The Hydro Muscle is a soft linear actuator which utilizes hydraulic pressure and elastic properties of its core for actuation. The Hydro Muscle has been recruited to actuate bio-inspired robot systems using a classic set point tracking feedback control system. A more efficient method is to develop a model-based control system which uses a dynamic model of the Hydro Muscle. The dynamic behavior of the Hydro Muscle which describes the relation between the forces exerted to the resultant motion can be studied with the help of a dynamic viscoelastic model. A dynamic viscoelastic model defines the force exerted by the Hydro Muscle as a function of the hydraulic pressure, the tensile expansion of the Hydro Muscle and the rate of its tensile expansion. Multivariable linear regression is employed to generate a model to relate fluid pressure, tensile expansion, and the rate of tensile expansion to the force exerted by the Hydro Muscle. The developed model can be utilized to implement a model-based control algorithm for the force control of individual joints. This model-based control design could be extended to systems involving multiple Hydro Muscles to allow for a modular control system. The design and test of multi-fiber Hydro Muscle actuated biologically inspired ankle is considered to study control strategies for multi-fiber system. A set-point tracking control algorithm with a proportional differential controller is used to minimize the tracking error. Modular force variation with sequential recruitment of Hydro Muscle is studied.

L’étude se situe dans le cadre de la recherche de gains de performance de structures d’isolations passives pour l’offshore profond. Le travail proposé a pour support des analyses expérimentales et numériques de tubes revêtus par des matériaux isolants utilisés en eau profonde pour transporter du fluide chaud. Le raboutage des tubes en acier, préalablement revêtus en atelier, nécessite un dégagement du revêtement aux extrémités pour réaliser l'opération d'assemblage (généralement par soudure). La partie dégagée est ensuite recouverte par un nouveau matériau pouvant être appliqué sur site. Ainsi l’isolation de cette partie du tube (Field Joint), qui est soumise à des chargements thermomécaniques en service, doit être optimisée pour assurer une durée de vie compatible avec les contraintes de l’exploitation offshore en eau profonde. Le travail comporte principalement quatre parties : - la modélisation du comportement thermique pour analyser l’évolution en temps et en espace de la température du matériau au cours de la fabrication, de la pose et en service sachant que pour les matériaux d’isolation le comportement mécanique est fortement dépendant de la température,- une partie expérimentale pour l’analyse du comportement des matériaux isolants en fonction de la température et en fonction de la pression hydrostatique qui est le principal chargement mécanique de ces structures en service,- la modélisation du comportement mécanique des isolants,- et une partie modélisation et simulation du comportement en service d'assemblages multi-matériaux de type industriel, avec prise en compte du comportement non-linéaire des constituants. / Ultra deep offshore oil exploitation presents new challenges to offshore engineering and operating companies. Such applications require the use of pipelines with an efficient thermal protection. Passive insulation materials are commonly used to guarantee the thermal performance of the pipes, and syntactic foams are now the preferred material for this application. The mechanical behaviour of such insulation materials is quite complex, associating time-dependent behaviour of polymers with damage behaviour of glass microspheres. In order to allow an optimisation of such systems, while ensuring in-service durability, accurate numerical models of insulation materials are thus required. During the service life in deep water, hydrostatic pressure is the most important mechanical loading of the pipeline, so this study aims to describe the mechanical behaviour of the material under such loading. Using a hyperbaric chamber, the analysis of the evolution of the volumetric strain with time, with respect to the temperature, under different time-evolutions of the applied hydrostatic pressure is presented in this paper. Such experimental results associated with the mechanical response of the material under uniaxial tensile creep tests, allow the development of a thermo-mechanical model, so that representative loadings can be analysed.

Title: Changes in the mechanical parameters of women's hair during pregnancy Matters: We can look from different angles on the hair - as on a nanocomposite fiber and as on biomaterial changing with the origin and age. The hair doesn't differ only by lenght, stucture and color but also by diameter and shape. It reflects the overall health of the individual and all the processes in the organism of the individual and thus also the pregnancy. During pregnancy, hormonal changes take place which have an effect on the hair. Many women experience faster hair growth, extension and increased volume of the hair during pregnancy. This status is only temporary and lasts only to the childbirth. Aim: The aim of this work was to show the influence of pregnancy on mechanical parameters of hair and what direction this influence takes. Next, using questionnaires, to better solve the effect of particular pregnancy parameters on the hair, i.e. pregnancy order, sex of the child. Then, evaluate the whole problem using statistical tests and so make better sense of it. Methods: We'd selected a group of 64 pregnant women; hair samples were cut from them in the nape area each month throughout pregnancy. Each measurement started with evaluation of hair diameter with the use of optical microscope. Next, the hair had been...

Title: Changes in the mechanical parameters of women's hair during pregnancy Matters: We can look from different angles on the hair - as on a nanocomposite fiber and as on biomaterial changing with the origin and age. The hair doesn't differ only by lenght, stucture and color but also by diameter and shape. It reflects the overall health of the individual and all the processes in the organism of the individual and thus also the pregnancy. During pregnancy, hormonal changes take place which have an effect on the hair. Many women experience faster hair growth, extension and increased volume of the hair during pregnancy. This status is only temporary and lasts only to the childbirth. Aim: The aim of this work was to show the influence of pregnancy on mechanical parameters of hair and what direction this influence takes. Next, using questionnaires, to better solve the effect of particular pregnancy parameters on the hair, i.e. pregnancy order, sex of the child. Then, evaluate the whole problem using statistical tests and so make better sense of it. Methods: We'd selected a group of 64 pregnant women; hair samples were cut from them in the nape area each month throughout pregnancy. Each measurement started with evaluation of hair diameter with the use of optical microscope. Next, the hair had been...

Cette étude a pour objectif principal d’établir une stratégie de modélisation robuste, fiable et performante pour décrire des propagations de fissures d’échelle centimétrique en régime ductile dans des composants industriels. Le modèle d’endommagement de GTN écrit en grandes déformations est utilisé pour modéliser l’endommagement ductile. Ce modèle conduit généralement à une localisation de la déformation, conformément à l’expérience. L’échelle caractéristique de ce phénomène est introduite dans les équations de comportement via l’adoption d’une formulation non locale.Sur le plan numérique, ce modèle non local rend bien compte de la localisation dans une bande d’épaisseur donnée lorsqu’on raffine suffisamment le maillage. Par ailleurs, le problème de verrouillage numérique associé au caractère initialement isochore de la déformation plastique est limité en utilisant une formulation à base d’éléments finis mixtes. Enfin, la distorsion des éléments totalement cassés (i.e. sans rigidité apparente), qui pourrait nuire à la bonne convergence des simulations numériques, est traitée par une régularisation viscoélastique.L’ensemble de ces ingrédients sont appliqués pour simuler la propagation de fissure dans un milieu infini plasticité confinée), de sorte à établir un lien avec les approches globales en J-Δa. L’émoussement, l’amorçage et la (grande) propagation de fissure sont bien prédits. Le modèle est également appliqué à une tuyauterie métallique testée en grandeur réelle dans le cadre du projet européen Atlas+. Après une phase d’identification des paramètres sur éprouvette, les réponses globales et locales d’autres éprouvettes et du tube sont confrontés aux résultats expérimentaux. Ces résultats illustrent le degré de robustesse, de fiabilité et de performance qu’on peut attendre du modèle. / The major goal of this work is to establish a robust, reliable and efficient modeling technique so as to describe ductile tearing over a distance of several centimeters in industrial cases. The GTN damage model expressed in the context of finite strains is chosen to model ductile damage. Generally, the model leads to strain localization in agreement with experimental observations. The characteristic length scale of this phenomenon is introduced into the constitutive equations through the use of a nonlocal formulation.On a numerical ground, the nonlocal model controls the width of the localization band as soon as the mesh is sufficiently refined. Besides, the issue of volumetric-locking associated with plastic incompressibility is handled using a mixed finite element formulation. Finally, the distortion of broken elements (i.e. without any stiffness), which may affect the computational convergence of numerical simulations, is treated using a viscoelastic regularization.The improved GTN model is applied to simulate crack propagation under small-scale yielding conditions, so as to establish a relation with the global (J-Δa) approach. Crack tip blunting, crack initiation and (large) crack propagation are well captured. The model is also applied to a full-scale metallic pipe in the framework of the UE project Atlas+. After a phase of parameter calibration based on the experimental results on some small specimens, the global and local responses of other small specimens and of the full-scale pre-cracked pipe are compared with the experimental results. The results illustrates the robustness, the reliability and the efficiency of the current model.

In this thesis we design and develop algorithms for predicting the rheological behavior of polymer melts based on the results of detailed atomistic simulations and guided by theories of the Dynamics of Polymers and fundamental Principles of Science of the Non-Equilibrium Thermodynamics. More specifically: 1) We propose a new rheological constitutive model for the time evolution of the tensor conformation tensor C of chains in a polymer melt (and hence the stress tensor τ) using the generalized bracket formalism of Beris and Edwards. The new constitutive model includes terms that describe a whole range of phenomena and are successfully used to describe the rheological properties of commercial polyethylene resins. 2) We developed a new methodology that allows direct connection of the results of atomistic simulations with molecular reptation theory for entangled polymers. The final result of the methodology is the calculation of the function ψ(s,t) which expresses the probability that the segment s along the contour of the primitive path remain in the original tube after time t. 3) We extended the Rouse theory for systems without polymer chain ends, as the polymer rings. While there have been previous theoretical work, a comprehensive analysis of the Rouse model of cyclic polymers was still lacking; here we develop the theory in its entirety. / Στα πλαίσια της παρούσας διατριβής σχεδιάσαμε και αναπτύξαμε αλγορίθμους πρόβλεψης της ρεολογικής συμπεριφοράς πολυμερικών τηγμάτων βασιζόμενοι στα αποτελέσματα λεπτομερών ατομιστικών προσομοιώσεων, καθοδηγούμενοι όμως από Θεωρίες της Δυναμικής των Πολυμερών αλλά και από θεμελιώδεις αρχές της Επιστήμης της Θερμοδυναμικής Εκτός Ισορροπίας. Πιο συγκεκριμένα: 1) Προτείνουμε αρχικά ένα νέο ρεολογικό καταστατικό μοντέλο για τη χρονική εξέλιξη του τανυστή διαμορφώσεων C των αλυσίδων σε ένα πολυμερικό τήγμα (και κατ’ επέκταση για τον τανυστή των τάσεων τ) κάνοντας χρήση του φορμαλισμού των γενικευμένων αγκυλών των Beris και Edwards. Το νέο καταστατικό μοντέλο περιλαμβάνει όρους που περιγράφουν ένα ολόκληρο φάσμα φαινομένων και χρησιμοποιήθηκε με επιτυχία για την περιγραφή των ρεολογικών ιδιοτήτων εμπορικών ρητινών πολυαιθυλενίου. 2) Αναπτύξαμε μια καινούργια μεθοδολογία που επιτρέπει την άμεση σύνδεση των αποτελεσμάτων των ατομιστικών προσομοιώσεων με τη μοριακή θεωρία του ερπυσμού για διαπλεγμένα πολυμερή. Το τελικό αποτέλεσμα της μεθοδολογίας είναι ο υπολογισμός της συνάρτησης ψ(s,t) που εκφράζει την πιθανότητα το σημείο s κατά μήκος του περιγράμματος του πρωτογενούς δρόμου των αλυσίδων να παραμένει στον αρχικό σωλήνα μετά από χρόνο t. Επεκτείναμε τη θεωρία Rouse και για συστήματα πολυμερικών αλυσίδων δίχως άκρα, όπως αυτά των πολυμερικών δακτυλίων. Παρότι στίγματα της θεωρίας είχαν παρουσιαστεί και σε προηγούμενες εργασίες από άλλους ερευνητές, στην παρούσα διατριβή αναπτύξαμε τη θεωρία στην ολότητά της.