This thesis investigates the influence of wheelset structural flexibility and track flexibility on the vehicle-track dynamic interaction, mainly in terms of wheel-rail forces up to 200 Hz, using simulations and measurements. The previous knowledge in this field is first reviewed and summarized, then two case studies are selected for investigation. The first case study involves a locomotive running on a tangent track section at a speed of 140 km/h, while the second one deals with a newly designed motor coach running at two adjacent and tangent track sections with different track components and at speeds up to 280 km/h. For the locomotive case study, the wheelset dynamic properties are first investigated through experimental modal analysis (EMA) for a frequency range of 0-500 Hz, assuming free boundary conditions. The EMA results showed relatively low wheelset eigenfrequencies. A three-dimensional finite element (FE) model, which also includes the wheelset gear-box, is then developed and validated against the measurements for frequencies up to 200 Hz with good agreement. The FE results displayed a significant influence of the wheels’ flexibility on the wheelset’s total structural flexibility. In order to assure proper representation of the track flexibility the vertical and lateral dynamic track properties at a sleeper are measured through a special vehicle at standstill, and measured track irregularities are used. In the numerical simulations, the wheelset structural flexibility is introduced using the calculated eigenmodes above while so-called moving track models are used to model the track flexibility. The simulated wheel-rail forces are then validated against measured ones obtained from corresponding on-track measurements. Results from the simulations highlight the importance of proper track flexibility modelling and track data and also show a significant influence of the wheelset structural flexibility on the lateral track forces. For the motor coach case study, the wheelset dynamic properties are determined through numerical modal analysis using a rather simple FE model and a number of eigenmodes are then introduced in the simulations. The vertical and lateral track dynamic properties at selected track sections are measured using the standstill technique but rolling stiffness measurements, where the vertical track flexibility in the frequency range 5-50 Hz is measured continuously along the track, are also included. The track flexibility is introduced through moving track models. Measured track irregularity and vertical track roughness are also considered. Basic numerical simulations, where the calculated track forces are compared to measured ones, are first performed and followed by a set of parametric studies. The results display a significant influence of the track flexibility on vertical wheel-rail forces for frequencies above 80 Hz, with higher forces for the stiffer track (but weaker rails). The effect of wheelset structural flexibility on the lateral force is also confirmed. The parametric studies highlight the importance of track flexibility modelling and show that modifications of the vertical track receptance, motivated by uncertainties in the pertinent measurements, can improve the simulated forces. / QC 20100701

Este trabalho apresenta uma análise multicorpos de combinação veicular de carga com chassi de semirreboque flexível, para avaliação de dinâmica lateral. O contexto é dado por um breve panorama do transporte rodoviário de cargas no Brasil. No intuito de melhorar seus produtos, os fabricantes de implementos rodoviários têm utilizado metodologias de desenvolvimento baseadas em simulação virtual. Nessas circunstâncias, análises dinâmicas são realizadas, geralmente levando-se em conta a hipótese de corpos rígidos (não deformáveis). Subjetivamente, é sabido que a inclusão da flexibilidade em um modelo numérico o aproxima do fenômeno real, mas são raros os trabalhos que analisam quantitativamente essa diferença. Assim, neste estudo é proposta uma abordagem para consideração da flexibilidade estrutural do chassi de um semirreboque em simulações de tráfego. Procede-se a discretização do quadro do implemento em elementos finitos, para realização de análise de vibração livre, na qual são determinados os modos (autovetores) e as frequências naturais (autovalores) da estrutura. Utilizando metodologia de superposição modal, os modos de vibração são classificados para compor, por combinação linear, a flexibilidade da estrutura nas análises dinâmicas em ferramenta comercial de MBS (sistemas multicorpos). São realizadas, então, simulações de manobras representativas da dinâmica lateral de combinações veiculares, com ênfase à estabilidade em rolagem. Os efeitos globais da inserção de flexibilidade modal no chassi do semirreboque são avaliados por meio de métricas específicas, baseadas em normas ISO de dinâmica lateral para veículos pesados. Os resultados das simulações, apresentados em forma gráfica e tabelas, mostram a grande influência da flexibilidade estrutural do chassi no desempenho dinâmico da combinação veicular analisada. Grandezas relevantes como aceleração lateral (no domínio do tempo e da frequência), ângulo de rolagem e força atuante nos pneus, além de fenômenos físicos como a transferência lateral de carga em curvas, são fortemente afetados pela flexibilidade do quadro. Agrega-se ao trabalho desenvolvido uma forma simplificada de equacionar analiticamente a rolagem de um semirreboque flexível. É realizada também uma análise de sensibilidade da rigidez torcional do chassi quanto ao número de travessas. / This work presents a lateral dynamics multibody analysis of a heavy articulated vehicle with a flexible frame for the semi-trailer. The context is given by a short perspective of the load carrying transportation scenery in Brazil. In order to build better products, the trailer manufacturers have been using development methodologies based on virtual simulation. In these circumstances, dynamic analyses are carried out, considering the hypothesis of rigid (non-deformable) bodies. Subjectively, it is known that the inclusion of flexibility in a numerical model brings it closer to reality, but very few studies work on giving numbers to this difference. Thus, this study presents an approach for taking into account the frame structural flexibility of a semi-trailer in traffic simulations. The frame of the semi-trailer is represented by a finite element model, and a free vibration analysis of this structure is carried out. The mode shapes (eigenvectors) and natural frequencies (eigenvalues) are determined. With a mode superposition method, the vibration modes are classified, for the purpose of building the structural flexibility (by linear combination) of the chassis in the dynamic analyses of the MBS software. Typical maneuvers of lateral dynamics are simulated, testing the roll stability of the combined vehicle model. The global effects for considering the mode flexibility in the semitrailer frame are evaluated through specific metrics, based on ISO standards for heavy vehicles lateral dynamics. The strong influence of the frame structural flexibility, when analyzing the articulated vehicle transient behavior, is showed by simulation results, which are presented in graphics and tables. Important measurements, such as lateral acceleration (in time and frequency domains), roll angle and vertical force on tires, besides physical phenomenon like lateral load transfer, are significantly modified by the flexibility of the frame. A simplified approach for writing the analytical equations of the flexible semi-trailer roll dynamics is added to the study. A torsional stiffness sensitivity analysis is also performed, regarding the number of transversal members in the semi-trailer chassis.

Este trabalho apresenta uma análise multicorpos de combinação veicular de carga com chassi de semirreboque flexível, para avaliação de dinâmica lateral. O contexto é dado por um breve panorama do transporte rodoviário de cargas no Brasil. No intuito de melhorar seus produtos, os fabricantes de implementos rodoviários têm utilizado metodologias de desenvolvimento baseadas em simulação virtual. Nessas circunstâncias, análises dinâmicas são realizadas, geralmente levando-se em conta a hipótese de corpos rígidos (não deformáveis). Subjetivamente, é sabido que a inclusão da flexibilidade em um modelo numérico o aproxima do fenômeno real, mas são raros os trabalhos que analisam quantitativamente essa diferença. Assim, neste estudo é proposta uma abordagem para consideração da flexibilidade estrutural do chassi de um semirreboque em simulações de tráfego. Procede-se a discretização do quadro do implemento em elementos finitos, para realização de análise de vibração livre, na qual são determinados os modos (autovetores) e as frequências naturais (autovalores) da estrutura. Utilizando metodologia de superposição modal, os modos de vibração são classificados para compor, por combinação linear, a flexibilidade da estrutura nas análises dinâmicas em ferramenta comercial de MBS (sistemas multicorpos). São realizadas, então, simulações de manobras representativas da dinâmica lateral de combinações veiculares, com ênfase à estabilidade em rolagem. Os efeitos globais da inserção de flexibilidade modal no chassi do semirreboque são avaliados por meio de métricas específicas, baseadas em normas ISO de dinâmica lateral para veículos pesados. Os resultados das simulações, apresentados em forma gráfica e tabelas, mostram a grande influência da flexibilidade estrutural do chassi no desempenho dinâmico da combinação veicular analisada. Grandezas relevantes como aceleração lateral (no domínio do tempo e da frequência), ângulo de rolagem e força atuante nos pneus, além de fenômenos físicos como a transferência lateral de carga em curvas, são fortemente afetados pela flexibilidade do quadro. Agrega-se ao trabalho desenvolvido uma forma simplificada de equacionar analiticamente a rolagem de um semirreboque flexível. É realizada também uma análise de sensibilidade da rigidez torcional do chassi quanto ao número de travessas. / This work presents a lateral dynamics multibody analysis of a heavy articulated vehicle with a flexible frame for the semi-trailer. The context is given by a short perspective of the load carrying transportation scenery in Brazil. In order to build better products, the trailer manufacturers have been using development methodologies based on virtual simulation. In these circumstances, dynamic analyses are carried out, considering the hypothesis of rigid (non-deformable) bodies. Subjectively, it is known that the inclusion of flexibility in a numerical model brings it closer to reality, but very few studies work on giving numbers to this difference. Thus, this study presents an approach for taking into account the frame structural flexibility of a semi-trailer in traffic simulations. The frame of the semi-trailer is represented by a finite element model, and a free vibration analysis of this structure is carried out. The mode shapes (eigenvectors) and natural frequencies (eigenvalues) are determined. With a mode superposition method, the vibration modes are classified, for the purpose of building the structural flexibility (by linear combination) of the chassis in the dynamic analyses of the MBS software. Typical maneuvers of lateral dynamics are simulated, testing the roll stability of the combined vehicle model. The global effects for considering the mode flexibility in the semitrailer frame are evaluated through specific metrics, based on ISO standards for heavy vehicles lateral dynamics. The strong influence of the frame structural flexibility, when analyzing the articulated vehicle transient behavior, is showed by simulation results, which are presented in graphics and tables. Important measurements, such as lateral acceleration (in time and frequency domains), roll angle and vertical force on tires, besides physical phenomenon like lateral load transfer, are significantly modified by the flexibility of the frame. A simplified approach for writing the analytical equations of the flexible semi-trailer roll dynamics is added to the study. A torsional stiffness sensitivity analysis is also performed, regarding the number of transversal members in the semi-trailer chassis.

La planification par scénarios est devenue un outil organisationnel extrêmement populaire. Elle stimule la réflexion stratégique et contribue à surmonter la pensée limitée à travers l’imagination de futurs multiples. Son objectif est de comprendre l’environnement mais encore évaluer les options stratégiques en dépit des scénarios proposés. Malgré cette popularité, force est de constater que très peu de travaux ont traité ses bienfaits sur l’organisation. L’objectif de cette recherche est, donc, l’étude de son impact sur le développement de la flexibilité et l’orientation entrepreneuriale. Notre recherche s’appuie sur une étude quantitative menée auprès de 133 cadres évoluant dans le secteur social et médico-social en France. Les résultats font apparaître une relation positive entre la planification par scénarios, la flexibilité stratégique et l’orientation entrepreneuriale. / Scenario planning has become an extremely popular organizational tool. It stimulates strategic thinking and helps overcome the limited thinking across the imagination of multiple futures. Its aim is to understand the environment but also to evaluate strategic options in spite of the proposed scenarios. Despite this popularity, there is inadequate research and theory to support its benefits to the organization. The objective of this research is to study its impact on the development of flexibility and entrepreneurial orientation. Our research is based on quantitative survey of 133 executives of French companies in the social and medico-social sector. The results confirm the expected relationships and reveal scenario planning to be an important determinant of strategic flexibility and entrepreneurial orientation.

Este trabalho apresenta uma análise multicorpos de combinação veicular de carga com chassi de semirreboque flexível, para avaliação de dinâmica lateral. O contexto é dado por um breve panorama do transporte rodoviário de cargas no Brasil. No intuito de melhorar seus produtos, os fabricantes de implementos rodoviários têm utilizado metodologias de desenvolvimento baseadas em simulação virtual. Nessas circunstâncias, análises dinâmicas são realizadas, geralmente levando-se em conta a hipótese de corpos rígidos (não deformáveis). Subjetivamente, é sabido que a inclusão da flexibilidade em um modelo numérico o aproxima do fenômeno real, mas são raros os trabalhos que analisam quantitativamente essa diferença. Assim, neste estudo é proposta uma abordagem para consideração da flexibilidade estrutural do chassi de um semirreboque em simulações de tráfego. Procede-se a discretização do quadro do implemento em elementos finitos, para realização de análise de vibração livre, na qual são determinados os modos (autovetores) e as frequências naturais (autovalores) da estrutura. Utilizando metodologia de superposição modal, os modos de vibração são classificados para compor, por combinação linear, a flexibilidade da estrutura nas análises dinâmicas em ferramenta comercial de MBS (sistemas multicorpos). São realizadas, então, simulações de manobras representativas da dinâmica lateral de combinações veiculares, com ênfase à estabilidade em rolagem. Os efeitos globais da inserção de flexibilidade modal no chassi do semirreboque são avaliados por meio de métricas específicas, baseadas em normas ISO de dinâmica lateral para veículos pesados. Os resultados das simulações, apresentados em forma gráfica e tabelas, mostram a grande influência da flexibilidade estrutural do chassi no desempenho dinâmico da combinação veicular analisada. Grandezas relevantes como aceleração lateral (no domínio do tempo e da frequência), ângulo de rolagem e força atuante nos pneus, além de fenômenos físicos como a transferência lateral de carga em curvas, são fortemente afetados pela flexibilidade do quadro. Agrega-se ao trabalho desenvolvido uma forma simplificada de equacionar analiticamente a rolagem de um semirreboque flexível. É realizada também uma análise de sensibilidade da rigidez torcional do chassi quanto ao número de travessas. / This work presents a lateral dynamics multibody analysis of a heavy articulated vehicle with a flexible frame for the semi-trailer. The context is given by a short perspective of the load carrying transportation scenery in Brazil. In order to build better products, the trailer manufacturers have been using development methodologies based on virtual simulation. In these circumstances, dynamic analyses are carried out, considering the hypothesis of rigid (non-deformable) bodies. Subjectively, it is known that the inclusion of flexibility in a numerical model brings it closer to reality, but very few studies work on giving numbers to this difference. Thus, this study presents an approach for taking into account the frame structural flexibility of a semi-trailer in traffic simulations. The frame of the semi-trailer is represented by a finite element model, and a free vibration analysis of this structure is carried out. The mode shapes (eigenvectors) and natural frequencies (eigenvalues) are determined. With a mode superposition method, the vibration modes are classified, for the purpose of building the structural flexibility (by linear combination) of the chassis in the dynamic analyses of the MBS software. Typical maneuvers of lateral dynamics are simulated, testing the roll stability of the combined vehicle model. The global effects for considering the mode flexibility in the semitrailer frame are evaluated through specific metrics, based on ISO standards for heavy vehicles lateral dynamics. The strong influence of the frame structural flexibility, when analyzing the articulated vehicle transient behavior, is showed by simulation results, which are presented in graphics and tables. Important measurements, such as lateral acceleration (in time and frequency domains), roll angle and vertical force on tires, besides physical phenomenon like lateral load transfer, are significantly modified by the flexibility of the frame. A simplified approach for writing the analytical equations of the flexible semi-trailer roll dynamics is added to the study. A torsional stiffness sensitivity analysis is also performed, regarding the number of transversal members in the semi-trailer chassis.

Mes travaux de thèse ont porté sur les matériaux hybrides organiques-inorganiques (MOFs) qui constituent une nouvelle classe de matériaux cristallins et nanoporeux, formés de centres métalliques interconnectés par des ligands organiques, dont les applications pour la séparation de gaz d'intérêt industriel ou la catralyse sont très prometteuses. Je me suis particulièrement intéressée aux Soft Porous Crystals, qui présentent une flexibilité structurale de grande amplitude en réponse à des stimuli externes tels que la température, la pression mécanique ou l'adsorption de molécules. Afin de mieux comprendre la très large gamme des comportements observés pour la flexibilité des MOFs, j'ai développé au cours de ma thèse une méthodologie complète de ces matériaux en combinant différentes méthodes de simulation moléculaire classique et quantique.Dans un premier temps, j'ai étudié les propriétés mécaniques de ces nouveaux matériaux flexibles dans le régime élastique. J'ai identifié la signature élastique des SPC et mis en évidence l'origine microscopique de la flexibilité structurale de ces matériaux hybrides. Ensuite j'ai étudié la stabilité mécanique de ces matériaux en fonction de la température, de la pression mécanique et de l'adsorption de molécules. Et notamment au phénomène d'amorphisation sous pression et au polymorphisme induit par l'intrusion de fluide de certaines MOFs. Dans un dernier temps, j'ai étudié l'influence de la géométrie, de la topologie structurale et de la fonctionnalisation des matériaux de la famille des ZIFs sur leurs propriétés d'adsorption d'eau. J'ai alors montré comment les propriétés d'hydrophobicité de ces matériaux peuvent être modulées. / The topic of this thesis is the thermodynamical, mechanical and adsorptive behavior of Soft Porous Crystals (SPCs). Porous metal-organic frameworks (MOF) are a novel class of crystalline materials with promising industrial applications such as gas adsorption and separation processes. The Soft Porous Crystals feature dynamic frameworks displaying reversible structural deformations of large amplitude in response to external physical constraints such as temperature, mechanical pressure or gas adsorption. I have developed a new methodology based on classical and quantum calculations in order to study these flexible metal-organic frameworks. I first studied the mechanical properties of different SPCs in order to link the local elastic behaviour of these materials and the structural flexibility. These results shed light onto the microscopic origin of stimuli-induced structural transitions in flexible MOFs, showing that the framework flexibility and existence of structural transition are clearly visible in their local elastic propertiesThen, I looked the mechanical stability of hybrid organic-inorganic frameworks under mechanical pressure and gas adsorption. In particular, I studied the pressure-induced amorphization of ZIF-8 and the polymorphism phenomenon induced by fluid intrusion. Finally, I was interested in the impact of geometry and functionalization on water adsorption properties of zeolitic imidazolate frameworks (ZIFs). I demonstrated how topology, geometry, and linker functionalization drastically affect the water adsorption properties of these materials, tweaking the ZIF materials from hydrophobic to hydrophilic.

Fluorescent proteins are valuable tools as biochemical markers for studying cellular processes. Red fluorescent proteins (RFPs) are highly desirable for in vivo applications because they absorb and emit light in the red region of the spectrum where cellular autofluorescence is low. The naturally occurring fluorescent proteins with emission peaks in this region of the spectrum occur in dimeric or tetrameric forms. The development of mutant monomeric variants of RFPs has resulted in several novel FPs known as mFruits. Though oxygen is required for maturation of the chromophore, it is known that photobleaching of FPs is oxygen sensitive, and oxygen-free conditions result in improved photostabilities. Therefore, understanding oxygen diffusion pathways in FPs is important for both photostabilites and maturation of the chromophores. We used molecular dynamics calculations to investigate the protein barrel fluctuations in mCherry, which is one of the most useful monomeric mFruit variants, and its GFP homolog citrine. We employed implicit ligand sampling and locally enhanced sampling to determine oxygen pathways from the bulk solvent into the mCherry chromophore in the interior of the protein. The pathway contains several oxygen hosting pockets, which were identified by the amino acid residues that form the pocket. We calculated the free-energy of an oxygen molecule at points along the path. We also investigated an RFP variant known to be significantly less photostable than mCherry and find much easier oxygen access in this variant. We showed that oxygen pathways can be blocked or altered, and barrel fluctuations can be reduced by strategic amino acid substitutions. The results provide a better understanding of the mechanism of molecular oxygen access into the fully folded mCherry protein barrel and provide insight into the photobleaching process in these proteins.