Submitted by Marcos Wanderley (marcos.wanderley@ufcg.edu.br) on 2018-07-25T22:10:41Z No. of bitstreams: 1 LEYLLANNE RENALLE BATISTA DE ALMEIDA - DISSERTAÇÃO(PPGEPM) 2017.pdf: 12325381 bytes, checksum: fce49fc6ad696f06078e766798c43c30 (MD5) / Made available in DSpace on 2018-07-25T22:10:41Z (GMT). No. of bitstreams: 1 LEYLLANNE RENALLE BATISTA DE ALMEIDA - DISSERTAÇÃO(PPGEPM) 2017.pdf: 12325381 bytes, checksum: fce49fc6ad696f06078e766798c43c30 (MD5) / A ampla utilização do método sísmico de prospecção na indústria de petróleo para gerar imagens das estruturas geológicas que encontram-se em subsuperfície e para o monitoramento dos reservatórios de petróleo torna essencial o conhecimento das propriedades petrofísicas e dos fatores que as afetam. Neste contexto, esta pesquisa tem como objetivo realizar o estudo petrofísico e petrográfico de trinta amostras de rochas sedimentares (arenitos e calcários), provenientes de formações estadunidenses, consideradas padrões na indústria. Foram realizados ensaios de caracterização petrofísica convencional, por métodos laboratoriais, empíricos - através dos modelos de substituição de fluidos - e simulações por modelos computacionais, utilizando os softwares Avizo Fire 8.1 e COMSOL Multiphysics 5.1, bem como a análise composicional a partir da difratometria de raios X e da descrição de lâminas delgadas em microscópio ótico. Os ensaios petrofísicos foram realizados em diferentes condições de pressão e saturação. As propriedades petrofísicas foram influenciadas por diversos parâmetros, que se diferenciam de acordo com o tipo litológico da rocha. A saturação das rochas não atingiu 90%, sendo para as rochas de matriz dolomítica muito inferior quando saturadas com óleo, possivelmente devido às mesmas serem molháveis a água. A saturação fluida influencia definitivamente nas propriedades elásticas das rochas em ambos os métodos estudados. Quando saturados com óleo, a maioria dos plugues apresentaram velocidades compressionais maiores em comparação às outras condições de saturação (seca ou saturada com água). Os modelos de Gassmann e Brown & Korringa mostraram-se mais representativos para as ondas compressionais, sendo em alguns casos eficientes também para as cisalhantes. O modelo de Biot mostrou-se mais eficiente para as ondas cisalhantes, principalmente nos arenitos. O método computacional mostrou-se eficaz visto que a velocidade compressional, pelo menos para um dos pontos receptores escohidos, se aproxima ou coincide com o valor medido laboratorialmente. Os resultados obtidos mostram que o conjunto de amostras estudado apresenta um bom potencial para reservatório. A composição mineralógica por DRX apresentou um bom ajuste com a densidade de grãos medidas convencionalmente. / The wide use of seismic prospecting method in the oil industry to generate images of geological structures that are found in subsurface and to the monitoring of petroleum reservoirs makes it essential to the knowledge of the petrophysical properties and the factors that affect them. In this context, this research aims to carry out the petrophysical and petrographical study of 30 samples of sedimentary rocks (sandstones and limestones) from American formations, considered standards in the industry. Petrophysical characterization tests were carried out by conventional laboratory methods, empirical-through fluid-replacement models and simulations by computer models, using the software Avizo Fire 8.1 and COMSOL Multiphysics 5.1, as well as the compositional analysis from the x-ray diffractometry and thin sections description in optical microscope. The petrophysical tests were performed under different conditions of pressure and fluid saturation. The petrophysical properties were influenced by several parameters, which differ according to the lithological rock type. The saturation of rocks not reached 90%, being much lower for dolomitic matrix rocks when saturated with oil, possibly due to their water wettability. Fluid saturation influences definitely in elastic properties of rocks in both methods studied. When saturated with oil most of the samples show higher compressional velocities as compared to other conditions of saturation (dry or saturated with water). The models of Gassmann and Brown & Korringa were more representative for the compressionais waves, being efficient in some cases also for the shear ones. Biot model proved to be more efficient for shear waves, especially in sandstones. The computational method proved effective as the compressional velocity, at least for one of the receivers, approaches or matches the value measured in the laboratory. The results obtained show that the set of samples studied presents good potential for reservoir. The mineralogical composition by DRX presented a good fit with the grain density measured conventionally.

Hydrated cement paste (HCP), which is present in various cement-based materials, includes a number of constituents with distinct nano-structures. The elastic properties of the HCP crystals are calculated using molecular dynamics (MD) methods. The accuracy of estimated values is verified by comparing them with the results from experimental tests and other atomistic simulation methods. The outcome of MD simulations is then extended to predict the elastic properties of the C-S-H gel by rescaling the values calculated for the individual crystals. To take into account the contribution of porosity, a detailed microporomechanics study is conducted on low- and high-density types of C-S-H. The obtained results are verified by comparing the rescaled values with the predictions from nanoindentation tests. Moreover, the mechanical behavior of the HCP crystals is examined under uniaxial tensile strains. From the stress-strain curves obtained in the three orthogonal directions, elastic and plastic responses of the HCP crystals are investigated. A comprehensive chemical bond and structural damage analysis is also performed to characterize the failure mechanisms of the HCP crystals under high tensile strains. The outcome of this study provides detailed information about the nonlinear behavior, plastic deformation, and structural failure of the HCP phases and similar atomic structures.

A rock mass is characterised by the properties of the intact rock and the fractures. Considering the impact of both constituents is of vital importance for assessing the behaviour of the rock mass. In particular in the case of complex or heterogeneous rock mass compositions. A discrete approach, by using the Discrete Fracture Network (DFN) methodology, enables for the consideration of these aspects.This master’s thesis concerns the evaluation of elastic properties of the Singö deformation zone. A discrete approach has been applied by three-dimensional discrete fracture network modelling, using previously evaluated DFN parameters. The elastic properties have then been obtained by analytical means by using the methodology developed by Davy et al. (2018).The results show that in comparison to earlier evaluations of the elastic properties of the Singö zone, the respective Young’s moduli and Poisson’s ratios obtained by this thesis may indicate a weaker material. However, this study differs from the earlier evaluation by more extensive DFN modelling and the application of a state of stress which is more representative of the surroundings of the zone in Forsmark. The analysis indicates that theadequate model size is slightly larger than the maximum studied DFN model size. A suggested future improvement would be a re-evaluation and updating of the DFN parameters. As a concluding remark, the methodology of Davy et al. (2018) may prove successful in the future for the application to deformation zones. / En bergmassa karakteriseras av egenskaperna hos det intakta berget och dess sprickor. Det är därmed av vikt att båda dessa beståndsdelar beaktas vid utvärdering av bergmassans beteende, speciellt vid komplexa eller heterogena bergartssammansättningar.Detta examensarbete syftar till att utvärdera deformationsegenskaper för den så kallade Singözonen. Ett diskret angreppsätt har tillämpats genom modellering av tredimensionella diskreta spricknätverk med hjälp av tidigare utvärderade DFN-parametrar. Deformationsegenskaperna har sedan utvärderats med hjälp av metodiken som presenteras i Davy et al. (2018).Jämfört med tidigare utvärderade deformationsegenskaper hos Singözonen så indikerar resultaten av denna masteruppsats en svagare bergmassa, med hänsyn till uppskattade värden på E-moduler och tvärkontraktionstal. Däremot skiljer sig modelleringsprocessen i detta arbete mot de som utförts i de tidigare studierna. Detta med hänsyn till omfattningen av DFN-modelleringen samt tillämpandet i detta arbete av en spänningsansats som är mer representativ för Forsmarksområdet. Vidare indikerar resultaten att den representativa modellvolymen är något större än den största modellvolym som tillämpats i detta arbete. Förslagsvis kan en utvärdering och eventuell uppdatering av de använda DFN-parametrarna utgöra en möjlig utveckling eller förbättring av det arbete som utförts i detta mastersarbete. Slutligen kan det konstateras att framtida tillämpningar av den metodik som tagits fram av Davy et al. (2018) verkar lämplig att applicera på deformationszoner.

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L’élastographie-IRM du sein (MRE) est une technique d’imagerie fonctionnelle non invasive utilisant les propriétés visco-élastiques des tissus et qui permet comme en élastographie-échographie d’évaluer la rigidité d’une lésion. Il est également possible, à la différence de l’élastographie-échographie, d’évaluer le degré de viscosité d’une lésion, et ainsi grâce à la combinaison élasticité/viscosité, comparée à l’analyse des paramètres IRM classiques comme la morphologie ou la cinétique de rehaussement, d’améliorer la caractérisation lésionnelle. Très peu d’études en élastographie-IRM du sein ont été menées à ce jour, essentiellement du fait d’une problématique instrumentale et de mise à disposition d’une antenne dédiée sein équipé d’un dispositif de génération des ondes de cisaillement dans le sein. Dans un premier temps, nous avons pu établir et optimiser une séquence élasto-IRM du sein sur une série de 10 volontaires saines. Cette séquence basée sur un principe de séquence Spin Echo EPI-MRE 3D, a permis l’acquisition de 50 coupes en 10 minutes sur un sein, compatible avec la pratique clinique en IRM du sein. Une approche multifréquence à 37,5 Hz, 75 Hz et 112,5 Hz a été ensuite testée sur les trois dernières volontaires puis transférées à notre population de patientes. Cette séquence multifréquence permettait la continuité de diffusion des ondes dans le sein. 50 patientes présentant des lésions indéterminées ou suspectes du sein (37 cancers, 13 bénins) ont ensuite été incluses dans ce protocole et examinées par IRM du sein classique avec séquence supplémentaire élasto-IRM. Certaines patientes étaient aussi examinées en élasto-échographie. Les données IRM morphologiques, dynamiques et de visco-élasticité IRM ont été corrélées à l’histologie. Nous avons pu montrer que les paramètres visco-élastiques IRM étaient fortement corrélés avec le score de malignité d’une lésion (Bi-RADS ACR) et avec le caractère différentiel bénin/malin. C’est notamment le paramètre Gd qui représente l’élasticité, qui était plus faible en cas de lésion suspecte BI-RADS 5. Le paramètre Gl était plus élevé dans les lésions malignes par rapport aux lésions bénignes, avec un niveau de viscosité statistiquement supérieur dans les lésions malignes. Le meilleur paramètre semble être le rapport y (Gl/Gd) qui était aussi significativement élevé dans les lésions malignes par comparaison avec les lésions bénignes du sein, et qui a été analysé comme un facteur indépendant. En pratique, l’ajout de la séquence MRE à un examen IRM du sein classique a permis dans notre étude d’améliorer significativement la sensibilité de l’IRM (de 78 à 91 %) sans perte de spécificité, celle-ci étant initialement très bonne dans cette étude. Nous n’avons pas en revanche établi de lien entre la fibrose, la quantification vasculaire ou la nécrose pour expliquer ces phénomènes de visco-élasticité des tumeurs. En conclusion, l’élasto-IRM peut s’avérer utile pour améliorer le diagnostic de lésions du sein en IRM. Une poursuite des travaux avec optimisation de la séquence pour qu’elle puisse permettre l’analyse des deux seins sera nécessaire pour sa diffusion en pratique clinique. Ce travail pourrait idéalement se poursuivre sur une plus grande série de patientes. / MR-elastography (MRE) is a non-invasive functional Imaging technique using tissue mechanical visco-elastic properties to evaluate tissue stifness. MRE is different from elasticity Imaging in ultrasound, as it is possible to evaluate tumour viscosity. Combining viscosity and elasticity may improve MRI accuracy, in comparison with classical morphological and kinetics criteria. Only very few studies are focused on breast MRE, because of low availability of dedicated breast coils with MRE devices. Firstly, we developed and optimized a breast MRE sequence on a population of 10 volunteers. This sequence is based on a Spin Echo EPI-MRE 3D, and it was possible to acquire 50 slices on one breast in 10 minutes, which is applicable in a clinical routine in breast MRI. Secondly, a multi-frequency approach 37,5 Hz, 75 Hz and 112,5 Hz has been evaluated on the last three volunteers, then transferred to our patient’s population. A continous diffusion of waves within the breast was possible with this multifrequency approach sequence. 50 patients presenting undetermined or suspicious breast lesions (37 cancers, 13 benign lesions) were included in this study and examined with a standard breast MRI and MRE sequence. Some patients were also examined with shear-wave ultrasound elastography (ARFI mode, Siemens ®). Morphological, kinetic and visco-elastic MR parameters were correlated to pathology. We demonstrated that MR visco-elastic properties were strongly correlated with Bi-RADS ACR malignancy score of a breast lesion and with malignant and benign status. The best parameter was Gd (dynamic modulus), which corresponded to lesion stiffness. Gd was lower in case of BI-RADS 5 lesions. Gl parameter (Loss modulus) was higher in malignant lesions in comparison with benign lesions, with viscosity level statistically higher in malignant lesions. The best criterion was the ratio y (Gl/Gd), which was significantly higher in malignant lesions in comparison with benign lesions; ratio y was statistically an independent factor. In practice, addition of a MRE sequence to a standard breast MRI improved significantly breast MRI Sensitity (78 to 91 %) without reduction in specificity; Sp was anyway initially high in our study. Nevertheless, we didn’t demonstrate a statistical correlation with fibrosis, vascular grading or necrosis with MRE parameters, to explain visco-elastic properties of breast tumours. In conclusion, MR-elastography may be useful to improve breast MRI accuracy. In future studies, MRE sequence may be optimized to allow a bilateral acquisition on both breasts, which would be useful in clinical practice. Future works could include higher number of patients to confirm our results.

Les matériaux cellulaires poreux de type mousse présentent un grand intérêt pour de nombreuses applications. Leurs propriétés thermiques, mécaniques, acoustiques dépendent fortement de leur microstructure complexe. Afin de mieux comprendre la relation microstructure/propriétés mécaniques de ces matériaux, une modélisation micromécanique basée sur une méthode d’homogénéisation périodique et le lemme de Hill est proposée pour prédire les propriétés élastiques effectives de ces matériaux. Une approche basée sur le diagramme de Voronoï est utilisée pour générer des structures de mousse périodiques réalistes plus ou moins irrégulières, couvrant une large gamme de matériaux . Différents types de mousses à forte porosité sont générés, non seulement des matériaux cellulaires à pores ouverts mais aussi des matériaux cellulaires à pores fermés. Des comparaisons avec des résultats issus de tomographie X d’architectures réelles 3D de mousses valident ces approches de Voronoï. Les simulations numériques permettent d’étudier l’influence des paramètres morphologiques des mousses sur les propriétés élastiques effectives. De nouvelles lois analytiques génériques de propriétés effectives sont déduites pour des mousses à cellules ouvertes de type Kelvin. Une attention particulière est portée sur la détermination de l’élément de volume représentatif (VER). Des méthodes statistiques spécifiques sont proposées pour déterminer le VER approprié aux modèles de mousse. Dans le cas des mousses polymères isolantes à cellules fermées irrégulières anisotropes, la confrontation avec des résultats d’essais mécaniques confirme la validité des modèles développés. / Thanks to the excellent combination of physical, mechanical and thermal properties, foam materials bring new possibilities to extend the range of the properties for engineering, which is limited by fully dense solids. In this study, a micromechanical modeling based on Hill's lemma (Hill's lemma periodic computational homogenization approach) is proposed for predicting the effective elastic properties of foam materials. An approach based on Voronoi diagram is used to generate realistic periodic foam structures, including regular and irregular open-cell structures, and irregular closed-cell structures. First, the influences of morphological parameters of open-cell foams on the effective elastic properties are studied. The generated structures allow representing the details of the microstructure and cover a large range of foam materials for engineering purposes. With the assessments, new generic analytical laws are proposed for Kelvin open-cell foams by considering their morphological parameters. Second, the tomography images are analysed to obtain the morphological description of the real irregular open-cell structure. With these morphological parameters, numerous numerical realistic structures are generated. Specific statistic methods are proposed to determine the Representative Volume Element (RVE) for foam models. Third, the anisotropic irregular closed-cell foam is studied. The numerical structures are generated with the morphological description of the reconstructed tomography structure and the effective elastic properties of the closed-cell foam models are estimated. The numerical results show the satisfying agreement with the experimental results.

In the design of rail track structures where the subgrade cannot achieve the desired capacity, enabling the required standard of track geometry to be maintained for the speed, axle load and tonnage to be hauled, a capping layer of granular material is placed between the natural ground or the embankment fill material and the ballast to protect the underlying weaker layers. In spite of the important role played by the capping layer, very little research has been carried out on its performance. The current practice of design of the capping layer, therefore, is based on working stress philosophy where reduced levels of stresses are assumed not to degrade the subgrade. Even on tracks containing a thick ballast layer that ensures allowable levels of working stress the subgrade has been found to have permanently deformed. Design of capping layers based on plastic deformation, therefore, appears appropriate. This thesis aims at determining the load levels that cause detrimental plastic deformation in the capping layer. The suite of material properties that characterise plastic deformations of capping layer is neither readily available nor easily determined. This thesis proposes a cheaper method of evaluating a range of capping layer material properties using penetration tests on specimens contained in California Bearing Ratio (CBR) test moulds coupled with a finite element modelling based back calculation technique. The suite of material properties thus determined are used for the simulation of the behaviour of capping layers under the boundary and loading conditions similar to those in practice. The predicted results are validated using laboratory experiments on large size capping layer specimens.

The complete and accurate thermodynamic and kinetic description of any systemis crucialfor understanding and predicting its properties. A particular interest is in systemsthat are used for some practical applications and have to be constantly improved usingmodification of their composition and structure. This task can be quite accuratelysolved at a fundamental level by density functional theory methods. Thesemethods areapplied to two practically important systems Fe-Cr and TiC-ZrC.The elastic properties of pure iron and substitutionally disordered Fe-Cr alloy are investigatedas a function of temperature and concentration using first-principles electronicstructurecalculations by the exact muffin-tin orbitals method. The temperature effectson the elastic properties are included via the electronic, magnetic, and lattice expansioncontributions. It is shown that the degree of magnetic order in both pure iron andFe90Cr10 alloy mainly determines the dramatic change of the elastic anisotropy of thesematerials at elevated temperatures. A peculiarity in the concentration dependence ofthe elastic constants in Fe-rich alloys is demonstrated and related to a change in theFermi surface topology.A thermodynamic model for the magnetic alloys is developed from first principles andapplied to the calculation of bcc Fe-Cr phase diagram. Various contributions to the freeenergy (magnetic, electronic, and phonon) are estimated and included in the model. Inparticular, it is found that magnetic short range order effects are important just abovethe Curie temperature. The model is applied for calculating phase equilibria in disorderedbcc Fe-Cr alloys. Model calculations reproduce a feature known as a Nishizawahorn for the Fe-rich high-temperature part of the phase diagram.The investigation of the TiC-ZrC system includes a detailed study of the defect formationenergies and migration barriers of point defects and defect complexes involvedin the diffusion process. It is found, using ab initio atomistic simulations of vacancymediateddiffusion processes in TiC and ZrC, that a special self-diffusion mechanism isoperative for metal atom diffusion in sub-stoichiometric carbides. It involves a noveltype of a stable point defect, a metal vacancy ”dressed” in a shell of carbon vacancies.It is shown that this vacancy cluster is strongly bound and can propagate through thelattice without dissociating. / <p>QC 20120604</p> / HERO-M

The measurement and monitoring of the elastic properties of cement-based materials is very important for assessing their quality, integrity and performance. Due to the nonhomogeneous and time-dependent characteristics of these materials, it is difficult to observe the developments in elastic properties with traditional destructive methods. The aim of this thesis is to determine and monitor elastic properties of mortar specimens made with different cements by using resonant frequency and ultrasonic pulse velocity test methods, and to obtain relationships between these elastic properties. For this purpose, eight different cement mortar mixtures were prepared with different constituent CEM I cements. Dynamic elastic moduli, static elastic moduli, dynamic Poisson&rsquo / s ratio and strength of these mixtures were observed for different ages. The relationships between these elastic properties are determined and the results obtained from two different nondestructive test methods are compared. Although nondestructive tests made it possible to obtain elastic properties of mortar mixtures, the results revealed that it is very difficult to develop a single relationship between different elastic properties of mortars with varying mixture proportions. This situation is mainly due to the anisotropy and nonlinear behavior of the mortar and the difficulty of describing the actual behavior of mortar by formulations defined for perfectly elastic materials.

Ce travail de recherche vise à étudier les propriétés élastiques par microscopie acoustique du combustible nucléaire dans trois situations particulières: combustible en utilisation normale en réacteur nucléaire, combustible stocké après la période d’irradiation et combustible en conditions extrêmes suite à un accident nucléaire. Les mesures réalisées sur les échantillons irradiés ont conduit à plusieurs résultats majeurs: validation d’une loi corrélant la vitesse des ondes de Rayleigh à la densité du dioxyde d’uranium irradié ou frais; détermination de la porosité dans le combustible irradié; évaluation du gonflement de la matrice en fonction du taux de combustion dans la gamme 0-100 GWdt-1M; développement d'un modèle empirique capable de prévoir la variation de module de Young en fonction du taux de combustion en prenant même en compte la teneur en dopants (Gd2O3, CeO2) ; quantification de l’évolution du module de Young du combustible suite à l'endommagement en stockage ; premières mesures sur du corium. Enfin, grâce au lien entre les propriétés thermiques et élastiques, différentes propriétés thermiques de l'UO2 ont été calculées en mesurant la vitesse de l'onde de surface de Rayleigh seule. / The focus of the present thesis is the determination of the elastic properties of nuclear fuel using high frequency acoustic microscopy. The nuclear fuel is considered under three different conditions: during its normal life in reactor, after its discharge and disposal in interim or long-term storage and subsequently to its severe degradation caused by a nuclear accident. Measurements performed on irradiated fuels allowed to validate a law between the density of fresh and irradiated fuel and the Rayleigh wave velocity; the determination of the irradiated fuel porosity and matrix swelling in the broad burnup range 0-100 GWdt-1M; the development of an empirical model capable of predicting the evolution of Young's modulus versus burnup correcting also for the additives content (Gd2O3, CeO2); Young's modulus evolution due to alpha-decay damage as in-storage condition; first corium measurements. Moreover, several UO2 thermal parameters were calculated only by means of the Rayleigh wave velocity thanks to the link between thermal and elastic properties.