Esta dissertação insere-se nas áreas de qualidade laboratorial e de ensaios de controle de concreto, especificamente quanto à propriedade módulo estático de deformação ou módulo de Young. A motivação do trabalho é a elevada variabilidade de resultados experimentais observada pelo meio técnico nacional em ensaios interlaboratoriais, cujos resultados indicam desvios-padrão totais da ordem de 3,5 GPa, valor significativo para o controle tecnológico de obras de construção civil. Os objetivos buscados foram a identificação das parcelas da variabilidade oriundas da produção e do ensaio, com especial atenção àquela originada na instrumentação para medida das deformações durante o ensaio, e a discussão da aplicabilidade do conceito semiprobabilístico normativo à propriedade módulo de deformação do concreto. Além disso, a própria discussão da aplicabilidade da sistemática de pesquisa e análise sobre este tipo de ensaio e de material constou como um objetivo do trabalho. Para tal, desenvolveu-se um programa experimental em duas etapas: a primeira foi destinada às avaliações de acurácia (precisão e exatidão) do método de ensaio. As avaliações se deram segundo roteiros da área metrológica para validação de métodos e sistemas de medida. De quatro instrumentações para medida das deformações testadas, uma se mostrou mais precisa (identificada como clip gages) e outra se mostrou a mais suscetível a erros sistemáticos e aleatórios entre as testadas (identificada como compressômetro com dois relógios comparadores). Recomendou-se a ampliação do programa experimental para o âmbito interlaboratorial, pois, a rigor, o método de ensaio vigente não poderia ser considerado validado em termos de acurácia baseando-se unicamente nos resultados deste programa experimental. Porém, concluiu-se pela possibilidade de aceitação prática do método independentemente da utilização de três de um total de quatro tipos de instrumentação para medida das deformações testados em ensaio, sem que houvesse prejuízo para a produção ou o controle tecnológico usual desta propriedade. Na segunda etapa, obteve-se um Diagrama de Dosagem e estudou-se um cenário de fornecimento de concreto sob critérios estatísticos diferentes de atendimento à especificação de módulo de deformação: utilização do valor característico e do valor médio, com diferença de 4 GPa entre eles. Estimou-se um aumento da ordem de 9% no deslocamento vertical de uma viga simples bi-apoiada quando executada com o concreto de menor módulo em relação à execução com o de maior módulo. Por sua vez, o concreto de maior módulo exigiria um aumento no consumo de cimento da ordem de até 200 kg/m3, se conservados todos os insumos materiais e os demais parâmetros tecnológicos contidos nos traços. Concluiu-se pela aplicabilidade do uso da sistemática empregada na avaliação da acurácia do método de ensaio e do uso do conceito semiprobabilístico para esta propriedade. / This work is developed into the areas of laboratorial quality and concrete control tests, specifically focusing on the static modulus of elasticity or Young´s modulus. The motivation of this work is the high variability of experimental results observed by national technicians in interlaboratorial tests. These results show total standard deviations of around 3.5 GPa, a significant value for the technological control for civil construction. The main objectives are the identification of the variability fragments derived from the production and test, specially the ones related to the instrumentation for measuring deformations during the test, and the discussion of the semi-probabilistic concept applicability on the concrete Young´s modulus control. Moreover, the discussion of the applicability of the procedure used in this work and its analysis are also objective pursued here. The experimental program was developed in two steps: the first step covered the accuracy assessments (precision and exactness) of test method. The assessments were carried out according to instructions from Metrology concepts for the validation of the methods and the measure systems. One out of four instrumentations for measuring the tested deformations proved to be more precise (identified as clip gages) and another one proved to be more susceptible to systematic and random errors (identified as a compressometer with two dial indicators). The extension of the experimental program to an interlaboratorial scope is recommended because the current test method could not be considered valid based only on the results of this experimental program. However, it was shown that the practical acceptance of the test method for three among the four kinds of instrumentations analyzed, without damaging the production or the usual technological control of this property, is possible. On the second step, a mix design diagram was obtained and a case of supply of concrete under different statistical criteria (fulfillment the modulus of elasticity specification): the use of the characteristic value and the average value, with difference of 4 GPa between them. An increase of 9% on the vertical transference of a simple dual supported beam was observed when using a lower modulus concrete, when compared to another one with a higher modulus. On the other hand, the modulus increase would require an increment in the cement consumption up to 200 kg per cubic meter, if all the material inputs and further technological parameters is maintained. The final conclusion was that the procedure used on the assessment of the test method accuracy and the semi-probabilistic concept on this material property is applicable.

Orientador: Maria Beatriz Duarte Gavião / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-24T16:50:05Z (GMT). No. of bitstreams: 1 Muller_CristinaEmokeErika_M.pdf: 2322583 bytes, checksum: 34487fb1a63db95bab0032e52585a63e (MD5) Previous issue date: 2014 / Resumo: O presente estudo, de caráter experimental, teve como objetivo a avaliação de pontos-gatilho miofasciais (PG) do músculo trapézio descendente (TPz) por imagens de ultrassonografia bidimensional em escala de cinza (US 2D) e elastografia ultrassonográfica (ELASTO), bem como avaliar a eficácia das técnicas de acupuntura (AC) e eletroacupuntura (EA) na diminuição da dor em mulheres com síndrome da dor miofascial (SDM) associada a queixas de dor nas regiões de cabeça, pescoço e parte superior do tronco. Uma amostra de conveniência de 24 voluntárias, com idades entre 20 e 40 anos (27,33±5,05), IMC entre 18,03 e 27,09 Kg/m² (22,59±3,11), ciclo menstrual regular, presença de ao menos um PG ativo em ambos os TPz, queixa de dor local e/ ou referida há pelo menos seis meses foi selecionada para o estudo. Após a assinatura do Termo de Consentimento Livre e Esclarecido (TCLE), as voluntárias foram randomizadas em três grupos, sendo: dois grupos de tratamento (AC e EA) e um grupo controle (SHAM). Oito sessões de tratamento foram então realizadas, duas vezes por semana, durante aproximadamente um mês, levando em consideração o ciclo menstrual das voluntárias. Imagens do músculo trapézio foram adquiridas pelas técnicas de US 2D e ELASTO para avaliação e diagnóstico das propriedades mecânicas e viscoelásticas do tecido miofascial e a comparação dessas características pré e pós-tratamento. Nas imagens de US 2D, as áreas dos PG foram mensuradas. Nos elastogramas adquiridos pela ELASTO, o índice de resistência (IR) foi calculado. Tanto as voluntárias quanto o examinador eram cegos em relação aos grupos. A intensidade de dor geral e localizada nos TPz direito e esquerdo (TPzD e TPzE, respectivamente) pré e pós-tratamento foi mensurada com o auxílio da escala visual analógica (EVA). A ocorrência de fatores influenciadores e as fases do ciclo menstrual foram monitoradas. Os dados foram analisados quanto à normalidade e simetria. Na avaliação intragrupo todos os dados apresentaram distribuição normal, sendo analisados pelo teste t student para dados pareados. Observou-se diminuição da intensidade de dor geral para o grupo AC (P<0,001) e de dor geral e local para a EA (geral, P=0,027; TPzD, P<0,001; TPzE, P=0,005); sem resultados estatisticamente significantes para o grupo SHAM (geral, P=0,296; TPzD, P=0,052; TPzE, P=0,198). Quanto à avaliação de PG nas imagens de US 2D , observou-se diminuição da área do PG para ambos os TPzD e TPzE nos grupos AC (TPzD e TPzE, P<0,001) e EA (TPzD, P=0,003; TPzE, P=0,005); e não para o grupo SHAM (TPzD, P=0,117; TPzE, P=0,093). Em relação à ELASTO, os dados não apresentaram significância estatística para a amostra analisada, contudo, o IR de ambos os lados apresentou-se menor após o tratamento para a EA e AC, e maior para a SHAM. Na comparação entre grupos, diferenças estatisticamente significantes não foram observadas para as variáveis testadas. Os resultados do presente trabalho sugerem a possibilidade de utilização da US 2D e ELASTO na caracterização do tecido miofascial e de PG, apontando para a possibilidade de confirmação objetiva de efeitos subjetivos de tratamentos propostos para a SDM. Ainda, as técnicas de AC e EA demonstraram eficácia no alívio da dor geral, sendo a efetividade da EA observada também na diminuição da intensidade de dor local. O nível de significância adotado foi ?=0,05 / Abstract: The aim of this study was to evaluate upper trapezius (TPz) myofascial trigger points (MTrP) through two-dimensional ultrasonography (2D US) and ultrasound elastography (ELASTO) images, as well as, to evaluate the effectiveness of acupuncture (AC) and electroacupuncuture (EA) in decreasing pain in women with myofascial pain syndrome (MPS) associated with head, neck and upper back complaints. A convenience sample of 24 volunteer aged between 20 and 40 years (27.33±5.05 years), body mass index (BMI) from 18.03 to 27.09Kg/m² (22.59±3.11), presenting regular menstrual cycle, at least one active MTrP at both right and left TPz (RTPz and LTPz, respectively) and local or referred pain for up to six months were selected. After signing the Informed Consent Form (ICF), subjects were randomized into three groups, being: two treatment groups (AC and EA) and one control group (SHAM). Eight treatment sessions were than performed, two times per week, for nearly one month, considering each volunteer menstrual cycle. Pre, post-treatment Intensity of pain was assessed by visual analogue scale (VAS) as well as MTrP mean area and strain ratio (SR) by 2D US and ELASTO, respectively, in way to myofascial tissue mechanical and viscoelastic properties assessment and diagnosis. Both, volunteers and examiner were blinded for the three groups. Influencing factors and menstrual cycle phases were monitored. Data were analyzed for normality and symmetry. All intragroup data were normally distributed, so, were analyzed by Student¿s t test for paired data. Decrease in pain intensity was observed for AC (general, P<0.001) and EA (general, P=0.027; RTPz, P<0.001; LTPz, P=0.005); without any significant result for SHAM (general, P=0.296; RTPz, P=0.052; LTPz, P=0.198). Decreased MTrPs area occurred for both sides in AC (RTPz and LTPz, P<0.001) and EA (RTPz, P=0.003; LTPz, P=0.005); on the other hand, SHAM results were not significant (RTPz, P=0.117; LTPz, P=0.093). Concerning ultrasound elastography, although not statistically significant, post-treatment SR in both sides were lower than the beginning for EA and AC, and higher for SHAM group. Regarding within group comparison, no statistically significant difference were observed for the tested variables. 2D US and ELASTO presented the possibility of MTrPs and surrounding tissue diagnosis and characterization, pointing to the possibility of objective confirmation of subjective MPS treatment effects. Also, EA and AC were effective in decreasing general pain intensity, being EA also effective in local pain intensity relief. The level of significance was ?=0.05 / Mestrado / Anatomia / Mestra em Biologia Buco-Dental

Les matériaux super-élastiques sous forme de couche minces présentent un domaine d’applications assez large. Grâce à leur aptitude à accommoder de grandes déformations de manière réversible, les films super-élastiques peuvent être utilisés comme sous couches entre le substrat et les revêtements dures. Cela permet d’améliorer significativement de nombreuses propriétés telles que : l’adhésion, le taux d’usure et le coefficient de frottement. Elles peuvent également être utilisées dans la fabrication des dispositifs médicaux tels que les stents. Bien que les alliages β-métastable à base de titane présentent des propriétés remarquables, une grande partie de la littérature publiée sur les films super-élastiques est consacrée aux alliages Ni-Ti. Ainsi, le but de ce travail est de développer de nouvelles couches super-élastiques de type β-métastable, obtenues par pulvérisation cathodique magnétron. Dans ce sens, deux types d’alliages ont été étudiés, les alliages binaires Ti-Nb et l’alliage quaternaire Ti-Nb-Ta-Zr. Après une description du dispositif expérimental utilisé pour la synthèse des couches, nous étudions plus particulièrement l’influence des paramètres de dépôt sur les propriétés des revêtements. La morphologie des revêtements a été caractérisée par microscope électronique à balayage. La diffraction de rayons X a été employée pour l’étude de la microstructure et la texture des films déposés. Enfin, l’effet super-élastique a été caractérisé par deux méthodes, l’indentation sphérique et la compression de micro-piliers usinés par faisceau d’ions focalisés / Superelastic thin films have a fairly wide field of applications. Thanks to their ability to accommodate a large deformation reversibly, superelastic films may be used as intermediate layers between the substrate and the hard layers. This significantly improves many properties such as adhesion, wear and coefficient of friction. They can also be used in the manufacture of medical devices such as stents. Although β-metastable titanium-based alloys have excellent properties, much of the published literature on the superelastic films is devoted to Ni-Ti. Thus, the purpose of this work is to develop new superelastic β-metastable titanium-based films, obtained by magnetron sputtering. After describing the experimental device used for the synthesis of thin films, we study more specifically the influence of deposition parameters on the properties of coatings. The morphology was characterized by the observation of fractured cross-sectional by scanning electron microscope. The X-ray diffraction was used to study the microstructure and texture of the deposited films. Finally, the superelastic effect was characterized by two methods, the spherical indentation and micro-pillars compression machined by focused ion beam

Reinforced concrete frames, infilled with brick/concrete block masonry, are the most common type of structures found in multi-storeyed constructions, especially in developing countries. Usually, the infill walls are considered as non-structural elements even though they alter the lateral stiffness and strength of the frame significantly. Approximately 80% of the structural cost from earthquakes is attributable to damage of infill walls and to consequent damages of doors, windows and other installations. Despite the broad application and economical significance, the infill walls are not included in the analysis because of the design complexity and lack of suitable theory. But in seismic areas, ignoring the infill-frame interaction is not safe because the change in the stiffness and the consequent change in seismic demand of the composite structural system is not negligible. The relevant experimental findings shows a considerable reduction in the response of infilled frames under reverse cyclic loading. This behaviour is caused by the rapid degradation of stiffness, strength, and low energy dissipation capacity resulting from the brittle and sudden damage of the unreinforced masonry infill walls. Though various national/international codes of practice have incorporated some of the research outcomes as design guidelines, there is a need and scope for further refinement. In the initial part of this work, a numerical modelling and linear elastic analysis of masonry infilled RC frames has been done. A multi-storey multi-bay frame infilled with masonry panels, is considered for the study. Both macro modelling and micro modelling strategies are adopted. Seismic loading is considered and an equivalent static analysis as suggested in IS 1893, 2002 is done. The results show that the stiffness of the composite structure is increased due to the obvious confinement effects of infill panels on the bounding frame. A parametric study is conducted to investigate the influence of size and location of openings, presence/absence of infill panels in a particular storey and elevation irregularity in terms of floor height. The results show that the interaction of infill panel changes the seismic response of the composite structure significantly. Presence of openings further changes the seismic behaviour. Increase in openings increases the natural period and introduce newer failure mechanisms. Absence of infill in a particular storey (an elevation irregularity) makes it drift more compared to adjacent storeys. Since the structural irregularities influence the seismic behaviour of a building considerably, we should be cautious while construction and renovation of such buildings in order to take the advantage of increased strength and stiffness obtained by the presence of infill walls. A nonlinear dynamic analysis of masonry infilled RC frames is presented next. Material non linearity is considered for the finite element modelling of both masonry and concrete. Concrete damage plasticity model is employed to capture the degradation in stiffness under reverse cyclic loading. A parametric study by varying the same parameters as considered in the linear analysis is conducted. It is seen that the fundamental period calculation of infilled frames by conventional empirical formulae needs to be revisited for a better understanding of the real seismic behaviour of the infilled frames. Enhancement in the lateral stiffness due to the presence of infill panel attracts larger force and causes damage to the composite system during seismic loading. Elevation irregularities included absence of infill panels in a particular storey. Soft storey shows a tendency for the adjacent columns to fail in shear, due to the large drift compared to other storeys. The interstorey drift ratios of soft storeys are found to be larger than the limiting values. However this model could not capture the separation at the interfaces and related failure mechanisms. To improve the nonlinear model, a contact surface at the interface is considered for a qualitative analysis. A one bay one storey infilled frame is selected. The material characteristics were kept the same as those used in the nonlinear model. Contact surface at the interface was given hard contact property with pressure-overclosure relations and suitable values of friction at the interface. This model could simulate the compressive diagonal strut formation and the switching of this compressive strut to the opposite diagonal under reverse cyclic loading. It showed an indication of corner crushing and diagonal cracking failure modes. The frame with central opening showed stress accumulation near the corners of opening. Next, the micro modelling strategy for masonry suggested by Lourenco is studied. This interface element can be used at the masonry panel-concrete frame interface as well as at the expanded masonry block to block interface. Cap plasticity model (modified Drucker – Prager model for geological materials) can be used to describe the behaviour of masonry (in terms of interface cracking, slipping, shearing) under earthquake loading. The blocks can be defined as elastic material with a potential crack at the centre. However, further experimental investigation is needed to calibrate this model. It is required to make use of the beneficial effects and improve upon the ill-effects of the presence of infills. To conclude, infill panels are inevitable for functional aspects such as division of space and envelope for the building. Using the lateral stiffness, strength contribution and energy dissipation capacity, use of infill panels is proposed to be a wiser solution for reducing the seismic vulnerability of multi-storey buildings.

A l'échelle nanométrique, les solides peuvent changer de forme par diffusion de surface, et présentent alors des propriétés de mouillage qui s'apparentent à celles des liquides. Dans cette thèse, nous nous sommes plus particulièrement intéressés au comportement de mouillage des nano-solides sur des substrats nanopatternés, comportant par exemple des piliers ou des tranchées. Sur ces substrats, les nanoparticules (ou ilots) solides peuvent être multi-stables : c'est-à-dire qu'ils peuvent présenter plus d'un état localement stable. Comme les liquides, les solides ont été observés par exemple dans des états dits de Wenzel (pénétrant dans la structure du substrat) ou de Cassie-Baxter (ne pénétrant pas). Grâce à une combinaison de simulations Monte Carlo Cinétiques et de modèles analytiques, nous avons étudié la stabilité de ces états et leur dynamique de transition. Plus particulièrement, avons mis en évidence le rôle de la diffusion de surface et de la nucléation bidimensionnelle sur la dynamique de transition. Nous avons aussi montré que les contraintes élastiques augmentent la stabilité des états de Cassie-Baxter, et mènent à de nouveaux états, avec des morphologies asymétriques ou partiellement empalées dans les nanostructures. Finalement, nous avons proposé de contrôler les transitions de mouillage à l'aide de l'électromigration induite par un faisceau d'électrons. Nos résultats ouvrent la voie vers une nouvelle direction pour les investigations expérimentales / At the nanometer scale, solids can change shape thanks to surface diffusion and therefore display wetting properties that can be likened to those of liquids. This doctoral thesis intends to study particularly the wetting behaviour of nano-solids located on nanopatterned substrates, containing for instance pillars or trenches. Upon these substrates, solid nanoparticles (or islands) can be multi-stable – that is to say they can display more than one locally-stable state. Just like liquids, solids have been observed for example in the context of the so-called Wenzel state (penetrating the very structure of the substrate) and Cassie-Baster state (no penetration). By combining Kinetic Monte Carlo simulations with analytical models, we conducted a study on the stability of these states along with their dynamics of transition. In particular, we highlighted the specific roles that surface diffusion and bidimensional nucleation play in regards to the dynamics of transition. We also demonstrated that elastic constraints increase the stability of Cassie-Baxter states and lead to new states, with either asymmetric morphologies or morphologies that are partially impaled into the nanostructures. Last but not least, we proposed to control wetting transitions using the electromigration brought on by an electron beam. Our results pave the way for a new direction in the field of experimental investigations

On s’intéresse à la simulation d’écoulements compressibles multi-matériaux et, notamment, aux interactions fluide/structure dans les régimes transitoires et en dynamique rapide. Le but est de pouvoir décrire l’évolution de matériaux de lois de comportement très différentes à l’aide d’un modèle unique. Les milieux sont seulement différenciés par leurs équations d’état et sont séparés par une interface dite sharp. Les matériaux peuvent être des fluides ou des solides élastiques et sont soumis à de grandes déformations. Le modèle est écrit dans le formalisme eulérien. Le schéma numérique est résolu sur des grilles cartésiennes pour des simulations en trois dimensions.Une extension du modèle permet de décrire les déformations plastiques des solides. / We are interested in the simulation of compressible multimaterial flows and especially influid/structure interactions in transient states and fast dynamics. We aim to describe the evolution of materials of very different constitutive laws with an unified model. The materials are only differentiated by their own constitutive laws and are separated by a sharp interface. They can be as well fluids or elastic solids and under go large de formations. The model is written in the Eulerian framework. The numerical scheme is solved on Cartesian grids for simulations in three dimensions. An extension of the elastic model is added to describe the plastic deformations of solids.

Ce travail de thèse a pour objet l'étude de l'influence de la plasticité sur le délaminage et le flambage de films minces déposés sur substrats. Il repose sur une approche mixte combinant des simulations atomistiques et des calculs analytiques basés sur la théorie des plaques minces de Föppl-von Kármán (FvK). Les simulations ont permis de caractériser, au cours de la formation d'une ride droite, un mécanisme de glissement localisé dans l'interface en pied de cloque entraînant une augmentation de la déflexionmaximale de la ride. Ce mécanisme de glissement est également présent lorsque le délaminage piloté par le flambage du film mince est lui aussi observé. En l'intégrant dans le modèle élastique de FvK, la forme de la ride droite ainsi que le processus de délaminage ont ensuite été caractérisés. Le bon accord trouvé entre les simulations atomistiques et le modèle explique notamment le délaminage des cloques sans introduire de dépendance entre l'énergie d'adhésion et la mixité modale. L'initiation du cloquage à partir d'une marche d'interface créée par des dislocations venant du substrat a également été étudiée.Les simulations révèlent qu'avant flambage, le film se décolle à la fois sur le haut et sur le bas de la marche. Un mécanisme de glissement est là aussi identifié. Une déformation critique de flambage qui tient compte de ces phénomènes a été déterminée en modélisant le film mince sur la marche dans le formalisme de FvK. Les résultats des simulations couplés au modèle élastique expliquent, comme il est par ailleurs observé expérimentalement, pourquoi les cloques se forment préférentiellement au-dessus dedéfauts tels que des marches. / The purpose of this thesis is to study the influence of plasticity on the delamination and buckling of thin films deposited on substrates. Combining atomistic simulations and analytic calculations performed in the framework of continuum mechanics, the microscopic processes consisting in the sliding of the atoms located at the base of the blister has been characterized during the formation of a straight-sided blister. This sliding effect has been found to increase the maximum deflection of the buckling structure. It also modifies the delamination process of the interface. Taking into account this sliding into the Föppl-von Kármán theory of thin plates (FvK), the shape of the straight-sided blister and the delamination process have been then characterized. The agreement found between the atomistic simulations and the model explains how the buckling-driven delaminationproceeds without introducing any dependence between the adhesion energy and the mode of mixity. The initiation of the buckling from a dislocation-induced interface step has been also investigated. The simulations show that, before buckling, the film delaminates on both sides of the step and a sliding mechanism is also observed. A critical buckling strain accounting for thesephenomena has been analytically determined in the FvK framework. The simulation results and the elastic model explain, as it has also been experimentally observed, why blistering preferentially occurs above step-like defects.

Le procédé Smart CutTM, utilisé pour le transfert de films minces sur substrat est basé sur la fissuration du silicium. La propagation des fissures est initiée à partir de défauts bidimensionnels induits par implantation d'hydrogène, les « H-platelets ». Des études précédentes ont montré que la fissuration du Si peut également être obtenue à partir de défauts nommés « He-plates » qui ont la particularité d'avoir un diamètre dix fois supérieur. L'objectif de ce travail était d'étudier la formation de ces défauts et leur évolution sous flux d'hydrogène jusqu'à la propagation des fissures. Dans une première partie, la formation des « He-plates » a été étudiée pour différentes orientations de substrats et discutée par rapport à la contrainte compressive bi-axiale induite par l'implantation. Les résultats montrent que les mécanismes qui gouvernent la formation des « He-plates » sont les mêmes que pour les « H-platelets ». Dans une seconde partie, l'évolution des « He-plates » en présence d'H a été étudiée en utilisant une approche expérimentale originale qui couple implantations d'hydrogène et observations par microscopie électronique en transmission. Les expériences montrent que la croissance des « He-plates » est gouvernée par la diffusion de l'hydrogène qui dépend de la température et du taux d'endommagement. Enfin, leur croissance est décrite à l'aide d'un modèle cinétique et, leur coalescence a été analysée en relation avec un modèle élastique. La propagation rectiligne de fissures à partir de ces précurseurs offre des perspectives intéressantes pour une utilisation industrielle. / The Smart CutTM process, used in the transfer of thin films on substrates is based on the cracking of silicon. The crack propagation is initiated from bi-dimensional defects induced by H-implantation, the H-platelets. Previous studies showed that the propagation of cracks in Si can also be triggered from defects named He-plates which have the particular feature of having a diameter ten times larger. The aim of this work was to study the formation of these defects and their evolution until the crack propagation under H supply.In a first part, the formation of He-plates was studied for different substrate orientations and discussed regarding the bi-axial compressive stress induced by implantation. Results show that the mechanisms that govern the He-plate formation are the same than for H-platelet formation. In a second part, the evolution of He-plates under H supply was studied by using an original experimental approach that combines H-implantation and transmission electron microscopy observations. Experiments show that the growth of He-plates is controlled by the diffusion of hydrogen which depends on temperature and damage rate. Finally, the growth is described by a kinetic model and their coalescence was analyzed with regard to an elastic model. The straight propagation of cracks from He-plates offers promising outlook for an industrial use.

Cette étude a consisté à caractériser l'influence de la plasticité sur les formes de cloques observées à la surface des films minces déposés sur substrat à l'aide de simulations par éléments finis. Dans une première partie, nous nous sommes intéressés à l'influence que peut avoir la plasticité du film sur les morphologies observées expérimentalement sur la surface de films d'or. Les simulations ont ainsi permis de caractériser la déstabilisation d'une cloque circulaire sous l'effet d'une surpression exercée sur la surface extérieure du film, menant à la formation de cloques en forme de «donut» et «croissant». Pour ce faire, un modèle 3D incluant une loi élasto-plastique a d'abord été considéré pour décrire le cloquage d'un film ductile. Un analogue à 2D moins coûteux en ressources numériques a ensuite été utilisé en imposant une pliure plastique sur la circonférence de la cloque. Les différentes morphologies de cloques en fonction de la surpression extérieure et de la contrainte interne ont ainsi été déterminées. Un bon accord a été obtenu entre les simulations numériques et les observations expérimentales confirmant le rôle de la surpression et de la plasticité dans cette déstabilisation. Dans la seconde partie, l'effet sur la propagation des rides des marches d'interface résultant de la déformation plastique du substrat a été étudié. A partir de simulations par éléments finis intégrant un modèle de zones cohésives prenant en compte la mixité modale, l'influence de la hauteur des marches et de leur orientation par rapport à l'axe de compression, orientation liée à la cristallographie, a été caractérisé. / This study consisted to characterize the influence of plasticity on the shapes of blisters observed on the surface of thin films deposited on substrates using finite element simulations. In the first part, we looked at the possible influence of the plasticity of the film on the morphologies observed experimentally on the surface of gold films. The simulations thus enabled to characterize the destabilization of a circular blister under the effect of an overpressure exerted on the outer surface of the film, leading to the formation of croissant and donut like blisters. To do this, a 3D model including an elasto-plastic law was first considered to describe the buckling of the ductile film. A similar 2D model which is less expensive in numerical computing resources was then used by imposing a plastic folding on the circumference of the blister. The different morphologies of blisters have been then determined as a function of the external overpressure and internal stress. A good agreement was obtained between numerical simulations and experimental observations confirming the role of the overpressure and plasticity in this destabilization. In the second part, the effect on the spread of straight blisters of interface steps resulting from the plastic deformation of the substrate was investigated. From finite element simulations incorporating a cohesive zone model taking into account a modal mixity, the influence of the step heights and their orientations with respect to the compression axis, an orientation related to crystallography, was characterized.

This work has as main objective to analyze the influence of the ceramic block geometry in the mechanical performance of the structural masonry, under centered compression, when mortars with resistance varied are used. Two types of ceramic blocks geometries are studied: one with drained walls (BPV) and the other with solid walls (BPM), possessing approximate resistances of 30MPa, in relation to their liquid area; also four mortar lines with resistances between 4MPa and 17Mpa were used. The experimental program includes the following compression essays: units, prisms and small walls, in which five prisms of two and three overlapping rows and four small walls of two and half blocks were made by 4 height rows. Also, the module of elasticity, so much for the mortars, blocks and prisms, as for the small walls was obtained. Among the several essayed combinations, the variance analysis of the samples submitted to the compression was made. Based on the analysis of the results, it may be concluded that the BPM block, is more efficient for the use in structural masonry than the BPV one, when an increment in the resistance of the masonry is needed, increasing the mortar resistance; that efficiency may be defined in the relation of the prisms resistance (two and three blocks) and of the small walls by the block. The small walls built with BPM blocks present a significant capacity to absorb strains, when high resistance mortar is used (the one used in this work); as for the BPV block, that difference was not so expressive. Therefore, the use of placement mortar with those resistances may potentiate the ceramic blocks masonry, depending on the geometry and the mechanical properties of the adopted blocks. / Este trabalho tem como objetivo principal analisar a influência da geometria do bloco cerâmico no desempenho mecânico da alvenaria estrutural, sob compressão centrada, quando utilizadas argamassas com resistências variadas. Estudam-se dois tipos de geometrias de blocos cerâmicos: uma de paredes vazadas (BPV) e outra com paredes maciças (BPM), possuindo resistências aproximadas de 30MPa em relação a área líquida dos mesmos; também foram utilizados quatro traços de argamassa com resistências entre 4MPa e 17MPa. O programa experimental abrange os seguintes ensaios de compressão: unidades, prismas e pequenas paredes. Foram confeccionados cinco prismas de duas e três fiadas sobrepostas e quatro pequenas paredes de dois blocos e meio por quatro fiadas de altura. Também foi obtido o módulo de elasticidade, tanto para as argamassas, blocos e prismas, quanto para as pequenas paredes. Entre as várias combinações ensaiadas, foi feito a análise de variância das amostras submetida à compressão. Com base na análise dos resultados, pode-se concluir que o bloco BPM é mais eficiente para o uso em alvenaria estrutural do que o BPV, quando se necessita um acréscimo na resistência da alvenaria, aumenta-se a resistência da argamassa, essa eficiência pode ser definida na relação da resistência dos prismas (dois e três blocos) e das pequenas paredes pela do bloco. As pequenas paredes construídas com blocos BPM apresentam uma significativa capacidade de absorver esforços, quando utilizada argamassa com resistência elevada (adotada nesse trabalho); quanto ao bloco BPV, essa diferença não foi tão expressiva. Sendo assim, a utilização de argamassa de assentamento com essas resistências pode potencializar a alvenaria de blocos cerâmicos, dependendo da geometria e das propriedades mecânicas dos blocos adotados.