Le pli vocal humain possède des propriétés vibratoires exceptionnelles. Il est capable de supporter de grandes déformations, pour différent type de chargement, de manière répétée et réversible. Ces propriétés vibro-mécaniques particulières sont étroitement liées à sa microstructure: une structure multi-couches complexe fortement hétérogène composées de réseaux de fibres protéique. Cependant, il est encore aujourd'hui difficile de décrire précisément l'implication des spécificités microstructurales du pli dans son comportement biomécanique.Afin de préciser ce lien et d'aller vers une meilleure compréhension du comportement du tissu vocal, cette étude se propose d'aborder la problématique sous trois approches complémentaires, mélant caractérisation microstructurale, caractérisation mécanique et modélisation numérique. Dans un premier temps, la microstructure du pli a été étudiée emph{ex vivo} à l'aide d'une technique originale basée sur la tomographie à rayon X. L'usage de tomographie synchrotron par contraste de phase a permis de révéler la structure du tissu à différentes échelles. En particulier, des clichés 3D à forte résolution de la structure fibreuse des couches supérieures et musculaires du tissu ont pu être acquis. Ces clichés ont donné lieu à une analyse 3D quantitative de l'arrangement fibreux, permettant la détermination de descripteur d'orientation et de géométrie 3D des fibres.Dans un second temps, le comportement mécanique du tissu sous différentes conditions de chargement a été étudié. Un protocole a été proposé, afin de caractériser un même échantillon en traction, en compression et en cisaillement. Ces essais ont permis de compléter les connaissances existantes sur la biomécanique de pli, et constitue des données de références importantes pour la construction et la validation de modèle numérique.A partir des données acquises expérimentalement, un modèle micro mécanique a été développé. Ce modèle a la spécificité de prendre en compte l'arrangement 3D du tissu à travers une représentation idéalisée mais pertinente de sa microstructure fibreuse. Les réponses macroscopiques prédites pour différents chargements ont pu être comparées à l'expérience pour validation. A l'échelle microscopique, la cinématique des fibres au cours du chargement a pu être simulée. Les micromécanismes ayant lieu au cours de la déformation du réseau fibreux ont ainsi pu être identifiés, ouvrant de nouvelles perspectives dans la compréhension des propriétés multi-échelles du tissu. / The human vocal fold owns exceptional vibratory properties. It is capable of withstanding large deformations, for different types of loading, in a repeated and reversible manner. These particular vibro-mechanical properties are closely linked to its microstructure: a multi-layer complex structure composed of highly heterogeneous protein fibre networks. However, it is still difficult today to describe precisely the implication of the microstructural specificities of the fold in its biomechanical behaviour.In order to clarify this link and to move towards a better understanding of the behaviour of the vocal tissue, this study proposes to approach the problem under three complementary approaches, combining microstructural characterization, mechanical characterization and numerical modelling. First, the microstructure of the fold was studied emph{ex vivo} using an original technique based on X-ray tomography. The use of synchrotron tomography in phase retrieval mode has revealed the structure of the tissue at different scales. In particular, high-resolution 3D images of the fibrous structure of the upper and muscular layers of the tissue were acquired. These images gave rise to a quantitative 3D analysis of the fibrous arrangement, allowing the determination of descriptors of orientation and 3D geometry of the fibers.In a second step, the mechanical behaviour of the fabric under different loading conditions was studied. A protocol has been proposed to characterize the same sample in tension, compression and shear. These tests have complemented existing knowledge on fold biomechanics, and constitute important reference data for the construction and validation of digital models.Finally, based on the data acquired experimentally, a micro-mechanical model was developed. This model has the specificity to take into account the 3D arrangement of the tissue through an idealized but relevant representation of its fibrous microstructure. The macroscopic responses predicted for different loading conditionds could be compared to the experiment for validation. At the microscopic scale, the kinematics of the fibres during the loading could be simulated. The micromechanisms that occur during the deformation of the fibrous network could thus be identified, opening new perspectives in the understanding of the multi-scale properties of the tissue.

[pt] O presente trabalho de pesquisa estuda a modelagem numérica de solos residuais no que se refere ao seu comportamento mecânico, a partir da análise micro-mecânica, utilizando como ferramenta de modelagem o método dos elementos discretos (MED), o qual permite a representação do solo como meio particulado 2D por meio de elementos discretos circulares. Diversos são os fenômenos micro e macro-estruturais presentes nos solos residuais, os quais condicionam sua resposta mecânica, podendo-se mencionar a dupla estrutura e dupla porosidade, a presença de uma matriz argilosa, a condição não saturada, a cimentação e quebra de grãos, e a presença de pequenos blocos de rocha não alterada. A partir do estudo destes fenômenos foram propostas formulações matemáticas que os descrevem, as quais foram implementadas no código de elementos discretos DEMlib. Após a calibração e validação do programa de análise implementado, a influência de cada um destes fenômenos na resposta mecânica do solo foi estudada pela simulação dos ensaios edométrico e de cisalhamento direto em amostras discretas com compacidade variada, criticando os resultados e obtendo conclusões. Em seguida estes fenômenos foram estudados de forma combinada no intuito de reproduzir a resposta de alguns solos residuais jovens e maduros. Encerrando o trabalho foram resumidas as conclusões obtidas e apontadas sugestões para um aprofundamento e desenvolvimentos subseqüentes da linha de pesquisa implementada. / [en] The present research studies the numerical modeling of the mechanical behavior of residual soils, by a micro-mechanical analysis, using as modeling tool the discrete elements method (DEM), which allows the representation of the soil as 2D particle assembly of circular discrete elements. There are several micro and macro structural phenomena present in residual soils, which determine its mechanical response: double structure and double porosity of soil mass, the presence of a clay-like matrix, partially saturated condition, grain cementation, grain crushing, and the presence of small blocks of not-weathered parental rock. Based on the study of these phenomena, mathematical formulations have been proposed in order to describe them, which have been implemented in the DEMlib discrete elements code. After calibration and validation of the implemented analysis program, the influence of each phenomena in soil response was studied by simulating edometrical and direct shear tests in discrete samples with several densities, criticizing the results and getting conclusions. Afterwards, these phenomena were studied in a combined way in order to reproduce the response of some young and mature residual soils. To finish up this work the conclusions obtained have been summarized and suggestions for deepening and further developing of the implemented research line have been stated.

Ziel dieser Arbeit ist es, eine Verbindung zwischen der Mikrostruktur teilkristalliner Polymere und derer mechanischen Eigenschaften auf der Mikro- und Nanometerskala aufzubauen. Dazu wurden Methoden der Rasterkraftmikroskopie verwendet um sowohl orts- als auch zeitaufgelöst Kristallisations-, Deformations- und Diffusionsprozesse in der Mikrostruktur von elastomerem Polypropylen (ePP) abzubilden. Die mechanischen Eigenschaften wurden simultan mit Mikrozugversuchen bestimmt. So konnte beispielsweise ein Zusammenhang zwischen abnehmender Kristall-Kristall-Distanz und einem Ansteigen des Elastizitätsmoduls während der Kristallisation nachgewiesen werden. Weiterhin war es möglich die Veränderung der nano-mechanischen Eigenschaften während der Kristallisation einzelner kristalliner Lamellen in deren direkter Umgebung mit MUSIC-mode Rasterkraftmikroskopie zu untersuchen. Laterale Querexpansion (auxetisches Verhalten) konnte bei uniaxialen Zugversuchen für die Kreuzschraffur-Struktur elastomeren Polypropylens auf der Größenskala einiger Mikrometer nachgewiesen werden. Zusätzlich wurde eine Orientierungsabhängigkeit dieses Effekts beobachtet. Außerdem wurde die Diffusion einzelner Kristalle in der Mikrostruktur von ePP beobachtet. Die Heterogenität dieser Diffusion lässt auf eine kristallin-amorph Grenzschicht um alle Kristalle schließen.

No description available.

In the absence of a fusion neutron source, research on the structural integrity of materials in the fusion environment relies on current fission data and simulation methods. Through investigation of the Fe-Cr system, this detailed study explores the challenges and limitations in the use of currently available radiation sources for fusion materials research. An investigation of ion-irradiated Fe12%Cr using nanoindentation with a cube corner, Berkovich and spherical tip, and micro-cantilever testing with two different geometries, highlighted that the measurement of irradiation hardening was largely dependent on the type of test used. Selected methods were used for the comparison of Fe6%Cr irradiated by ions and neutrons to a dose of 1.7dpa at a temperature of 288°C. Micro-cantilever tests of the Fe6%Cr alloy with beam depths of 400 to 7000nm, identified that size effects may significantly obscure irradiation hardening and that these effects are dependent on radiation conditions. Irradiation hardening in the neutron-irradiated alloy was approximately double that of the ion-irradiated alloy and exhibited increased work hardening. Similar differences in hardening were observed in an Fe5%Cr alloy after ion-irradiation to a dose of 0.6dpa at 400°C and doses rates of 6 x 10^-4dpa/s and 3 x 10^-5dpa/s. Identified by APT, it was shown that increased irradiation hardening was likely to be caused by the enhanced segregation of Cr observed in the alloy irradiated with the lower dose rate. These observations have significant implications for future fusion materials research in terms of the simulation of fusion relevant radiation conditions and micro-mechanical testing.