and/or application of a new technique. Chapter I presents an introduction to photothermal phenomena and describes the construction of classical Thermal Lens (TL) instruments in the single and double-beam configurations. Solid-liquid interfaces were studied in chapters II-IV using variations of the classical TL instrumentation. A new photothermal signal was characterized, indicating the formation of an inverted thermal lens at the interface. Z-scan experiments in the reflection configuration were used to determine the change in the refractive index of an interface close to the critical angle, and a similar methodolody was used to measure the thermal diffusivity of opaque samples. In Chapters V-VII, the deformation of liquid surfaces was studied by laser-induced Marangoni effect and the generation of capillary waves. Heat transfer through the liquid-gas interface was monitored by Transverse Photothermal Deflection. In all cases, the influence of surfactants was studied by forming a monolayer on the surface of the liquids. It was observed that a tiny amount of surfactants was able to cease the motion of liquid induced by surface tension gradients and to increase significantly the heat transfer through the interface. The results indicate a correlation between phase transitions of the monolayers and the attenuation of the surface deformation as well as the increase in the heat transfer. Finally, chapter VIII is a collection of other works that derived from the studies related to the instrumentations developed.
169

Pavimentos flexíveis com revestimento asfáltico = avaliação estrutural a partir dos parâmetros de curvatura da bacia de deformação / Flexible pavements : structural evaluation based on deflection basin parameters

Lopes, Flaviane Melo 20 August 2018 (has links)
Orientador: Rita Moura Fortes / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo. / Made available in DSpace on 2018-08-20T02:21:51Z (GMT). No. of bitstreams: 1 Lopes_FlavianeMelo_M.pdf: 8802487 bytes, checksum: aac710475cf4e380e179dca7eeef82be (MD5) Previous issue date: 2012 / Resumo: No Brasil é significativo o crescimento do uso do equipamento tipo Falling Weight Deflectometer - FWD para o levantamento deflectométrico e posterior caracterização estrutural de pavimentos existentes. Esta caracterização ainda é realizada somente através da medida de deflexão máxima. Contudo, o conhecimento isolado da deflexão máxima (D0) pode não ser suficientemente conclusivo para se diagnosticar a condição estrutural do pavimento. Sendo assim, o presente estudo tem como objetivo, por meio de estudo paramétrico, propor uma metodologia simplificada de avaliação da condição estrutural de pavimentos asfálticos com base granular utilizando as medições da bacia deflectométrica. A determinação de parâmetros de curvatura da bacia de deformação, obtidos através de um levantamento deflectométrico, serão utilizados para o desenvolvimento de correlações destes com as deformações críticas geradas na estrutura do pavimento quando solicitado. Através das correlações obtidas, propõem-se modelos simplificados para estimar a vida remanescente de um pavimento em função dos parâmetros deflectométricos. A metodologia proposta mostrou-se promissora. O aproveitamento das informações da bacia deflectométrica pode auxiliar na solução de restauração do pavimento, evitando defeitos precoces por falhas no diagnóstico / Abstract: In Brazil it is significant the increase in the use of an equipment type Falling Weight Deflectometer - FWD for deflection analysis and structural characterization of existing pavements. This characterization is still held only through a maximum deflection measure. However, the isolated association of maximum deflection (D0) may not be conclusive enough to diagnose the structural condition of the pavement. Thus, the current study aims, through parametric study, to propose a simplified structural assessment methodology of asphalt pavement condition with granular base using measurements of deflection basin. The determination of deflection basin parameters, obtained through deflection measurements, will be used for the development of these correlations with significant deformation of pavement structure generated when prompted. Through the correlations obtained simplified models will be proposed to estimate the remaining life of a pavement according to deflection parameters. The proposed methodology has proved to be promising. The use of the information on deflection basin can help out in troubleshooting pavement rehabilitation, avoiding premature failures in diagnosing faults / Mestrado / Transportes / Mestre em Engenharia Civil
170

Développement d'une méthode d'analyse structurelle de bâtiments en béton armé : application aux poutres renforcées par des armatures PRF / Development of a structural analysis methodology for reinforced concrete buildings : application for beams with Fiber-Reinforced Polymer (FRP) reinforcements

Confrere, Adeline 30 March 2015 (has links)
La corrosion de l'acier dans le béton a été identifiée comme la principale cause des détériorations et déficiences structurelles. Les coûts de réparations et réhabilitations aux Etats-Unis, au Canada et dans la majorité des pays européens représentent un pourcentage important des dépenses liées aux infrastructures. En raison de leur résistance à la corrosion, de leur légèreté et d'une grande résistance à la traction, les armatures alternatives en PRF de verre, carbone ou basalte sont étudiées depuis une vingtaine d’années. Les propriétés mécaniques des armatures en polymères renforcés de fibres au comportement élastique diffèrent de celle de l'acier au comportement élasto-plastique. La substitution des armatures métalliques par des PRF va modifier les comportements structuraux généralement observés dans des structures béton armé traditionnelles. Cela va également induire un changement au niveau des calculs de dimensionnement de la structure. En particulier, dans le cas d'une poutre en béton armé standard, la rupture en flexion de la poutre sera habituellement par rupture des armatures en traction dans le cas de l'acier, alors que la rupture par compression du béton sera préférable pour les poutres renforcées par des PRF. L'objectif de cette thèse est une meilleure compréhension du système {béton + armatures en polymères renforcés de fibres} en vue de dimensionner des structures de bâtiment avec ces armatures alternatives. Ces armatures PRF ont déjà été utilisées pour des tabliers de ponts ou des voies de train à sustentation magnétique, mais aucune application pour des bâtiments à part quelques rares cas de construction d'hôpitaux où les pièces attenantes aux salles contenant des appareils magnétiques, tels que l'IRM afin d’éviter les phénomènes de résonance. Même si les renforcements PRF semblent une solution prometteuse vis-à-vis des problèmes de corrosion, les designers et ingénieurs sont confrontés à de nombreuses questions quant à l'utilisation de ces matériaux pour une application bâtiment, que ce soit pour la mécanique des structures ou des aspects économico-environnemental. Cette thèse s'inscrit donc dans la problématique de conception de structures en béton armé innovantes et plus durables / The corrosion of steel elements embedded in concrete was identified as the main cause of structural deteriorations and deficiencies in buildings. Repair and rehabilitation costs in the USA, Canada and most European countries represent a substantial percentage of expenses related to infrastructures. Alternative FRP reinforcements in glass, carbon or basalt have been studied for the past twenty years owing to their resistance to corrosion, their light weight and their considerable tensile strength. The mechanical properties of fiber-reinforced polymers with an elastic behavior differ to the mechanical properties of steel, with an elastic-plastic behavior. This induces a change of the dimension calculations of the structure. In particular, in the case of a standard reinforced concrete beam, the flexural ultimate strength would usually be located in the reinforcements in traction for steel reinforcements, while a crushing failure of the concrete would be preferable in FRP beams. The objective of this thesis is to better understand the system {concrete + fiber-reinforced polymer reinforcements} in view of dimensioning building structures with these alternative reinforcements. These FRP reinforcements have already been used for bridge decks and magnetic suspension train tracks but no applications have been found for buildings except a few rare cases of hospital buildings or rooms adjoined to others containing magnetic apparatus, for example Magnetic Resonance Imagery (MRI), which are reinforced with FRP reinforcements to avoid resonance problems. Even if FRP reinforcements would appear to be a promising solution in terms of corrosion problems, designers and engineers have been confronted with many questions relative to the use of these materials in a building application, both in terms of the mechanics involved for the structures and economic and environmental issues. This thesis is therefore focused on the design aspect of concrete structures comprising innovating and more durable reinforced concrete

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