No description available.

Objectives: We evaluate the movement patterns of left-sided radicular syndrome patients on the basis of intervertebral disc herniation L4/L5 or L5/S1 and test group to verify expected verge asymmetry between selected muscles and changes in their timing. Participants: 10 patients with left-sided radicular syndrome caused by intervertebral disc herniation were objects of the reserarch L4/L5 or L5/S1 (7 men, 3 women, average age 37,4 ± 10,67 years old). 6 healthy individuals without vertebrogenic problems were part of the reserarch (2 men, 4 women, average age 27,4 ± 2,6 years old) Methods: During specific tests focused on stabilizing function of musculosceletal system, selected muscles activity was recorded for both groups by SEMG Data analysis: The variation significance between experimental and test group was evaluated by two-tailed t-test. Significance level of p=0.05 was selected for statistical hypothesis testing. Results: We have proved statistically significant asymmetry between right and left side for patients with radicular syndrom. Significant variations were found for muscles timing between group with herniation and test group. Conclusion: Selected muscles activity and involvement sequence changes (timing) were found for patients with intervertebral disc herniation during postural tests,...

La caractérisation du comportement des matériaux bitumineux est primordiale pour pouvoir dimensionner les structures de chaussées, mais aussi pour prédire de manière plus précise leur durée de vie. En effet, ces matériaux sont soumis à des phénomènes complexes, mécaniques, thermiques, physiques et chimiques qui apparaissent souvent de manière couplée. Devant la complexité des problèmes observés et avec l’apparition des nouveaux matériaux et nouvelles techniques de fabrication, des études avancées de laboratoire et des modélisations rhéologiques sont nécessaires. Les méthodes existantes permettent de caractériser les matériaux en laboratoire grâce à l’utilisation de presses hydrauliques très couteuses. De plus, la plupart de ces essais ne sont pas adaptés à une utilisation directe sur chaussées. Dans cette thèse, un essai dynamique qui repose sur le phénomène de propagation d’onde a été développé pour caractériser les enrobés bitumineux dans le domaine viscoélastique linéaire. Il s’agit d’un essai non destructif, bien moins couteux que les essais existants et qui pourrait à terme s’adapter à une utilisation in-situ. Des méthodes complexes d’analyse inverse de propagation d’ondes en milieu viscoélastique ont été mises au point afin d’obtenir les propriétés thermomécaniques des enrobés bitumineux à partir des signaux mesurés expérimentalement. Les propriétés viscoélastiques linéaires de différents enrobés bitumineux déterminées à partir de l’essai dynamique développé ont été comparées aux résultats obtenus avec des essais cycliques plus conventionnels de traction-compression. / Characterizing the behaviour of bituminous materials is essential for the design of pavement structures and to predict their service life more accurately. Indeed, these materials are subjected to complex phenomenon, mechanical, thermal, physical and chemical that are often coupled. Due to the complexity of the phenomenon observed and with the emergence of new materials and new production techniques, advances laboratories studies and rheological modelling are necessary. With the existing methods, it is possible to characterize the materials in laboratories using expensive hydraulic presses. Moreover, most of these tests cannot be used directly on pavement structures. In this thesis, a dynamic test based on wave propagation was developed to characterize bituminous mixtures in the linear viscoelastic domain. It is a nondestructive test, far less expensive than the existing tests and that could be adapted for in situ measurements. Complex methods of inverse analysis of wave propagation in a viscoelastic medium were developed to obtain the thermomechanical properties of bituminous mixtures from the signals measured experimentally. The linear viscoelastic properties of different mixtures obtained from the developed dynamic test were compared to the results of more conventional cyclic tension-compression tests.

L'objectif de ces travaux de thèse est de proposer des approches de modélisation et d'expérimentation de l'impact de structures déformables et indéformables sur différents milieux. Différents modèles analytiques et des simulations numériques sont développés en comparaison aux résultats expérimentaux. Une première partie se consacre à la caractérisation de la similitude entre la réponse à l'impact à l'eau d'un solide et la réponse d'un solide impactant une structure déformable. Des simulations éléments finis (EF) et SPH sont réalisées pour l'impact à l'eau d'un tube cylindrique (sans rupture). Un modèle analytique d'impact à l'eau est proposé pour prédire l'évolution de l'effort (pic, durée). L'analyse des résultats permet de dimensionner un programmateur d'impact solide reproduisant le pic d'effort. Des simulations EF de l'impact sur un tube cylindrique, à géométrie adapté, dans la direction longitudinale, sont réalisées et comparées à quelques expériences tests. Le «flambage dynamique» (dû au comportement inélastique du matériau et aux ondes de déformations) des tubes est alors observé. Une seconde partie traite du cas de la perforation sous impact d'une tôle mince à faibles vitesses d'impact (< 10 m/s, vitesse de déformation < 1000 s-1). Des essais sur puits de chute instrumenté (force, déplacement, déformée de tôle, avancée de fissure) sont analysés. Des simulations EF en éléments coques avec un critère de rupture ductile par endommagement sont réalisées. Les paramètres de rupture dynamique sont identifiés par méthode inverse à l'aide d'essais de résilience Charpy sur l'alliage d'aluminium de désignation 2024 T3. Une analyse des pics de force lors de l'impact permet une meilleure compréhension des mécanismes de perforation. En parallèle, un nouveau modèle analytique, basé sur les énergies impliquées lors de l'impact, est proposé et comparé aux simulations EF. L'étude numérique de la perforation est étendue aux grandes vitesses d'impact et de déformation (100 - 1000 m/s, vitesse de déformation <100 000 s-1) pour identifier les transitions des différents mécanismes de perforation connus (pétalisation, fragmentation des pétales, fragmentation complète). / The objective of this work is to propose approaches to model and to assess experimentally the structural impact on different media. A variety of analytic models and numerical simulations are developed comparing to experimental results. The first part of this work presents a discussion on the similitude between a water impact and an impact on a deformable solid structure. Water impact simulations of a deformable cylinder (without rupture) are performed by finite elements (FE, Coupled Eulerian Lagrangian) and SPH analysis. An analytical model of water impact is proposed for the prediction of peak force evolution. The analysis of results permits to design an impact programmer reproducing this peak force. FE longitudinal impact simulations on cylindrical tubes, with an adapted geometry, are performed and compared with some experiments. The “dynamic buckling” of tubes under impact (due to the material inelastic behavior and to strain waves) is observed. The second part deals with the low velocity perforation (< 10 m/s, strain rate < 1000 s-1) of thin plates. Some experiments on an instrumented drop test (force, displacement, plate shape, crack propagation) are analyzed. Shell FE simulations, with a damage rupture criteria implemented are performed. Parameters are identified by inverse method with the help of Charpy tests made on 2024 T3 aluminum alloy. An analysis of the peak force, during impact, leads to a good understanding of the perforation mechanism. In parallel, a new analytical model, based on an energetic approach of the perforation, is proposed and compared with FE simulations. The numerical perforation study is extended to high velocities and high strain rates (100 - 1000m/s, strain rate < 100 000 s-1) in order to identify different well-known transitions of perforation (Petalisation, petals' fragmentation, total plate's fragmentation).

Orientador: Antonio Celso Fonseca de Arruda / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-26T12:30:34Z (GMT). No. of bitstreams: 1 Souza_VictorCesarde_M.pdf: 2933493 bytes, checksum: ad3ab87009ea90dcb39a5fd7757c4c9a (MD5) Previous issue date: 2015 / Resumo: Projeto, construção e avaliação de desempenho de simulador de testes de impacto de dispositivos de retenção infantis. A solução construtiva objetivou simular uma colisão automobilística e utiliza manequins representativos de crianças para fins de efeito demonstrativo e de convencimento sobre a necessidade de se reter crianças em veículos automotores. Trata-se de um trenó, guiado, que se desloca sobre trilhos sendo tracionado por cabo de aço e, capaz de, sem dano permanente, colidir contra uma barreira de impacto deformável. O equipamento foi concebido para fácil instalação em locais públicos e utiliza motor de indução para tracionar o cabo de aço e sistemas de automatização de aferição da velocidade, de aceleração e parada do motor. A instrumentação eletrônica utilizada na montagem do simulador permite avaliação do desempenho do equipamento para velocidades de até 20 Km/h / Abstract: Design, construction and evaluation of impact tests simulator performance of child restraint systems. The constructive solution aimed to simulate an automobile collision and uses dummies representing children for the purposes of demonstration effect and conviction about the need to retain children in motor vehicles. This is a sled, guided, moving on rails being pulled by steel cable and capable of, without permanent damage, crash into a deformable barrier impact. The equipment is designed for easy installation in public places and induction motor uses to pull the cable and speed measurement automation systems, acceleration and engine stop. The electronic instrumentation used in the simulator assembly allows assessment of equipment performance for speeds up to 20 km / h / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Chatter vibration is a common problem for the manufacturing industry that limits the productivity, accuracy and surface quality of machined parts. This study is focused on the out of process methods, such as Stability Lobe Diagrams (SLD), that ensure the selection of the optimal cutting parameters in which the machining process is stable. Previous studies have found that the dynamic properties of the spindle change with the rotational speed. This fact can also affect the accuracy of the SLD predictions, since, the traditional structural dynamic tests such as the Experimental Modal Analysis (EMA) are carried out at static state. An alternative method for the calculation of speed - dependant SLD using a Contactless Excitation Response System (CERS) was proposed. The modal characteristics, such as natural frequencies and damping ratio were determined by EMA tests carried out at idle state whereas CERS measurements were performed at increasing rotational speeds up to 14000 rpm. Subsequently, the SLD at static and dynamic state were computed. Finally, it was concluded that there was not a significant variation of the dynamic properties and SLD prediction with spindle speed at the tested speed range (0 rev/min to 14000 rev/min). / Chatter är ett vanligt problem inom tillverkningsindustrin som begränsar produktiviteten och minskar noggrannheten och kvalitén på bearbetade ytor. Denna studie fokuserar på processkilda metoder, till exempel stabilitetsdiagram (SLD), vilka säkerställer valet av optimala skärparametrar för en stabil skärprocess. Tidigare studier har visat att spindelns dynamiska egenskaper är beroende av rotationshastigheten. Detta påverkar även noggrannheten vid skattningen av SLD eftersom traditionella strukturdynamiska tester, som experimentell modalanalys (EMA), utförs under statiskt tillstånd. En alternativ metod för bestämning av hastighetsberoende SLD med hjälp av ett beröringsfritt excitering- och svarssystem (CERS) föreslås. De modala egenskaperna, som till exempel egenfrekvens och dämpning, bestämdes med hjälp av EMA med stillastående spindel medan mätningar med CERS utfördes med ökad rotationshastighet upp till 14000 varv/min. Efter detta beräknades SLD för de båda fallen. Till sist drogs slutsatsen att testerna inte påvisade någon större skillnad, vare sig dynamiska egenskaper eller SLD skattning, för spindelhastigheter inom det testade intervallet (0 till 14000 varv/min).

Este trabalho apresenta estudos, ensaios e análises de resultados a respeito do comportamento à fadiga das estruturas de concreto armadas com barras isoladas e telas soldadas, começando pelas lajes de pontes, seus elementos mais sensíveis à fadiga. A parte experimental desta pesquisa consiste na investigação experimental do comportamento à fadiga de lajes de concreto armado, executadas com e sem pré-lajes armadas com barras de aço isoladas ou em tela soldada. Foram realizados ensaios de fadiga de barra ao ar em 36 corpos de prova de CA50 f10 mm, isoladas e em tela, com o objetivo de construir a Curva de Wöhler dessas barras de produção nacional. Além disso, foram ensaiadas 20 lajes executadas com e sem pré-lajes de concreto, montadas com diversas configurações de armadura, submetidas a ensaios estáticos e dinâmicos. A configuração de armadura adotada nas lajes da pesquisa foi baseada nas utilizadas com freqüência neste tipo de elemento das pontes. A escassez de dados precisos a respeito do comportamento de lajes armadas com barras ou com telas soldadas de fabricação brasileira submetidas a ações cíclicas conduziu ao propósito de se elaborar uma pesquisa de caráter experimental sobre esse tema, cujos resultados e conclusões pudessem fornecer informações mais precisas a respeito do desempenho das lajes. / This research presents the studies, tests and the analysis of the results about the behavior of concrete structures reinforced with rebars or steel mesh due to fatigue loading, starting with bridge slabs which are the most susceptible elements to fatigue. The experimental part of this research consists in testing the behavior due to fatigue of concrete slabs, with or without pre-slabs and reinforced with continuous bars or steel mesh. Axial testing in air of 36 specimens of CA50 f10 mm in continuous bars and mesh were made in order to build the Wöhler Curve for Brazilian conditions. Beyond that, tests were made in 20 concrete slabs with pre-slabs, with several reinforcements arrangement. The 20 slabs were submitted to static and dynamic loading. The reinforcement configuration was based on the commonly used for these elements. The scarcity of more precise data about the behavior of concrete slabs reinforced with rebars or welded mesh made in Brazil submitted to cycle loading was the major reason to make a research based on the testing results about this theme, which results and conclusions are capable of producing more accurate information about the behavior of the slabs.

Este trabalho descreve um dormente monobloco de concreto protendido, o qual foi projetado para atender as características de uma via ferroviária brasileira. O dormente apresentou comportamento e resistência semelhantes aos dormentes de concreto comumente fabricados em vários países. A fim de verificar e aprovar o projeto, o dormente foi submetido a ensaios estáticos e dinâmicos, segundo as especificações da norma americana AREMA. Verificado e aprovado o projeto, dezoito dormentes foram fabricados sem e com fibras de aço, no teor de 60 kg/'M POT.3' (aproximadamente 0,75 % por volume). Ensaios estáticos e dinâmicos foram realizados em dormentes com e sem fibras de aço, com o objetivo de quantificar o benefício das fibras de aço à resistência estrutural do dormente. As fibras aumentaram o momento fletor de primeira fissura e o momento último, aumentaram significativamente a força de início de escorregamento dos fios de protensão e reduziram o espaçamento e a abertura das fissuras. As fibras também acrescentaram grande ductilidade aos dormentes e diminuíram a tensão nos fios de protensão, nos estágios mais avançados do carregamento. Sob ação dinâmica, as fibras reduziram a tensão nos fios de protensão mais tracionados em aproximadamente 100%, o que elevou significativamente a resistência do dormente à fadiga. Dormentes fabricados com menor força de protensão apresentaram excelente comportamento plástico e grande ductilidade, especialmente o dormente com fibras / This work describes a prestressed concrete monoblock railway sleeper designed according to a brazilian railway track. The sleeper was tested according to the Arema specifications in order to verify the project. The sleeper presented a structural behavior similar to the concrete railway sleepers used worldwide. After the preliminary tests, eighteen sleepers were manufactured without and with steel fibers contents of 60 Kg/'M POT.3' (about 0.75% by volume) and they were tested under static and dynamic loading to evaluate the fiber contribution on the resistance. Steel fibers increased the first crack and ultimate bending moments, reduced the deflection under ultimate load and increased significantly the slip force of the prestressing tendons. Reinforcing the sleeper with fibers also reduced the crack width and the spacing between cracks, adding higher ductility to the sleepers and decreasing the stress in the prestressing tendons under higher loads. The fibers increased significantly the fatigue strength under cyclic loading, decreasing the stress in the prestressing tendons in about 100%. The test results showed that sleepers manufactured with lower prestressed force have higher toughness, especially those reinforced with steel fibers

Este trabalho apresenta estudos, ensaios e análises de resultados a respeito do comportamento à fadiga das estruturas de concreto armadas com barras isoladas e telas soldadas, começando pelas lajes de pontes, seus elementos mais sensíveis à fadiga. A parte experimental desta pesquisa consiste na investigação experimental do comportamento à fadiga de lajes de concreto armado, executadas com e sem pré-lajes armadas com barras de aço isoladas ou em tela soldada. Foram realizados ensaios de fadiga de barra ao ar em 36 corpos de prova de CA50 f10 mm, isoladas e em tela, com o objetivo de construir a Curva de Wöhler dessas barras de produção nacional. Além disso, foram ensaiadas 20 lajes executadas com e sem pré-lajes de concreto, montadas com diversas configurações de armadura, submetidas a ensaios estáticos e dinâmicos. A configuração de armadura adotada nas lajes da pesquisa foi baseada nas utilizadas com freqüência neste tipo de elemento das pontes. A escassez de dados precisos a respeito do comportamento de lajes armadas com barras ou com telas soldadas de fabricação brasileira submetidas a ações cíclicas conduziu ao propósito de se elaborar uma pesquisa de caráter experimental sobre esse tema, cujos resultados e conclusões pudessem fornecer informações mais precisas a respeito do desempenho das lajes. / This research presents the studies, tests and the analysis of the results about the behavior of concrete structures reinforced with rebars or steel mesh due to fatigue loading, starting with bridge slabs which are the most susceptible elements to fatigue. The experimental part of this research consists in testing the behavior due to fatigue of concrete slabs, with or without pre-slabs and reinforced with continuous bars or steel mesh. Axial testing in air of 36 specimens of CA50 f10 mm in continuous bars and mesh were made in order to build the Wöhler Curve for Brazilian conditions. Beyond that, tests were made in 20 concrete slabs with pre-slabs, with several reinforcements arrangement. The 20 slabs were submitted to static and dynamic loading. The reinforcement configuration was based on the commonly used for these elements. The scarcity of more precise data about the behavior of concrete slabs reinforced with rebars or welded mesh made in Brazil submitted to cycle loading was the major reason to make a research based on the testing results about this theme, which results and conclusions are capable of producing more accurate information about the behavior of the slabs.

Este trabalho descreve um dormente monobloco de concreto protendido, o qual foi projetado para atender as características de uma via ferroviária brasileira. O dormente apresentou comportamento e resistência semelhantes aos dormentes de concreto comumente fabricados em vários países. A fim de verificar e aprovar o projeto, o dormente foi submetido a ensaios estáticos e dinâmicos, segundo as especificações da norma americana AREMA. Verificado e aprovado o projeto, dezoito dormentes foram fabricados sem e com fibras de aço, no teor de 60 kg/'M POT.3' (aproximadamente 0,75 % por volume). Ensaios estáticos e dinâmicos foram realizados em dormentes com e sem fibras de aço, com o objetivo de quantificar o benefício das fibras de aço à resistência estrutural do dormente. As fibras aumentaram o momento fletor de primeira fissura e o momento último, aumentaram significativamente a força de início de escorregamento dos fios de protensão e reduziram o espaçamento e a abertura das fissuras. As fibras também acrescentaram grande ductilidade aos dormentes e diminuíram a tensão nos fios de protensão, nos estágios mais avançados do carregamento. Sob ação dinâmica, as fibras reduziram a tensão nos fios de protensão mais tracionados em aproximadamente 100%, o que elevou significativamente a resistência do dormente à fadiga. Dormentes fabricados com menor força de protensão apresentaram excelente comportamento plástico e grande ductilidade, especialmente o dormente com fibras / This work describes a prestressed concrete monoblock railway sleeper designed according to a brazilian railway track. The sleeper was tested according to the Arema specifications in order to verify the project. The sleeper presented a structural behavior similar to the concrete railway sleepers used worldwide. After the preliminary tests, eighteen sleepers were manufactured without and with steel fibers contents of 60 Kg/'M POT.3' (about 0.75% by volume) and they were tested under static and dynamic loading to evaluate the fiber contribution on the resistance. Steel fibers increased the first crack and ultimate bending moments, reduced the deflection under ultimate load and increased significantly the slip force of the prestressing tendons. Reinforcing the sleeper with fibers also reduced the crack width and the spacing between cracks, adding higher ductility to the sleepers and decreasing the stress in the prestressing tendons under higher loads. The fibers increased significantly the fatigue strength under cyclic loading, decreasing the stress in the prestressing tendons in about 100%. The test results showed that sleepers manufactured with lower prestressed force have higher toughness, especially those reinforced with steel fibers