Após o aumento de potência do reator IEA-R1 de 2 MW para 5 MW observou-se um aumento da taxa de corrosão nas placas laterais de alguns elementos combustíveis e algumas dúvidas surgiram com relação ao valor de vazão utilizada nas análises termo-hidráulicas. A fim de esclarecer e medir a distribuição de vazão real pelos elementos combustíveis que compõe o núcleo do reator IEA-R1, um elemento combustível protótipo, sem material nuclear, chamado DMPV-01 (Dispositivo para Medida de Pressão e Vazão), em escala real, foi projetado e construído em alumínio. A vazão no canal entre dois elementos combustíveis é muito difícil de estimar ou ser medida. Esta vazão é muito importante no processo de resfriamento das placas laterais. Este trabalho apresenta a concepção e construção de um elemento combustível instrumentado para medir a temperatura real nestas placas laterais para melhor avaliar as condições de resfriamento do combustível. Quatorze termopares foram instalados neste elemento combustível instrumentado. Quatro termopares em cada canal lateral e quatro no canal central, além de um termopar no bocal de entrada e outro no bocal de saída do elemento. Existem três termopares para medida de temperatura do revestimento e um para a temperatura do fluido em cada canal. Três séries de experimentos, para três configurações distintas, foram realizadas com o elemento combustível instrumentado. Em dois experimentos uma caixa de alumínio foi instalada ao redor do núcleo para reduzir o escoamento transverso entre os elementos combustíveis e medir o impacto na temperatura das placas externas. Dada a tamanha quantidade de informações obtidas e sua utilidade no projeto, melhoria e capacitação na construção, montagem e fabricação de elementos combustíveis instrumentados, este projeto constitui um importante marco no estudo de núcleos de reatores de pesquisa. As soluções propostas podem ser amplamente utilizadas para outros reatores de pesquisa. / After the IEA-R1 upgrade from 2 MW to 5 MW it was observed that the corrosion rate increased in a lateral plate of one fuel element and some issues appeared concerning the flow values used in the thermal-hydraulic analysis. In order to clear it up and measure the actual flow distribution among the fuel elements composing the IEA-R1 active core, a dummy element without nuclear fuel material, called DMPV-01 (Pressure and Flow Measurement Device), full scale, was designed and manufactured in aluminum. The flow rate in the channel between two fuel assemblies is very difficult to estimate or measure. This flow rate is very important to the cooling process of the external plates. This work presents the design and construction of an instrumented fuel assembly in order to measure the actual temperature in these lateral plates. Fourteen thermocouples were installed in this instrumented fuel assembly. Four in each lateral channel, one in the inlet nozzle and one in the outlet nozzle. There are three thermocouples in each channel to measure the clad temperature and one thermocouple to measure the fluid temperature. Three series of experiments, for three different core configuration were carried out with the instrumented fuel assembly. In two experiments a box was installed around the core to reduce the cross flow between the fuel assembly and measure the impact in the temperatures of external plates. Given the amount of information generated and its utility in the design, improvement and qualification in construction, assembly and manufacturing of instrumented fuel, this project turned out to be an important landmark on the thermal-hydraulic study of research reactor cores. The proposed solutions could be useful for other research reactors.

Esta Tese aborda, de modo original e pioneiro, importantes aspectos da Engenharia de Fundações do Sul de Minas: a) sistematização de conhecimentos sobre a Geologia regional; b) identificação e caracterização da prática de fundações; c) definição (com a formação de um banco de dados) dos perfis mais representativos do subsolo de suas principais cidades; d) estudo dos parâmetros físicos, químicos e geomecânicos de um solo típico; e) implantação de campo experimental de fundações da Universidade Federal de Lavras, com a realização de provas de carga. Grande ênfase foi dada aos itens (a), (c) e (e). Priorizou-se o estudo das fundações de baixa capacidade de carga, no estudo do comportamento carga-recalque de ensaios de placa, de provas de carga a compressão em estacas-broca isoladas e de tubulões curtos instrumentados. Destacam-se as análises sobre os efeitos de forma, profundidade, melhoramento do terreno de fundação e de inundação nas fundações rasas e da variação L/d na resistência lateral unitária das estacas, sendo valorizadas as fórmulas empíricas com base no SPT. São apresentadas fórmulas de previsão de carga, em função do SPT, para sapatas, estacas de pequeno diâmetro e tubulões curtos e um estudo de custos, onde se mostra que a opção indiscriminada por tubulões é inadequada para certas faixas de carga de trabalho. Adicionalmente, são feitas recomendações para intensificar o uso de sondagens tendo em vista a grande variabilidade das propriedades dos solos regionais e para aumentar os fatores de segurança nestas fórmulas onde houver possibilidade de ocorrência de colapso no solo. / This work presents, at time, important aspects of Foundation Engineering at Southern Region of Minas Gerais State: a) systematization of the knowledge about regional geology; b) identification and characterization of practice in foundations; c) definition (though establishment of a data base) of most representative sub-soil profiles at main cities at the region; d) study of physical, chemical and geomechanical parameters of a typical soil; e) implementation of a experimental field for foundation studies at Federal University of Lavras, by execution of load tests. A large emphasis was given to items a, c and e. The study of foundations of low load capacity was prioritized when testing plates, isolated piles under compression and short drilled piers with sensors. Analysis such as form effects, depth, soil improvement and flooding on shallow foundations and variation of L/d on the lateral unity resistance by emphasizing the empiral equations based on SPT were all pointed out. Mathematical equations are presented for load estimation as function of SPT for small diameter piles and short drilled piers as well as a cost study where it can bem shown that the undistinguished alternative for piers is inadequate for some load values. In addition, due to soil spatial variability and safety factor increment on soils subject for colapse, recommendations on intensive use of SPT test are given.

La question générale de cette recherche porte sur l’identification et l’analyse de la diversité des usages de systèmes techniques complexes, les Véhicule Utilitaires Légers (VUL), réalisés par un groupe hétérogène d’utilisateurs professionnels pour contribuer à une typologie des usages. Cette dernière est destinée à servir de ressource informationnelle pour les acteurs de la conception de ces véhicules. Ce travail s’articule autour de deux orientations.■ La première orientation vise l’analyse de la diversité des usages afin d’en faire ressortir des critères structurant. Pour cela, nous proposons une unité d’analyse transverse à l’ensemble des activités : les « usages situés d’un système multi-instrumenté (SMI) ». Nous les définissons comme l’ensemble des actions de l’utilisateur dirigées vers un but et servant une activité générale et située, impliquant tout ou une partie du SMI en tant que médiateur ou objet de l’activité. Un SMI représente le sous-système d’instruments construit par l’utilisateur à partir d’un système technique complexe.Les analyses s’appuient sur deux séries d’observations (exploratoires et systématiques outillées) auprès d’une diversité d’utilisateurs. Les résultats montrent qu’il existe des dimensions plus larges que les différents pôles de l’activité instrumentée influençant la réalisation des usages. En effet, l’utilisateur entretient des interrelations complexes avec les ressources de son action ; les caractéristiques de l’activité générale que les usages permettent et les caractéristiques de la situation au sein de laquelle ils sont réalisés. Il existe ainsi différents types d’usages en fonction de la place du SMI au sein de l’usage et de l’objet de l’usage.■ La seconde orientation poursuit un travail de réduction de la diversité des usages dans une perspective de catégorisation. Créer une catégorisation induit la définition d’une unité d’analyse qui sous-tend la construction des catégories et les variables permettant leur discrimination. Pour cela, nous proposons de mobiliser une seconde unité d’analyse, les « classes de situations d’usages d’un SMI », permettant de monter en généralisation à travers l’identification de variables structurant les usages.Mais la simple construction d’une catégorisation n’est pas suffisante au regard des caractéristiques des processus de conception de l’entreprise et des différents besoins informationnels de ses acteurs. Nous proposons donc un premier travail de compréhension de ces processus, des tâches des différents acteurs qui y contribuent et de leurs besoins informationnels associés en termes d’usages des utilisateurs finaux. Pour cela, une série d’entretiens semi-directifs a été menée auprès d’acteurs de la conception : 1) dont certaines tâches impliquent la prise en compte des usages des VUL ; 2) réalisant des activités distinctes à différentes périodes et/ou processus de conception. Les résultats offrent des lignes directrices pour contribuer à l’évolution de la typologie des usages.Ces différents travaux permettent de proposer différentes pistes de développement de la typologie des usages existante dans l’entreprise. Celles-ci couvrent deux dimensions : 1) les données fournies par la typologie et leur mode de présentation ; 2) la méthode de mise à jour de ces données. / The main purpose of this research is based on identifying and analysing the usages diversity of complex technical systems, Light Commercial Vehicles (LCV), carried out by heterogeneous professional users so as to contribute to a typology of usages. The aim of the typology is to serve as an informational resource for the actors of the design process. This work revolves around two directions. ■ The first direction focuses on the analysis of the usages diversity so as to be able to put to the fore the structuring criteria. To this end, we propose a transversal analysis unit to all the activities: “the situated usages of a multi instrumented system (MIS)”. We define them as all the user’s actions directed towards a specific goal that performs a general and situated activity, and involves all or part of the MIS as a mediator or object of the activity. The MIS represents the sub-instrumental system built from a complex technical system by the user. The analyses are based on two sets of observations (exploratory and systematic ones) among a variety of users. The results show that there are wider dimensions to the several poles of the instrumented activity influencing the realization of the usages. Indeed, the user is having complex interrelations with the resources of his action and with the characteristics of the global activity allowed by the usages and the characteristics of the situation under which they are produced. Therefore there are different types of usages depending on the SMI position within the usage and the object of the usage.■ The second direction aims at a reduction of the usages diversity purpose so as to achieve of categorization. Creating a categorization implies the need to define an analysis unit that underlies the construction of categories and variables allowing their discrimination. To this end, we propose to highlight a second analysis unit, “the usages situations’ classes of a SMI”, to enable further generalization through variables that structure the usages.But the sole conception of a categorization is not sufficient enough compared to the company’s design characteristics and to the various informative needs of its actors. As a consequence we propose a first task to apprehend the understanding of the processes involved as well as the different agents’ assignments which contribute to this understanding and to the informational needs in terms of final users’ usages they may require. In order to do so, a series of semi structured interviews were held with those involved in design: 1) some tasks imply the necessity to take into account LCV usages; 2) the performing of distinct activities at various set times and/or design processes. The results offer guidelines to contribute to the evolution of the typology of usages.These various works conducted enable us to propose different ways of developing the existing typology of usages in the company. They cover two dimensions: 1) the data provided by typology itself and one’s way to present it; 2) the methodology used to update the data.

In der vorliegenden Arbeit werden Holzwerkstoffe im statischen Biegeversuch und im Schlagbiegeversuch vergleichend geprüft. Ausgewählte Holzwerkstoffe werden thermisch geschädigt, zudem wird eine relevante Kerbgeometrie geprüft. Ziel der Untersuchungen ist die Eignung verschiedenartiger Werkstoffe für den Einsatz in sicherheitsrelevanten Anwendungen mit Schlagbelastungen zu prüfen. Hierzu werden zunächst die Grundlagen der instrumentierten Schlagprüfung und der Holzwerkstoffe erarbeitet. Der Stand der Technik wird dargelegt und bereits durchgeführte Studien werden analysiert. Darauf aufbauend wird eine eigene Prüfeinrichtung zur zeitlich hoch aufgelösten Kraft-Beschleunigungs-Messung beim Schlagversuch entwickelt. Diese wird anhand verschiedener Methoden auf ihre Eignung und die Messwerte auf Plausibilität geprüft. Darüber hinaus wird ein statistisches Verfahren zur Überprüfung auf ausreichende Stichprobengröße entwickelt und auf die durchgeführten Messungen angewendet. Anhand der unter statischer und schlagartiger Biegebeanspruchung ermittelten charakteristischen Größen, wird ein Klassenmodell zum Werkstoffvergleich und zur Werkstoffauswahl vorgeschlagen. Dieses umfasst integral die mechanische Leistungsfähigkeit der geprüften Holzwerkstoffe und ist für weitere Holzwerkstoffe anwendbar. Abschließend wird, aufbauend auf den gewonnenen Erkenntnissen, ein Konzept für die Bauteilprüfung unter Schlagbelastung für weiterführende Untersuchungen vorgeschlagen. / In the present work wood-based materials are compared under static bending load and impact bending load. Several thermal stress conditions are applied to selected materials, furthermore one relevant notch geometry is tested. The objective of these tests is to investigate the suitability of distinct wood materials for security relevant applications with the occurrence of impact loads. For this purpose the basics of instrumented impact testing and wood-based materials are acquired. The state of the technology and a comprehensive analysis of original studies are subsequently presented. On this basis an own impact pendulum was developed to allow force-acceleration measurement with high sample rates. The apparatus is validated by several methods and the achieved signals are tested for plausibility. A general approach of testing for adequate sample size is implemented and applied to the tested samples. Based on the characteristic values of the static bending and impact bending tests a classification model for material selection and comparison is proposed. The classification model is an integral approach for mechanical performance assessment of wood-based materials. In conclusion a method for impact testing of components (in future studies) is introduced.

Roll compaction is a continuous process commonly used in the pharmaceutical industry for dry granulation of moisture and heat sensitive powder blends. It is intended to increase bulk density and improve flowability. Roll compaction is a complex process that depends on many factors, such as feed powder properties, processing conditions and system layout. Some of the variability in the process remains unexplained. Accordingly, modeling tools are needed to understand the properties and the interrelations between raw materials, process parameters and the quality of the product. It is important to look at the whole manufacturing chain from raw materials to tablet properties. The main objective of this thesis was to investigate the impact of raw materials, process parameters and system design variations on the quality of intermediate and final roll compaction products, as well as their interrelations. In order to do so, we have conducted a series of systematic experimental studies and utilized chemometric tools, such as design of experiments, latent variable models (i.e. PCA, OPLS and O2PLS) as well as mechanistic models based on the rolling theory of granular solids developed by Johanson (1965). More specifically, we have developed a modeling approach to elucidate the influence of different brittle filler qualities of mannitol and dicalcium phosphate and their physical properties (i.e. flowability, particle size and compactability) on intermediate and final product quality. This approach allows the possibility of introducing new fillers without additional experiments, provided that they are within the previously mapped design space. Additionally, this approach is generic and could be extended beyond fillers. Furthermore, in contrast to many other materials, the results revealed that some qualities of the investigated fillers demonstrated improved compactability following roll compaction. In one study, we identified the design space for a roll compaction process using a risk-based approach. The influence of process parameters (i.e. roll force, roll speed, roll gap and milling screen size) on different ribbon, granule and tablet properties was evaluated. In another study, we demonstrated the significant added value of the combination of near-infrared chemical imaging, texture analysis and multivariate methods in the quality assessment of the intermediate and final roll compaction products. Finally, we have also studied the roll compaction of an intermediate drug load formulation at different scales and using roll compactors with different feed screw mechanisms (i.e. horizontal and vertical). The horizontal feed screw roll compactor was also equipped with an instrumented roll technology allowing the measurement of normal stress on ribbon. Ribbon porosity was primarily found to be a function of normal stress, exhibiting a quadratic relationship. A similar quadratic relationship was also observed between roll force and ribbon porosity of the vertically fed roll compactor. A combination of design of experiments, latent variable and mechanistic models led to a better understanding of the critical process parameters and showed that scale up/transfer between equipment is feasible.

Cette thèse vise à une meilleure compréhension de la dynamique du voilier et à la validation des outils numériques de prédiction de performances et d’optimisation par l'étude expérimentale in situ du problème aéro-élastique d'un gréement. Une instrumentation est développée sur un voilier de 8m de type J80 pour la mesure dynamique des efforts dans le gréement, de la forme des voiles en navigation, du vent et des attitudes du bateau. Un effort particulier est apporté à la mesure des caractéristiques géométriques et mécaniques des éléments du gréement, la calibration des capteurs et au système d'acquisition des données. Les principaux résultats montrent que le voilier instrumenté est un outil adapté pour les mesures instationnaires et soulignent l'amplitude de variation d'effort rencontrée en mer (20 à 50% de l'effort moyen dans une houle modérée). En outre, les variations du signal d'effort sont déphasées avec l'angle d'assiette, créant un phénomène d'hystérésis. Le comportement dynamique d'un voilier en mouvement diffère ainsi de l'approche quasi-statique. Les simulations numériques proviennent du code ARAVANTI, couplage implicite d’un code structure éléments finis ARA et d’un code fluide parfait, limitant son domaine de validité aux allures de près Les résultats de simulation sont très proches des cas stationnaires et concordent bien avec les mesures en instationnaire dans une houle de face. L'expérimentation numérique d'un gréement soumis à des oscillations harmoniques en tangage souligne l'importance de l'approche Interaction Fluide Structure (IFS) et montre que l’énergie échangée par le système avec la houle est reliée à la fréquence réduite et l'amplitude du mouvement. Certaines informations n'étant pas disponibles sur le voilier instrumenté, une expérience contrôlée en laboratoire est développée. Elle consiste en un carré de tissu tenu par deux lattes en oscillation forcée. Les mesures sur cette « voile oscillante » permettent d'étudier les phénomènes IFS avec décollement et sont utilisées pour la validation du couplage ARA-ISIS entre un code fluide Navier-Stokes (RANS) et le même code structure. / This work presents a full scale experimental study on the aero-elastic wind/sails/rig interaction in real navigation condition with the aim to give a reliable database of unsteady measurement. This database is used for the investigation of the dynamic behavior and loads in the rigging and for an experimental validation of an unsteady Fluid Structure Interaction (FSI) model. An inboard instrumentation system has been developed on a 8 meter yacht (J80 class) to simultaneously and dynamically measure the navigation parameters, yacht's motion, sails flying shape, wind and loads in the rigging. A special effort is made on mechanical and geometrical characteristics measurement, sensors calibration and data acquisition system synchronization. Results show that the instrumented boat is a reliable tool to measure the unsteady phenomena in navigation. Dynamic measurements at sea underline the load variation encountered, which represent 20 to 50% of the mean value in a moderate sea state. Oscillations of loads exhibit phase shift with the trim angle, reason for an hysteresis phenomenon, which shows that the dynamic behavior of a sail plan subject to yacht motion clearly deviates from the quasi-steady theory. Simulations are made with ARAVANTI, an implicit coupling of a Finite Element Method structural model ARA and an inviscid fluid model which restricts the simulation domain to upwind conditions. The simulation results compare very well with the experimental data for steady sailing conditions and show a good agreement in unsteady conditions (head swell). Numerical investigation of a sail plan submitted to harmonic pitching motion underlines the importance of FSI modeling and shows that the energy exchanged by the system with the swell increases with the motion reduced frequency and amplitude. Some information is not accessible on the instrumented boat and requires developing a controlled test case in laboratory. The experiment consists of a spinnaker fabric square mounted on two carbon battens moved in forced oscillation. This test case is used to study FSI phenomena with a separated flow and gives experimental results for the validation of the coupling ARA-ISIS of a RANS fluid model with the same structure model.

Esta Tese aborda, de modo original e pioneiro, importantes aspectos da Engenharia de Fundações do Sul de Minas: a) sistematização de conhecimentos sobre a Geologia regional; b) identificação e caracterização da prática de fundações; c) definição (com a formação de um banco de dados) dos perfis mais representativos do subsolo de suas principais cidades; d) estudo dos parâmetros físicos, químicos e geomecânicos de um solo típico; e) implantação de campo experimental de fundações da Universidade Federal de Lavras, com a realização de provas de carga. Grande ênfase foi dada aos itens (a), (c) e (e). Priorizou-se o estudo das fundações de baixa capacidade de carga, no estudo do comportamento carga-recalque de ensaios de placa, de provas de carga a compressão em estacas-broca isoladas e de tubulões curtos instrumentados. Destacam-se as análises sobre os efeitos de forma, profundidade, melhoramento do terreno de fundação e de inundação nas fundações rasas e da variação L/d na resistência lateral unitária das estacas, sendo valorizadas as fórmulas empíricas com base no SPT. São apresentadas fórmulas de previsão de carga, em função do SPT, para sapatas, estacas de pequeno diâmetro e tubulões curtos e um estudo de custos, onde se mostra que a opção indiscriminada por tubulões é inadequada para certas faixas de carga de trabalho. Adicionalmente, são feitas recomendações para intensificar o uso de sondagens tendo em vista a grande variabilidade das propriedades dos solos regionais e para aumentar os fatores de segurança nestas fórmulas onde houver possibilidade de ocorrência de colapso no solo. / This work presents, at time, important aspects of Foundation Engineering at Southern Region of Minas Gerais State: a) systematization of the knowledge about regional geology; b) identification and characterization of practice in foundations; c) definition (though establishment of a data base) of most representative sub-soil profiles at main cities at the region; d) study of physical, chemical and geomechanical parameters of a typical soil; e) implementation of a experimental field for foundation studies at Federal University of Lavras, by execution of load tests. A large emphasis was given to items a, c and e. The study of foundations of low load capacity was prioritized when testing plates, isolated piles under compression and short drilled piers with sensors. Analysis such as form effects, depth, soil improvement and flooding on shallow foundations and variation of L/d on the lateral unity resistance by emphasizing the empiral equations based on SPT were all pointed out. Mathematical equations are presented for load estimation as function of SPT for small diameter piles and short drilled piers as well as a cost study where it can bem shown that the undistinguished alternative for piers is inadequate for some load values. In addition, due to soil spatial variability and safety factor increment on soils subject for colapse, recommendations on intensive use of SPT test are given.

O presente trabalho visou determinar a tenacidade à fratura dinâmica, KID, primeiramente pelos conceitos da Mecânica da Fratura Elástica Linear (MFEL) e posteriormente pela Mecânica da Fratura Elasto-Plástica (MFEP), JID, em materiais que em operação podem estar sujeitos a impactos em diferentes temperaturas. Os materiais estudados, de uso na indústria aeronáutica, foram uma liga de titânio Ti6Al4V (norma SAE AMS 4911), na condição recozida e uma liga de aço inoxidável PH 15-5 (norma SAE AMS 5659), na condição H1000. Os corpos de prova pré-trincados e entalhados foram retirados nas orientações L-T e L-S, a fim de que fossem determinadas e comparadas a relação tenacidade/densidade ou tenacidade específica dos materiais estudados. Em seguida os corpos de prova foram ensaiados sob condições de carga dinâmica em uma máquina de ensaio Charpy instrumentado, marca Instron-Wolpert PW30, conforme a norma ASTM-E23, com velocidade de carregamento de 5,52 m/s e nas temperaturas de 23 e 400ºC. Os valores das tenacidades, posteriormente comparados e correlacionados, foram obtidos de acordo com as expressões matemáticas mencionadas na literatura. A razão entre as energias estimadas de iniciação (Ei) e de propagação (Ep), (Ei/Ep), foi obtida a partir dos gráficos de carga-deslocamento x tempo. A determinação e caracterização dos aspectos macro e microscópicos da fratura foram realizadas através de microscopia ótica e de varredura. Em seguida, confrontaram-se os valores e os aspectos preponderantes dos mecanismos de fratura apresentados por cada material. / The present work aimed to evaluate the dynamic fracture toughness, KID, firstly using the Linear Elastic Fracture Mechanics parameter, (LEFM), and secondly using the Elasto-Plastic Fracture Mechanics (EPFM), JID. The materials used in this work are from aeronautic grade and are subjected to in service impact loads and temperature variation. The materials are a titanium alloy Ti6Al4V (standard SAE AMS 4911), in the annealed condition and a PH 15-5 stainless steel (standard SAE AMS 5659), H1000 condition. Both precracked and notched specimens were taken in the L-T and L-S directions, for the evaluation and comparison of the toughness/density ratio, i. e., the specific dynamic fracture toughness of the materials studied. Therefore, the specimens were tested under dynamic load using an Instron-Wolpert PW30 Instrumented Charpy Equipment, following the ASTM-E23 standard, with load speed of 5,52 m/s at 23 and 400ºC. The fracture toughness values were compared using mathematical expression from literature. The ration between the initiation (Ei) and propagation (Ep) energies, (Ei/Ep), was obtained from the load-displacement x time. The characterization of the macro and microscopic aspects of the fracture mechanisms were carried out using optical microscope and scan electronic microscope. The fracture toughness values and the fractographic observations were correlated and compared for the two materials studied.

Une méthode d’analyse des topographies résiduelles, obtenues par essais de nanoindentation Berkovich sur trois échantillons de nickel polycristallins cubiques à faces entrées (CFC), a été développée dans cette thèse. L’objectif de la méthode est d’évaluer la richesse de l’information contenue dans les empreintes pour l’identification de tout ou partie des paramètres d’une loi de plasticité monocristalline. La création d’une base de données de topographies résiduelles, mesurées par microscopie à force atomique (AFM), constitue la partie expérimentale du travail. Les distributions et dimensions de bourrelets montrent une grande sensibilité à l’orientation relative indenteur/grain et au taux d’écrouissage. Les topographies obtenues s’avèrent être de véritables « empreintes digitales » du mécanisme de plasticité à l’échelle du grain. L’élaboration sous le code ZéBuLon d’un modèle éléments finis (EF) 3D de l’essai de nanoindentation Berkovich, intégrant la loi de Méric-Cailletaud, permet de retrouver les observations expérimentales. Une étude numérique confirme la sensibilité de la topographie à l’orientation relative indenteur/grain et aux paramètres plastiques, notamment aux coefficients de la matrice d’interaction des dislocations présentes sur les systèmes de glissement. Afin d’évaluer la richesse du contenu informatif des empreintes, un indice d’identifiabilité est proposé. Son calcul est basé sur la multi-colinéarité des vecteurs de sensibilité des topographies résiduelles aux paramètres de la loi. Il permet de quantifier, en fonction des données topographiques prises en compte, le caractère mal posé du problème d’identification paramétrique. Les résultats obtenus montrent que l’identification de quatre à cinq paramètres de la loi de Méric-Cailletaud est envisageable en exploitant seulement deux empreintes. Ces travaux ouvrent la voie à l’identification du comportement à l’échelle du cristal, guidée par l’identifiabilité paramétrique. / In this thesis, a method is developed to analyse the residual topographies obtained by Berkovich nanoindentation tests on three face-centered cubic (FCC) polycrystalline nickel samples. The purpose is to measure the information richness of imprints for identifying all or part of parameters of a single crystal plasticity law. The experimental part consists in creating a residual topography database by atomic force microscopy (AFM) measurements on the samples. Pile-up distributions and sizes are largely sensitive to the indenter/grain relative orientation and the hardening rate. The topographies are true “fingerprints” of the plasticity mechanism at the grain scale. A 3D finite element (FE) modelling of nanoindentation test is developed using the code ZeBuLon and making use of the Méric-Cailletaud law. Numerical results show a good agreement with experimental observations and are largely sensitive to the indenter/grain relative orientation and the plastic parameters, including the interaction matrix coefficient specifying the interaction between dislocations on different slip systems. To measure the imprint information content, an identifiability index is proposed. Its calculation is based on the multicollinearity among the sensitivity vectors of topographies to the law parameters. According to the considered topographies, it measures if the numerical model updating problem is ill-posed. The results show that four to five parameters of the Méric-Cailletaud law can be identified by considering two topographies. This work paves the way for identifying the material behaviour at the grain scale using parametric identifiability

No description available.