• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 67
  • 6
  • 2
  • 1
  • Tagged with
  • 76
  • 46
  • 26
  • 21
  • 18
  • 15
  • 14
  • 13
  • 12
  • 10
  • 10
  • 9
  • 9
  • 9
  • 8
  • 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.
41

Classificação da aderência pneu-pavimento pelo índice combinado IFI - Internacional Friction Index para revestimentos asfálticos. / Adherence tire-asphalt through the classification index IFI - International Friction Index to Asphalt Pavements.

Marcia Aps 04 October 2006 (has links)
A caracterização da macrotextura e microtextura da superfície de pavimentos asfálticos pode ser obtida por meio de diversos tipos de equipamentos que possuem características distintas. Os resultados dos ensaios obtidos por esses diferentes equipamentos foram comparados e harmonizados por uma grande pesquisa desenvolvida pela PIARC (Permanent International Association of Road Congress, atualmente denominada de World Road Association) que converteu estes diferentes valores em um índice internacional combinado denominado de IFI - International Friction Index. Posteriormente, a ASTM especificou o emprego deste índice por meio da publicação da norma E 1960-98 Standard Practice for Calculating International Friction Index of a Pavement Surface. Nesta tese foram avaliados a textura e o atrito em doze tipos de revestimentos asfálticos com características distintas: usinados a quente de diversas graduações, tratamentos superficiais, microrrevestimentos a frio e lamas asfálticas, por meio de aparelhagem portátil: ensaios de mancha de areia e Pêndulo Britânico, respectivamente. Estes diferentes revestimentos apresentam uma gama de textura variando de aberta e rugosa a fechada e polida. Os resultados geraram um banco de dados com 417 valores de campo, sendo 178 referentes à macrotextura, 166 à microtextura e 73 à drenabilidade. Com estes dados, foram calculados valores de IFI, compostos pelos parâmetros Sp e F60, resultando em 165 pares de valores. Com base na experiência prática e análises estatísticas, demonstrou-se a validade de uso de equipamentos portáveis para a determinação dos valores de IFI e estabeleceram-se critérios e faixas de classificação para a aderência em função do par de valores de IFI (Sp; F60). Esta classificação possibilita os órgãos viários a usarem o IFI (Sp; F60) como uma ferramenta de gerência de pavimentos para avaliarem as condições de aderência em pista molhada de suas vias ou de locais específicos, objetivando, quando necessária, a realização de intervenções. / The characterization of the macrotexture and microtexture of asphalt pavements surfaces can be obtained by means of different types of equipment presenting different characteristics. The results of the essays obtained by these different equipment were compared and harmonized by an ample research developed by PIARC (Permanent International Association of Road Congress, now denominated World Road Association) which converts these different values into an international combined index denominated IFI - International Friction Index. Later, the ASTM specified the employment of this index by publishing norm E 1960-98 Standard Practice for Calculating International Friction Index of a Pavement Surface. In this thesis, texture and friction were evaluated on twelve types of asphalt pavings with different characteristics: hot asphalt mixes of different gradations, asphalt surface treatments, cold-mixed micro-surfacing and slurry seals, by means of portable equipment, sand patch and British pendulum essays, respectively. These different pavings present a range of texture varying from open and rough to closed and polished. The results generated a database with 417 field values, being 178 related to macrotexture, 166 to microtexture and 73 to drainability. With these data, IFI values were calculated, composed by parameters Sp and F60, resulting in 165 pairs of values. Based on practical experience and on statistical analyses, the validity of using portable equipment for determining the IFI values was demonstrated and classification criteria and bands for adherence were established in function of the pair of IFI values (Sp; F60). This classification allows road organisms to use IFI (Sp; F60) as a pavement management tool to assess the adherence conditions on the wet lanes of their roads or on specific sites, aiming to conduct interventions, whenever necessary.
42

Viabilidade t?rmica de um forno solar fabricado com sucatas de pneus

Varela, Pedro Henrique de Almeida 26 July 2013 (has links)
Made available in DSpace on 2014-12-17T14:58:22Z (GMT). No. of bitstreams: 1 PedroHAV_DISSERT.pdf: 2659101 bytes, checksum: 089bb4653a9ce23c256b8c7cfed002c8 (MD5) Previous issue date: 2013-07-26 / The proposed design provides a solar furnace alternative, box-like, low-cost operation to be used in cooking, comprising three scrap tires to make the recycling thereof. The tires were coupled to each other, forming an enclosure, which stood on its bottom covered by a parable multiple mirrors made from a urupema (sieve indigenous) and the inner sides of the oven aluminum sheet painted black, obtained from beer cans, thus being made to obtain the increase in the concentration of solar radiation incident on the inside of the prototype studied. Two tires were attached, leaving an air layer between them, with the function of thermal insulation. The third tire aimed to support the other two and thermally insulate the bottom of the oven. Externally was placed a metal frame with flat mirrors to reflect the incident rays into the oven, having a mobility to correct the apparent motion of the sun. Its primary feature is the viability of clean, renewable energy to society by tackling the ecological damage caused by the large-scale use of wood for cooking food. The tests show that the furnace reached the maximum temperature of 123.8 ?C and baking various foods such as pizza, bun, and other lasagne in an average time 50 minutes. Proves the feasibility of using the oven. Presenting still able to improve their performance with the addition of new materials, equipment and techniques / O projeto proposto apresenta um forno solar alternativo, tipo caixa, de baixo custo para ser utilizado na opera??o de coc??o, composto por tr?s sucatas de pneus, para fazer a reciclagem dos mesmos. Os pneus foram acoplados entre se, formando um recinto, onde se colocou em sua parte inferior uma par?bola coberta por m?ltiplos espelhos confeccionada a partir de uma urupema (peneira ind?gena) e nas laterais internas do forno chapas de alum?nio pintadas da cor preta, obtidas de latas de cerveja, sendo feito assim para a obten??o do aumento na concentra??o da radia??o solar incidente no interior do prot?tipo estudado. Dois pneus foram unidos, ficando uma camada de ar entre eles, com a fun??o de isolante t?rmico. O terceiro pneu teve a finalidade de suporte para os outros dois e isolar termicamente o fundo do forno. Externamente foi colocada uma estrutura met?lica com espelhos planos para refletir os raios incidentes para o interior do forno, possuindo uma mobilidade para a corre??o do movimento aparente do sol. O seu aspecto primordial ? a viabiliza??o de energia limpa e renov?vel para a sociedade, combatendo os danos ecol?gicos causados pela utiliza??o em larga escala de lenha para a coc??o de alimentos. Os ensaios mostram que o forno chegou ? temperatura m?xima de 123,8?C, assando v?rios alimentos como pizza, bolo, lasanha entre outros em um tempo m?dio de 50 minutos. Comprova-se a viabilidade da utiliza??o do forno. Apresentando ainda condi??es de melhorar seu desempenho com adi??o de novos materiais, equipamentos e t?cnicas
43

Comportamento preferencial de leitões na fase de creche em ambiente enriquecido / Preferred behavior for piglets in nursery stage in enriched environment

Leal, Guilherme Brunno de Medeiros 09 March 2016 (has links)
Submitted by Cássia Santos (cassia.bcufg@gmail.com) on 2016-07-28T12:41:14Z No. of bitstreams: 2 Dissertação - Guilherme Brunno de Medeiros Leal - 2016.pdf: 1377496 bytes, checksum: be97f29665e29f6b6646be9497341b6a (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-07-28T14:26:56Z (GMT) No. of bitstreams: 2 Dissertação - Guilherme Brunno de Medeiros Leal - 2016.pdf: 1377496 bytes, checksum: be97f29665e29f6b6646be9497341b6a (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-07-28T14:26:56Z (GMT). No. of bitstreams: 2 Dissertação - Guilherme Brunno de Medeiros Leal - 2016.pdf: 1377496 bytes, checksum: be97f29665e29f6b6646be9497341b6a (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-03-09 / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / The welfare's absence in animal breeding has a direct impact on food production, affecting internal trade and especially exports. Environmental enrichment is the improvement of facilities in order to make the environment more appropriate to behavioral needs. Inserting objects in the environment such as, tires, chains, ropes, plastic bottles, wood or plastic bars are the most common types of environmental enrichment. However, only few tests have been made on swine's preference by the types of objects available to enrich its environment. It was aimed to evaluate the preferred behavior, as well as, animal performance (daily feed intake, daily weight gain, feed conversion) and lesion rates in pigs in the nursery stage using different types of objects (tire and metal chain), and scenarios (suspended, embedded in the wall, fixed on the floor). The experiment was performed in a commercial farm from July 30 to September 21, 2015. The animals were housed in collective cages, partially slatted floor, equipped with semi-automatic feeders and nipple drinkers. Every room with eight cages 113,02 ft² each, which makes a 2712,51 ft² experimental area. 696 pigs were used in Choice Genetics® breed, with an average age of 21 days, average weight of 12,34 pounds, divided between males and females. The pigs were divided into the treatment groups of 29 animals. The experimental design was a randomized block, with four different presentation scenarios of objects (control = without enriching object; T + C suspended = tire + suspended metal chain; T + C wall = tire and embedded metal chain on the wall; T + C floor = tire and fixed metal chain on the floor), repeated six times in a row. Camcorders were used for filming and subsequent evaluation of the behavior recorded every 10 minutes during 11 hours per day (7 a.m. to 6 p.m.), once in a week, 41 days. In the treatments with environmental enrichment, there were differences in the interaction with enriching objects (P <0.05). Regarding the presentation and the type of object, the animals preferred the suspended position and metal chain, respectively. The animal performance factors (daily feed intake, daily weight gain, feed conversion), and lesion rates, were not influenced by environmental enrichment. / A ausência do bem-estar na produção animal, repercute diretamente na produção dos alimentos, afetando o comércio interno e, principalmente, as exportações. O enriquecimento ambiental consiste no aperfeiçoamento das instalações com o objetivo de tornar o ambiente mais adequado às necessidades comportamentais. Inserir no ambiente, pneus, correntes, cordas, garrafas pet, barras de madeiras ou plástico são os tipos mais comuns de enriquecimento ambiental. Entretanto, poucos testes têm sido realizados quanto à preferência dos suínos pelos tipos de objetos disponíveis para enriquecimento do ambiente. Objetivou-se avaliar o comportamento preferencial, desempenho zootécnico (consumo diário de ração, ganho em peso diário, conversão alimentar) e escore de lesão em suínos na fase de creche com diferentes tipos de objetos (pneu e corrente de metal), e esquemas de apresentação (suspenso, enraizado na parede, fixo no piso). O experimento foi conduzido em granja comercial, no período de 30 de julho a 21 de setembro de 2015. Os animais foram alojados em baias coletivas, de piso parcialmente ripado, providas de comedouro semiautomático e bebedouro tipo chupeta. Cada sala com 8 baias de 10,5 m2 cada, totalizando uma área experimental de 252 m2. Foram utilizados 696 suínos da linhagem Choice Genetics®, com idade média de 21 dias, peso médio inicial de 5,6 kg, divididos entre machos e fêmeas. Os suínos foram distribuídos nos tratamentos em grupos de 29 animais. O delineamento experimental utilizado foi em blocos ao acaso, com quatro diferentes esquemas de apresentação dos objetos (Controle – sem objeto enriquecedor; P + C suspenso – pneu + corrente de metal suspensa; P + C parede – pneu e corrente de metal enraizado na parede; P + C piso – pneu e corrente de metal fixo no piso), repetidos seis vezes no tempo. Foram utilizadas câmeras filmadoras, para gravação de imagens e posterior avaliação dos comportamentos a cada 10 minutos durante 11 horas diárias (7 h às 18 h), uma vez por semana, durante 41 dias. Nos tratamentos com enriquecimento ambiental houve diferença na interação com os objetos enriquecedores (P<0,05). Em relação a apresentação e o tipo de objeto, os animais preferiram quando na posição suspenso e corrente de metal, respectivamente. As variáveis de desempenho zootécnico (consumo diário de ração, ganho em peso diário, conversão alimentar) e escore de lesão não foram influenciadas pelo enriquecimento ambiental.
44

Avaliação do uso da banda de rodagem de pneus inservíveis triturada como suporte ao desenvolvimento de biofilmes em um reator anaeróbio de leito expansível / Granulated tread of scrap tires as support for the development of biofilms in an expanded bed anaerobic reactor

Cristiano Luchesi Niciura 24 June 2005 (has links)
A presente pesquisa teve como objetivo a avaliação do uso da banda de rodagem de pneus inservíveis triturada (BPIT) como suporte ao desenvolvimento de biofilmes em um reator anaeróbio de leito expansível (RALEx), em escala plena, com volume de 32m3, empregado no tratamento de esgoto sanitário. A utilização desse material como suporte apresentou-se como proposta inovadora, com grande potencial de aplicação. Para partida do sistema foram utilizados 6,0m3 de lodo proveniente do reator UASB da Estação de Tratamento de Esgoto Jardim das Flores de Rio Claro – SP, tendo sido alcançado o equilíbrio dinâmico aparente após 80 dias de operação. A BPIT mostrou-se eficiente como recheio do RALEx, tendo em vista que promoveu remoção média de 70% de matéria orgânica, em termos de DBO (amostras não filtradas), quando operado com tempo de detenção hidráulico médio de 3,2h, velocidade ascensional média de 5,7m/h (sem recirculação do efluente), e carga orgânica volumétrica média de 5,4kgDQO/m3.dia. A remoção média de sólidos em suspensão no sistema foi de 65% (com teor residual no efluente de 95mg/L) e a porcentagem de metano no biogás manteve-se próxima a 65%. Assim como os demais reatores anaeróbios, verificou-se que a remoção de nitrogênio e fósforo no RALEx foi relativamente baixa, com valores inferiores a 10%. Avaliou-se também a perda de carga no leito de BPIT, obtendo-se valores extremamente baixos para todas as granulometrias testadas, em torno de 4cm/m de leito, e determinou-se a velocidade mínima de fluidificação em 39m/h. Nos ensaios preliminares, verificou-se que o diâmetro equivalente das partículas de BPIT foi de 4,3mm, com coeficiente de desuniformidade de 1,61 e massa específica de 1,14g/cm3. A BPIT mostrou-se competitiva também no aspecto econômico, tendo em vista que o custo de aquisição foi 12,8 vezes inferior ao do carvão ativado granular e 1,6 vezes superior ao da areia (materiais comumente utilizados como recheio de RALEx). / The present research had as objective the assessment of granulated tread of scrap tires (GTST) as support for the development of biofilms in an expanded bed anaerobic reactor (EBAR), in full scale, with a total volume of 32m3, employed for wastewater treatment. The use of this material as support was presented as an innovating proposal, with a high application potential. To start up the system 6.0m3 of sludge coming from the UASB reactor from Jardim das Flores Wastewater Treatment Plant, Rio Claro – SP, were used. The apparent dynamic equilibrium was reached 80 days after operating start up. GTST showed itself as efficient in the packing of the EBAR, where it removed an average of 70% of organic matter, in terms of BOD (non-filtered samples), when operated with hydraulic detention time of 3.2h, mean ascension velocity of 5.7m/h (without effluent re-circulation), and mean volumetric organic load of 5.4kgCOD/m3.day. The mean suspended solids removal in the system was of 65% (with 95mg/L of residual content in the effluent) and the percent of methane in biogas was close to 65%. Likewise in other anaerobic reactors, it was seen that nitrogen and phosphorous removal in the EBAR was relatively low, with values below 10%. Headloss was also assessed in the bed of the GTST, where extremely low values were obtained for all tested granulometry, around 4cm/m in the bed. In the preliminary essays, it was verified that the equivalent diameter of GTST particles was of 4.3mm, with disuniformity coefficient of 1.61 and specific mass of 1.14g/cm3. GTST was also competitive in the economical aspect, where the acquisition cost was 12.8 times lower than granular activated carbon and 1.6 times higher than sand (materials commonly used as EBAR packing material).
45

Modélisation des forces de contact entre le pneu d’un avion et la piste / Modeling the contact forces between an aircraft tire and the runway

Jones, Logan 26 June 2012 (has links)
Lorsqu’un avion atterrit, la force principale nécessaire pour arrêter l’avion est obtenue par le freinage. Par une réduction de la vitesse de rotation des roues, les freins provoquent une vitesse de glissement entre les pneus et la piste. C’est cette différence de vitesse qui génère la force de freinage capable de stopper l’avion. La modélisation de cette force est essentielle pour l’estimation de la longueur de piste à l’atterrissage. Les modèles classiques utilisés par les avionneurs sont assez simplistes et dérivent expérimentalement des modèles de frictions les plus simples. De sorte que ces modèles sont dans l’incapacité d’estimer l’influence de paramètres clefs influençant la force de freinage. Il s’agit, en particulier de la pression des pneus, de la nature de la gomme, de la température ambiante et de celle de la gomme, de l’état de la piste, de sa texture, etc. L’objectif de la thèse a été de développer un modèle de contact pneu-piste capable d’estimer la force de freinage. C’est le « Brush Model » qui a servi de base à cette modélisation. En phase de freinage la zone de contact est constituée d’une première zone de déformation de la gomme qui crée une force résistante en suivant la loi de Hooke, puis d’une seconde zone de glissement dont la force de résistance suit la loi de Coulomb. Ce modèle a été amélioré grâce aux résultats de la mécanique des structures pour la loi de Hooke et grâce aux résultats de la tribologie pour la loi de Coulomb. Ces deux modélisations faisant appel aux données issues de la science des matériaux. L’ensemble de ces modélisations a été enrichi par une coopération avec plusieurs centres de recherches ayant fourni de nombreux résultats expérimentaux. Le modèle obtenu a ensuite été confronté avec des résultats d’essais en vol obtenus avec « Airbus Operations S.A.S ». La thèse a validé le prétraitement des données d’essais ainsi que le processus d’identification qui a permis de montrer l’accord du modèle avec les résultats expérimentaux obtenus lors des essais en vol. Cette modélisation donne des résultats très encourageants, elle permet une compréhension beaucoup plus approfondie des effets de l’environnement sur les forces de freinage. De sorte que cette thèse a permis d’améliorer très sensiblement la compréhension fondamentale des phénomènes en jeu lors du freinage, au contact entre le pneu et la piste. Chez Airbus, les résultats obtenus vont servir de base pour les travaux à venir sur ce thème. / As an aircraft lands on a runway, the principal force acting to stop the aircraft within the confines of the runway is generated by the brakes. The brakes cause the tire’s rotational speed to slow down with regards to the aircraft’s speed over the ground. This difference in speed causes friction and it is this friction that is the principal force to stop the aircraft. In order to be able to estimate the stopping distance of an aircraft an understanding of this friction is essential. Traditionally, aircraft manufactures have relied on simplistic, empirically derived friction models. However, these empirical models cannot estimate the influence of several key factors that are known (scientifically) to affect friction such as the rubber temperature, the runway texture, the ambient air temperature and the rubber composition to name a few. This PhD work aims to develop a frictional model that can be used to estimate the friction developed between an aircraft tire and the runway. A model commonly known as the Brush Model, is derived for usewith aircraft tires and runways. The underlying physics of this model are developed using the established scientific theories of tribology, material science and strength of materials. Coordination with several research institutes provides experimental results to reinforce the model. The model is then compared with flight test results obtained from a partnership with Airbus OperationsS.A.S. The PhD works demonstrates the entire validation process from flight test data cleaning, the derivation of a curve-fitting algorithm and the matching of derived model with the flight test data. The modeling has shown very encouraging results. It allows for a much deeper understanding of the environmental effects on friction. This PhD work has greatly improved the fundamental understanding of friction and will serve as a base for future works with Airbus.
46

Étude numérique de l'influence de la texture de chaussée sur la résistance au roulement / The numerical study of the influence of texture on the floor rolling resistance

Bui, Quoc Huong 28 January 2014 (has links)
Le secteur des transports représente 50% de la consommation mondiale en produits pétroliers. Une part significative de l'énergie est dissipée par le fonctionnement de la suspension et par la déformation du pneu. La texture de surface de chaussée et son interaction avec le pneu jouent un rôle certain dans cette dissipation d'énergie. Le travail présenté dans ce mémoire est consacré à la modélisation du contact entre un pneu et une chaussée en conditions de roulement dans le but d'évaluer la résistance au roulement. Le choc d'une sphère sur un demi-espace viscoélastique est d'abord étudié. Ensuite, le contact viscoélastique d'un objet roulant sur une surface lisse est modélisé avec une suspension attachant l'objet roulant à une masse qu'il supporte. Enfin, une méthode multipoint linéarisée est proposée pour l'étude du roulement sur une surface rugueuse sans suspension dans un premier temps, et avec suspension dans un second temps. La condition de roulement est introduite. Les surfaces rugueuses sont soit des surfaces composées d'aspérités sphériques, soit des surfaces de chaussées réelles. Les résultats numériques font apparaître une dissymétrie dans la distribution de pression de contact dans la direction du roulement. La force de résistance au roulement, définie comme le couple par rapport à l'axe de l'essieu divisé par le rayon de la roue, est calculée à partir de la distribution de pression. L'influence de différents paramètres sur cette force tels que la vitesse de roulement, la taille des aspérités ainsi que la raideur de la suspension est analysée / The transport accounts for about 50 percent of the fuel consumption. A significant proportion of energy is lost by the suspension and the deformation of the tyre. One of the important factors in the energy loss is the texture of the road and its interaction with the tyre. The present work deals with the numerical modelling of the contact between a tyre and a road in rolling conditions in order to evaluate the rolling resistance. First, the collision of a sphere and a viscoelastic halfspace is studied. Then the viscoelastic contact of a body rolling on an smooth surface is investigated with a suspension between a mass and the rolling body. Finally a linearised multipoint method is proposed for the study of the rolling contact on a rough surface first without suspension and then with a suspension. The rolling condition is introduced in the model. The rough surfaces are surfaces composed of spherical asperities or real road surfaces. Numerical results reveal an asymmetry in the distribution of the contact pressure in the rolling direction. The rolling resistance force, classically defined as the momentum opposing the rolling divided by the radius of the tyre, is calculated using the distribution of the contact pressure. The effects of different parameters on the rolling resistance force such as the rolling speed, the size of the asperities and the stiffness of the suspension are analysed
47

Contribution to the modelling of aircraft tyre-road interaction / Contribution à la modélisation de l'interface pneu-piste du train d'atterissage des avions

Kiébré, Rimyalegdo 10 December 2010 (has links)
La présente thèse est une partie du projet national français dénommé MACAO (Modélisation Avancée de Composants Aéronautiques et Outils associés). En collaboration avec Messier-Dowty (constructeur d'atterrisseurs d'avion), cette thèse contribue à une meilleure compréhension du comportement du pneu sur piste dans le domaine de l'aéronautique. L'objectif est de mettre en place des modèles capables de représenter le torseur des efforts au niveau de l'interface pneu-piste lors des différentes manœuvres de l'avion au sol en régime établi. Une priorité est accordée aux modèles dont les paramètres sont physiquement interprétables. De ce fait, un état de l'art des modèles de pneu en régime établi est d'abord réalisé. Un classement de ces modèles selon leurs motivations et limitations est aussi proposé. A l'aide de cette classification et en prenant en compte les exigences de l'étude, un choix a priori de modèles a été analysé. Les limites de ces modèles sont soulignées et une amélioration est proposée. Par ailleurs, une étude exhaustive de la déformation du pneu en situation de virage a été menée. Elle a permis de décrire la génération de la composante longitudinale de la force totale au niveau de l'interface pneu-piste. Elle est dite force longitudinale induite. Puis, en prenant en compte cette force, il a été possible d'expliquer pourquoi le moment d'auto-alignement peut repasser par zéro sans que le pneu ne soit en glissement total. Enfin, l'analyse de sensibilité est proposée comme une méthode permettant de déterminer les paramètres les plus influents de chaque modèle. Ces paramètres doivent alors être déterminés avec précision afin de réduire l'incertitude sur le modèle. / This thesis is a part of the French national project called MACAO (Modélisation Avancée de Composants Aéronautiques et Outils associés). In collaboration with Messier-Dowty company (a landing gears manufacturer), the thesis has contributed to better understand the actual literature studies in the field of aircraft tyre-road interaction modelling and therefore, to help making an optimal choice of model for a specifie application. The objectives have been to propose models for representing the tyre behaviour on the ground with respect to the aircraft run types. Physical oriented models are preferred. To complete this study, a literature survey of the previous researches in tyre modelling for steady­state responses is first carried out. Then, based on the main factors playing an important role in tyre modelling, it is proposed a classification for the physical and the semi-empirical models, which are also investigated. Based on this classification, the study requirements and the measurement data constraints, an a priori choice of suitable models are studied. A further investigation of the tyre deformation at pure lateral slip is carried out. It has allowed to physically describe the mechanism of generation of the longitudinal component of the tyre force at pure lateral slip. This force is refened as induced longitudinal force. By taking this force into consideration, it has been possible to explain why the self-aligning moment can drop to zero before the tyre gets to full sliding at pure lateral slip. Besides, the sensitivity analysis is proposed as a means for determining the parameters that have most influence on the model output and thus, are responsible for the output uncertainty.
48

Critérios para avaliação pericial da macro e microtextura de pavimento asfáltico em local de acidente de trânsito / Criteria for the expert evaluation of macro and micro texture of the asphalt pavement at traffic accident sites

Bucharles, Luciano Gardano Elias 28 March 2014 (has links)
Muito embora a micro e a macrotextura dos pavimentos sejam importantes para o tráfego seguro, principalmente em condição de pista molhada e com velocidades superiores a 50 km/h, nos locais de acidentes de trânsito no Brasil esses parâmetros não são avaliados quando das perícias técnicas. Assim, o objetivo principal desta tese é estabelecer critérios de avaliação de pavimentos asfálticos que possam integrar um protocolo para a perícia técnica em locais de acidentes de trânsito. Foi baseada em coleta de dados de micro e de macrotextura dos revestimentos asfálticos em três rodovias no Estado do Paraná, num total de 106 locais, e em quatro vias urbanas na cidade de Londrina-PR, num total de 148 locais, todas com velocidades permitidas iguais ou superiores a 50 km/h, especificamente em trechos onde ocorreram acidentes de trânsito, o que permitiu a determinação da aderência na interface pneu/pavimento, se os valores encontram-se dentro das faixas de aceitabilidade do DNIT, da ANTT e da ARTESP e se houve efetiva contribuição do pavimento para a ocorrência e para a severidade dos acidentes. Dos 106 acidentes rodoviários analisados, em 19 deles as alturas médias de mancha de areia, parâmetro empregado para avaliar a macrotextura, apresentaram-se com valor inferior ao mínimo recomendado (0,60 mm), enquanto que dos 148 acidentes ocorridos em vias urbanas, 22 ocorreram em trechos com alturas médias de mancha de areia também inferiores ao valor mínimo recomendado. Nesses casos também foram realizados ensaios de microtextura, com uso do pêndulo britânico, e posteriormente foram calculados os valores do Índice de Atrito Pneu-Pavimento Internacional (International Friction Index, IFI). Os resultados e as análises deste trabalho indicam que uma melhor condição de macrotextura pode reduzir entre 6% e 19% as energias cinéticas envolvidas nos acidentes em rodovias e de 3% a 11% em vias urbanas, com real possibilidade de redução tanto das avarias produzidas nos veículos quanto, principalmente, das lesões nas vítimas. Dada a importância da micro e da macrotextura, recomenda-se que o protocolo de avaliação de pavimentos para perícias técnicas em locais de acidentes de trânsito em rodovias e em vias urbanas estabeleça a realização dos ensaios de Pêndulo Britânico e de Mancha de Areia em até 24 horas após o evento e que a área a ser levantada contemple toda a extensão das marcas de frenagem dos veículos envolvidos ou, no caso de inexistência de marcas, que compreenda uma extensão de 10 a 70 metros, respectivamente para vias com velocidade máxima permitida de 40 km/h e de 120 km/h. Espera-se, complementarmente, que um protocolo com critérios simples e objetivos, como o desenvolvido neste trabalho, permita a adoção de políticas públicas preventivas, de maior alcance e periodicidade, com as avaliações não somente nos trechos onde ocorrem acidentes, mas ao longo das vias. / Although the micro and macro textures of pavements are important factors for safe driving, especially on wet tracks and with speeds above 50 km/h, such parameters are not even evaluated during technical inspections in traffic accident sites in Brazil. Thus, the main purpose of this thesis is to establish criteria for the evaluation of asphalt pavements that may become integral part of a protocol for technical inspection in traffic accident sites. This work is based on the collection of data concerning the micro and macro texture of asphalt pavements on three roads in the State of Paraná, totaling 106 locations, and on four urban streets in the city of Londrina, State of Paraná, totaling 148 locations. All such locations have a speed limit of equal to or higher than 50 km/h, especially on the sites where traffic accidents occurred, which allowed for the determination of the tire/pavement adherence, and whether the values found were in accordance with the acceptable levels established by DNIT, ANTT and ARTESP, and whether there was effective contribution on the part of the pavement for the occurrence as well as the severity of the accidents. Out of the 106 road accidents that were analyzed, it was observed that in 19 of them the average heights of the sand spot, a parameter used to evaluate the macro-texture, were lower than the minimum value recommended (0,60 mm), while out of the 148 accidents taken place in urban streets, 22 took place in areas where the average heights of the sand spot were also lower than the recommended minimum value. In the case of the accidents that occurred in places where the heights of the sand spots were lower than the minimum recommended, micro texture essays were also carried out by use of the British Pendulum Tester, and later the values of the International Friction Index (IFI) were calculated. The results and the analyzes of this work indicated that a better condition in the macro texture would reduce the kinetic energies involved in road accidents between 6% and 19%, and from 3% to 11% on urban streets, with the real possibility of minimizing both damages caused to the vehicles and especially the lesions on the victims. Given the importance of micro and macro textures, it is recommended that the protocol for the evaluation of pavements for the purpose of technical inspection in traffic accident sites both on roads and urban streets require the carrying out of the British Pendulum Tester and the Sand Spot within 24 hours of the time of the accident and that the area to be tested should include the entire extension of the braking skid marks of the vehicles involved in the accident, or, in the case of inexistence of such marks, covering 10 to 70 meters, respectively, for locations where the permitted maximum speed is 40 km/h, and for locations where the permitted maximum speed is 120 km/h. It is additionally expected that a protocol having simple yet objective criteria, such as the ones developed in this work, will allow for the adoption of preventive public policies, having greater scope and periodical applications, not only on sites where accidents take place, but also on the entirety of roads and streets.
49

Painéis de resíduos madeireiros e de borracha de pneu associados à espuma poliuretana à base de mamona para aplicação como composições termoacústicas / Panels from wood and tire rubber wastes associated with castor-oil-based polyurethane foam for application as thermo-acoustic compositions

Bertolini, Marília da Silva 04 September 2014 (has links)
Questões ligadas ao desempenho térmico e acústico de edificações têm sido cada vez mais abordadas, num cenário em que ganham importância a economia de energia e o controle do ruído. O advento dos materiais compósitos propiciou o emprego de resíduos de processos que, aliados a materiais de origem renovável, contribuem para a obtenção de produtos de reduzido impacto ambiental. Neste contexto, o presente trabalho teve como objetivo a produção e caracterização de painéis de partículas e espuma poliuretana à base de óleo de mamona, para destinação em composições termoacústicas. Os painéis de partículas foram produzidos utilizando-se resíduos de madeira de Pinus sp., tratado com CCB (preservante de cromo, cobre e boro - base óxido), borracha de pneus inservíveis e adesivo poliuretano à base de óleo de mamona. Foram adotadas variações na produção dos painéis, quanto aos fatores: proporção e configuração da borracha, espessura e pressão de prensagem; verificando sua influência no desempenho dos painéis. As propriedades físicas e mecânicas dos painéis foram determinadas conforme a ABNT NBR 14810-3 (2006) e avaliadas segundo os principais requisitos de normas neste âmbito. Análises estatísticas (ANOVA) foram realizadas para verificação da influência dos fatores de produção, e de suas interações, nas propriedades físicas e mecânicas dos painéis. Também foram avaliadas a morfologia e estabilidade térmica dos painéis e espumas. O isolamento térmico foi avaliado pela determinação experimental da condutividade térmica. A absorção sonora dos painéis e espumas, em diferentes montagens, foi determinada por medições em câmara reverberante, conforme ISO 354 (1985). Os resultados das propriedades físicas e mecânicas dos painéis estiveram em grande parte condizentes com os documentos normativos. O teor de borracha e a sua interação com os demais fatores apresentaram influência estatística nas propriedades físicas e mecânicas dos painéis. A morfologia dos painéis e espumas permitiu visualizar sua adequação aos produtos propostos, por meio da porosidade. Em relação ao isolamento térmico e absorção sonora, os painéis e espumas, bem como as composições formadas, apresentaram desempenho coerente com produtos e normas utilizados como referência. Sendo assim, verificou-se a viabilidade de produção e aplicação dos painéis e espuma poliuretana à base de mamona em composições destinadas ao conforto termoacústico. / Issues relating to thermal and acoustic performance of buildings have been increasingly addressed in a scenario where energy savings and noise control are essential. Advent of composite materials enabled the use of residues from production processes that, coupled with renewable source materials, contribute to obtain products with low environmental impact. So, this study aimed to the production and characterization of particleboards and castor-oil-based polyurethane foam, for thermo-acoustic compositions. Panels were produced with residues of Pinus sp., treated with CCB (chromium, copper and boron basic oxide preservative), tire rubber wastes and castor-oil-based polyurethane adhesive. Variations in the production parameters were adopted: proportion and configuration of tire rubber; panels thickness; and pressing pressure, to determine their influence on panel performance. Physical and mechanical properties of particleboards were determined based on ABNT NBR 14810-3 (2006) and evaluated according to the main requirements of standards in this area. Statistical analysis (ANOVA) was performed to check the influence of production factors, and their interactions, in those properties. Morphology and thermal stability of foams and panels were also evaluated. Thermal insulation was evaluated by experimental values of thermal conductivity. Sound absorption of the panels and foams, in different assemblies, was determined by measurement in a reverberation room, according to ISO 354 (1985). Results of evaluated panel properties were consistent with the normative requirements. The tire rubber content and its interaction with other factors influenced in almost all physical and mechanical properties of the particleboards. Morphology of the foams and panels permitted confirming their suitability to the proposed product by the porosity. With respect to thermal insulation and sound absorption, panels and foams as well as the correspondent compositions showed performance consistent to the references. Therefore, it was demonstrated the production feasibility and applying of studied compositions intended for the thermo-acoustic comfort.
50

Béton à base de recyclats : influence du type de recyclats et rôle de la formulation / Concrete with waste aggregates : effect of aggregates type and role of composition

Serifou, Mamery 23 December 2013 (has links)
L‟élimination de certains déchets est un enjeu important en Côte d‟Ivoire. Une des solutions proposée est d‟envisager l‟utilisation de ces déchets comme granulats dans les bétons. Les travaux présentés dans ce document portent sur l‟incorporation de quatre différents déchets.La première étude porte sur un béton confectionné avec trois types de déchets : du verre concassé, du ciment durci concassé et des pneus découpés. Elle a été réalisée en deux phases. Dans la première ces déchets ont été incorporés à du béton pour remplacer 100% des graviers (substitution totale). Dans la seconde une substitution (massique) partielle de gravier a été réalisée dans les proportions suivantes 5, 10, 15, 20, 25 et 30 %, la matrice mortier et le rapport eau-ciment restant identiques. Après une maturation de 28 jours leurs résistances en compression ont été déterminées. Ces résultats montrent que les bétons de recyclât ont une résistance inférieure à celui des bétons de concassé de gravier. Toutefois, la résistance mécanique baisse avec l‟augmentation de la substitution. Une loi donnant la résistance en fonction du taux de recyclât a été établie. De plus, la spécificité des granulats de caoutchouc (résistance à la fissuration) est remarquée.Par ailleurs, les résistances des bétons de recyclât ont permis d‟établir une loi donnant la résistance en fonction des caractéristiques des agrégats et de leur fraction volumique. Une modélisation analytique a été proposée pour prédire la résistance des bétons en fonction de la taille et du volume des granulats recyclés.Les granulats issus du concassage des bétons frais (retour de toupie) utilisés comme substituant des granulats naturels a été menée pour évaluer leur potentiel. Un plan d‟expériences statistique à deux variables (% de recyclât dans le sable et % de recyclât dans le gravier) a été utilisé pour réduire le nombre de mesures. Les proportions de remplacement utilisées sont : 0%, 50% et 100%. Les propriétés mécaniques ont été déterminées par différentes méthodes destructives (résistance à la compression et à la traction) et non destructives (ondes ultrasonores pour évaluer l‟élasticité du matériau). De même, les propriétés physiques telles que la porosité accessible à l‟eau, la masse volumique ont été mesurées. Ces résultats montrent une bonne corrélation entre le pourcentage de remplacement et les propriétés physiques et mécaniques de ce béton / Waste management is an important issue for Côte d‟Ivoire. Among many possibilities, recycling wastes as aggregates for concrete is a solution that deserves to be evaluated. In this study four recycled aggregates are tested: crushed glass, tire cut rubber, hardened cement and fresh concrete waste. There properties are compared to those of natural aggregates.A first study is realized in Côte d‟Ivoire on glass, rubber and hardened cement. Concrete is realized and tested in compression (cylindrical 16x32 specimens). A mix with an increasing quantity of coarse aggregates is tested for each recycled material (20 %, 25 %, 30 % and 50 % in mass of fine and coarse aggregates). It is shown that the strength decreases with the replacement rate and that the decrease depends on the replacing material. The materials ranged in the following increasing order: rubber, glass, hardened cement and natural aggregates. A power law is established which gives the compressive strength as function of the mix and the materials characteristics. Analytical modeling was proposed for predincting the strength with respect to recycled aggregates size and volume.Another experiment is also made on glass and rubber, where partial replacement in increasing percentage is tested. Natural aggregates are partially replaced in the mix with the ranges of 5, 10, 20, 25 and 30 % by rubber and glass. The compressive strength is determined and a decrease is observed for the two materials. In the case of rubber a high decrease in observe with the replacement. In the case of glass a decrease occurs between 0 and 5 % replacement then the strength remains constant with the replacement rate. The third experiment is made with partial replacement of fresh recycled concrete (excess of ready-mixed concrete from concrete mixing plant which is hardened and then crushed). A plan of experiments is made which allows a polynomial law to be drawn giving the strength as a function of the recycled proportion. Other properties (Young modulus, P wave velocity, porosity, density, etc) have been determined and their relation with replacement rate computed.

Page generated in 0.0385 seconds