Within the aerospace design, analysis and optimization community, there is an increasing demand to finalize the preliminary design phase of the wing as quickly as possible without losing much on accuracy. This includes rapid generation of designs, an early adaption of higher fidelity models and automation in structural analysis of the internal structure of the wing. To perform the structural analysis, the aerodynamic load can be transferred to the wing using many different methods. Generally, for preliminary analysis, indirect load transfer method is used and for detailed analysis, direct load transfer method is used. For the indirect load transfer method, load is discretized using shear-moment-torque (SMT) curve and applied to ribs of the wing. For the direct load transfer method, the load is distributed using one-way Fluid-Structure Interaction (FSI) and applied to the skin of the wing. In this research, structural analysis is performed using both methods and the nodal displacement is compared. Further, to optimize the internal structure, iterative changes are made in the number of structural members. To accommodate these changes in geometry as quickly as possible, the parametric design method is used through Engineering SketchPad (ESP). ESP can also provide attributions the geometric feature and generate multi-fidelity models consistently. ESP can generate the Nastran mesh file (.bdf) with the nodes and the elements grouped according to their geometric attributes. In this research, utilizing the attributions and consistency in multi-fidelity models an API is created between ESP and Nastran to automatize the multi-fidelity structural optimization. This API generates the design with appropriate parameters and mesh file using ESP. Through the attribution in the mesh file, the API works as a pre-processor to apply material properties, boundary condition, and optimization parameters. The API sends the mesh file to Nastran and reads the results file to iterate the number of the structural member in design. The result file is also used to transfer the nodal deformation from lower-order fidelity structural models onto the higher-order ones to have multi-fidelity optimization. Here, static structural optimization on the whole wing serves as lower fidelity model and buckling optimization on each stiffened panel serves as higher fidelity model. To further extend this idea, a parametric model of the whole aircraft is also created.<br>

Filtros orgânicos são amplamente utilizados em formulações fotoprotetoras, com habilidade de absorver radiações ultravioleta (UV). Contudo, parte destes compostos possuem limitações, como: fotoinstabilidade, permeação cutânea e fotossensibilização e entre outros. Este trabalho envolveu a síntese de matriz mesoporosa do tipo SBA-15, encapsulação/incorporação de &#961;-metoxicinamato de octila (MCO), benzofenona-3 (BZF-3) e avobenzona (AVO) na SBA-15 para aplicação em formulações fotoprotetoras. Fez-se a determinação da eficácia in vitro dos filtros encapsulados/incorporados combinados a ingrediente cosmético; o preparo de bastão fotoprotetor e determinação eficácia estimada; a avaliação do potencial de irritação ocular dos bastões por HET-CAM - Hen\'s Egg Test - Chorioallantoic Membrane, e a avaliação da permeação/retenção cutânea e perfil de biodistribuição dos filtros. Para a caracterização dos materiais foram empregadas técnicas físico-químicas e analíticas. As medidas de adsorção/dessorção de N2 mostrou que as amostras dos filtros solares encapsulados/incorporados apresentaram diminuição na área superficial e volume de poro (V), indicando que os filtros solares foram encapsulados/incorporados na superfície e nos poros da SBA-15. Os resultados de Espalhamento de raios X a baixo ângulo evidenciaram que os filtros solares não afetaram a estrutura hexagonal da SBA-15. Por TG/DTG e análise elementar foi possível determinar a quantidade de filtros solares na superfície e nos mesoporos da SBA-15. Enquanto, as curvas DSC e DTA revelaram aumento na estabilidade térmica da AVO e BZF-3, quando encapsulados/incorporados. Os resultados da eficácia fotoprotetora in vitro monstraram que a combinação dos três filtros solares encapsulados/incorporados na SBA-15 promoveram aumento de 52% no fator proteção solar (FPS), enquanto que, na formulação fotoprotetora contendo os três filtros encapsulados/incorporados, o aumento foi de 94%. O ensaio de HET-CAM evidenciou que os bastões contendo SBA-15 e os filtros encapsulados/incorporados não foram irritantes. O ensaio de permeação/retenção cutânea monstrou que o processo de encapsulação/incorporação da BZF-3 promoveu diminuição de sua permeação em todos os tempos de exposição. As quantidades permeadas de AVO e MCO ficaram abaixo do limite de quantificação nos tempos 6 e 12 h, no entanto, no tempo de 24 h foi possível quantificá-los. As quantidades dos filtros solares retidas na pele a partir da formulação contendo os filtros solares encapsulados/incorporados na SBA-15 (F4) foram menores (tempos 6 e 12 h) em comparação à formulação contendo os filtros solares não encapsulados (F3). A investigação da biodistribuição dos filtros solares monstrou que a retenção total na pele, como na derme, foi menor na formulação F4 em comparação à F3. O estudo comparativo entre pele suína e a pele humana monstrou que as quantidades de BZF-3 e AVO permeadas e retidas na pele suína foram superiores do que em relação à humana para ambas as formulações (F4 e FR). Pela técnica de biodistribuição, foi possível determinar que os filtros solares oriundos das formulações F3 e referência (FR) apresentaram maior retenção destes compostos na derme do que em outras camadas da pele. Contudo, observou-se que os filtros encapsulados apresentaram taxa reduzida de retenção na derme. / Organic Filters are chemical compounds widely used in sunscreens formulations with the ability to absorb ultraviolet radiation (UV). Despite the effectiveness of these compounds in UV radiation protection, disadvantages related to their photo instability, potential skin permeation and photo sensibility pose significant challenges for improving these products. The aim of this work was to synthesize mesoporous matrix SBA-15, encapsulation/entrapping of octyl methoxycinnamate (OMC), benzophenone-3 (BZF-3) and avobenzone (AVO) into SBA-15 for application in photoprotective formulations. It was accessed in vitro photoprotection efficacy and in vitro photostability assay of encapsulated/entrapped UV filters combined with cosmetic ingredient and photoprotective stick formulations; evaluation of the ocular irritation potential of photoprotective stick formulations by in vitro method HET-CAM - Hen\'s Egg Test - Chorioallantoic Membrane; evaluation the skin permeation/deposition and biodistribution profile of photoprotective stick formulations. The decrease in the surface area and in mesoporous volume (V) observed in the nitrogen adsorption desorption isotherms of encapsulated/entrapped samples indicated that UV filters were efficiently encapsulated/entrapped into SBA-15. Additionally, SAXS results showed that UV filters did not affected the hexagonal structure of the mesoporous material and that these compounds filled the SBA-15 pores. TG/DTG and elemental analysis were efficient tools to confirm the presence and the quantity of UV filters into SBA-15. DTA and DSC curves of encapsulated/entrapped materials showed that the thermal stability of AVO and BZF-3 were increased. On the other hand, DSC curves of encapsulated/entrapped materials demonstrated that thermal stability of OMC was not increase. The in vitro photoprotective efficacy results demonstrated that the combination of the three sunscreens encapsulated/entrapped into SBA-15 increased 52.0% the SPF values, while the stick formulation containing the UV filters encapsulated/entrapped, the increase was 94.0%. Delivery experiments using porcine skin demonstrated that the encapsulation/entrapping process of UV filters resulted the decreased of BZF-3 permeation and deposition in skin (6 and 12 hours). The cutaneous biodistribution profile of UV filters showed that the deposition of these compounds from encapsulated/entrapped stick formulation (F4) was significantly lower than that from UV filters stick formulations (F3) in the total slices of the skin and dermis. The comparative study between porcine skin and human skin demonstrated that the amounts of BZF-3 and AVO permeated and deposited in porcine skin were higher than in human skin for both formulations (F4 and FR - reference formulation). By the biodistribution technique it was possible to determine that the UV filters from the formulations F3 and FR presented higher retention of these compounds in the dermis than in other layers of the skin. On the other hand, it was observed that the encapsulated UV filters presented low retention rate into dermis.

Filtros orgânicos são amplamente utilizados em formulações fotoprotetoras, com habilidade de absorver radiações ultravioleta (UV). Contudo, parte destes compostos possuem limitações, como: fotoinstabilidade, permeação cutânea e fotossensibilização e entre outros. Este trabalho envolveu a síntese de matriz mesoporosa do tipo SBA-15, encapsulação/incorporação de &#961;-metoxicinamato de octila (MCO), benzofenona-3 (BZF-3) e avobenzona (AVO) na SBA-15 para aplicação em formulações fotoprotetoras. Fez-se a determinação da eficácia in vitro dos filtros encapsulados/incorporados combinados a ingrediente cosmético; o preparo de bastão fotoprotetor e determinação eficácia estimada; a avaliação do potencial de irritação ocular dos bastões por HET-CAM - Hen\'s Egg Test - Chorioallantoic Membrane, e a avaliação da permeação/retenção cutânea e perfil de biodistribuição dos filtros. Para a caracterização dos materiais foram empregadas técnicas físico-químicas e analíticas. As medidas de adsorção/dessorção de N2 mostrou que as amostras dos filtros solares encapsulados/incorporados apresentaram diminuição na área superficial e volume de poro (V), indicando que os filtros solares foram encapsulados/incorporados na superfície e nos poros da SBA-15. Os resultados de Espalhamento de raios X a baixo ângulo evidenciaram que os filtros solares não afetaram a estrutura hexagonal da SBA-15. Por TG/DTG e análise elementar foi possível determinar a quantidade de filtros solares na superfície e nos mesoporos da SBA-15. Enquanto, as curvas DSC e DTA revelaram aumento na estabilidade térmica da AVO e BZF-3, quando encapsulados/incorporados. Os resultados da eficácia fotoprotetora in vitro monstraram que a combinação dos três filtros solares encapsulados/incorporados na SBA-15 promoveram aumento de 52% no fator proteção solar (FPS), enquanto que, na formulação fotoprotetora contendo os três filtros encapsulados/incorporados, o aumento foi de 94%. O ensaio de HET-CAM evidenciou que os bastões contendo SBA-15 e os filtros encapsulados/incorporados não foram irritantes. O ensaio de permeação/retenção cutânea monstrou que o processo de encapsulação/incorporação da BZF-3 promoveu diminuição de sua permeação em todos os tempos de exposição. As quantidades permeadas de AVO e MCO ficaram abaixo do limite de quantificação nos tempos 6 e 12 h, no entanto, no tempo de 24 h foi possível quantificá-los. As quantidades dos filtros solares retidas na pele a partir da formulação contendo os filtros solares encapsulados/incorporados na SBA-15 (F4) foram menores (tempos 6 e 12 h) em comparação à formulação contendo os filtros solares não encapsulados (F3). A investigação da biodistribuição dos filtros solares monstrou que a retenção total na pele, como na derme, foi menor na formulação F4 em comparação à F3. O estudo comparativo entre pele suína e a pele humana monstrou que as quantidades de BZF-3 e AVO permeadas e retidas na pele suína foram superiores do que em relação à humana para ambas as formulações (F4 e FR). Pela técnica de biodistribuição, foi possível determinar que os filtros solares oriundos das formulações F3 e referência (FR) apresentaram maior retenção destes compostos na derme do que em outras camadas da pele. Contudo, observou-se que os filtros encapsulados apresentaram taxa reduzida de retenção na derme. / Organic Filters are chemical compounds widely used in sunscreens formulations with the ability to absorb ultraviolet radiation (UV). Despite the effectiveness of these compounds in UV radiation protection, disadvantages related to their photo instability, potential skin permeation and photo sensibility pose significant challenges for improving these products. The aim of this work was to synthesize mesoporous matrix SBA-15, encapsulation/entrapping of octyl methoxycinnamate (OMC), benzophenone-3 (BZF-3) and avobenzone (AVO) into SBA-15 for application in photoprotective formulations. It was accessed in vitro photoprotection efficacy and in vitro photostability assay of encapsulated/entrapped UV filters combined with cosmetic ingredient and photoprotective stick formulations; evaluation of the ocular irritation potential of photoprotective stick formulations by in vitro method HET-CAM - Hen\'s Egg Test - Chorioallantoic Membrane; evaluation the skin permeation/deposition and biodistribution profile of photoprotective stick formulations. The decrease in the surface area and in mesoporous volume (V) observed in the nitrogen adsorption desorption isotherms of encapsulated/entrapped samples indicated that UV filters were efficiently encapsulated/entrapped into SBA-15. Additionally, SAXS results showed that UV filters did not affected the hexagonal structure of the mesoporous material and that these compounds filled the SBA-15 pores. TG/DTG and elemental analysis were efficient tools to confirm the presence and the quantity of UV filters into SBA-15. DTA and DSC curves of encapsulated/entrapped materials showed that the thermal stability of AVO and BZF-3 were increased. On the other hand, DSC curves of encapsulated/entrapped materials demonstrated that thermal stability of OMC was not increase. The in vitro photoprotective efficacy results demonstrated that the combination of the three sunscreens encapsulated/entrapped into SBA-15 increased 52.0% the SPF values, while the stick formulation containing the UV filters encapsulated/entrapped, the increase was 94.0%. Delivery experiments using porcine skin demonstrated that the encapsulation/entrapping process of UV filters resulted the decreased of BZF-3 permeation and deposition in skin (6 and 12 hours). The cutaneous biodistribution profile of UV filters showed that the deposition of these compounds from encapsulated/entrapped stick formulation (F4) was significantly lower than that from UV filters stick formulations (F3) in the total slices of the skin and dermis. The comparative study between porcine skin and human skin demonstrated that the amounts of BZF-3 and AVO permeated and deposited in porcine skin were higher than in human skin for both formulations (F4 and FR - reference formulation). By the biodistribution technique it was possible to determine that the UV filters from the formulations F3 and FR presented higher retention of these compounds in the dermis than in other layers of the skin. On the other hand, it was observed that the encapsulated UV filters presented low retention rate into dermis.

Ce travail comporte deux parties. La première partie est une étude bibliographique sur la modélisation du frottement sec et sur les différentes lois de frottement qui ont été introduites pour rendre compte des instabilités du mouvement des solides soumis à la friction sèche. La deuxième partie est une étude théorique et numérique d'un problème modèle dynamique où une lois de type Coulomb avec coefficient de frottement dépendant de la vitesse de glissement est appliquée à un solide élastique. Le cadre des inclusions différentielles est introduit pour traiter rigoureusement les modèles à nombre fini de degré de liberté et à pression de contact imposée. Ce cadre sert ensuite à l'analyse en détail d'un problème unidimensionnel d'une couche élastique glissant avec frottement sur une fondation rigide plane. On montre l'existence et l'unicité de la solution lorsque le coefficient de frottement est croissant, mais lorsque celui-ci comporte au moins une portion décroissante, ce qui est le cas dans la plupart des modélisation, on montre que le problème admet en général une infinité de solutions. Cela amène à considerer un critère de choix de solution appelé critère de retard maximal. Par ailleurs, on introduit une condition de frottement perturbée qui consiste en l'ajout d'une masse de surface et qui redonne aussi l'unicité de la solution. On montre le lien entre le critère de retard maximal et cette condition perturbée. On présente aussi des schémas numériques, des résultats de stabilité et de convergence, ainsi que des expériences numériques. On donne enfin des perspectives pour les problèmes en dimension deux ou trois. On présente des simulations numériques significatives, obtenues à l'aide d'un schéma numérique basé sur une méthode de type directions alternées, et sur la perturbation par une masse de surface.

La réponse à des vibrations et l'étude de la stabilité des pentes ont une place particulière dans l'étude des milieux granulaires. Ces études peuvent d'une part nous renseigner sur le comportement des milieux granulaires présents dans le milieu naturel et souvent soumis à ces deux types de sollicitations (avalanches de grains, éboulements de roches, dynamique des dunes, tremblements de terre, ...). D'autre part, elles permettent d'appréhender ces milieux comme des systèmes modèles hors équilibre et d'analyser les résultats à la lumière de ceux obtenus sur la dynamique des systèmes vitreux. Nous avons tout d'abord étudié expérimentalement par des méthodes optiques et acoustiques la réponse d'un milieu granulaire lentement incliné. La dynamique présente deux régimes : un régime de petits réarrangements indépendants et localisés est suivi d'un régime intermittent caractérisé par de grands événements de type "précurseurs" au voisinage de l'angle d'avalanche. Ce régime dit de "précurseurs" correspond à un mouvement collectif de l'ensemble des grains situés à la surface de l'empilement. Nous mettons en évidence l'importance du détail microscopique de l'interaction entre les grains et de la condition à la limite à la base de l'empilement sur la dynamique du système dans ce régime. La dynamique globale du système a été étudiée et comparée à un modèle simple de type automate cellulaire. Dans un second temps, nous avons étudié numériquement la réponse d'un milieu granulaire soumis à des vibrations. Le comportement du système présente des caractéristiques qui sont communes à tous les systèmes hors équilibre (distributions non-gaussiennes des déplacements, ralentissement et hétérogénéités de la dynamique,...). L'influence de la condition à la limite au fond de l'empilement sur la structuration de celui-ci et sur le ralentissement de la dynamique a également été discutée. Nous avons, en particulier, mis en évidence une zone d'épaisseur environ égale à 5 diamètres de grains où des hétérogénéités dynamiques et de fortes corrélations entre les mouvements des grains apparaissent.

Most materials used in many industries such as plastic, food, pharmaceuticals, electronics, dye, etc. exhibit viscoelastic properties under their processing or flow conditions. Due to the elasticity of such materials, deformation-stress in addition to their hydrodynamic behavior differ from simple Newtonian fluids in many important respects. Rod climbing, siphoning, secondary flows are all common examples to how a viscoelastic fluid can exhibit quite distinctive flow behavior than a Newtonian fluid would do under similar flow conditions. In industrial processes involving flow of viscoelastic materials, understanding complexities associated with the viscoelasticity can lead to both design and development of hydrodynamically efficient processes and to improved quality of the final products. In the present study, the main objective is to develop two dimensional finite volume based convergent numerical algorithm for the simulation of viscoelastic flows using nonlinear differential constitutive equations. The constitutive models adopted are Oldroyd-B, Phan-Thien Tanner (PTT) and White-Metzner models. The semi-implicit method for the pressure-linked equation (SIMPLE) and SIMPLE consistent (SIMPLEC) are used to solve the coupled continuity, momentum and constitutive equations. Extra stress terms in momentum equations are solved by decoupled strategy. The schemes to approximate the convection terms in the momentum equations adopted are first order upwind, hybrid, power-law second order central differences and finally third order quadratic upstream interpolation for convective kinematics QUICK schemes. Upwind and QUICK schemes are used in the constitutive equations for the stresses. Non-uniform collocated grid system is employed to discretize flow geometries. As test cases, three problems are considered: flow in entrance of planar channel, stick-slip and lid driven cavity flow. Detailed investigation of the flow field is carried out in terms of velocity and stress fields. It is found that range of convergence of numerical solutions is very sensitive to the type of rheological model, Reynolds number and polymer contribution of viscosity as well as mesh refinement. Use of White-Metzner constitutive differential model gives smooth, non oscillatory solutions to much higher Weissenberg number than Oldroyd-B and PTT models. Differences between the behavior of Newtonian and viscoelastic fluids for lid-driven cavity, such as the normal stress effects and secondary eddy formations, are highlighted. In addition to the viscoelastic flow simulations, steady incompressible Newtonian flow of lid-driven cavity flow at high Reynolds numbers is also solved by finite volume approach. Effect of the solution procedure of pressure correction equation cycles, which is called inner loop, on the solution is discussesed in detail and results are compared with the available data in literature.

La fatigue à nombre de cycles élevé (HCF) est un mode de défaillance courant et dangereux pour les aubages de turbomachines. Elle est induite par les efforts dynamiques élevés générés lors de résonances présentes dans la plage de fonctionnement de ces machines. Les dispositifs amortisseurs basés sur l'utilisation du frottement sec, tels que les nageoires ou les frotteurs sous-plateformes, permettent de réduire les amplitudes vibratoires, voire de repousser les fréquences de résonance hors des zones de fonctionnement. Cependant la conception de ces dispositifs reste encore largement basée sur l'empirisme et ils peuvent être la source d'un effet de désaccordage potentiellement nuisible. L'objectif ici est de développer des modélisations adaptées au traitement du problème de vibration des aubages en présence de frottement sec, ceci afin de mieux maîtriser les comportements physiques mis en jeu et donc, de mieux maîtriser leur processus de conception. Plusieurs modélisations numériques sont testées et confrontées à des résultats de référence. Une comparaison entre procédures de résolution temporelle et fréquentielle est menée et montre l'efficacité des méthodes fréquentielles. La méthode fréquentielle de la balance harmonique à plusieurs harmoniques est adaptée au problème et exploitée dans le cadre d'une étude énergétique. Cette étude conduit à une meilleure compréhension des phénomènes mis en jeu lors de l'aplatissement des pics en fonctionnement ; elle permet de démontrer que l'alternance des états de contact glissant et bloqué est à l'origine de cet aplatissement et non la dissipation d'énergie comme souvent avancé dans la littérature. Enfin, la méthode est exploitée pour décrire le comportement des disques aubés désaccordés. La méthode de Monte Carlo est utilisée pour obtenir les caractéristiques statistiques de la réponse forcée d'un système discret, en tenant compte des variations stochastiques des paramètres du contact notamment, la charge normale, la raideur du contact et le coefficient de frottement. Les résultats obtenus permettent de mieux comprendre les effets de la nature variable de ces paramètres fondamentaux sur la dynamique d'ensemble du système non linéaire.

Le présent travail portait sur l'étude des effets de la supplémentation haptique sur la stabilité posturale debout et assise du sujet jeune et âgé. La question si les informations haptiques fournies par un support mobile améliorent la stabilité autant qu'un support fixe a peu été étudiée. Le présent travail visait à contribuer à une meilleure compréhension des mécanismes sous-jacents à l'effet stabilisateur potentiel d'un support type « canne mobile ». Les analyses portaient sur le centre de pression (COP). Les résultats des premières deux études confirment notre hypothèse générale sur l'effet de la supplémentation haptique indépendant de l'âge et de la mobilité du support. Si une résistance suffisante est fournie à l'opposé des oscillations du corps par le support les participants amélioraient leur stabilité. Dans la troisième étude, nous avons également manipulé des entrées visuelles et les résultats suggèrent qu'un manque de vision peut être compensé par la supplémentation. Dans la quatrième étude, nous avons également analysé la coordination inter-segmentaire. Les résultats suggèrent un meilleur contrôle postural avec la supplémentation alors qu'elle n'influence pas la coordination inter-segmentaire. La cinquième étude visait à déterminer si la supplémentation permettait d'améliorer la robustesse du système à des perturbations. Les résultats suggèrent que les sujets jeunes réduisent le temps de la première correction du COP avec la supplémentation alors que les sujets âgés corrigent leur COP plus tôt que les jeunes et ne bénéficient pas de cette dernière. Les résultats expérimentaux laissent envisager l'application du paradigme « canne mobile » à la locomotion. / This work was dedicated to the study of the effects of haptic supplementation on postural stability of young and old adults during standing and sitting tasks. The question of whether haptic information provided by a mobile support improves stability similar to a fixed support has been rarely studied. The present work aimed to contribute to a better understanding of the underlying mechanisms of the potential stabilizing effect of haptic information provided by a cane-like support. The analysis focused on the center of pressure (COP). The results of the first two studies confirmed our general hypothesis about the effect of haptic supplementation independent of age and the mobility of the support. If sufficient resistance is provided by the support against body sway participants improved their postural stability. In the third study, we also manipulated visual inputs and the results suggested that a lack of vision can be compensated due to supplementation. In the fourth study, we also analyzed the inter-segmental coordination. The results suggested a better postural control due to supplementation whereas it does not affect the inter-segmental coordination. The fifth study aimed to determine whether haptic supplementation improves the system's robustness to sudden perturbations. The results suggested that only young participants reduce the time to the first COP correction due to supplementation while elderly correct the COP earlier than young adults, even without additional haptic information, and therefore do not benefit from haptic supplementation. Overall, the experimental results open the way for the application of the “mobile-stick” experimental paradigm to locomotion.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-10-18T20:27:50Z No. of bitstreams: 1 JosianeMariaDeMacedoFernandes_TESE.pdf: 1245335 bytes, checksum: 5135bc4fc7856839af432f3c4f427beb (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-10-23T22:17:47Z (GMT) No. of bitstreams: 1 JosianeMariaDeMacedoFernandes_TESE.pdf: 1245335 bytes, checksum: 5135bc4fc7856839af432f3c4f427beb (MD5) / Made available in DSpace on 2017-10-23T22:17:47Z (GMT). No. of bitstreams: 1 JosianeMariaDeMacedoFernandes_TESE.pdf: 1245335 bytes, checksum: 5135bc4fc7856839af432f3c4f427beb (MD5) Previous issue date: 2017-06-28 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Neste trabalho ? desenvolvida uma estrat?gia de controle n?o linear baseada no controle por modos deslizantes com compensa??o neural para estabiliza??o de sistemas subatuados sujeitos a vibra??es torcionais. No intuito de analisar o desempenho da abordagem proposta, a lei de controle foi implementada em uma coluna de perfura??o. As colunas de perfura??o s?o discretizadas em n partes. A atua??o ? dada no top drive, ou na mesa rotativa na extremidade superior da coluna, e todo o restante da coluna n?o recebe atua??o. As vibra??es torcionais abordadas neste trabalho s?o do tipo stick-slip, que ? o caso mais cr?tico desse tipo de vibra??o, cuja n?o linearidade ? geralmente causada pelo atrito entre a coluna e a forma??o, podendo ocorrer em qualquer ponto ao longo da coluna e deve ser levado em considera??o na modelagem. O controle por modos deslizantes apresenta robustez frente a incertezas param?tricas e perturba??es. A estrat?gia adotada n?o requer o conhecimento pr?vio de incertezas e n?o linearidades do sistema. No entanto, a fun??o descont?nua utilizada na lei de controle pode gerar o fen?meno de chattering, que em atuadores mec?nicos ? indesej?vel. Para atenuar o chattering, uma fun??o suave ? utilizada no lugar da descont?nua, sendo essa abordagem ocasionadora de diminui??o no desempenho do controlador. Nesse ponto, t?cnicas de intelig?ncia artificial podem contribuir na lei de controle para devolver o desempenho ou parte dele ao sistema. Duas arquiteturas de rede s?o empregadas para estimar a compensa??o, uma rede do tipo perceptron de m?ltiplas camadas e uma rede de fun??es de base radial. As superf?cies de controle s?o definidas como uma combina??o linear dos erros dos estados do sistema e uma rede neural ? adicionada para compensar a forma??o de ciclos limites, comumente apresentados ap?s a perda de efic?cia. Resultados s?o apresentados para demonstrar a performance do sistema de controle proposto. / In the present work, a nonlinear control strategy based on sliding mode method and artificial neural networks is presented. This approach can be applied to stabilize nonlinear under actuated systems subjected to torsional vibrations. In order to evaluate the proposed approach, the control law was implemented in a drill string. Drill strings are addressed due to their nonlinear and underactuated dynamics. The drill strings are discretized in n parts. The control output is given at the top drive whereas the other string parts are not directly actuated. Torsional vibrations employed in this work are stick-slip, which is the more critic way of torsional vibrations. Stick-slip is a nonlinearity usually caused by friction between the drill string and rock formations and can occurs at any point along its length. Sliding mode control is a very robust technique even with parametric uncertainties and external perturbations. There is no need of previous knowledge of uncertainties and nonlinearities. The discontinuous function adopted at the control law can lead to the undesired chattering effect. The discontinuous function can be replaced by a smooth function to avoid chattering, but this also implies on decrement of the system performance. In order to attenuate this effect, a compensation is added to the control law. Two different artificial neural network architectures are investigated: multilayer perceptrons and radial basis functions. The sliding surfaces are defined as a linear combination of tracking errors. The neural network is employed to mitigate the generated limit cycle. Numerical results are presented in order to demonstrate the performance of the control system.

L’objectif de cette thèse est d’approfondir la connaissance sur la génération et la propagation des ondes à travers l’interface de contact afin de contrôler leurs effets sur le frottement, contrôler les instabilités et réduire les phénomènes d'usure. Le travail est organisé en deux parties principales. La première partie est axée sur une analyse non-linéaire par éléments finis en grandes transformations; la rupture dynamique à l’interface de contact avec frottement, qui sépare deux corps (isotropes et élastiques) en condition de pré-charge statique, est simulée. On définit comme étant une rupture une zone, initialement en adhérence, qui change son état en devenant glissante. Les propriétés des ruptures sont analysées pour une surface plane entre deux matériaux différents en fonction de l’énergie de nucléation; l’effet de la rugosité de surface est ensuite analysée. En outre, la rupture "cumulatives" dans les aspérités et les conditions pour le couplage ou le non-couplage entre les ondes qui se propagent dans les deux corps sont étudiées. Dans la deuxième partie, l'amorçage du glissement entre deux corps en contact constitués de matériaux différents et séparés par une interface avec frottement, est simulée. L’évolution, en fonction du temps, des forces globales (normale et tangentielle) a été mise en relation avec les phénomènes locaux qui se déroulent à l’interface. L'analyse montre comment les micro-slips à l'interface, en agissant comme ruptures localisées, déclenchent les macro-slips entre les deux corps. L'interaction entre les dynamiques locale du contact et globale du système a été aussi étudiée. Enfin, une analyse paramétrique est menée en fonction de plusieurs paramètres (loi de contact, coefficient de frottement, amortissement matériau, charge normale, etc.). Les résultats mettent en avant le rôle-clé des micro-slips et des précurseurs (propagations d'ondes détectables qui ont lieu pour des valeurs de la force tangentielle globale inférieures à la valeur prévue par la loi de frottement) dans l'amorçage du macro-slip entre les deux corps. En fonction de leur distribution et de leur intensité, l'évolution des forces de contact change en passant d'un comportement de type stick-slip à un glissement continu. La dynamique locale au contact (propagation des ondes et ruptures) a été reliée au comportement global du système (stick-slip, glissement continu, vibrations induites); l'effet des paramètres du contact et du système sur le transfert d'énergie vibrationnelle entre le contact glissant et le système a également été examinée: en fonction de leurs valeurs, on peut avoir différentes modalités d'excitation du système (par une distribution de micro-slips ou par des macro-slips) et différentes processus de propagation et dissipation d'énergie. Les résultats numériques obtenus dans les deux parties de la thèse sont cohérents avec les résultats expérimentaux de la littérature. / This thesis is addressed to the understanding of the mechanisms at the origin of the contact wave fields at frictional interfaces and its relationship with the local characteristics of the surfaces in contact, as well as with the global dynamics and macroscopic frictional behaviour of the system. The aim of this work is to provide insights on the generation and propagation of the waves through the contact both to avoid instabilities and to control their effect on friction. The work is organized in two main parts. The first part presents the development of a non-linear finite element analysis in large transformations of the dynamic rupture at the interface with contact friction separating two bodies (isotropic and elastic) without relative motion. A rupture is considered when an initially sticking zone shifts in sliding state. The properties of the obtained ruptures are analyzed for a flat interface between dissimilar materials in function of the nucleation energy; then the effect of the interface roughness is analyzed. The differentiated rupture inside the asperities and the conditions for coupling and uncoupling between the waves radiating in the two bodies have been also investigated. In the second part, the analysis deals with the sliding onset between two bodies in contact. The sliding between two bodies made of different isotropic elastic materials and separated by a frictional interface is simulated. The evolution along the time of the global normal and tangential forces is analyzed, relating it to the local phenomena occurring at the interface. This part tries to investigate how micro-slips at the interface, acting as distributed ruptures, trigger the macro-slips between the two bodies. The interaction between local and global dynamics is also studied. Finally a numerical parameter space study is carried out, as a function of several system parameters (contact law, friction coefficient, material damping, normal load, translational velocity and regularization time). The results show the key role of the micro-slips and precursors (detectable wave propagations that occur at tangential global force well below the critical value expected by the friction law) in triggering the macro-slip between the two bodies. Depending on their distribution and magnitude the evolution of the contact forces passes from stick-slip-like behaviour to continuous sliding. The local dynamics at the contact (wave and rupture propagation) is linked to the global behaviour of the system (stick-slip, continuous sliding, induced vibrations); the effect of the contact and system parameters on the transfer of vibrational energy between the sliding contact and the system is investigated. The numerical results obtained by the two parts of the work show a good agreement with experimental results in literature.