Dissertations / Theses on the topic 'Resistance maximale en traction'

Compostos elastoméricos a base de borracha natural (NR) e copolímero de butadieno-estireno (SBR) utilizados na banda de rodagem de pneus são tradicionalmente reticulados com enxofre. O uso de peróxidos e co-agentes na reticulação desses compostos ainda é um desafio a se superar com relação às propriedades viscoelásticas requeridas, de extrema importância para um bom desempenho e vida útil dos pneus. Neste trabalho foi avaliado o uso de peróxidos sem e com co-agentes na reticulação de compostos NR/SBR com o intuito de avaliar a eficiência destes na manutenção das propriedades relevantes em relação a um composto tradicionalmente usado na confecção de banda de rodagem de pneus. Onze formulações com diferentes sistemas de reticulação foram preparadas, sendo uma de referência. Foram avaliadas propriedades físicas como dureza, densidade, tração, resistência ao rasgamento, resiliência, abrasão e DPC, e o comportamento dos compostos de NR/SBR com relação ao inchamento em tolueno. As propriedades dinâmicomecânicas dos compostos NR/SBR foram analisadas por DMA e RPA. Os compostos NR/SBR contendo somente peróxidos não apresentaram propriedades comparáveis ao composto de referência vulcanizado com enxofre. Os compostos contendo os sistemas peróxidos/co-agentes, BIS F 40 A-Retilink T40 (composto 10) e BIS F 40 A-Retilink TA 70 (composto 11) apresentaram os melhores resultados. O composto 10 e o composto de referência (composto 1) apresentaram valores similares de tan d a 60°C e tan d a 0°C (DMA), os quais estão correlacionados às propriedades de resistência ao rolamento e tração no molhado, respectivamente. Os resultados mostraram a possibilidade de uso de certos sistemas peróxido/co-agente em compostos de NR/SBR, em substituição ao sistema com enxofre, sem perda de propriedades, tendo como vantagem a redução de componentes na formulação, redução de tempo de processamento, e consequentemente custo da produção de bandas de rodagem.
Rubber compounds based on natural rubber (NR) and styrene-butadiene rubber (SBR) used on tire tread are traditionally crosslinked with sulfur. The use of peroxides and co-agents in crosslinking of these compounds is still a challenge to be achieved, considering the required viscoelastic properties which are extremely important for a good tire performance and lifetime. In this work it was evaluated the use of peroxide systems with and without co-agents as crosslinking agents for NR/SBR compounds, with the aim of evaluating the efficiency of maintaining the key properties related to the traditionally used in the manufactory of tire tread. Eleven formulations with different systems were prepared, a one as a reference. Physical properties such as hardness, density, tensile strength, tear, resilience, abrasion and compression set and the behavior of NR/SBR compounds in relation of swelling Toluene were evaluated. The dynamic mechanical properties of the NR/SBR cured compounds were analysed by DMA and RPA. The NR/SBR compounds cured with only peroxide had poorer properties when compared to the reference compound vulcanized with sulfur. On the other hand, the compounds cured with proxide/co-agents, BIS F40 plus Retilink T40 (compound 10) or plus T70A (compound 11) showed better results.The compound 10 and the reference compound (compound 1) showed similar results of tan d 60 °C and tan d 0 °C (DMA), which are correlated to rolling resistance and wet traction, respectively. The results demonstrate the possibility of using a peroxide/co-agent as a cure system in NR/SBR compound instead of a sulfur-cured compound for tire tread applications, without the loss of desirable properties, lower processing times and consequently reducing manufacturing costs.

L'objectif de ce travail est double : i) determiner l'evolution de la sensibilite mecanique du pmma-choc a la temperature et a la vitesse de deformation, ii) caracteriser l'endommagement genere dans ce materiau suite a une sollicitation de traction. Aux grandes deformations, les resultats obtenus lors de nos essais de traction a rupture du pmma-choc a differentes temperatures et vitesses de deformation ont montre une influence considerable de ces parametres sur le comportement global. Cette etude a permis d'identifier une transition du comportement ductile/fragile dans des conditions experimentales precises. Plus specialement, la sensibilite a la vitesse de deformation et a la temperature sur le seuil d'ecoulement nous a conduit a apprehender la nature des mecanismes elementaires qui, a l'echelle moleculaire, sont a l'origine du comportement macroscopique du pmma-choc. Les donnees recueillies a partir des mesures experimentales ont ete confrontees a un modele moleculaire decrivant les processus elementaires de la deformation en termes de mecanismes thermiquement actives. Ce modele est celui developpe par ree-eyring. Les resultats obtenus a partir de cette modelisation ont permis en se basant sur ceux issus d'une analyse viscoelastique de montrer que les mecanismes de deformation regissant le debut de la plasticite au seuil d'ecoulement sont aussi bien a la relaxation principale de la deformation de la phase elastomerique contenue dans les particules de renforcement du pmma-choc. La caracterisation l'endommagement a ete realisee par mesures mecaniques et une nouvelle technique d'essais interrompus a ete mise point. Elle offre en plus de sa facilite de realisation, un moyen de quantification de l'endommagement corrige des phenomenes structuraux. L'evolution du marqueur d'endommagement, mesure a travers cette technique, en fonction de la deformation definit une chronologie de l'endommagement pendant un essai de traction.

Nous recherchons l'influence de l'etat de surface des subjectiles des substrats de l'assemblage colle a simple recouvrement en biseau, sur son comportement mecanique fin lorsqu'il est sollicite en traction simple et en fatigue par traction ondulee. Au cours de son endommagement, nous localisons, en utilisant simultanement l'extensometrie a jauges electriques et l'emission acoustique, l'amorcage, la croissance, le developpement des microfissures et des criques, tout le long du recouvrement et pendant toute la duree de vie de l'eprouvette. En appliquant plusieurs sables sur les subjectiles prealablement rectifies, nous avons defini la rugosite optimale pour laquelle les qualites de mouillabilite, et la resistance mecanique a la traction et a la fatigue sont les meilleures. Une analyse simplifiee du comportement elastique du joint a ete elaboree en faisant intervenir un correcteur d'extremite. Nos resultats montrent qu'il existe une adequation satisfaisante avec l'experience

Le soudage du bois est une technique d'assemblage sans adhésif de deux pièces de bois, leur soudure étant produite par friction mécanique sous pression des deux pièces. Ce procédé, applicable à des pièces de bois plates, d'essences identiques ou différentes, se prête à la fabrication de meubles et à la menuiserie. Cependant, le joint obtenu n'est pas de classe "extérieur", ce qui le réserve à un usage "intérieur". En effet, un joint destiné à une utilisation extérieure ou en milieu à humidité variable doit présenter une résistance élevée à l'eau. L'objectif principal de cette thèse est d'étudier la résistance à l'eau du bois soudé. A cet effet, des méthodes d'essais complémentaires et non-destructrices ont été utilisées, comme le scanner ou l'imagerie par résonance magnétique (IRM). L'influence des paramètres de soudage et des propriétés du bois sur, d'une part, la formation et la propagation des fissures dans la ligne de soudure, et sur, d'autre part, la densité et l'absorption d'eau de la soudure a été ainsi étudiée. Les expériences de cette thèse seront menées sur des échantillons de pin (Pinus sylvestris) de dimensions 200 mm x20 mm x 40 mm, coupés dans la direction longitudinale du fil du bois. La Norme Européenne EN 205 a servi de cadre pour déterminer la résistance des échantillons de pin en traction-cisaillement. Les méthodes d'essais (non-destructrices) ont été utilisées selon leur pertinence: le scanner a servi à étudier la formation et la propagation des fissures; l'imagerie par résonance magnétique (IRM) a permis quant à elle de caractériser la pénétration et l'infiltration d'eau dans le bois soudé.Le mécanisme d'adhérence du pin a été étudié grâce à la RMN MAS (spectrométrie à résonance magnétique nucléaire avec polarisation croisée et rotation à l?angle magique) du carbone13 et à la micro-densitométrie par rayons X. Ces différentes méthodes, non destructrices, offrent l'avantage d'une analyse non invasive et l'élimination de facteurs parasites liés à la préparation et à la coupe du bois. Voici en résumé les résultats obtenus les plus marquants: (1) Le scanner et l'imagerie par résonance magnétique (IRM) sont des méthodes de recherche particulièrement polyvalentes et adaptées à l'étude des bois soudés. (2) L'utilisation de bois de coeur, une pression de soudage de 1.3 Mpa et un temps de soudage de 1.5 s permettent d'augmenter la résistance à l'eau du pin soudé. (3) Des tests d'optimisation ont montré que la résistance du pin en traction-cisaillement est plus sensible aux variations de temps de soudage qu'au temps de refroidissement et qu'elle peut être optimisée à plus de 9.7 MPa en respectant une pression de 1.3 Mpa, un temps de soudage > 3.5 s et un temps de refroidissement < 60 s. (4) La résistance à l'eau du bois soudé peut être améliorée dans une certaine mesure en faisant varier paramètres de soudage et propriétés des essences, mais dans tous les cas, le recours à un imperméabilisant naturel et écologique reste nécessaire. (5) Le pin soudé possède une résistance à l'eau et en traction-cisaillement inhabituellement élevée, cela pouvant s'expliquer par une teneur en composés extractifs augmentée. (6) Des essais sous IRM ont montré que les causes de rupture du joint varient suivant l'essence: faible résistance à l'eau de la ligne de soudure dans le cas du hêtre soudé, retrait et expansion du bois dans le cas du pin soudé. (7) Les extractifs du pin améliorent nettement la résistance à l'eau du joint soudé, mais à un niveau qui ne lui permet cependant pas la certification "extérieur" sans protection. En revanche, il peut être certifié "semi-extérieur" avec protection
Wood welding is a mechanical friction process allowing the assembly of timber without any adhesives. The process consists of applying mechanical friction, under pressure, alternately to the two wood surfaces to be welded. This process can be applied to weld two flat pieces of timber, originating from the same or different tree species, and can be used in the manufacture of furniture and wood joinery. The only limitation is that the joint is not exterior-grade, but only suitable for interior joints. Exterior use, or use in an environment with varying humidity demands water resistance of the welded joints. The main objective of this thesis is to study the water resistance of the welded wood. This is complemented with special attention to non-destructive test methods such as X-ray Computed Tomography (CT-) scanning and Magnetic Resolution Imaging (MRI). The influence of welding parameters and wood properties on crack formation and crack propagation in the weldline was investigated. The influence of these parameters on weldline density and water absorption in the weldline were also studied. Investigations in this thesis are based on welded samples of Scots pine (Pinus sylvestris) of the dimensions 200 mm × 20 mm × 40 mm which were cut in the longitudinal direction of the wood grain. The tensile-shear strength of the welded Scots pine samples were determined using European standard EN 205. Different non-destructive methods such as X-ray Computed Tomography (CT-) scanning to study crack formation and propagation, and magnetic Resolution Imaging (MRI) to characterize water penetration and the distribution mechanism in welded wood were used. Solid state CPMAS 13C NMR spectrometry and X-ray microdensitometry investigations were carried out to study the mechanism of adhesion in Scots pine. These various non-destructive methods offer the advantage of non-invasive analysis and the elimination of any artifacts present due to preparation and sectioning. The most important results are summarized as follows: (1) X-ray Computed Tomography (CT-) scanning and Magnetic Resolution Imaging (MRI) are versatile research methods applicable to investigations of welded woods. (2) Water resistance of welded Scots pine can be increased using heartwood, a welding pressure of 1.3 MPa, and a welding time of 1.5 s. (3) Optimization tests showed that the tensile-shear strength of Scots pine was more sensitive to welding time changes than holding time and could be optimized to more than 9.7 MPa using 1.3 MPa welding pressure, > 3.5 s welding time, and < 60 s holding time. (4) Changing welding parameters and wood properties can increase water resistance of welded wood to some extent, but treating the weldline with certain natural and environmentally-friendly water repellents is still necessary. (5) Welded Scots pine shows unusually high water resistance and tensile-shear strength. This may be explained by there being more extractives compounds in Scots pine. (6) MRI experiments showed that the origin of the joint failure in welded beech is poor water resistance of the weldline, while swelling and shrinkage of wood are the main reasons for joint failure of welded Scots pine. (7) Extractives in Scots pine dramatically improve water resistance of the welded joint, but not to a level to classify the joint as an unprotected exterior grade. However, it can qualify as a joint for protected semi-exterior application

O objetivo do presente trabalho foi avaliar a resistência à tração de botões ortodônticos fixados em esmalte bovino, utilizando-se três sistemas adesivos, com e sem contaminação com sangue humano. Foram selecionados noventa incisivos bovinos nos quais foram fixados botões de aço inoxidável com base de 3,5 mm de diâmetro, utilizando-se os sistemas adesivos Magic Bond (Vigodent) e resina TPH (Dentisply), Fill Magic Ortodôntico (Vigodente) e adesivo Transbond Plus Self Etching Primer (3M) e resina TPH. Para cada sistema adesivo 15 espécimes foram colados após contaminação da área com sangue humano e 15 sem contaminação (controle), resultando em seis grupos. Após colagem, os botões foram submetidos a ensaios de tração até deslocamento do mesmo e os resultados foram transformados para MPa. Os dados obtidos foram analisados estatisticamente (p 0,05) utilizando análise de variância a um critério (ANOVA) e teste de Tuckey. Para comparar os grupos contaminados com sangue com os controles utilizou-se Teste t de Student. A resistência à tração obtida (MPa), considerando-se os valores encontrados nos grupos estudados ocorreram na seguinte ordem: Adesivo Transbond Plus Self Etching Primer e resina TPH sem (2,66 1,41) e com contaminação (2,29 1,11); Adesivo Magic Bond e resina TPH sem (2,23 0,94) e com contaminação (1,68 0,78); e, Adesivo Fill Magic Ortodôntico sem (1,20 0,34) e com contaminação (0,51 0,37). Houve maior resistência à tração nos botões fixados sem contaminação e ocorreram diferenças estatisticamente significantes entre os diferentes sistemas adesivos utilizados.
The objective of this work was to evaluate the tensile strenght of orthodontic buttons settled in bovine enamel, using three systems adhesive, with and without contamination with human blood. Ninety bovine incisors had been selected in which stainless steel buttons had been fixed with base of the 3,5 mm of diameter, using themselves adhesive systems Magic Bond (Vigodent) and resin TPH (Dentisply), Fill Magic Ortoodôntico (Vigodente) and adhesive Transbond Plus Self Etching Primer (3M) and resin TPH. For each adhesive system 15 specimens had been glue after contamination of the area with human blood and 15 without contamination (control), resulting in six groups. After glue, the buttons had been submitted the assays tractive until displacement of the same and the results had been transformed for MPa. The gotten data had been analyzed for statistics (p 0,05) using analysis of variance to a criterion (ANOVA) and test of Tuckey. To compare the groups contaminated with blood with the controls Test t of Student was used. The tensile strenght gotten (MPa), considering the values found in the studied groups had occurred in the following order: Adhesive Transbond Plus Self Etching Primer and resin TPH without (2,66 1.41) and with contamination (2,29 1.11); Adhesive Magic Bond and resin TPH without (2,23 0,94) and with contamination (1,68 0,78); e, Adhesive Fill Magic Orthodôntico without (1,20 0,34) and with contamination (0.51 0,37). It had greater tensile strenght in the buttons settled without contamination and had occurred significant statistics differences between the different used adhesive systems.

У реології ґрунтів в якості фундаментальних властивостей розглядають: пружність; пластичність і в'язкість. Усі інші механічні властивості є складним поєднанням різних комбінацій цих трьох фундаментальних властивостей. Для дослідження механічних властивостей і мікроструктури ґрунту останнім часом стали активно застосовуватися реологічні методи. Вони дозволяють отримати ряд кількісних фізично обґрунтованих параметрів, з допомогою яких стає можливим прогнозувати зміну мікроструктури ґрунту при навантаженнях. Сучасні прилади дозволяють значно збільшити точність вимірювання реологічних параметрів і їх кількість. Реометри є високочутливими приладами для вимірювання взаємодії між частинками ґрунту в оброблюваному шарі. Застосування реометру для вивчення мікроструктури показана у великому ряді робіт. Для дослідження в'язкопружних властивостей чорнозему використано метод амплітудної розгортки з вимірювальною системою паралельних плато на модульному реометрі MCR-302. In the soil's rheology, fundamental properties are considered: elasticity; ductility and viscosity. All other mechanical properties are a complex combination of various combinations of these three fundamental properties. To study the mechanical properties and microstructure of the soil, lately, rheological methods have become actively used. They allow to obtain a number of quantitatively physically grounded parameters, by which it becomes possible to predict the change of soil microstructure under loads. Modern devices allow to significantly increase the accuracy of measurement of rheological parameters and their number. Rheometers are highly sensitive devices for measuring the interaction between soil particles in the treated layer. The use of the rheometer to study the microstructure is shown in a large number of papers. To study the viscoelastic properties of soil, the method of amplitude scanning with the measuring system of parallel plateau on the modular rheometer MCR-302 is used.

Cette these a utilise les criteres de whitney et nuismer, de pipes, et les modeles de tan et de degradation progressive par calcul aux elements finis (mdpc) pour etudier la resistance et le mecanisme d'endommagement de plusieurs types de plaques stratifiees portant des trous circulaires en traction monotone. Le comportement de fatigue en traction de trois stratifies tisses a egalement ete aborde. L'attention a ete principalement concentree sur la chute de rigidite secante. L'apparition et l'evolution des endommagements au fur et a mesure du nombre de cycles. Les tractions monotone et cyclique, radiographie, emission acoustique et microscopie ont ete adoptes pour verifier les resultats prevus et pour avoir le detail des mecanismes de l'endommagement au sein des materiaux composites non tisses et tisses. Les resultats dans le cas monotone montrent: les criteres utilises sont assez precis et simples a utiliser; les modeles de tan modifies dans cette these sont preferables pour les stratifies tisses et orthotropes et ces modeles peuvent donner des informations sur l'endommagement; le mdpc est preferable pour savoir le suivi d'endommagement; le mecanisme de l'endommagement dans le cas tisse est plus complexe que celui dans le cas non tisse. Les resultats dans le cas cyclique montrent: la courbe rationalisee de la chute de rigidite peut se diviser en trois stades; l'apparition et la propagation des endommagements observables se produisent pendant le troisieme stade et ces endommagements sont orientes de preference suivant les plis a 90; la propagation peut aussi se diviser en trois stades, dont un stade stable, un stade instable et un stade brutal; la tenue en fatigue des materiaux est principalement dominee par le stade stable pendant la propagation; la vitesse de l'evolution des endommagements est influencee par les sequences d'empilement; il existe un seuil de distance sur le ligament et un seuil de duree de vie au-dessus desquels la rupture catastrophique se produit

Etude experimentale sur des eprouvettes tubulaires minces soumises a une variation cyclique d'un angle de torsion sur laquelle est superposee une contrainte de traction constante. Determination d'une courbe de resistance a la fatigue pour chaque niveau de chargement primaire. L'effet du chargement primaire conduit, a une reduction sensible du terme d'endurance dans l'equation de resistance a la fatigue. La rupture a lieu par fatigue et non par deformation, plastique excessive. Analyse de la reduction de la duree de vie associee a l'application d'un changement primaire

Orientador: Paulo Sollero
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Na indústria aeronáutica o uso de juntas coladas, rebitadas, parafusadas e soldadas na união de partes estruturais é de extrema importância no projeto das aeronaves. No entanto, devido as suas vantagens, as juntas coladas representam uma das principais tecnologias disponíveis para a exploração de novos materiais e para o desenvolvimento de projetos inovadores de configurações estruturais. Atualmente muitas aplicações aeronáuticas de colagem estão em estruturas e peças secundárias, contudo esta tecnologia apresenta grandes potenciais que dependem de um processo robusto e do domínio do dimensionamento e certificação. A colagem de chapas adicionais, chamadas de doublers, em áreas mais críticas de fuselagem e asa conduz à redução de usinagem química e mecânica, provendo um melhor aproveitamento dos materiais. Portanto, o doubler colado é uma alternativa de junta bastante eficaz em substituição às outras alternativas presentes hoje na indústria aeronáutica, promovendo uma maior eficiência na transferência de carga, potencial de redução de custo, alta resistência à corrosão e à fadiga, característica de retardar a propagação de trincas e maior integração das peças. Desta maneira, este trabalho tem como objetivo estudar estruturas aeronáuticas metálicas reforçadas por doublers colados, usando modelos analíticos, numéricos e experimentais, com ênfase na análise de tensões do adesivo. Além disso, criou-se um software com interface amigável reunindo os modelos analíticos mais importantes na análise de doublers colados e o modelo analítico criado pelo autor deste trabalho, permitindo a comparação das tensões no adesivo com os modelos numéricos. Na parte experimental, por tratar-se de um estudo relativamente novo e sem normalização específica de ensaios disponíveis, foram desenvolvidas técnicas de análise com o uso do processamento digital de imagens e da extensometria, além do projeto dos corpos de prova. Foram também projetados e ensaiados subcomponentes utilizados para simular as aplicações reais de doublers colados, através do desenvolvimento de uma ferramenta de otimização paramétrica visando à redução do peso nas aeronaves
Abstract: In the aircraft industry the use of bonded, riveted, bolted and welded joints at the junction of structural parts are extremely important in aircraft design. However, due their advantages, bonded joints, represent one of the main technologies available for the exploration of new materials and to the development of innovative structural configurations. Nowadays several aircraft bonded applications are applied in structures and secondary parts, however, this kind of technology presents a huge potential that depends on a robust model, in an effective sizing process and in an accurate certification. The bonding process of additional plates, best-known as doublers, in critical fuselage areas and in wings lead to a reduction in chemical and mechanical machining, providing a better material use. Thus, to avoid chemical milling, in some critical areas of the fuselage, are installed additional plates. These plates are called doublers, and are bonded in the base plate as a reinforcement located to reduce the stress level. Therefore, the use of bonded doublers is a very effective alternative to replace other alternatives present today in the aviation industry, promoting greater efficiency in load transfer, lower cost, high corrosion resistance, lower crack propagation and greater integration of parts. Thus, this work aims to study aeronautical metal structural joints reinforced by bonded doublers, through the analysis by analytical, numerical and experimental models, with emphasis on stress analysis of adhesive. In addition, software was created with a friendly interface gathering the most important analytical models in the analysis of bonded doublers, and allowing within this software to make the comparison with numerical models. Due the lack of standard tests and its relatively new study, new proceedings were created. These techniques were developed by the use of digital image processing and strain gage. Several subcomponents were designed and tested to simulate the actual application of bonded doublers, through the development of an optimization process in order to reduce weight of the aircraft
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica

Master’s thesis deals with application of new suspension means for personal elevator instead of conventional steel wire rope includes calculation of traction. Followed by assessment of passive resistance generated by guiding elevator on guide rails and caused by various locations of suspension and guiding (car guide rails). In the last part of thesis contains a strength analysis of car frame by Finite elements method (FEM) in programme NX I-deas.

Avanço da tuberosidade tibial (ATT) é uma das técnicas para tratamento da ruptura do ligamento cruzado em cães desenvolvida por Montavon, Damur e Tepic (2002). O sucesso da técnica em reduzir ou eliminar as forças de deslocamento cranial da tíbia em joelhos com ruptura do ligamento cruzado cranial tem sido documentado em estudos experimentais e clínicos. No período pós-operatório a técnica, a falha do implante é relatada em 1 a 5% dos membros pélvicos operados. Este número foi atribuído a erro de técnica ou desenho inicial do implante que foi considerado insuficiente. Com objetivo de comparar a resistência biomecânica entre duas diferentes placas de ATT e minimizar a incidência de falhas de implante, foram realizados ensaios biomecânicos em 10 pares de membros pélvicos de cadáveres cães, no membro pélvico direito placa fixa por garfo e no membro pélvico esquerdo placa fixa por parafusos. Os ensaios foram realizados utilizando-se máquina universal de ensaios mecânicos Kratos® modelo 5002, dotada de célula de carga de 3000N com uma velocidade de ensaio de 20 mm/min. O parâmetro força e os gráficos gerados foram gravados por meio de sistema de aquisição analógica TRACOMP-W95 (TRCV61285). A média da carga máxima até a falha foi de 128,70 Kg/F (mínimo 104,55 Kg/F e máximo 151,80 Kg/F) e de 141,99 Kg/F (mínimo 111,60 Kg/F e máximo 169,65 Kg/F) no grupo utilizando \"garfo\" e parafusos respectivamente. O desvio padrão dos grupos \"garfo\" e parafuso foi baixo, 12,99 e 17,21 respectivamente. Foi encontrada diferença significativa (p = 0,0309) entre as médias dos grupos.
Tibial tuberosity advancement (TTA) is one of the techniques for treatment of cruciate ligament rupture in dogs developed by Montavon, Damur and Tepic (2002). The success of the technique in reducing or eliminating the forces of cranial tibial displacement in knees with ruptured cranial cruciate ligament as been documented in experimental and clinical studies. In the post-operative technique, implant failure is reported in 1-5% of hindlimbs operated. This number was attributed to technical error or the initial design of the implant that was considered insufficient. To compare the biomechanical strength between two different plates ATT and minimize the incidence of implant failures, biomechanical tests were performed on 10 pairs of hindlimbs cadaver dogs, the right hindlimb fixed plate and a fork in the left pelvic limbplate fixed by screws. As says were performed using a universal mechanical testing Kratos ® model 5002, equipped with a load cell of 3000N with a test speed of 20 mm / min. The strength parameter and graphs generated were recorded via analog acquisition system TRACOMP-W95 (TRCV61285). The mean load to failure was 128.70 kg/F (minimum 104.55 Kg and maximum 151.80 Kg/F) and 141.99 Kg/F (minimum 111.60 Kg/F and maximum 169.65 Kg/F) in the group using \"fork\" and screws respectively. The standard deviation of the groups \"fork\" and bolt was low, 12.99 and 17.21 respectively. Significant difference (p = 0.0309) between the means of the groups.

Cette thèse de doctorat a été développée au Laboratoire de Tribologie et Dynamique des Systèmes (LTDS) de l’Ecole Nationale des Travaux Publics de l’Etat (ENTPE), France. Il faisait partie d'un partenariat entre les sociétés françaises Afitexinov et EIFFAGE. Il a également bénéficié du soutien du programme brésilien de science sans frontières du CNPq. L'objectif de cette étude est de contribuer au développement de nouveaux géosynthétiques structurés pour le renforcement des couches bitumineuses des chaussées, ainsi que de méthodes de dimensionnement transférables vers l’ingénierie. En plus de fournir des informations utiles qui pourraient permettre la proposition d'une nouvelle méthode de conception pour les structures de chaussées renforcées. À cette fin, cinq complexes ont été conçues, quatre à deux couches et une entière, contenant le même type d’enrobé bitumineux quelle que soit la configuration. À partir des plaques à deux couches, trois ont été renforcées par la combinaison de deux géogrilles en fibre de verre (résistance à la traction maximale de 50 et 100 kN/m) avec deux émulsions comme couche d'accrochage (bitume pure et modifié par SBS). La première campagne expérimentale a porté sur la caractérisation du comportement des éprouvettes cylindriques renforcées par géogrille en fibre de verre dans le domaine de petites déformations à l'aide de essais cycliques de traction-compression. Une nouvelle méthode d'analyse d'interface a été proposée pour les essais de module complexes sur les échantillons renforcés par géogrille. D'après les résultats des tests, le comportement d'interface obtenu était viscoélastique linéaire (VEL) et il pourrait être modélisé par le modèle 2S2PD. La deuxième campagne expérimentale a porté sur la caractérisation à la charge de traction axiale monotone. Trois températures ont été combinées avec deux vitesses de déformation pour la caractérisation. Les résultats ont montré que la géogrille n'était pas très mobilisée, peut-être à cause du glissement de l'interface. La troisième campagne expérimentale concernait la caractérisation à la fatigue. Des essais de traction-compression sinusoïdale à 10°C, 10 Hz et à déformation contrôlée à différentes amplitudes ont été effectués. Les différents complexes présentaient une sensibilité distincte à la variation d'amplitude de déformation des courbes de Wöhler. Pour la méthode de dimensionnement française des chaussées, selon le paramètre ε6 obtenu dans ce travail, l'effet de renforcement de la géogrille était négligeable. La quatrième campagne expérimentale a porté sur la caractérisation sur la résistance à la propagation des fissures. L’essai four-point bending notched fracture (FPBNF) a été réalisé sur les échantillons en forme de poutre. Un dispositif de corrélation d'image numérique 3D a été utilisé pour calculer le champ de déformation pendant la propagation de la fissure ainsi que son hauteur. Un plateau de force, proportionnel à la résistance maximale à la traction de la géogrille, a été observé dans les résultats pour les échantillons renforcés grâce à la mobilisation de la géogrille lors de l'essai
This doctoral dissertation was developed at the Laboratory of Tribology and Dynamics of Systems (LTDS) at the Ecole Nationale des Travaux Publics de l’Etat (ENTPE), France. It was part of a partnership between the French companies Afitexinov and EIFFAGE Infrastructures. It also had the support of the Brazilian science without borders program from CNPq. The objective of this study is to contribute to the future development of new geosynthetics to the reinforcement of bituminous mixtures. As well as to provide useful information that could allow the proposition of new design method for reinforced pavement structures. To this end, five slab configuration was conceived, four bi-layered and one whole, containing the same type of bituminous mixture regardless of the configuration. From the bi-layered slabs, three were reinforced with the combination of two fiberglass geogrids (50 and 100kN/m maximum tensile strength) with two emulsions as tack coat (bitumen pure and modified by SBS). The last bi-layered slab was unreinforced, containing only emulsion bitumen pure on its interface. The first experimental campaign concerned the characterization of the behavior of cylindrical specimens reinforced by fiberglass geogrid at a small strain domain using cyclic tension-compression tests. A new interface analysis method was proposed for complex modulus tests of specimens reinforced by geogrid. From test results, the interface behavior obtained was linear viscoelastic (LVE) and it could be modelled by 2S2PD model. The second experimental campaign concerned characterization at monotonic axial tension loading. Three temperatures were combined with two strain rates of loading for the tension characterization. The results showed that the geogrid was not highly mobilized possibly due to a slippage in the interface. The third experimental campaign concerned fatigue characterization. Sinusoidal tension-compression tests at 10°C, 10Hz, and controlled strain at different amplitudes were carried out. The different configurations presented distinct susceptibility to strain amplitude variation of Wöhler curves. For the French design method for pavements, according to the parameter ε6 obtained in this work, the geogrid reinforcement effect was negligible. The fourth experimental campaign concerned the crack propagation resistance characterization. Four-point bending notched fracture (FPBNF) test was carried out using beams. 3D Digital Image Correlation device was used to calculate the strain field during the crack propagation as well as its tip. A force plateau, proportional to the geogrid maximum tensile strength, was observed in reinforced results related to the mobilization of the geogrid during the test

Determination du gradient d'endommagement de deux refractaires siderurgiques (magnesie-chrome) par un traitement thermique. Etude des contraintes a la rupture, des modules d'elasticite et des energies de rupture sur des echantillons de petite taille. Influence de l'inhomogeneite (agregats de magnesie) sur le comportement a la fissuration des eprouvettes

De nos jours, la politique écologique encourage les constructeurs automobiles à réduire le poids global du véhicule. Des tôles d'acier fines d'épaisseur différente optimisant chaque partie de l'assemblage sont utilisées et les sidérurgistes développent des aciers de plus en plus résistants à savoir l'Acier Haute Résistance Avancé (AHSS) avec un bon compromis entre résistance mécanique et ductilité (emboutissage). Lors des essais mécaniques de soudage hétérogène AHSS, des modes de fractures inhabituels sont observés, notamment le long de l'interface entre la zone affectée par la chaleur (ZAT) et la zone de fusion ou zone fondue (ZF). Ces fractures se produisent généralement avec une résistance inférieure à celle attendue pour ces soudures. Les objectifs de l'étude sont de comprendre les mécanismes de rupture au cours des essais mécaniques et de créer un modèle mécanique de FE conçu pour prédire la résistance mécanique des assemblages soudés. Tout d'abord, une étude de soudage hétérogène constituée de deux nuances d'acier bien connues d'ArcelorMittal vise à comprendre le mécanisme de défaillance et les paramètres affectant les modes de défaillance. Différentes configurations sont étudiées avec l'épaisseur. Le modèle FE est construit avec une réponse mécanique identifiée de chaque zone (matériaux de base, zones affectées par la chaleur et zone de fusion), en utilisant des modèles d'ArcelorMittal et des données expérimentales. Des critères de défaillance basés sur des dommages ductiles tenant compte de l'influence de la triaxialité sont utilisés et certains éléments cohésifs sont utilisés pour simuler une défaillance interfaciale. Deux configurations d'essais mécaniques dans le cas du soudage par résistance par points (essais de traction transversale et de traction) sont considérées. Les prédictions du modèle étaient très précises avec les modes de défaillance et les forces expérimentaux. Ensuite, cette méthode de modélisation FE a été appliquée avec succès à un boîtier de soudage par points très hétérogène comprenant un nouveau concept AHSS basse densité de troisième génération à forte teneur en aluminium et en manganèse. Les modes d'échec et les forces obtenues étaient comparables. De plus, la méthode de modélisation FE a été appliquée sur des configurations plus complexes, en particulier sur un assemblage soudé par points triple épaisseur. La robustesse du modèle pour prédire les modes de défaillance partielle et les forces d'une soudure par points triple épaisseur a été démontrée. En outre, la méthodologie de modélisation FE a été étendue à un autre type de soudage: le soudage à l'arc. Dans ce cas, deux feuilles sont soudées en configuration de chevauchement ab avec un fil d'apport. Le modèle FE permet de prédire la zone de rupture et la résistance de l'assemblage soudé
Nowadays, ecological policy encourages carmakers to reduce the global vehicle weight. Fine steel sheets assemblies with different thickness optimizing each part of the assembly are used and steelmakers develop steels which are more and more resistant namely Advanced High Strength Steel (AHSS) with a good compromise between mechanical strength and ductility (stamping). During the mechanical tests of heterogeneous AHSS welding, unusual fracture modes are observed, in particular along the interface between the Heat Affected Zone (HAZ) and the Fusion Zone or molten zone (FZ). These fractures generally occur with lower strength than expected for these welding. The objectives of the study are to understand fracture mechanisms during mechanical testing and create a mechanical FE model is developed to be able to predict mechanical strength of the welded assemblies. Firstly, a study of heterogeneous welding constituted of two well-known steel grades of ArcelorMittal aims at understanding failure mechanism and parameters affecting the failure modes. Different configurations are studied with thickness. FE model is built with mechanical response identified of each zone (base materials, heat affected zones and fusion zone), using ArcelorMittal models and experimental data. Failure criteria based on ductile damage taking into account the influence of the triaxiality are used and some cohesive elements are used to simulate interfacial failure. Two configurations of mechanical testing in the case of Resistance Spot Welding (cross tension and tensile shear tests) are considered. Model predictions were very accurate with experimental failure modes and strengths. Then, this FE modelling method was successfully applied to a highly heterogeneous spot welding case including a new third generation low density AHSS concept with high aluminum and manganese content. Failure modes and strengths obtained were comparable. Moreover, FE modelling method was applied on more complex configurations, in particular on a triple thick spot welded assembly. The robustness of the model to predict partial failure modes and strengths of a triple thick spot weld has been demonstrated. In addition, FE modelling methodology was extended to another welding type: arc welding. In this case, two sheets are welded in ab overlap configuration with a filler wire. FE model allows predicting the failure zone and strength of welded assembly

Objetivos: Este estudo teve por objectivo fazer uma comparação directa da resistência à tração entre membranas produzidas com o protocolo L-PRF (Leucocyte-Platelet Rich Fibrin) e A-PRF (Advanced-Platelet Rich Fibrin). Materiais e Métodos: Após a colheita de sangue de uma pessoa saudável e sem histórico de toma de anticoagulantes, procedeu-se à produção de membranas segundo os protocolos de L-PRF e A-PRF, previamente descritos na literatura. De seguida, as membranas (13 para cada protocolo) foram submetidas a um teste de tração, para os quais foram obtidos valores de tração máxima e de tração média. A análise estatística dos dados foi feita com recurso a teste t não pareado. Resultados: Relativamente à tração média o protocolo A-PRF obteve 0.0288 N.mm-2 e o L-PRF 0.0192 N.mm-2 (p<0.05 utilizando teste-t não pareado; n=13). Para a tração máxima registou-se para o protocolo A-PRF o valor de 0.0752 N.mm-2 e L-PRF 0.0425 N.mm-2 (p<0.05 utilizando teste t não pareado; n=13). Conclusão: Com este estudo foi possível concluir que o protocolo A-PRF permite obter membranas com valores de tração máxima e tração média mais elevados do que os obtidos para o protocolo L-PRF, apontando assim para uma maior resistência quando duas forças opostas são aplicadas sobre a membrana. Este facto, associado à otimização das suas propriedades celulares e biológicas, fazem do protocolo A-PRF uma escolha melhor em detrimento do L-PRF.
Purpose: This study aimed at comparing the resistance traction between membranes produced with the protocol L-PRF (Leucocyte-Platelet Rich Fibrin) versus the protocol A-PRF (Advanced-Platelet Rich Fibrin). Materials and Methods: After blood collection of a healthy individual with no history of anticoagulant usage, we produced fibrin membranes according to the protocols L-PRF and A-PRF, previously described in the literature. Afterwards the membranes (13 for each condition) were submitted to a traction test, assessing the maximal traction and the average traction obtained for each membrane. The data was analyzed using unpaired t-test. Results: Regarding average traction, the A-PRF protocol obtained a value of 0.0288 N.mm-2 and L-PRF 0.0192 N.mm-2 (p<0.05 using unpaired t-test; n=13). For maximal traction A-PRF obtained 0.0752 N.mm-2 and L-PRF 0.0425 N.mm-2 (p<0.05 using unpaired t-test; n=13). Conclusion: With this study, we conclude that the A-PRF protocol generates membranes with higher maximal traction average traction scores, which indicates an increased resistance when two opposing forces are applied to it. This fact, associated with the optimization of the cellular and biological properties, make A-PRF a better protocol for the preparation of fibrin membranes.

Objetivos: O presente estudo teve como objetivo comparar as propriedades mecânicas de resistência à tração e estrutura entre as membranas produzidas por A-PRF (Advanced- Platelet Rich Fibrin) e A-PRF+ (Advanced-Platelet Rich Fibrin+). Materiais e métodos: Recorrendo à colheita de sangue de um dador saudável sem história de uso de anticoagulantes ou imunossupressores, realizou-se a preparação das membranas seguindo as indicações protocolares definidas na literatura para A-PRF e A-PRF+. De um N=16/grupo, 13 membranas de A-PRF e 12 de A-PRF+ foram submetidas ao teste de tração, para a obtenção de valores referentes à tração máxima e tração média. Os dados obtidos foram analisados estatisticamente com o teste t não pareado. Após avaliação desta variável, as membranas foram observadas em MEV (Microscopia Eletrónica de Varredura). Resultados: Foram obtidos em relação à tração máxima, 0.0020 N.mm-2 para o A-PRF e 0.0022 N.mm-2 para A-PRF+. Relativamente à tração média, A-PRF obteve 0.0012 N.mm-2 , enquanto o A-PRF+ obteve 0.0015 N.mm-2 (p˂0,01). Nas observações de superfície com MEV, A-PRF+ mostrou ser o concentrado plaquetário mais poroso, com maior abundância de fibras e preservação celular. Conclusão: Este estudo permitiu concluir que o protocolo A-PRF+ foi capaz de produzir membranas com valores de tração máxima superiores aos obtidos pelo A-PRF, sendo os resultados indicativo de que o protocolo apresentou membranas com maior resistência e capacidade elástica ao serem tracionadas por duas forças opostas. A este fenómeno acrescenta-se a arquitetura demonstrada na matriz de A-PRF+ e as propriedades biológicas otimizadas descritas na literatura.
Purpose: This study aimed to formulate a comparison of the mechanical properties of tensile strength and structural organization between membranes produced by A-PRF (Advanced Platelet-Rich Fibrin) and A-PRF+ (Advanced Platelet-Rich Fibrin+). Materials and Methods: Blood was collected from a healthy donor with no history of anticoagulant or immunosuppressant use, the membranes were prepared following the protocol indications defined in the literature for A-PRF and A-PRF+. From an N=16 for each protocol, 13 membranes of A-PRF and 12 of APRF+ were submitted to the traction test, evaluating maximum and average traction. Data was statistically analyzed using the unpaired t test. Membranes were then carefully observed in SEM (Scanning Electron Microscopy). Results: For maximum traction were obtained 0.0020 for A-PRF and 0.0022 for A-PRF+. Regarding the average traction, A-PRF scored 0.0012 while A-PRF+ obtained 0.0015 (p=0.01 unpaired t-test). Surface morphology observations with SEM, A-PRF+ showed to be the most porous platelet concentrate, with greatest fiber abundance and cell preservation. Conclusion: This study allowed to conclude that A-PRF+ protocol was able to produce membranes with higher maximum traction results than those found for A-PRF, indicating that the protocol with low centrifugation time, presented membranes with better viscoelastic strength when they are stretched by two opposed forces. To this phenomenon is added the architecture demonstrated in the A-PRF+ matrix and the optimized biological properties described in literature. A-PRF+, by the view of the developed findings in this work, a better option compared to A-PRF. Keywords: “Platelet-Rich Fibrin”, “Viscoelastic”, “Tensile Strength”, “Rupture”, “Porosity”, “Low-Speed Centrifugation Concept”.

碩士
國立臺北科技大學
分子科學與工程系有機高分子碩士班
106
Nowadays, it is a mainstream to use silica nanoparticles as fillers for tire rubber materials. Compared to the traditional carbon black (CB) as filler for tire rubber, silica nanoparticles have better effect on the mechanical properties of tire rubber for wider range of applications. But silica nanoparticles can not be dispersed well in rubber because the compatibility between silica and rubber is not good enough. To overcome this problem, a silane coupling agent with more than one alkoxy group at its both ends has been used for the modification. In addition, the amount of silane coupling agent is also needed to be considered. In this study, a suitable amount of coupling agent was found, and then a series of hybrid compounds were prepared by adding a tackifier and using different mixing process methods. The reactivity of the silane coupling agent, dispersibility of the silica nanoparticles and dynamic properties of tire rubbers were studied by using various techniques of Pyrolysis-GCMS, SAXS, TEM, mixing sequence and DMA.

Research Doctorate - Doctor of Philosophy (PhD)
The incorporation of conveyor systems throughout industry has seen an increase in demand for systems that exceed the specification of conventional conveyors. This coupled with the demand to convey bulk materials over larger distances, at higher speeds and efficiencies, requires the development of a versatile design approach. This thesis explores the design aspects associated with modern pouch conveying systems, and how they vary, and can be adapted from theories used with conventional troughed conveyors. In particular, the indentation rolling resistance (IRR) is explored in detail, as this can account for up to 60% of the drag forces of a system. This is the drag force that arises due to an asymmetric pressure distribution as the idler roll shell indents the bottom cover of the belt. The potential idler roll arrangements for a generic pouch conveying system are analysed, and compared with experimental values. In addition to this, the drive traction attainable from suitable drive stations is analysed. Troughed conveyors typically wrap the conveyor belt around a large drive pulley, generating large amounts of traction. Given the layout of pouch conveying systems, a different approach is required, at multiple locations. As such, pouch conveyors are typically driven through simply supported drive stations, with small areas of contact with the belt. The useable traction from these point contact drives is considered. These theories are then united and applied to a dynamic package capable of handling multiple conveyor designs. This package utilises Finite Element Modelling (FEM) to model the viscoelastic nature of the system, based on the distributed drag forces, and inputs of the conveyor. Lastly, to qualify this theory, experimental analysis is conducted on an on-site installation, and compared with the theoretical results.

Development of electric vehicles is motivated by global concerns over the need for environmental protection. In addition to its zero-emission characteristics, an electric propulsion system enables high performance torque control that may be used to maximize vehicle performance obtained from energy-efficient, low rolling resistance tires typically associated with degraded road-holding ability. A simultaneous plant/controller optimization is performed on an electric vehicle traction control system with respect to conflicting energy use and performance objectives. Due to system nonlinearities, an iterative simulation-based optimization approach is proposed using a system model and a genetic algorithm (GA) to guide search space exploration. The system model consists of: a drive cycle with a constant driver torque request and a step change in coefficient of friction, a single-wheel longitudinal vehicle model, a tire model described using the Magic Formula and a constant rolling resistance, and an adhesion gradient fuzzy logic traction controller. Optimization is defined in terms of the all at once variable selection of: either a performance oriented or low rolling resistance tire, the shape of a fuzzy logic controller membership function, and a set of fuzzy logic controller rule base conclusions. A mixed encoding, multi-chromosomal GA is implemented to represent the variables, respectively, as a binary string, a real-valued number, and a novel rule base encoding based on the definition of a partially ordered set (poset) by delta inclusion. Simultaneous optimization results indicate that, under straight-line acceleration and unless energy concerns are completely neglected, low rolling resistance tires should be incorporated in a traction control system design since the energy saving benefits outweigh the associated degradation in road-holding ability. The results also indicate that the proposed novel encoding enables the efficient representation of a fix-sized fuzzy logic rule base within a GA.

Метою кваліфікаційної роботи є дослідження взаємодії з ґрунтом викопуючих робочих органів картоплезбирального комбайна з обґрунтуванням їх основних параметрів. У кваліфікаційній роботі магістра обґрунтовано конструктивні параметри викопуючих робочих органів комбайна; технологічні параметри картоплезбирального комбайна, (продуктивність, тяговий опір та споживану потужність); підібрано енергетичний засіб для агрегатування комбайна; проведено розрахунки на міцність. Розроблено CAD-моделі викопуючих робочих органів картоплезбирального комбайна та дискретно – елементну модель ґрунтового середовища. За результатами імітаційного моделювання взаємодії викопуючих робочих органів картоплезбирального комбайна з ґрунтом отримано ряд параметрів взаємодії (зусилля, напруження, частоти коливань, потужності). Розглянуто питання з охорони праці при роботі із картоплезбиральним комбайном та безпеки у надзвичайних ситуаціях.
The purpose of the qualification work is to study the interaction with the soil of the excavating working bodies of the potato harvester with the justification of their main parameters. The master's qualification work the constructive parameters of digging working bodies of the potato combine harvester are substantiated; technological parameters of the potato combine harvester (productivity, traction resistance and power consumption) are substantiated; the energy means for aggregation of the combine are selected; strength calculations were performed. CAD-models of digging working bodies of potato combine harvester and discrete-element model of soil environment are developed. According to the results of simulation modeling of the interaction of the digging working bodies of the potato harvester with the soil, a number of interaction parameters were obtained (effort, stress, oscillation frequency, power). The issues of labor protection when working with potato combines harvester and safety in emergencies are considered.