New modelling tools intended to contribute to the development of components for quieter vehicles are developed. The tools are based on continuum models for wave propagation in poro- and visco-elastic media. By using geometric attributes of the studied components, the computational cost may be radically decreased compared to traditional methods. By assigning known analytical functions for one or two of the spatial directions, the spatial dimension of the remaining numerical problem is reduced. This reduction of spatial dimensions is performed in two di↵erent ways. The first one treats wave propagation in infinitely extended homogeneous and hollowed cylindrical rods, or wave guides, consisting of visco-elastic media. The wave solutions obtained are then used to model rubber vibration isolators of finite length by mode-matching the fields to the radial boundary conditions of interest. The second one is a method for modelling rotationally symmetric multilayered structures consisting of poro-elastic, elastic and fluid domains. By using a harmonic expansion for the azimuthal spatial dependence, the original three-dimensional problem is split up into several, much smaller, two- dimensional ones, radically decreasing the computational load.Moreover, using a mixed measurement/modelling approach, the audible frequency range characteristics of a viscous damper from a truck is studied, illustrating the influence of the rubber bushings by which it is attached to surrounding structures.The modelling approaches presented in this thesis are intended as tools aiding the design process of new vehicles, enabling new technology striving for more sustainable vehicle concepts. More specifically, the tools aim to improve the modelling of sound and vibration properties which are often penalised when seeking new, more sustainable vehicle designs.

Durant la phase de construction des puits pétrolier, le ciment est coulé dans l'espace annulaire entre le cuvelage et la roche environnante. La gaine de ciment a pour but de tenir le cuvelage, garantir l'étanchéité des puits pétroliers, ou des réservoirs de stockage de CO2, et de protéger le cuvelage de la corrosion. Au cours de la vie du puits, cette gaine de ciment est soumise tout le long du puits à des sollicitations thermiques et mécaniques qui varient au cours du temps et qui peuvent modifier ses propriétés et altérer son étanchéité. L'objet de cette thèse est d'étudier l'effet de la température et des contraintes sur les propriétés mécaniques de la pâte de ciment en cours de prise et de la pâte de ciment durcie. L'approche est basée sur une étude expérimentale qui combine des essais calorimétriques, des mesures de vitesse des ondes et des essais oedométriques avec le système des cellules STCA (Slurry To Cement Analyzer) sur le ciment en cours de prise ainsi que des essais de compression uniaxiale et triaxiale sur la pâte de ciment durcie. Les résultats expérimentaux ont montré que la température et la pression accélèrent la cinétique d'hydratation et que la température affecte significativement les propriétés élastiques du matériau tandis que la pression ne les influence pas pour une gamme de pression limitée à 20MPa. Une modélisation de la cinétique d'hydratation associée à une technique d'homogénéisation est proposée afin d'interpréter les essais. On a mis aussi en évidence que lorsque la prise se fait sous contraintes mécaniques, des déformations irréversibles peuvent se développer dans la pâte de ciment, ce qui peut conduire à la formation d'un micro-annulaire entre la gaine ciment, le cuvelage et la formation géologique. Le comportement différé de la pâte de ciment durcie a été étudié à partir d'essais de fluage uniaxiaux et d'essais de compression isotrope. Les essais ont mis en évidence que le fluage sous chargement uniaxial est plus important pour un ciment hydraté à une température plus élevée, ce qui est attribué à une microstructure plus hétérogène. Un modèle visco-endommageable permettant de reproduire les phases de fluage primaire et tertiaire a été développé. Les essais de compression isotrope drainés et non-drainé isothermes sous forte contrainte ont montré un comportement différé avec hystérésis lors de cycles décharge-recharge. Ces essais ont été analysés à partir d'un modèle de comportement poro-visco-plastique. Le comportement élastoplastique à court terme a été abordé à l'aide des essais triaxiaux sous chargement déviatorique drainé. Ces essais ont mis en évidence que la température d'essai affecte fortement la surface de charge initiale et les déformations tandis qu'elle ne modifie pas significativement la surface de rupture. Un modèle de plasticité avec une surface de charge fermée et un écrouissage dépendant des déformations plastiques accumulées a été développé pour décrire ces essais. Enfin, une étude préliminaire sur les effets des cycles mécaniques et thermiques a été menée. Des cycles thermiques ne dépassant pas la température d'hydratation ne semblent pas affecter les propriétés mécaniques du matériau. Cependant, une dégradation très rapide avec le nombre de cycles mécaniques a été mise en évidence lorsque la contrainte dépasse 60% de la résistance en compression simple

Les travaux de modélisations présentes dans cette thèse concernent l'étude du comportement hydro-poro-mécanique des géomatériaux par l'approche numérique de changement d'échelle. Il s'agit d'exploiter un modèle géomatériaux conceptuel, du code de calcul par la méthode élément finis étendu (XFEM) ou IIM, conjointement avec des techniques d'homogénéisation, pour l'obtention des lois de comportement macroscopique tirées des relations de passage Micro-Macro. Dans ce modèle conceptuel, le volume élémentaire représentatif des milieux hétérogène est composé d'une matrice argileuse contenant des inclusions de minéraux de quartz et de calcite ou des pores. D'abord, cette procedure avec XFEM a été effectuée pour la détermination des propriétés effectives isotropes. Ensuite, Une étude sur l'influence de la distribution, la morphologie, et l'orientation des inclusions sur le comportement équivalent dans le domaine de l'élasticité linéaire a été réalisée par traverser nombreuse études numériques. Dans un troisièmes temps, nous avons modélisée le comportement mécanique non linaire des géomatériaux en utilisant XFEM et la méthode Newton-Raphson modifiée. Enfin, la modélisation du comportement hydraulique est réalisée par la méthode IIM, elle a été validée par la comparaison avec l'approche analytique.

Biot's theory when applied to homogeneous media (involving the macroscopic flow mechanism) cannot explain the high level of attenuation observed in natural porous media over the seismic frequency range. However, several successful mesocopic inhomogeneity models have been developed to account for P wave attenuation. In this thesis I further develop the approaches to tackle S wave velocity and attenuation, to simulate transient wave propagation in poroelastic media, and to construct new models for determining the effective parameters of porous media containing mesoscopic inhomogeneities. As an important application of the double-porosity dual-permeability (DPDP) model, I have reformulated the effective Biot model using the total-field variables. This gives rise to new and more general governing equations than the previous approach based on the host phase field variables (which become a special case of the more general treatment). The analytical transient solution and dispersion characteristics for the double-porosity model and also for a poro-viscoacoustic model are derived over the entire frequency range for a homogeneous medium. The comparison between the results of the two models shows that dissipation by local mesoscopic flow of the double porosity model is very hard to fit by a single Zener element over a broad band. I chose the relaxation function to approximate the dispersion behaviour of the double porosity model just around the source centre frequency. It is shown that for most water-filled sandstones having a double porosity structure, wave propagation can be well described by the poro-viscoaoustic model with a single Zener element in the seismic frequency range. The transient solution for heterogeneous double porosity media is obtained by a numerical pseudospectral time splitting technique. This method is extended to 2.5-D poro-viscoelastic media to capture both P and S wave behaviour. I also demonstrate that if the frequency is below several Hz, then a single Kelvin-Voigt element gives an even better result than a single Zener element. I propose a two-phase permeability spherical inclusion model and obtain the dispersion curves of phase velocity and dissipation factor for the composite. I then determine the effective dynamic permeability of porous media with mesoscopic heterogeneities over the whole frequency range. This result is used to check the validity of other measures of effective dynamic permeability, deduced from the effective hydraulic permeability by replacing the permeability of the components with their dynamic values as determined from the Johnson, Koplik and Dashen (JKD) model. I also investigate the scattering of plane transverse waves by a spherical porous inclusion embedded in an infinite poroelastic medium. The vector displacement wave equations of Biot’s theory are solved as an infinite series of vector spherical harmonics for the case of a plane S-wave incidence. Then, the non-self-consistent theory is used to derive the dispersion characteristics of shear wave velocity and attenuation for a porous rock having mesoscopic spherical inclusions which are designed to represent either the patchy saturation model or the double porosity model with dilute concentrations of identical inclusions. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1457632 / Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2009

No presente trabalho analisa-se o comportamento do aço de reforço ante à corrosão, com o uso dos inibidores: nitrito de sódio, fosfato de sódio e etalonamina, na água de poros contaminada com cloreto, e no concreto com a finalidade de analisar seus resultados e seus mecanismos diferenciados. Para cumprir este objetivo o presente trabalho divide-se em duas etapas: uma primeira etapa baseada em simular sinteticamente a água de poro de um concreto, cuja solução é KOH 28g/l+NaOH 4g/l. Essa água de poro é simulada em ambiente marinho, cuja solução é KOH 28g/l + NaOH 4g/l+NaCl 35g/l, e a esta solução referência incorporamse os inibidores (20g/l da cada um). Realizaram-se ensaios de espectroscopia de impedância eletroquímica (EIE) (após 3 e 72 horas de imersão) e curvas de polarização (após 72 horas de imersão) com vistas a obter respostas da cinética da corrosão ante a cada solução. Obteve-se o melhor comportamento para a água de poros. No caso da água de poro contaminada por cloretos, o melhor comportamento se obteve para o inibidor nitrito de sódio. Na segunda etapa adotou-se apenas o inibidor nitrito de sódio, pois estatisticamente as eficiências dos três inibidores foram muito similares. Analisou-se o nitrito de sódio em amostras reais de concreto armado contaminado com cloreto de sódio. Para isso se elegeram dois tipos de cimentos (CP IV e CP V) e três relações água-cimento (a/c-0.4, a/c-0.5, a/c- 0.65). Para simular o ambiente marinho, realizaram-se ensaios acelerados de cloretos. Comparam-se métodos de análises simuladas sinteticamente e reais, concluindo-se em ambos meios, embora fossem um solido e outro líquido o inibidor Nitrito de Sódio aumento a sua eficiência com os ciclos de exposição. / In this paper it is analyzed the behavior of reinforcing steel against corrosion using inhibitors: sodium nitrate, sodium phosphate and ethanolamine in water contaminated with chlorides pore and concrete, in order to analyzing the results and different mechanisms. To meet the objective of this work, it was divided into two stages, a first stage based on synthetically simulate the pore water of a concrete, through the following solution KOH 28g/l+NaOH 4g/l, this same solution simulated pore water to a marine environment it would be KOH 28g/l + NaOH 4g/l+NaCl 35g/l, it is then incorporated into both reference solutions inhibitors in a proportion, (20g/l de cada um). Assays were performed electrochemical impedance spectroscopy (EIE) (last 3 hours and 72 hours of immersion) and polarization curves (last 72 hours of immersion) in order to obtain responses corrosion kinetics in each solution. the best performance was obtained in the pore water. In the case of water contaminated with chlorides pore, the best performance was obtained in the presence of sodium nitrite inhibitor. In the second step was performed only with the inhibitor sodium nitrate, as statistically efficiencies of the three inhibitors were similar. Sodium nitrate was analyzed in real samples of reinforced concrete contaminated with chlorides of sodium. So they were chosen two types of cement CP- IV and CP-V, cement water three relationships 0.4, a/c-0.5, a/c- 0.65. In this case to simulate the marine environment, accelerated tests were performed chloride. They were compared the methods of analysis, simulated synthetically and simulated in real concrete.

No presente trabalho analisa-se o comportamento do aço de reforço ante à corrosão, com o uso dos inibidores: nitrito de sódio, fosfato de sódio e etalonamina, na água de poros contaminada com cloreto, e no concreto com a finalidade de analisar seus resultados e seus mecanismos diferenciados. Para cumprir este objetivo o presente trabalho divide-se em duas etapas: uma primeira etapa baseada em simular sinteticamente a água de poro de um concreto, cuja solução é KOH 28g/l+NaOH 4g/l. Essa água de poro é simulada em ambiente marinho, cuja solução é KOH 28g/l + NaOH 4g/l+NaCl 35g/l, e a esta solução referência incorporamse os inibidores (20g/l da cada um). Realizaram-se ensaios de espectroscopia de impedância eletroquímica (EIE) (após 3 e 72 horas de imersão) e curvas de polarização (após 72 horas de imersão) com vistas a obter respostas da cinética da corrosão ante a cada solução. Obteve-se o melhor comportamento para a água de poros. No caso da água de poro contaminada por cloretos, o melhor comportamento se obteve para o inibidor nitrito de sódio. Na segunda etapa adotou-se apenas o inibidor nitrito de sódio, pois estatisticamente as eficiências dos três inibidores foram muito similares. Analisou-se o nitrito de sódio em amostras reais de concreto armado contaminado com cloreto de sódio. Para isso se elegeram dois tipos de cimentos (CP IV e CP V) e três relações água-cimento (a/c-0.4, a/c-0.5, a/c- 0.65). Para simular o ambiente marinho, realizaram-se ensaios acelerados de cloretos. Comparam-se métodos de análises simuladas sinteticamente e reais, concluindo-se em ambos meios, embora fossem um solido e outro líquido o inibidor Nitrito de Sódio aumento a sua eficiência com os ciclos de exposição. / In this paper it is analyzed the behavior of reinforcing steel against corrosion using inhibitors: sodium nitrate, sodium phosphate and ethanolamine in water contaminated with chlorides pore and concrete, in order to analyzing the results and different mechanisms. To meet the objective of this work, it was divided into two stages, a first stage based on synthetically simulate the pore water of a concrete, through the following solution KOH 28g/l+NaOH 4g/l, this same solution simulated pore water to a marine environment it would be KOH 28g/l + NaOH 4g/l+NaCl 35g/l, it is then incorporated into both reference solutions inhibitors in a proportion, (20g/l de cada um). Assays were performed electrochemical impedance spectroscopy (EIE) (last 3 hours and 72 hours of immersion) and polarization curves (last 72 hours of immersion) in order to obtain responses corrosion kinetics in each solution. the best performance was obtained in the pore water. In the case of water contaminated with chlorides pore, the best performance was obtained in the presence of sodium nitrite inhibitor. In the second step was performed only with the inhibitor sodium nitrate, as statistically efficiencies of the three inhibitors were similar. Sodium nitrate was analyzed in real samples of reinforced concrete contaminated with chlorides of sodium. So they were chosen two types of cement CP- IV and CP-V, cement water three relationships 0.4, a/c-0.5, a/c- 0.65. In this case to simulate the marine environment, accelerated tests were performed chloride. They were compared the methods of analysis, simulated synthetically and simulated in real concrete.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work we present a computational study of the electroporation process of lipid membranes in the presence of water. First, we developed an investigation of the formation of pores through simulations based on classical molecular dynamics using NAMD code. Subsequently we developed ab initio study using density functional theory, as implemented in the SIESTA code. This analysis showed the formation of pores within the lipid bilayer 1ns after the application of external electric field, 300 K. We found that set temperatures above 300 K may reduce the simulation time. We also observed a rearrangement of water molecules of a Okuno Tanioka cone due to the action of the electric field. Interestingly, this induced an increase of the number of hydrogen bonds, which was not observed using apolar molecules such as chloroform. After, we performed the analysis of structural and electronic properties of the structures of phospholipids,which were extracted from the molecular dynamics calculations. It is noteworthy that the action of the electric field changed the energy gap of both the structures of isolated phospholipid as for the lipid bilayer configuration. Through maps of electrostatic potential, we showed that the electric field leads to a polarization of phospholipid, which induced a torque in the electric dipole moments of the water molecule. The rotation of the electric dipole moments gave rise to stress in the lipid bilayer, which by itself was not enough to break it. In summary, the presence of water was critical since under the action of an electric field the molecules rearranged to form a cone. This fact, associated with the weakening of the lipid membrane due the stress from the realignment electric dipole, was the responsible for the poration process. / Neste trabalho, apresentamos um estudo computacional do processo de eletroporação de membranas lipídicas na presença de água. Na primeira etapa, realizamos a dinâmica da formação de poros através de simulações baseadas na dinâmica molecular clássica, utilizando o código NAMD. Posteriormente, desenvolvemos um estudo ab initio, empregando a teoria do funcional da densidade, conforme implementada no programa SIESTA. Os resultados da primeira análise mostraram a formação de poros no interior da bicamada após 1ns de aplicação de um campo elétrico externo, a uma temperatura de 300 K. Também verificamos que, para temperaturas acima de 300 K, esse tempo se reduz. Observamos um rearranjo das moléculas de água na forma de um cone de Okuno Tanioka devido à ação do campo elétrico. Isso ocasiona um aumento no número de ligações de hidrogênio das mesmas, o que não foi observado com o uso de moléculas apolares como o clorofórmio. Na segunda etapa, realizamos a análise das propriedades eletrônicas e estruturais, utilizando as estruturas dos fosfolipídios provindas dos cálculos de dinâmica molecular. Mostramos que a ação do campo elétrico modifica o gap de energia tanto da estrutura do fosfolipídio isolado quanto para a configuração de bicamada lipídica. Através dos mapas do potencial eletrostático, mostramos que a ação do campo elétrico leva a uma polarização do fosfolipídio ocasionando um torque no momentos de dipolo elétrico da molécula. A rotação dos momentos de dipolo elétrico causa um estresse na bicamada, que por si só não é capaz de rompe-la. Dessa forma, a presença da água é fundamental, pois diante a ação do campo elétrico as moléculas se reordenam arranjando-se de maneira a formar um cone. Este fato, associado ao enfraquecimento da membrana lipídica, devido ao estresse causado pelo realinhamento nos momentos de dipolo elétrico, são a origem do processo de poração.

Legionella pneumophila, o agente etiológico da doença dos Legionários, é conhecida por desencadear a formação de poro em membranas de macrófagos derivados de medula óssea (BMMs) por mecanismos dependentes do sistema de secreção do tipo IV conhecido como Dot/Icm. Neste trabalho, foram utillizados vários mutantes de L. pneumophila em combinação com camundongos nocautes para investigar os fatores bacterianos e do hospedeiro envolvidos na formação de poro em BMMs. Observamos que apesar da atividade do Dot/Icm, a formação de poro não ocorre em BMMs deficientes para caspase-1 e Nlrc4. A formação de poro foi temporalmente associada com a secreção de IL-1b e precedeu a lise celular e a piroptose. A formação de poro foi dependente do Dot/Icm, mas independente de várias proteínas efetoras, da multiplicação bacteriana e da síntese de novo de proteínas. A flagelina, a qual é conhecida em ativar o inflamassoma de Nlrc4, foi necessária para a formação de poro; a bactéria mutante flaA falhou em induzir a permeabilização celular. Consequentemente, a transfecção da flagelina purificada foi suficiente para desencadear a formação de poro independente da infecção. Utilizando 11 diferentes espécies de Legionella, nós observamos alta formação de poro em resposta à L. micdadei, L. bozemanii, L. gratiana, L. jordanis e L. rubrilucens, e essa resposta estava correlacionada com a expressão de flagelina por essas espécies. Além disso, verificamos que as proteínas Asc e Caspase-11 apresentam fenótipo intermediário na formação de poro, sugerindo que outras vias podem estar envolvidas no processo. Observamos também que a formação de poro desencadeada por L. pneumophila difere daquela induzida pelo ATP. Em conjunto, nossos resultados sugerem que a formação de poro não é uma resposta específica de L. pneumophila nem o resultado de dano da membrana induzido pelo Dot/Icm. Ao invés disso, a formação de poro é uma resposta do hospedeiro altamente coordenada, dependente dos componentes do inflamassoma Nlrc4 e caspase-1 e é desencadeada em resposta a bactérias que expressam o sistema de secreção do tipo IV e flagelina. / Legionella pneumophila, the etiological agent of Legionnaires disease, is known to trigger pore formation in bone marrow-derived macrophages (BMMs) by mechanisms dependent on the type IVB secretion system known as Dot/Icm. Here, we used several mutants of L. pneumophila in combination with knockout mice to assess the host and bacterial factors involved in pore formation in BMMs. We found that regardless of Dot/Icm activity, pore formation does not occur in BMMs deficient in caspase-1 and Nlrc4/Ipaf. Pore formation was temporally associated with IL-1b secretion and preceded host cell lysis and pyroptosis. Pore-forming ability was dependent on bacterial Dot/Icm but independent of several effector proteins, multiplication and de novo protein synthesis. Flagellin, which is known to trigger the Nlrc4 inflammasome, was required for pore formation as flaA mutant bacteria failed to induce cell permeabilization. Accordingly, transfection of purified flagellin was sufficient to trigger pore formation independent of infection. By using 11 different Legionella species, we found robust pore formation in response to L. micdadei, L. bozemanii, L. gratiana, L. jordanis and L. rubrilucens, and this trait correlated with flagellin expression by these species. Furthermore, we found that Asc and Caspase-11 showed an intermediate phenotype in pore formation, suggesting that other pathways may be involved in this process. We also observed that the pore formation triggered by L. pneumophila differs from the pore induced by ATP. Together, the results suggest that pore formation is neither L. pneumophilaspecific nor the result of membrane damage induced by Dot/Icm activity; instead, it is a highly coordinated host cell response dependent on host Nlrc4 and caspase-1 and on bacterial flagellin and type IV secretion system.

In this dissertation, theoretical, computational, and experimental methodologies are introduced to determine the rate-dependent material properties of the brain tissue. Experiments have shown that the brain tissue is significantly rate-dependent. To examine the range of strain rates at which trauma might happen, a validated finite element (FE) human head model was initially employed to examine the biomechanics and dynamic behavior of the head and brain under impact and blast loads. The strain rates to cause traumatic brain injury (TBI) were found to be in the range of 36 to 241 1/s, under these types of loadings. These findings provided a good estimation prior to exploring the required experiments for characterizing the brain tissue. The brain samples were tested by employing unconfined compression tests at three different deformation rates of 10 (n= 10 brain samples), 100 (n=8), and 1000 mm/sec (n=12). It was found that the tissue exhibited a significant rate-dependent behavior with various compression rates. Two different material characterization approaches were proposed to evaluate the rate-dependent mechanical responses of the brain. In the first approach, based on the parallel rheological framework, a single-phase viscoelastic model which captures the key aspects of the rate-dependency in large strain behavior was introduced. The extracted material parameters showed an excellent constitutive representation of tissue response in comparison with the experimental test results (R^2=0.999). The obtained material parameters were employed in the FE simulations of the brain tissue and successfully verified by the experimental results. In the second approach, the brain tissue is modeled as a biphasic continuum, consisting of a compressible solid matrix fully saturated with an incompressible interstitial fluid. The governing equations based on conservation of mass and momentum are used to describe the solid-fluid interactions. This viscoelastic biphasic model can effectively estimate the rate-dependent tissue deformations, the hydrostatic pressure as well as fluid diffusion through the tissue. Although both single-phasic, as well as bi-phasic models, can successfully capture the key aspects of the rate-dependency in large strain deformation, it was shown the biphasic model can demystify more phenomenological behavior of this tissue that could not be perceived with yet established, single-phasic approaches.

No description available.