Submitted by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-02-23T14:07:59Z No. of bitstreams: 2 Dissertação_Matheus P. S. Silva.pdf: 2830915 bytes, checksum: c6f42e6a9aedf5ccc332c112b241847f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-02-23T14:08:14Z (GMT) No. of bitstreams: 2 Dissertação_Matheus P. S. Silva.pdf: 2830915 bytes, checksum: c6f42e6a9aedf5ccc332c112b241847f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-02-23T14:08:14Z (GMT). No. of bitstreams: 2 Dissertação_Matheus P. S. Silva.pdf: 2830915 bytes, checksum: c6f42e6a9aedf5ccc332c112b241847f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-10-16 / There is a major concern on the global stage with the scarcity of natural resources and global warming. In this context, the paving has been looking for alternatives aimed at reducing fuel consumption and the consequent reduction of the emission of greenhouse gases, highlighting the use of warm mixtures as an option. In the local scenario, the urban roads of the city of Manaus / AM show historically premature deterioration, instigating the evaluation of regional asphaltic compositions notably regarding permanent deformation. On the other hand, besides the usual pathologies, the frequent increase in the volume of traffic and loads has generated the appearance of new pathologies, not considered in the traditional methods of designing asphalt mixtures. These facts led to the study of the warm mixtures applied in the city of Manaus / AM, in terms of their mechanical performance, and in particular, from the perspective of triaxial compression and dynamic creep tests. In this research, the physical characterization of the composite materials of the asphaltic composite, the dosage of this mixture according to the Brazilian specifications, as well as the results obtained in the mechanical tests were evaluated. The physical characterization, the dosage and the mechanical behavior indicated: a) the asphalt binder was classified as type 50/70, meeting the specifications of the ANP. However, for the local reality, it does not present adequate, since in the range of service temperature has already reached its softening point; b) the mineral dosage indicated that the formulation studied can be used for Range B and C of DNIT; and c) the analysis of the Marshall parameters, from the point of view of the DNIT specification, showed that the researched composition can only be applied as a rolling layer; d) the results of the triaxial test indicated that the cohesion decreases drastically by the variation of the ambient temperature to the service condition; e) in the dynamic creep test, the mathematical model proved to be more adequate with respect to the traditional methodology, since the minimum deformation rate per cycle did not correspond to the transition point from the secondary stage to the tertiary stage; and f) all NF results, either by the mathematical or traditional method, indicate that the regional coatings are subject to premature pathologies of the permanent deformation type. / Há no cenário global uma grande preocupação com a escassez de recursos naturais e o aquecimento global. Neste contexto, a pavimentação vem buscando alternativas visando à redução no consumo de combustíveis e a consequente redução da emissão de gases causadores do efeito estufa, destacando-se como opção o uso de misturas mornas. No cenário local, as vias urbanas da cidade de Manaus/AM mostram historicamente prematura deterioração, instigando a avaliação das composições asfálticas regionais notadamente quanto à deformação permanente. Por outro lado, além das usuais patologias, o frequente aumento do volume de tráfego e de cargas tem gerado o surgimento de novas patologias, não consideradas nos métodos tradicionais de dimensionamento de misturas asfálticas. Tais fatos suscitaram o estudo das misturas mornas aplicadas na cidade de Manaus/AM, quanto ao seu desempenho mecânico, e em particular, sob a ótica dos ensaios de compressão triaxial e creep dinâmico. Nesta pesquisa, avaliou-se a caracterização física dos materiais partícipes do compósito asfáltico, a dosagem desta mistura de acordo com as especificações brasileiras, bem como os resultados obtidos nos ensaios mecânicos. A caracterização física, a dosagem e o comportamento mecânico indicaram: a) o ligante asfáltico classificou-se como do tipo 50/70, atendendo as especificações da ANP. No entanto, para a realidade local, não se apresenta adequada, uma vez que na faixa de temperatura de serviço já atingiu seu Ponto de amolecimento; b) a dosagem mineral indicou que a formulação estudada pode ser empregado para Faixa B e C do DNIT; e c) a análise dos parâmetros Marshall, sob a ótica da especificação do DNIT, mostrou que a composição pesquisada pode ser aplicada somente como camada de rolamento; d) os resultados do ensaio triaxial indicaram que a coesão diminui drasticamente pela variação da temperatura ambiental para condição de serviço; e) no teste de creep dinâmico, o modelo matemático mostrou-se mais adequado referente à metodologia tradicional, uma vez que a taxa mínima de deformação por ciclo não condizia com o ponto de transição do estágio secundário para o estágio terciário; e f) todos os resultados de FN, seja pelo método matemático ou tradicional, apontam que os revestimentos regionais estão sujeitos a prematuras patologias do tipo deformação permanente.

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Ce travail de recherche a pour objectif d’étudier le comportement au cisaillement des matériaux granulaires homogènes et hétérogènes par l’essai triaxial. Les travaux sont réalisés sur des billes de verre et comportent à la fois des essais triaxiaux de laboratoire et des simulations numériques en DEM (Discret Element Method). D’un point de vue expérimental, les essais sont tout d’abord réalisés sur des échantillons homogènes (billes monodisperses). Ensuite, on étudie des systèmes de billes monodisperses comportant une inclusion de grande taille et des mélanges de billes bidisperses pour représenter les cas hétérogènes. D’un point de vue numérique, une condition limite cylindrique paroi rigide, basée sur la formule de Lamé, est intégrée dans un code aux éléments discrets existant. Une série de procédures est proposée afin de modéliser l’essai triaxial dans des conditions comparables aux essais. Les résultats numériques et expérimentaux sont ensuite comparés, à la fois pour les systèmes monodisperses et pour les milieux hétérogènes. Le modèle numérique permet de reproduire de manière très satisfaisante la courbe déviatorique dans toutes les conditions expérimentales utilisées. Il permet également de décrire correctement les déformations volumiques de l’échantillon, malgré la simplicité de la condition aux limites utilisée. L’outil numérique développé constitue ainsi un complément intéressant aux essais expérimentaux. Il permet en effet d’étudier l’influence de paramètres micromécaniques sur le comportement global des matériaux. / This research work aims at studying the shear behavior of homogeneous and heterogeneous granular materials by triaxial test. The work is performed on glass beads both in laboratory tests and by numerical simulations in DEM (Discrete Element Method). From an experimental point of view, tests are first performed on homogeneous samples (monodisperse beads), then expands to heterogeneous cases like monodisperse systems comprising a large inclusion and bidisperse mixtures. From a numerical point of view, a cylindrical rigid wall boundary condition, based on the Lamé formula is integrated into an existing discrete elements code. A series of procedures is proposed to model the triaxial test in conditions similar to experimental tests. The numerical and experimental results are compared both for monodisperse and heterogeneous systems. The numerical model can reproduce deviatoric curves very satisfactorily in all experimental conditions. It also allows describing correctly the volumetric strains of the sample despite the simplicity of the boundary condition used. The developed numerical tool is an interesting complement to experiment triaxial tests. It makes it possible to study the influence of micromechanical parameters on the overall behavior of materials.

Magnetic sensors are deployed in many applications such as automotive, consumer electronics, navigation and data storage devices. Their market’s growth is driven by demands of higher performance; primarily to assist in the advancement of the Internet of Things (IoT) and smart systems. Challenging obstacles of miniaturization and power consumptions must be overcome. A leading sensor that has the potential to accelerate the development is the magnetic tunnel junction (MTJ) devices. Corrosion causes catastrophic consequences for industries. Preventive measures could save up to 35% of annual corrosion-related costs. An advanced corrosion sensing technique is developed based on iron nanowires. The iron nanowires are magnets which lose their magnetization when corroded. Their magnetization loss is monitored using sensitive MTJ sensor. Combined, the nanowires and the MTJ sensor realize a highly integrated sensor concept that enables corrosion sensing with an ultra-low power consumption of less than 1 nW, a sensitivity of 0.1 %/min, a response time of 30 minutes and an area of 128 μm2. Surgical tool development is accelerating in the healthcare sector. Cardiac catheterization specifically is a minimally invasive surgery that relies heavily on x-ray imaging and contrast dyes. A flexible tri-axis MTJ sensor is developed to help minimizing the need for x-ray imaging during the procedure. The flexible sensor can bend to a diameter of 500 μm without compromising the performance and can endure over 1000 bending cycles without fatigue. Three flexible sensors are mounted onto the tip of a 3 mm cardiac catheter, realizing a novel sensor-on-tube (SOT) tri-axis sensor concept. The sensor has a high sensitivity of 9 Ω/° and an MR ratio of 29%. It weighs 16 μg only, adds 5 μm to the catheter’s diameter and a total size 300 μm2. The prototype system estimated the heading angle with an RMS error value of 7° and tracked the orientation of the sensor with an acceptable accuracy. However, the sensor has a misalignment issue caused by the manual placement of the sensors. A high precision tool is needed for the assembly, and any further misplacement -within a reasonable margin of error- could be corrected by calibration algorithms.

Clay soils can be stabilized by the chemical reaction between the clay particles and lime to produce calcium aluminate and calcium silicate minerals. This cementation effect on clay particles result in increasing the strength of lime-treated clay soils. The mechanical strengths (compressive, tensile and shear strengths) of clay soils are improved from soft to stiff behavior by treating with lime and evolve along the curing time.An extensive experimental investigation has been carried out using laboratory reconstituted (compacted) expansive soils, covering a range of plasticity indices. Four selected soils with different fundamental physical and mechanical behaviors have been used to stabilize with lime. In addition to basic geomechanical characterization tests (modified proctor compaction, uniaxial compression strength, indirect tensile strength, oedometric compression, direct shear tests), a special focus was put on triaxial compression and extension tests upon drained and undrained conditions. Also, the development of swelling pressure upon wetting was also carefully investigated.The shear behavior of compacted clay soils is experimentally investigated by using both direct shear test and triaxial shear tests. These tests were conducted on saturated specimens for four selected soils. It is observed that the shear strength of both tests is evolving with addition of lime and with the plasticity index. In addition to the strength parameters, triaxial shear test was also used to determine the Young modulus of treated soils. It was noticed that the lime treatment increases the elastic modulus of selected clay soils.The triaxial compression system was modified to a triaxial extension system in order to evaluate the triaxial tensile strength of one of the tested soils (N1, from Quenast, Belgium). The pure tensile strength of soils can be determined from triaxial extension test at low confining pressures while high confining pressures induces shear failure.The failure criteria of lime-treated soils were studied in different stress planes to evaluate the shear and tensile strength obtained from triaxial extension test and triaxial compression test. A combined rupture criterion of original and modified Griffith criteria was applied. The results obtained from experimental testing have shown that at low confining pressures, the failure stress of extension test followed the Original Griffith Criterion started from pure tension, and at the higher confining pressures the failure stress followed the Modified Griffith (equivalent to Mohr-Coulomb, in this case).In application of this combined equation, the result of four selected soils obtained from triaxial tension test, direct shear test and triaxial compression test was plotted in the (sigma,to) in order to verify this equation. These experimental results match with the combined equation.This analysis revealed the strong interest of extension triaxial tests, with respect to more conventional indirect tension tests (also called splitting tests). Extension triaxial tests allow to control the drainage conditions and performed a full effective stress analysis of the stress-strain responses, including pre-failure behavior and ultimate strength criterion. Also, it provides a smooth transition between shear strength and tensile strength criterion, depending on the confining pressure of the test.At the end of this work, experimental results are analyzed and correlated with several parameters. Shear strength, compression index and swelling pressure were found to depend primarily on plasticity index for both treated and untreated materials. Many approaches in literature have also expressed these mechanical properties of soils in function of plasticity index. However, there are a few equations matching closely to testing results. For the development of swelling pressure upon wetting, a modified equation was proposed for experimental data for non-treated soils and lime-treated soils. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

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This research encompasses threemajor segments: a search for high-spin triaxial strongly deformed (TSD) bands in 164Hf, spectroscopy of high-spin normal deformed (ND) bands in 164Hf, and a low-spin search in 165Ta. In April 2010, an experiment was carried out using the ATLAS linear accelerator at Argonne National Laboratory (Argonne, IL). A thin (761 microgram/square centimeter) 94Zr target was impacted with a 330MeV 74Ge beam. This produced a 168Hf compound nucleus that decayed via the 4n channel to 164Hf. Offline data analysis was performed using coincidence relationships and gamma-ray intensity analysis to determine the decay pathways and Directional Correlation of Oriented Nuclei (DCO ratios) to determine level spin and parities. The highest extend of the 164Hf level scheme in previous works was near 32 hbar. This research has extended the previously known level scheme to 48 hbar. Seven new normal deformed bands and two triaxial strongly deformed bands have been added. Decay pathways of TSD bands to ND states have been firmly established. Intrinsic configurations of the bands were discussed based on Cranked Shell Model (CSM) calculations. A short discussion of new low-spin structures in 165Ta concludes the research. The experiment was carried out in August 2010 at Yale’s Wright Nuclear Structure Laboratory using their tandem linac. A 228MeV 51V beam was incident upon a 118Sn self-supporting thin target. Data was sorted into gamma-gamma matrices using the WNSL CSCAN code. Three new normal deformed low-spin structures were found, and one previously known but unpublished structure was confirmed, extended, and linked to the Yrast band.

Triaxial shear test is the most accurate test for deciding the undrained shear strength of clay. In every test the ratio between the horizontal and vertical stresses, the coefficient of earth pressure at rest (K0′), has to be decided. It’s widely believed that the choice of this parameter will influence the results, but it’s not known to what extent. In this thesis 20 consolidated undrained active triaxial shear tests on clay has been con- ducted with a K0′ at 0.6 and 0.8. The clay was collected with a 54 mm piston sampler at the Norwegian Geo-Test Site in Trondheim, Norway, on depth of 3.0 to 7.8 meters. Besides the triaxial testing, index tests and oedometer tests was conducted on every cylinder to do a gen- eral classification of the clay. The clay has a sensitivity of 9-20, a water content of 35-51 %, a plasticity index of 27-65 % and an over consolidation ratio of 2.6-6.8. The consolidation phase of the triaxial test was conducted in five loading steps with a rest time in-between to monitor the amount of pore water expelled at each stress level. The loading steps was 50 %, 75 % and 100 % of maximum cell pressure and thereafter at 50 % and 100 % of the maximum deviator stress. The shear phase was done at a speed of 1.5 % per hour to a total of 10 % axial strain. It is not possible to reach an unambiguous conclusion from the results, but the maximum shear strength of tests with a K0′ at 0.8 is 17 % higher, while the total amount of pore water extortion is equal between the two values. The amount of creep in the latest steps is on the other hand smaller for a K0′ at 0.8. This indicates that the soil is handling the stress level better than with a K0′ at 0.6.

Simplified mechanical loading paths, which represent more complex loading paths observed during penetration, were investigated using a triaxial chamber and a high-strength concrete. Objectives were to determine the effects that stress/strain (load) paths had on the material’s unconfined (UC) residual strength. The loading paths included hydrostatic compression (HC), uniaxial strain in compression (UX), and uniaxial strain load biaxial strain unload (UXBX). The experiments indicate that load paths associated with non-visible microstructural damage were HC and UX, which produced minimal impact on the residual UC strength (<30%), while the load paths associated with visible macro-structural damage were UXBX, which significantly reduced the UC strength (>90%). The simplified loading paths were also investigated using a material model driver code that was fit to a widely used Department of Defense material model. Virtual experiment data revealed that the material model investigated overestimated material damage and produced poor results when compared to experimental data.

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