Orientador: Jose Roberto de França Arruda / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-09-11T21:08:25Z (GMT). No. of bitstreams: 1 Albuquerque_ElsonLimade_M.pdf: 5441408 bytes, checksum: a2117bd817e2c8a2d88bf1324af63fd6 (MD5) Previous issue date: 2005 / Resumo: Neste trabalho de mestrado são investigadas as limitações do método dos elementos finitos na análise dinâmica de painéis reforçados. O painel foi modelado usando diferentes tipos de malha, mostrando que, dependendo do tamanho do elemento (ou número de graus de liberdade) usado na modelagem, o modelo não representa de uma maneira adequada a estrutura real. Para validar o modelo experimentalmente, foi construído um painel reforçado de alumínio e, através de métodos experimentais, foi feita uma análise modal. Os limites da modelagem pelo método dos elementos finitos, no que diz respeito às médias freqüências foram testados e comparados com resultados experimentais. Com a finalidade de reduzir o custo computacional, foi realizada uma comparação entre o método de elementos finitos e o método de elementos espectrais. Devido às incertezas de alguns parâmetros de entrada dos modelos, foram consideradas variações estatísticas em alguns parâmetros usando o Método de Monte Carlo e o Método da Superfície de Resposta. Os resultados mostraram que a partir de uma certa freqüência o método dos elementos finitos torna-se inviável devido ao alto custo computacional e que em altas freqüências o modelo dinâmico é sensível a pequenas variações nos parâmetros de entrada / Abstract: In this master's thesis work, finite element method limitations are investigated in the dynamic analysis of reinforced panels. The panel was modelled using different meshes in order to show that, depending on the element length (or the number of degree of freedom) used in the model, the model does not properly stand for the real structure. In order to assess experimentally the model, an aluminum reinforced panel was built and, through experimental methods, a modal analysis was carried out. The finite element modelling limits were tested and compared to experimental results regarding mid-frequencies. A comparison between finite element and spectral element methods was carried out for computational cost reduction purposes. Due to uncertainties of some model input parameters, a statistical variation was performed using Monte Carlo and Surface Response methods. Results have shown that, at high frequencies the finite element method is not appropriete for dynamic analysis due to high computational costs in high frequency and it is highly sensitive to small variations ofthe input parameters / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Elementos dentais endodonticamente tratados geralmente necessitam de retentores intrarradiculares para prover retenção e suporte ao processo restaurador. O objetivo deste estudo foi comparar a eficiência na distribuição de tensões de diferentes modelos de retentores intrarradiculares, através do método dos elementos finitos. Um modelo tridimensional de elementos finitos foi desenvolvido para representar um incisivo central superior endodonticamente tratado e restaurado com uma coroa total cerâmica, e quatro tipos diferentes de pinos pré-fabricados (dois convencionais, e dois modelos customizados) foram inseridos sob esse modelo e comparados quanto à distribuição das tensões às quais foram submetidos. Os quatro pinos diferem em formato e material de composição. O primeiro é um pino pré-fabricado metálico customizado referente à uma patente, com porção coronária anatômica (com curvaturas e formatos semelhantes à coroa anatômica) e flange rosqueável. O segundo pino pré-fabricado é semelhante em formato ao primeiro pino, mas será composto por fibra de vidro. O terceiro é um pino metálico pré-fabricado convencional, sem presença de flange. O quarto pino é semelhante ao terceiro pino em formato, mas será composto por fibra de vidro. Foi aplicada sobre os modelos uma mesma força estática média de 100 N com uma angulação de 135 graus ao longo eixo do dente no centro da face palatina do modelo, com o objetivo de simular a carga mastigatória e obter a distribuição das tensões. A avaliação apresentou os resultados considerando os critérios de Von Mises e tensões máximas principais. Os resultados mostraram que os pinos metálicos customizados resultaram em menores tensões à dentina e à estrutura coronária quando comparados aos pinos convencionais, e que ambos os pinos metálicos apresentaram menores tensões à estrutura coronária se comparados aos pinos em fibra de vidro. Em relação à estrutura dentinária, os pinos metálicos e os pinos em fibra de vidro apresentaram resultados semelhantes quanto à distribuição de tensões. Os modelos em fibra de vidro apresentaram resultados semelhantes em ambas as avaliações. Conclui-se que os modelos customizados foram superiores aos convencionais quando compostos pela liga metálica, mas semelhantes quando compostos por fibra de vidro. / Endodontically treated teeth commonly require a post to provide retention and support to the restorative process. The aim of this study was to compare the efficiency of the distribution stresses of different models of posts through the finite element method. A three-dimensional finite element model was developed to represent an endodontically treated maxillary central incisor restored with a ceramic crown, and four different types of prefabricated posts (two conventional and two customized models) have been inserted in that model and compared regarding the distribution of the stresses to which they were subjected. The four posts differ in size and material composition. The first is a custom metal prefabricated post relating to a patent, with anatomical coronal portion (with curvatures and format similar to the anatomical crown) and threaded flange. The second prefabricated post is similar in format to the first post, but is composed of fiberglass. The third is a conventional prefabricated metal post without the flange. The fourth post is similar to the third in format, but is composed of fiberglass. It was applied on the models the same average static occlusal force of 100N with an angle of 135 degrees to the tooth long axis in the palatal surface of the crown, with an objective of simulate the masticatory load and obtain the stress distribution. The evaluation presented the results considering the Von Mises and Maximum principal stress criteria. The results showed that the customized metal posts resulted in lower stresses to dentin and coronal tooth structure when compared to conventional posts, and both metallic posts had lower stresses in the coronal portion structure compared to glass fiber posts. Regarding the dentinal structure, metal posts and fiberglass posts showed similar results of stresses. The fiberglass models showed similar results in both evaluations. We conclude that the custom models were superior to conventional posts when composed by metal, but similar when composed of fiberglass.

"The potential hazard of using curbs on high-speed roadways has been a concern for highway designers for almost half a century. Curbs extend 75-200 mm above the road surface for appreciable distances and are located very near the edge of the traveled way, thus, they constitute a continuous hazard for motorist. Curbs are sometimes used in combination with guardrails or other roadside safety barriers. Full-scale crash testing has demonstrated that inadequate design and placement of these systems can result in vehicles vaulting, underriding or rupturing a strong-post guardrail system though the mechanisms for these failures are not well understood. For these reasons, the use of curbs has generally been discouraged on high-speed roadways. Curbs are often essential, however, because of restricted right-of-way, drainage considerations, access control, delineation and other curb functions. Thus, there is a need for nationally recognized guidelines for the design and use of curbs. The primary purpose of this study was to develop design guidelines for the use of curbs and curb-barrier combinations on roadways with operating speeds greater than 60 km/hr. The research presented herein identifies common types of curbs that can be used safely and effectively on high-speed roadways and also identifies the proper combination and placement of curbs and barriers that will allow the traffic barriers to safely contain and redirect an impacting vehicle. Finite element models of curbs and curb-guardrail systems were developed, and the finite element program, LS-DYNA, was used to investigate the event of a vehicle traversing several curb types. Finite element analysis was also used in the analysis of a vehicle impacting a number of curb-guardrail combinations. The results obtained from these analyses were synthesized with the results of previous studies, which involved full-scale crash testing, computer simulation, and other methods. The combined information was then used to develop a set of guidelines for using curbs and curb-barrier combinations on high-speed roadways."

Orientador: Fellippo Ramos Verri / Coorientador: João Maurício Ferraz da Silva / Banca: Fellippo Ramos Verri / Banca: José Benedito Oliveira Amorim / Banca: Virgílio Vilas Boas Fernandes Junior / Resumo: A perda do primeiro molar é uma situação comum na rotina do consultório e com isso surgem alternativas de tratamento para reabilitação, sendo uma delas, o fechamento de espaço através da mesialização do segundo molar. O uso de mini- implante proporciona ancoragem máxima, costuma ser bem tolerado pelo paciente e se destaca pela facilidade de instalação e remoção, apresentando dessa maneira desempenho clínico bastante favorável. O objetivo desse estudo foi analisar a distribuição de tensões em modelo que simula a mesialização de molar inferior utilizando diferentes tipos de mini-implantes. Embasado no método dos elementos finitos foi obtido modelo ósseo de mandíbula por recomposição de uma tomografia computadorizada realizada pelo software Invesalius (CTI, São Paulo, Brasil). O desenho do segundo molar foi obtido por técnica de recomposição tomográfica. Elementos de ancoragem auto-perfurantes da marca Neodent e também auto-rosqueantes da marca Titanium Fix foram desenhados e modelados por ferramenta de revolução do perfil desenhado no software Rhinoceros 3D, inseridos ao bloco ósseo e então submetidos a cargas de 200 cN. Os resultados foram calculados e analisados pelo programa Ansys 17.0 para verificação por meio da análise de mapas de deslocamento e tensões máximas principais, principalmente do osso cortical e indicaram que, dentro do modelo experimental, o ligamento periodontal apresentou valores baixos de tensão máxima principal, porém dentro dos valores fisiológicos para p... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The loss of the first molar is a common situation in the routine of the dentist and with this treatment alternatives for rehabilitation arises, one of them being the closure of space through the mesialization of the second molar. The use of mini-implants provides maximum anchorage, is well tolerated by the patient and stands out for ease installation and removal, thus presenting a very favorable clinical performance. The objective of this study was to analyze the stress distribution in a model that simulates the inferior molar mesialization using different types of mini- implants. Based on the finite element method, a mandible bone model was obtained by recomposing a computerized tomography performed by invesalius software (CTI, São Paulo, Brazil). The second molar design was obtained by a technique similar to the tomographic recomposition. Neodent self-piercing anchoring elements and also Titanium Fix self-piercing anchors were designed and modeled by a revolution tool in the Rhinoceros 3D software, inserted into the bone block and then subjected to loads of up to 200 cN. The results were calculated and analyzed by the Ansys 17.0 program for verification by means of the analysis of displacement maps and main maximum stresses, mainly of the cortical bone and indicated that, within the experimental model, the periodontal ligament presented low values of main maximum tension, however within the physiological values to provide the movement, with visualization of areas of compres... (Complete abstract click electronic access below) / Mestre

Induction machines are the most widely used type of electrical machines because of their robustness, simplicity, and relatively low cost. However, the small airgap in the induction machine makes them more susceptible to Unbalanced Magnetic Pull (UMP). This is because the magnitude of the UMP is a function of the degree of eccentricity, which is the ratio between the length of misalignment and the mean airgap length. The bearing-related failure accounts for approximately 41% of the total failures of induction machines; the percentages of bearing-related failure would be higher for applications in a harsher environment. In this thesis, the UMP caused by rotor eccentricity is investigated, because a small degree of rotor eccentricity is unavoidable due to the manufacturing tolerance and 80% of the mechanical faults could cause rotor eccentricity in electrical machines. When the rotor is not at the centre of the stator, the eccentric rotor causes an uneven airgap around the rotor, in which the magnetic permeance with the higher harmonics content will be created. The magnetomotive force (MMF) produces additional pole-pair ±1 magnetic flux around the airgap. The interaction between each magnetic flux with its pole pair ±1 magnetic flux produces UMP. As only the magnetic flux that crosses the airgap causes UMP, the magnetic flux is categorised into magnetising flux and airgap leakage flux, because both types of flux possess different characteristics at a different rotor slip. As the airgap leakage flux is difficult to calculate analytically, an empirical method is proposed to estimate the UMP caused by the airgap leakage flux. Then, the UMP caused by the magnetising flux can also be estimated by using the empirical method. The parameters for the empirical method can be found by using either the FEA or the experimental results. The damping effect of the magnetising flux in a parallel connected rotor bar is discussed and a damping coefficient is introduced to explain this scenario. The damping coefficient can also be used to calculate the UMP in a steady state analysis. UMP comparisons between the cage rotor and wound rotor induction machines are made. The wound rotor has a much higher UMP because the pole-specific wound rotor could not damp the additional pole pair ±1 magnetic flux. Therefore, a damper winding at the stator slot is also proposed in order to damp the UMP by producing a counteracting flux. In addition, analytical equations have also been derived for different scenarios, such as static eccentricity, dynamic eccentricity, axial-varying eccentricity, and skew rotor bars. Finite Element Analysis (FEA) and experimental work are used to demonstrate the derived analytical equation. Furthermore, the power losses caused by the rotor eccentricity are investigated. Iron losses, copper losses, and frictional loss are discussed and compared with both the analytical equation and the FEA results. In order to reduce the UMP in the induction machines, the two proposed methods are the slip control method and damper windings topology. The slip control method utilises the non-linearity characteristic of the UMP at different rotor slip. To find the optimum operating slip with the lowest UMP, the UMP/Torque ratio is introduced. The characteristics of the UMP/Torque ratio varies with the type and design of the induction machines. However, this method is only applicable when the machine is lightly loaded, because the magnetising flux is limited by the capped terminal voltage and the core saturation of the machine. For the damper winding topology, a circulating current flowing in the damper winding could produce a counteracting flux to damp the UMP. The proposed damper windings configuration is only suitable for the induction machine with an even pole pair number. Finally, comparisons between both UMP reduction methods are made.

This thesis investigated the different aspects and mechanisms of leak-before-break (LBB) assessment. The main objective was to improve the understanding of the transition between surface and through wall defects. While existing procedures generally idealise the through-wall crack into a rectangular shape, in reality a crack propagates with a shape depending on the loading. Comparison between the related solutions from established procedures have been undertaken. The apparent variation depending on the solutions used in the assessment has been highlighted. Two different methodologies have been employed to investigate the transition of flaw: (i) non-ideal through-wall and (ii) surface-breaking flaw propagation. The first approach consists of numerical models of non-idealised flaws in order to assess the effect on LBB parameters. For the second approach, experiments have been first carried out to visualise the shape of defect growths. To further study surface-breaking flaws, both experimental and numerical studies were performed. Fatigue tests on deeply notched plates with two crack aspect ratios were carried out. Strain evolutions on the back surface were recorded along the axes parallel and perpendicular to the crack. Numerical models have been prepared to investigate a larger scope. Behaviour of growing surface-breaking defects was examined. Based on the work conducted in this research, the major findings can be summarised as follows: - The existing solutions to carry out a LBB assessment using available procedures were reviewed and discussed. For axial flaws, SIF solutions were found similar and in good agreement with FEA values. Reference stress solutions showed significant difference between BS 7910 and API 579-1/ASME FFS-1. When compared to experimental data, API's solutions were able to distinguish between leak and break cases. - Flaw geometry assumption for through-wall crack yet to become idealised did not always reflect the actual behaviour, especially for COA calculation. In this case, FEA can be used as a good predictive tool for LBB to estimate margins when assessing leak rate. - The experiment using metallic specimens showed that high stress/strain on back surface would provide a good estimate of the crack propagation as it approached break-through. This offers a more accurate monitoring mechanism. Strain-mapping devices such as gauges could be used.

La compression élastique est la thérapeutique conservatrice la plus efficace pour la prise en charge de l'insuffisance veineuse et pour le traitement de la maladie veineuse chronique et de ses complications. Malheureusement, en pratique, les objectifs thérapeutiques ne sont pas toujours atteints ce qui souligne le manque de connaissance actuel concernant les mécanismes qui permettent aux Bas Médicaux de Compression (BMC) d'apporter les bienfaits thérapeutiques. Pour apporter des éléments de réponse, une étude numérique de l’action des BMC sur les veines a été réalisée. Dans un premier temps, une nouvelle méthodologie a été développée pour prévoir les pressions transmises aux parois des veines superficielles et pour quantifier la diminution de la pression transmurale et du calibre que la compression engendre. Une étude de sensibilité réalisée à partir du modèle Eléments Finis développé a permis de mettre en évidence les principaux paramètres qui conditionnent l’action des BMC. Il a ensuite été utilisé pour simuler différents scénarios d’application en lien avec la compression en post-sclérothérapie pour répondre à des problématiques industrielles. Dans une deuxième phase de l’étude, une méthode de modélisation numérique de la réponse des veines profondes à la contraction musculaire lors du port d’un BMC a été développée. Une étude de sensibilité a permis d’apporter des éléments de réponse quant à l’influence relative des aponévroses musculaires, de la contraction musculaire et du port d’un BMC. Ces travaux ouvrent des perspectives d’études nouvelles sur le développement d’outils pour permettre aux fabricants de BMC d’adapter le niveau de compression à chaque patient. / Compression therapy is a highly effective modality for treating venous disorders of the lower leg and is considered as the “gold standard” for non-operative therapy. However the mechanisms by which Medical Compression Stockings (MCS) benefit the control and treatment of venous insufficiency are neither clearly understood nor have they been conclusively demonstrated. In the present study, the biomechanical response of the lower leg veins to elastic compression is modelled in order to address some of the issues relating to the mechanisms by which it achieves its medical function. First, a new methodology has been developed in order to predict the pressure transmitted to the superficial vein wall during external compression and to quantify the resulting variations of transmural pressure and of the vein cross sectional area. A parametric study was performed to study the influence of the model parameters on the response of the vein. The developed model was also used to simulate different scenarii related to the use of elastic compression after sclerotherapy. In a second step, a numerical approach was developed to model the biomechanical response of deep veins to elastic compression. A parametric study was performed to evaluate the relative influence of the muscular aponeurosis, muscular contraction and external compression applied by MCS. The obtained results bring a new insight on MCS mechanical action and its possible benefits. They also open up new perspectives, especially, regarding the development of new tools to assist MCS manufacturers in adapting the level of compression to the location of the deep vein, the morphology of the patient and the severity of the disease.

Orientador: Tarcisio José de Arruda Paes Junior / Banca: Lafayette Nogueira Junior / Banca: Sâmia Carolina Mota Cavalcanti Sacorague / Resumo: O presente estudo teve como objetivo avaliar as características mecânicas de próteses parciais fixas adesivas, confeccionadas em resina composta de uso indireto, reforçadas por uma malha de nylon. Para a confecção da matriz dos espécimes e estudo das tensões nas estruturas, foi realizada análise qualitativa pregressa análise de elementos finitos (FEA). A pesquisa in vitro simula uma prótese parcial fixa de três elementos com inserção entre os primeiros pré-molares e os primeiros molares superiores (n = 60; 10 por grupo). Três dos seis grupos passaram por ciclagem mecânica. Os grupos experimentais foram: G1-prótese fixa convencional; G2 - prótese convencional ciclada; G3 - prótese com reforço da malha posicionada na vertical; G4 - Prótese com reforço da malha posicionada na vertical ciclada; G5 - Prótese com reforço da malha posicionada na horizontal; G6 - Prótese com reforço da malha posicionada na horizontal ciclada.Todos os grupos passaram por ensaio de carga máxima a fratura (EMIC). Os resultados não apresentaram diferença estatística entre os grupos. Concluiu-se que a utilização da malha nylon proporcionou estabilidade, mesmo após a fratura da peça, pois as partes não se separam, além disso, os resultados obtidos in vitro puderam validar os dados in sílico / Abstract: The present study aimed to evaluate the mechanical characteristics of adhesive fixed partial dentures, made from composite resin of indirect use, reinforced by a nylon mesh. A finite element analysis (FEA) was used to compile the specimen matrix and to study the stresses in the structures. In vitro research, simulated a fixed partial denture of three elements with insertion between the first premolars and the major maxillary molars (n = 60; 10 per group). Three of the six groups underwent mechanical cycling. The experimental groups were: G1 - conventional fixed prosthesis; G2 - conventional cyst prosthesis; G3 - prosthesis with reinforcement of the mesh positioned vertically; G4 - Prosthesis with reinforcement of the mesh positioned in the cycled vertical; G5 - Prosthetics with mesh reflux positioned horizontally; G6 - Prosthetics with mesh reinforcement positioned horizontally cycled. All groups underwent maximum fracture loading test (EMIC). The results do not present a statistic between the groups. It was concluded that the use of the nylon mesh provided stability, even after fracture of the part, as parts do not separate, besides, the results obtained in vitro could validate the data in silica / Mestre

No description available.

Atletas de diversas modalidades esportivas estão sujeitos a sofrer lesões no complexo dento-maxilo-facial por diversos impactos mecânicos, como choques contra o solo, outros atletas, bolas, etc. As principais preocupações dos cirurgiões-dentistas em relação a esses choques são as lesões irreversíveis em elementos dentais e/ou bases ósseas. A melhor estratégia para controlar a ocorrência e gravidade dessas lesões é a utilização de protetores bucais invidualizados, que além da proteção, não diminuem o desempenho dos atletas. Para avaliar a eficiência dos protetores bucais a análise por elementos finitos foi empregada, e o objetivo do presente trabalho foi avaliar o comportamento mecânico do protetor em EVA de diversas espessuras diferentes. A análise por elementos finitos foi conduzida utilizando a geometria de um incisivo central obtida por meio de tomografia computadorizada. A simulação foi constituída pelo esmalte e dentina do elemento dental, protetor bucal em EVA e uma esfera de borracha que era o objeto impactante. As geometrias foram transformadas em elementos sólidos e apenas os nós do terço apical da dentina radicular foram fixados. O pré-processamento foi realizado no Hypermesh® e no LS-PrePost®,o processamento foi feito pelo software LS-DYNA®.O estudo foi observado em 3D. Foram observadas a máxima e a tensão mínima principal no esmalte e na dentina em cinco variáveis: com protetor bucal de 1mm, 2mm, 3mm e 4mm, e como grupo controle foi utilizada uma geometria simples sem EVA. A tensão mínima principal no esmalte ocorreu no centro da face vestibular e seu valor foi maior sem o protetor bucal e diminuiu com o aumento da espessura do protetor, a tensão máxima no esmalte ocorreu na união entre esmalte e dentina na face vestibular. Na dentina a tensão máxima principal ocorreu na face vestibular da raiz e a tensão mínima ocorreu na face palatina. Os resultados mostraram que o protetor bucal foi benéfico, diminuindo as tensões compressivas e de tração no esmalte, porém não mostrou significante melhoria quando as tensões na dentina foram comparadas. / In different sports, the athletes are likely to experience injuries on teeth, soft tissue and bone, usually by mechanic trauma, such as falling on the ground, shocking against other player, balls, etc. The dentist main concerns are the permanent injuries on teeth and bone complex. The best strategy to fight these impairments still is the prevention, using individualized sports mouthguards. To evaluate the efficacy of the mouthguards, the finite element analysis was used, and the purpose of the present study was to evaluate the mechanical behavior to the EVA mouthguard on different thickness. The finite element analysis was made using geometry of a superior central incisor, which was acquired by computerized tomography. The simulation was made with enamel and dentin from the tooth, an EVA mouthguard and a rubber sphere that was the impacting object. All geometries was transformed into solid elements and the knots on the apical third of the root dentin were fixed. The pre-process was made using Hypermesh® and LS-PrePost® e and processing of data was made on LS-DYNA® software. The results were the maximum and minimum main stress on the enamel and dentin solids in five different situations: no mouthguard and mouthguard with thickness of 1mm, 2mm, 3mm and 4mm. The minimum main stress on the enamel was measured at the center of the vestibular surface and the higher value was observed with no mouthguard and the values decreased as the thickness of the mouthguard increased, the maximum main stress on enamel occurred near the amelodentin junction on the vestibular surface, but no significant changes were observed among the situations. As for the dentin the maximum main stress occurred on the buccal surface of the root, and the minimum main stress on the lingual surface. The results show that the mouthguard was efficient decreasing the compressive and tensile stress on enamel, but did not make significant improvement as on both stresses on dentin.