Dissertations / Theses on the topic 'Strength anisotropy'
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1
O'Neill, Deirdre A. (Deirdre Anne). "Undrained strength anisotropy of an overconsolidated thixotropic clay." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14634.
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Denli, Alper Kaan. "Effect Of Discontinuity Roughness And Anisotropy On Shear Strength." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12604948/index.pdf.
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Discontinuity surfaces generally consist of undulations termed as roughness. It is well known that surface roughness plays an important role on the shear strength and shear behavior of discontinuities. However, the effect of roughness will not be the same when the direction of shearing changes. This effect causes variation of shear strength with shearing direction or in other words anisotropy on shear strength.
In this thesis, an experimental study was performed to investigate the effect of roughness and anisotropy on shear strength. For this purpose, joint samples were prepared using a model material and direct shear tests were conducted at different normal stress levels and shearing directions.
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Modén, Carl. "Transverse anisotropy in softwoods : modelling and experiments /." Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3988.
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Tong, Chong-Sze. "Anisotropy in repulsion and dispersion forces between atoms in molecules." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278386.
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Catapano, Anita. "Stiffness and strength optimisation of the anisotropy distribution for laminated structures." Paris 6, 2013. http://www.theses.fr/2013PA066062.
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Cette thèse porte sur le développement d’une nouvelle stratégie pour l’analyse et la conception optimale de structures anisotropes par rapport à la rigidité et à la résistance. Nous considérons des structures avec une géométrie donné et caractérisés par un champ de rigidité et de résistance anisotropes et variables. Le travail a été divisé en trois parties. Dans la première partie nous présentons les différents concepts et instruments utilisé pour développer la recherche. Dans la deuxième partie nous proposons une formulation invariante, à travers la méthode polaire, de différents critères de rupture polynomiaux pour matériaux orthotropes. Apres, nous considérons le problème de déterminer l’orientation optimale de plis orthotropes pour maximiser leur résistance. Dans la dernière partie nous abordons le problème de la conception optimale de structures stratifiés. Notre approche est inspiré par une stratégie à deux étapes déjà existent pour la seule maximisation de la rigidité. Avant tout nous avons défini un nouveau critère de rupture valide pour un stratifié modelé comme une plaque homogène équivalente et après, conscientes d’avoir deux fonctionnels à minimiser, l’énergie complémentaire et le failure index du critère développé, nous avons formalisé le problème à travers une minimisation séquentielle de deux fonctionnels. Dans la première étape de la stratégie nous avons développé trois algorithmes pour déterminer la distribution optimale des paramètres matériaux d’une structure donnée. Dans la deuxième étape nous avons résolu le problème de déterminer un empilement adapte à la distribution optimale des paramètres trouvé à l’étape précédenteIn this thesis we deal with the problem of determining the best distribution of the anisotropy for a laminated structure that has to be simultaneously the stiffest and the strongest one. The work has been divided into three main parts. In the first part we presented all the concepts and tools that we have used to develop the research. In the second part we have proposed a tensor invariant formulation, through the polar method, of different polynomial failure criteria for orthotropic sheets. Then, we considered the problem of determining the optimal material orientation to maximise strength by the minimisation of the failure index. The last part of the thesis is dedicated to the development of a new strategy to optimise simultaneously the stiffness and strength of a laminated structure. Our approach is inspired from an already existing hierarchical strategy for the only stiffness maximisation. First of all we defined a new laminate level failure criterion valid for an equivalent homogenised plate. Then, conscious of having two functional, the complementary energy and the laminate failure index, to be minimised at the same time, we proved that the first step of the strategy can be stated as two problems characterised by two functional that are sequentially minimised, preserving only the orthotropy direction. In the first step of the strategy we developed three different algorithms to determine the optimal distribution of material parameters for a given structure. Finally we dealt with the problem of determining the laminate stacking sequence satisfying the optimal distribution of material parameters issued from the first step of the hierarchical strategy
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Wang, Wenhai Zavaliangos Antonios. "Towards an improved understanding of strength and anisotropy of cold compacted powder /." Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/1865.
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Galen, Steven Zavaliangos Antonios. "Path dependence and strength anisotropy of mechanical behavior in cold-compacted powders /." Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/438.
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Zdravkovic, Lidija. "The stress-strain-strength anisotropy of a granular medium under general stress conditions." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/8919.
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Ho, Man Lee. "Theoretical approach to quantify influence of inherent anisotropy on undrained steady state strength of sand /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202005%20HO.
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Kurauchi, Martim Hideki Nakayama. "Uma abordagem de ensaio de resistência mecânica de carvão vegetal." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-28042015-110831/.
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A indústria de ferro e aço corresponde a cerca de 8% das emissões globais de CO2. O carvão vegetal é uma alternativa existente ao uso de carvão fóssil e coque na indústria metalúrgica e é utilizado em alguns altos fornos no Brasil. Embora possua algumas vantagens em termos de maior reatividade e menor teor de cinzas em relação ao coque, o carvão vegetal possui baixa resistência mecânica e alta friabilidade, dificultando o transporte, manuseio e os processos. Não existem normas para avaliar a resistência à compressão de carvão vegetal, e os métodos existentes empregados em outras pesquisas consistem em preparar corpos de prova livres de defeitos e comprimi-los na direção das fibras. Por se tratar de um material com formato irregular, granular e anisotrópico, estes ensaios podem não revelar o comportamento de um leito de carvão vegetal, como um todo, quando sujeito a cargas compressivas. Isto pode não representar condições industriais, onde a carga sobre o carvão não é aplicada exclusivamente na direção das fibras, mas é aplicada de maneira aleatória. Esta dissertação propõe uma abordagem para se quantificar os efeitos da aplicação de cargas compressivas sobre um leito de carvão vegetal distribuído aleatoriamente. Isto representa uma tentativa de simular condições mais próximas das industriais, como ocorreria em um alto forno, em vez de fazer a análise de pedaços individuais de carvão. Foi montado um aparato consistindo em um tubo contendo um leito de carvão e com um êmbolo empurrado por máquina de ensaio universal. As experiências consistem em utilizar o aparato para realizar repetições de ensaios de compressão de carvão de tamanho inicial controlado. Assim, é obtida uma distribuição granulométrica em função da carga aplicada, que é classificada por peneiramento e pesagem. A partir disto, a distribuição granulométrica é analisada de forma qualitativa e quantitativa com uso de ferramentas estatísticas. Através dos índices de quebra e sobrevivência, o método produz resultados reprodutíveis com número de repetições suficiente. Desta forma, é possível prever o comportamento de um leito de carvão vegetal sob compressão.The iron- and steel industry is responsible for about 8% of the total global CO2 emissions. Charcoal is an existing alternative to the use of coal and coke in the metallurgical industry and is used in some blast furnaces in Brazil. Although it has some advantages against coke in terms of higher reactivity and lower ash contents, charcoal has inherently low mechanical strength and high friability, imposing difficulties to its transportation, handling and use in processes. There are no standards to evaluate charcoal compression strength, and the existing methods used in other researches consist in using prepared specimens and compressing them in the direction of the fibres. As charcoal is irregular shaped, granular and anisotropic, these tests may not reveal the behaviour of a charcoal bed, as a whole, when undergoing compressive loads. This may not relate to industrial conditions, where the load on charcoal is not exclusively applied on the direction of the fibres, but is randomly applied instead. This dissertation proposes an approach to quantify the effects of applying load on randomly distributed bulk charcoal. This represents an attempt of simulating conditions similar to what is expected in the industrial practice, such as in a blast furnace, rather than analysing individual pieces of charcoal. An apparatus has been prepared consisting of a tube and a piston that is pushed by an universal test machine. The experiments consist in carrying out repeated tests of compression of controlled sized charcoal with the apparatus. A particle size distribution is obtained as a function of the applied load, which is then classified by screening and weighing. Based on that, the particle size distribution is analysed both qualitative and quantitatively by using statistical tools. By means of the friability and survivability indexes, the method generates reproducible results with a sufficient number of repeats. In this way, it is possible to predict the behaviour of charcoal bulk under compression.
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Ispir, Mustafa Erdem. "A Laboratory Study Of Anisotropy In Engineering Properties Of Ankara Clay." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613779/index.pdf.
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Anisotropy in engineering properties of soils occurs due to the depositional process forming the soil fabric and/or different directional stresses in soil history. This study investigates the anisotropy in undrained shear strength and drained compressibility of preconsolidated, stiff and fissured Ankara Clay. The compressibility behavior is determined using standard oedometer testing while the shear strength anisotropy is investigated through large diameter unconsolidated-undrained triaxial testing on undisturbed samples taken in vertical and horizontal directions from several deep excavation sites along the Konya Road in Çukurambar-Balgat Area, Ankara. According to the results achieved, Ankara Clay is slightly anisotropic in compressibility, with an anisotropy ratio between 0.72 and 1.17 in terms of coefficient of volume compressibility for several pressure ranges between 50 kPa and 1600 kPa. On the other hand, while a slight anisotropy in undrained shear strength at a ratio ranging between 0.87 and 1.19 in terms of deviator stress can be observed in Ankara Clay, considering the great variation in the test results of samples in same direction which mostly overlaps with the range of results obtained in the other direction, it has been concluded that the Ankara Clay located in this area can be regarded as isotropic in terms of shear strength for practical purposes.
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Noorian-Bidgoli, Majid. "Strength and deformability of fractured rocks." Doctoral thesis, KTH, Mark- och vattenteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155719.
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This thesis presents a systematic numerical modeling framework to simulate the stress-deformation and coupled stress-deformation-flow processes by performing uniaxial and biaxial compressive tests on fractured rock models with considering the effects of different loading conditions, different loading directions (anisotropy), and coupled hydro-mechanical processes for evaluating strength and deformability behavior of fractured rocks. By using code UDEC of discrete element method (DEM), a series of numerical experiments were conducted on discrete fracture network models (DFN) at an established representative elementary volume (REV), based on realistic geometrical and mechanical data of fracture systems from field mapping at Sellafield, UK. The results were used to estimate the equivalent Young’s modulus and Poisson’s ratio and to fit the Mohr-Coulomb and Hoek-Brown failure criteria, represented by equivalent material properties defining these two criteria. The results demonstrate that strength and deformation parameters of fractured rocks are dependent on confining pressures, loading directions, water pressure, and mechanical and hydraulic boundary conditions. Fractured rocks behave nonlinearly, represented by their elasto-plastic behavior with a strain hardening trend. Fluid flow analysis in fractured rocks under hydro-mechanical loading conditions show an important impact of water pressure on the strength and deformability parameters of fractured rocks, due to the effective stress phenomenon, but the values of stress and strength reduction may or may not equal to the magnitude of water pressure, due to the influence of fracture system complexity. Stochastic analysis indicates that the strength and deformation properties of fractured rocks have ranges of values instead of fixed values, hence such analyses should be considered especially in cases where there is significant scatter in the rock and fracture parameters. These scientific achievements can improve our understanding of fractured rocks’ hydro-mechanical behavior and are useful for the design of large-scale in-situ experiments with large volumes of fractured rocks, considering coupled stress-deformation-flow processes in engineering practice.QC 20141111
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Ismael, Mohamed [Verfasser], Heinz [Akademischer Betreuer] Konietzky, Heinz [Gutachter] Konietzky, and Gonzales Jorge [Gutachter] Castro. "Inherent strength and stiffness anisotropy of laminated rocks / Mohamed Ismael ; Gutachter: Heinz Konietzky, Jorge Castro Gonzales ; Betreuer: Heinz Konietzky." Freiberg : Technische Universität Bergakademie Freiberg, 2019. http://d-nb.info/1226101070/34.
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Leung, Ho Yee. "The anisotropic small strain stiffness of completely decomposed tuff and its effects on deformations associated with excavations /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202005%20LEUNG.
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Strickland, Julie N. "Anisotropic Nature of Radially Strained Metal Tubes." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc822747/.
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Metal pipes are sometimes swaged by a metal cone to enlarge them, which increases the strain in the material. The amount of strain is important because it affects the burst and collapse strength. Burst strength is the amount of internal pressure that a pipe can withstand before failure, while collapse strength is the amount of external pressure that a pipe can withstand before failure. If the burst or collapse strengths are exceeded, the pipe may fracture, causing critical failure. Such an event could cost the owners and their customers millions of dollars in clean up, repair, and lost time, in addition to the potential environmental damage. Therefore, a reliable way of estimating the burst and collapse strength of strained pipe is desired and valuable. The sponsor currently rates strained pipes using the properties of raw steel, because those properties are easily measured (for example, yield strength). In the past, the engineers assumed that the metal would be work-hardened when swaged, so that yield strength would increase. However, swaging introduces anisotropic strain, which may decrease the yield strength. This study measured the yield strength of strained material in the transverse and axial direction and compared them to raw material, to determine the amount of anisotropy. This information will be used to more accurately determine burst and collapse ratings for strained pipes. More accurate ratings mean safer products, which will minimize risk for the sponsor’s customers. Since the strained metal has a higher yield strength than the raw material, using the raw yield strength to calculate burst and collapse ratings is a conservative method. The metal has even higher yield strength after strain aging, which indicates that the stresses are relieved. Even with the 12% anisotropy in the strained and 9% anisotropy in the strain aged specimens, the raw yield strengths are lower and therefore more conservative. I recommend that the sponsor continue using the raw yield strength to calculate these ratings. I set out to characterize the anisotropic nature of swaged metal. As expected, the tensile tests showed a difference between the axial and transverse tensile strength. The correlation was 12% difference in yield strength in the axial and transverse directions for strained material and 9% in strained and aged material. This means that the strength of the metal in the hoop (transverse) direction is approximately 10% stronger than in the axial direction, because the metal was work hardened during the swaging process. Therefore, the metal is more likely to fail in axial tension than in burst or collapse. I presented the findings from the microstructure examination, standard tensile tests, and SEM data. All of this data supported the findings of the mini-tensile tests. This information will help engineers set burst and collapse ratings and allow material scientists to predict the anisotropic characteristics of swaged steel tubes.
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Dinh, Quoc Dan. "Brazilian test on anisotropic rocks." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2011. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-76331.
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The present work describes investigations on the anisotropic strength behavior of rocks in the splitting tensile test (Brazilian test). Three transversely isotropic rocks (gneiss, slate and sandstone) were studied in the Lab. A total of more than 550 indirect tensile strength tests were conducted, with emphasis was placed on the investigation of the influence of the spatial position of anisotropic weakness plane to the direction of the load on the fracture strength and fracture or fracture mode. In parallel, analytical solutions were evaluated for stress distribution and developed 3D numerical models to study the stress distribution and the fracture mode at the transversely isotropic disc. There were new findings on the fracture mode of crack propagation, the influence of the disc thickness, the influence of the applying loading angle and angle of the loading-foliation for transversely isotropic materialInhalt der Arbeit sind Untersuchungen zum anisotropen Festigkeitsverhalten von Gesteinen beim Spaltzugversuch (Brazilian Test). Laborativ wurden drei transversalisotrope Gesteine (Granit, Schiefer und Sandstein) untersucht. Insgesamt wurden mehr als 550 Spaltzugversuche durchgeführt, wobei der Schwerpunkt auf die Untersuchung des Einflusses der räumlichen Lage der Anisotropieebene zur Richtung des Lasteintrages auf die Bruchfestigkeit und das Bruchbild bzw. den Bruchmodus gelegt wurde. Parallel dazu wurden analytische Lösungen zur Spannungsverteilung ausgewertet sowie numerische 3D-Modelle entwickelt, um die Spannungsverteilung sowie den Bruchmodus bei einer transversalisotropen Scheibe zu untersuchen. Es wurden neue Erkenntnisse zum Bruchmodus, der Rissausbreitung, des Einflusses der Scheibendicke, dem Einfluss des Lasteinleitungswinkel sowie des Winkels Lasteintrag - Anisotropieebene für transversalisotropes Material gewonnen
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Navarro, Fabiano Cabañas [UNESP]. "Influência da petrografia sobre a anisotropia à tensão de compressão e dilatação térmica de rochas ornamentais." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/103006.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Considerando um conjunto de 21 tipos de rochas utilizadas como revestimento e subdivididas em quatro conjuntos por afinidade da composição mineral (rochas carbonáticas, quartzosas, feldspáticas e quartzo-feldspáticas) foram realizados ensaios tecnológicos para a determinação do coeficiente de dilatação térmica linear e da resistência à compressão uniaxial, bem como a anisotropia dessas propriedades. Os dados tecnológicos obtidos foram correlacionados com informações petrográficas qualitativas e quantitativas referentes à composição mineral, variações texturais e estruturais determinadas em seções ortogonais entre si a partir de um sistema de referência (xyz) baseado na foliação e lineação macroscopicamente visíveis. A análise integrada dos dados utilizando estatística convencional e multivariada procurou apontar as variáveis petrográficas mais relevantes para as duas propriedades tecnológicas enfocadas e suas respectivas anisotropias. A dilatação térmica e sua anisotropia são influenciadas principalmente pela composição mineral e pela orientação preferencial dos minerais embora as microfissuras desempenhem papel importante em alguns casos. A tensão de compressão mostra sua variabilidade e anisotropia influenciadas pela granulação média, tipos de contatos minerais predominantes e padrões de microfissuras mais ou menos definidos por influência da foliação presente. Constatou-se que no conjunto analisado a presença da foliação não implica necessariamente em anisotropia das duas propriedades estudadas.
The anisotropy of thermal expansion coefficient and compressive tensile strength were determined for 21 commercially used stones gathered in four set according the main mineral composition named carbonatic, quartz-rich, feldspar-rich and quartz-feldspar-rich rocks. Using a coordinate reference system (xyz) based on the macroscopic visible foliation and lineation the samples were submitted to normalized laboratorial analyses for determination of the both technological properties and the petrographical features such as mineral composition, texture and fabric. Additionally was carried out measurements of weathered area and microcrack quantification by image analysis and texture quantification by U-stage methods. In order to understand the relationship between the anisotropy measured and petrographical data it was applied traditional and multivariate statistical analysis. The results pointed to the great significance of mineral composition and the crystallographic preferred orientation for thermal expansion and respective anisotropy, especially to monomineralic and/or foliated rocks, in spite of some cases microcracks play this role. The compressive strength is mainly controlled by a complex interaction between grain size distribution, grain boundary and microcrack patterns related or not to foliation.
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Reis, Rodrigo Martins. "Comportamento tensão-deformação de dois horizontes de um solo residual de gnaisse." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-06112006-163715/.
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Neste trabalho estuda-se o comportamento tensão-deformação de dois horizontes de um solo residual de gnaisse, pertencentes a um perfil típico da cidade de Viçosa-Minas Gerais, na condição saturada e sob diferentes valores de sucção. O estudo apóia-se em ensaios de caracterização física e mineralógica, em ensaios destinados às análises porosimétricas e morfológicas (lâminas delgadas), e em ensaios de compressão triaxial realizados em corpos de prova não saturados e saturados, estes sujeitos a diferentes direções de cisalhamento, em ambos solos, e distintas trajetórias de tensão, no solo jovem. Nos ensaios triaxiais saturados mostra-se que a resistência dos dois solos foi independente da direção de cisalhamento e que a deformabilidade revelou-se mais anisotrópica no solo maduro, que no solo jovem, este visualmente mais heterogêneo. Mostra-se, que o intercepto de coesão cresce com a sucção numa relação que pode ser bem representada por uma função hiperbólica e que o ângulo de atrito interno praticamente não apresentou variação com a sucção matricial. Apresenta-se uma alternativa de previsão da envoltória de resistência, baseada nos parâmetros de resistência do solo saturado e nos resultados de ensaio correspondente a uma sucção conhecida. A curva de plastificação do solo jovem pôde ser representada razoavelmente bem pela curva adotada nos modelos derivados da mecânica dos solos dos estados críticos (Cam-Clay modificado). A curva é centrada no eixo hidrostático e sua forma não apresenta mudança marcante durante o encruamento do solo, o qual foi obtido através da união de pontos com o mesmo trabalho plástico.This thesis deals with the stress-strain behavior of a mature soil and a young soil from a typical residual soil of gneiss, as found in Viçosa-MG. This behavior is analyzed under saturated and non saturated conditions. The study rests on physical and mineralogical characterization tests, on porosimetric and morphological analyses (thin section) and on triaxial compression tests performed with saturated and non saturated soil. Saturated young and mature specimens were sheared according to different directions and saturated young soil was also sheared following various stress path. It is shown that the shear strength of saturated soil, both mature and young is independent of shearing direction. However, the visually more homogeneous mature soil showed to be more anisotropic, regarding the deformability, than the young residual soil that visually seems to be heterogeneous. The cohesion intercept tends to increase with soil suction according to a non linear relationship that can be adjusted through a hyperbolic function, while the angle of shearing stress was not influenced by soil suction. An alternative to forecast unsaturated shear strength envelope based on results of saturated soil and on tests performed at a known suction is also presented. The yielding curve of young soil was found to be fairly predicted using modified Cam-Clay model. The yield curve is centered along the hydrostatic axis of stress and its shape didnt change during soil strain hardening that was obtained by joining the points to that exhibited the same plastic work.
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Navarro, Fabiano Cabañas. "Influência da petrografia sobre a anisotropia à tensão de compressão e dilatação térmica de rochas ornamentais /." Rio Claro : [s.n.], 2006. http://hdl.handle.net/11449/103006.
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Orientador: Antonio Carlos ArturBanca: Antenor Braga Paraguassú
Banca: José Eduardo Rodrigues
Banca: Maria Heloisa Barros de Oliveira Frascá
Banca: Peter Christian Hackspacher
Resumo: Considerando um conjunto de 21 tipos de rochas utilizadas como revestimento e subdivididas em quatro conjuntos por afinidade da composição mineral (rochas carbonáticas, quartzosas, feldspáticas e quartzo-feldspáticas) foram realizados ensaios tecnológicos para a determinação do coeficiente de dilatação térmica linear e da resistência à compressão uniaxial, bem como a anisotropia dessas propriedades. Os dados tecnológicos obtidos foram correlacionados com informações petrográficas qualitativas e quantitativas referentes à composição mineral, variações texturais e estruturais determinadas em seções ortogonais entre si a partir de um sistema de referência (xyz) baseado na foliação e lineação macroscopicamente visíveis. A análise integrada dos dados utilizando estatística convencional e multivariada procurou apontar as variáveis petrográficas mais relevantes para as duas propriedades tecnológicas enfocadas e suas respectivas anisotropias. A dilatação térmica e sua anisotropia são influenciadas principalmente pela composição mineral e pela orientação preferencial dos minerais embora as microfissuras desempenhem papel importante em alguns casos. A tensão de compressão mostra sua variabilidade e anisotropia influenciadas pela granulação média, tipos de contatos minerais predominantes e padrões de microfissuras mais ou menos definidos por influência da foliação presente. Constatou-se que no conjunto analisado a presença da foliação não implica necessariamente em anisotropia das duas propriedades estudadas.
Abstract: The anisotropy of thermal expansion coefficient and compressive tensile strength were determined for 21 commercially used stones gathered in four set according the main mineral composition named carbonatic, quartz-rich, feldspar-rich and quartz-feldspar-rich rocks. Using a coordinate reference system (xyz) based on the macroscopic visible foliation and lineation the samples were submitted to normalized laboratorial analyses for determination of the both technological properties and the petrographical features such as mineral composition, texture and fabric. Additionally was carried out measurements of weathered area and microcrack quantification by image analysis and texture quantification by U-stage methods. In order to understand the relationship between the anisotropy measured and petrographical data it was applied traditional and multivariate statistical analysis. The results pointed to the great significance of mineral composition and the crystallographic preferred orientation for thermal expansion and respective anisotropy, especially to monomineralic and/or foliated rocks, in spite of some cases microcracks play this role. The compressive strength is mainly controlled by a complex interaction between grain size distribution, grain boundary and microcrack patterns related or not to foliation.
Doutor
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Santos, Roberto Aguiar dos. "Comportamento anisotrópico de um solo laterítico compactado." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-22032016-104302/.
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A compactação de aterros pode gerar comportamento anisotrópico, a depender do teor de umidade de compactação, entre outros fatores. O principal objetivo deste estudo foi investigar alguns aspectos relacionados à anisotropia inerente induzida pela compactação de um solo laterítico. Após realizar a caracterização mineralógica, geotécnica e microestrutural deste solo, estudou-se a resistência ao cisalhamento, condutividade hidráulica, compressibilidade e deformabilidade. O solo estudado foi classificado como laterítico arenoso (LA\') e apresentou agregação relativa da ordem de 12%. A metodologia desenvolvida no intuito de corrigir o aumento na massa específica seca das camadas inferiores, causado pelo processo de compactação, mostrou-se eficaz. A partir da curva de compactação foram consideradas amostras representativas das três condições de umidade de compactação: ramo seco, umidade ótima e ramo úmido. Corpos de prova foram talhados paralelamente e ortogonalmente às camadas de compactação. Os ensaios de porosimetria revelaram um comportamento bimodal na distribuição do tamanho de poros e também que o teor de umidade de compactação não interferiu no tamanho dos microporos. Para o solo compactado no ramo seco e na umidade ótima, a resistência ao cisalhamento correspondente à direção ortogonal se mostrou superior àquela correspondente à direção paralela às camadas de compactação. Por outro lado, a resistência ao cisalhamento no ramo úmido mostrou-se praticamente independente da direção de talhagem dos corpos de prova. Este comportamento se deve à maior capacidade do solo, em um dado teor de umidade, em absorver a energia aplicada e distribuí-la na direção paralela e ortogonal. Com relação às propriedades elásticas do material, observou-se que o aumento do teor de umidade de compactação contribui para redução da anisotropia de deformabilidade. Dentre as propriedades investigadas, a anisotropia de condutividade hidráulica das amostras correspondente ao ramo úmido foi a mais pronunciada, exibindo fluxo oito vezes maior na direção vertical que na horizontal. Finalmente, as discussões e análises presentadas nesta pesquisa mostraram que o grau de anisotropia depende diretamente do teor de umidade de compactação e que diminui com incremento das tensões aplicadas no solo.Compacted embankments can have anisotropic behavior, depending on several factors, including the compaction water content. The aim of this study was to investigate some aspects regarding the inherent anisotropy of a lateritic soil, caused by the compaction process. After performing the geotechnical, mineralogical and microstructural characterization, properties of shear strength, hydraulic conductivity, compressibility and deformability were investigated. This soil this soil was classified as lateritic sand. The grainsize distribution curve indicates 12% the fine particle aggregation. The methodology developed in order to correct the increase in dry density of the lower layers, generated by the compression process, was effective. From the compaction curve, representative samples corresponding to the three compaction water content conditions, representing the dry side, the optimal water content and the wet side were considered. Specimens were trimmed parallel and orthogonally to the compaction layers. The porosimetry tests showed a bimodal behavior in the pore size distribution and also that the compaction water content did not influence the size of the micropores. For the compacted soil sample corresponding to the dry side and optimum water content, the shear strength corresponding to the orthogonal direction was higher than that corresponding to the parallel direction to the compaction layers. However, they were almost equal for both the orthogonal and the parallel directions to the compaction layers. This behavior is due to the higher capacity of the soil at a given moisture content, to absorb the energy applied and distribute it in parallel and orthogonal direction. The analysis the values of maximum shear modulus of the material showed that increasing compaction water content reduces the anisotropy degree. Among the investigated properties, the hydraulic conductivity anisotropy of the samples corresponding to the wet branch was the most pronounced, showing permeability eight times higher in the vertical direction than that in the horizontal direction. Finally, the discussions and analyzes presented in this study showed that the degree of anisotropy directly depends on the compaction water content and decreases with increase confining stress applied to the soil specimens.
21
Nicolas, Elias Antonio. "Estudo de criterios de resistencia de materiais anisotropicos aplicados a madeira." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257999.
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Orientador: Nilson Tadeu MasciaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-07T08:37:01Z (GMT). No. of bitstreams: 1 Nicolas_EliasAntonio_D.pdf: 5212612 bytes, checksum: 6374b5ff3649878b30250be16c1a8e76 (MD5) Previous issue date: 2006
Resumo: Esta pesquisa refere-se ao estudo de critérios de resistência de materiais anisotrópicos, especialmente o critério tensorial de resistência de TSAI- WU, com aplicações teóricas e experimentais para a madeira. Neste sentido foi realizada uma revisão teórica dos principais temas relacionados à presente pesquisa, como: critérios gerais de resistência, fórmula de hankinson, critério de TSAIWU, modos de ruptura da madeira, fatores que influenciam na resistência da madeira,equipamentos e corpos-de-prova para realização de ensaios uniaxiais e biaxiais, prescrições de cálculo das normas de estruturas de madeira. O objetivo principal deste trabalho foi determinar os parâmetros de resistência do critério tensorial de TSAI-WU, com a finalidade de definir uma superfície de ruptura, para a espécie de madeira estudada, cupiúba (Goupia glabra), e comparar os dados dos ensaios com as estimativas do critério. No estudo experimental foram realizados os seguintes ensaios: tração e compressão, uniaxiais, com ângulos das fibras inclinados em relação ao carregamento (0°, 15°, 30°, 45°, 60°, 75° e 90°); ensaios de cisalhamento paralelo às fibras e ensaios de compressão biaxial. As estimativas do critério de TSAI- WU ficaram próximas das estimativas da fórmula de Hankinson e também dos dados dos ensaios uniaxiais de tração e compressão. Por outro lado, para ensaios biaxiais, o critério de TSAI-WU sofre grande influência do coeficiente de interação.De um modo geral, o critério de TSAI-WU apresenta bons resultados, facilidade de utilização se comparado a outros critérios, devido especialmente a seu caráter tensorial, podendo ser aplicado na avaliação de resistência da madeira e de outros materiais anisotrópicos
Abstract: This research deals with the study of anisotropic material failure criteria, specifically TSAI- WU tensor failure criteria, and theoretical and experimental applications for wood. Thus it was carried out a theoretical revision of the principal themes related to this research: general failure criteria, Hankinson's formula, TSAI-WU tensor criterion, failure modes of wood, factors that affect wood strength, equipaments and specimens for development of uniaxial and biaxial tests and rules of design codes of wood structures. The main objective of this work was to determine the TSAI-WU tensor failure criterion parameters, with the purpose of defining the failure surface, for the wood specie Cupiúba (Goupia Glabra) and of comparing the test results and criterion estimates as well. In the experimental development it was performed the following axial tests: tension and compression, with inclined grain angles in related to the load (0°, 15°, 30°, 45°, 60°, 75° and 90°); shear tests and biaxial compression. The estimates of TSAI-WU criterion were close of Hankinson's formula and the tension and compression tests results too. On the other hand, for biaxial compressive test, TSAI- WU criterion influence ofthe interaction coefficient (F12). In general, TSAI- WU criterion can be applied to evaluate wood strength and other anisotropic materials too, by presenting good results and facility in utilizing especially when comparing to other criteria due to its tensor form
Doutorado
Estruturas
Doutor em Engenharia Civil
22
Adel, Norelhayate. "Influence d'un adjuvant proteique sur la texture poreuse et les proprietes mecaniques et thermiques d'un beton cellulaire autoclave." Toulouse 3, 1987. http://www.theses.fr/1987TOU30219.
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Etude en vue de la realisation de murs legers, isolants, homogenes, l'anisotropie de structure pouvant augmenter la resistance vertical et diminuer la conductivite horizontale. Etude de l'effect d'un siliceux, poudre d'aluminium et eau, autoclave a 175**(o)c. Les resultats s'expliquent par la structure dissymetrique vis-a-vis de l'eau des molecules proteiques, hydrophobes d'un cote et hydrofuges de l'autre
23
Anop, Hanna. "Directing through low ionic strength, free polymers and metallic nanoparticles the self-organization of viral rod-shaped colloids." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0119.
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Les bactériophages en forme de filament, en raison de leurs propriétés physiques uniques, telles que leur monodispersité en taille et leur haute stabilité colloïdale, sont largement utilisés en matière molle en tant que système modèle de bâtonnets colloïdaux. En dispersions aqueuses, l'auto-organisation de ces virus s’est révélée être essentiellement conduite par l’entropie, ce qui implique des interactions purement répulsives entre les particules virales. Dans cette thèse, en modifiant la nature des interactions entre les bâtonnets viraux, nous avons étudié leur auto-organisation en phase cristal-liquides. Dans ce but, nous avons d'abord étudié un système de bâtonnets purement répulsifs à très basse force ionique, et longue répulsion électrostatique. Le comportement de phase de ces suspensions a été déterminé par l’utilisation de la diffusion des rayons X aux petits angles et de la microscopie optique. Nous avons montré que la phase Smectique-A n’est pas stable dans les cas de forte répulsion électrostatique entre particules virales et que le système présente une transition directe de la phase de Cholestérique à la phase Smectique-B en augmentant la fraction volumique. De plus, nos résultats mettent en évidence que les virus dans ces conditions ne forment pas de verres colloïdaux à forte concentration, ce qui contredit de récents travaux réalisés sur le même système.Dans une deuxième partie, nous avons modifié les interactions entre particules virales passant de purement répulsives à attractives en ajoutant des polymères libres aux suspensions, ce qui conduit à un effet de déplétion. En utilisant des polymères dont la taille est similaire au diamètre des bâtonnets, l'auto-organisation des virus, initiée dans la phase cristal-liquide cholestérique, conduit à une croissance de superstructures hélicoïdales. Dans ces structures, les bâtonnets sont principalement orientés le long de l'axe principal et présentent un ordre positionnel à longue portée, démontré par la diffusion des rayons X aux petits angles et le suivi de particules individuelles en microscopie optique. Les diagrammes de phase dse mélanges virus/polymères ainsi que la stabilité dans le temps des superstructures hélicoïdales ont été déterminés et comparés pour deux tailles différentes de polymères.Dans la dernière partie, nous avons favorisé les interactions attractives de Van der Waals dans notre système en introduisant des nanoparticules d'or dans des colloïdes hybrides auto-assemblés à base de virus. Ainsi, différents colloïdes hybrides consistant en un (en forme de sceptre) ou deux (dibloc) virus attachés à la même nanoparticule d'or ont été produits. Cette approche utilisant les nanoparticules d'or a été étendue afin de lier ensemble deux virus de différentes longueurs pour obtenir des diblocs colloïdaux asymétriques. L'auto-organisation des particules en forme de sceptre et des diblocs symétriques induite par déplétion a été explorée et les diagrammes de phases correspondants ont été établis. Nous avons ainsi montré que les interactions de Van der Waals entre nanoparticules d'or favorise la formation de fibrilles de type Smectique-B dans lesquelles les particules de virus sont organisées en une succession de couches séparées par des couches de nanoparticules d’or. Finalement, nous avons étudié l'effet de l'introduction d'une faible asymétrie dans de ces colloïdes hybrides et l’effet sur la ségrégation potentielle de leurs blocs respectifs au travers de la formation de phase lamellaire de type Smectique-A.Dans cette thèse, nous avons ainsi démontré une manière efficace de contrôler l'auto-organisation de colloïdes en forme de filament en modifiant leurs interactions, ce qui conduit à la formation de diverses morphologies auto-assemblées originalesFilamentous bacteriophages, due to their unique physical properties, such as size monodispersity and high colloidal stability, are widely used in soft condensed matter as a system of rod-shaped colloids. In aqueous dispersions, self-organization of these viruses has been shown to be essentially driven by entropy, which means purely repulsive (hard core) interactions between viral particles. In this thesis, by varying the nature of the interactions between viral rods, we have studied their resulting self-organization into liquid crystalline phases. For this purpose, we have first investigated the system of purely repulsive rods at very low ionic strength, where thick electric double layers are present. The phase behavior of virus suspensions at very low ionic strength has been determined using small angle X-ray scattering (SAXS) and optical microscopy techniques. We have found that the Smectic-A phase is not stable in case of high electrostatic repulsion between viral particles and that the system undergoes a direct Cholesteric to Smectic-B phase transition by increasing rod concentration. Moreover, our results evidence that viruses with thick double layers do not form colloidal glasses at high concentrations, which contradicts recently reported findings for the same system.In a second part, we have tuned viral particle interactions from purely repulsive to attractive ones by adding non-adsorbing polymers in their suspensions, which act as depletant agent. By using polymers with coil size comparable to the rod diameter, virus self-organization initiated from the Cholesteric liquid crystalline phase results in a growth of original chiral superstructures, called helical bundles. Viruses are mostly oriented along the main bundle axis and exhibit long-range positional order, as proved by SAXS and by single particle tracking using optical microscopy. Phase diagrams of virus/polymer two-component mixtures as well as the stability with time of the resultant helical superstructures have been determined and compared for two different polymer sizes.In the last part, we have increased Van der Waals attractive interactions in our viral system by introducing gold nanoparticles into self-assembled hybrid virus-based colloids. Thus, different hybrid virus-based colloids consisting of one (scepter-like) or two (diblocks) viral filaments attached to the same gold nanoparticle have been produced. This approach using gold nanobead has been extended to link together two bacteriophages of different lengths to achieve asymmetric colloidal diblocks. Self-organization of scepter-like particles and symmetrical diblocks driven by soft effective attraction has been explored and the corresponding phase diagrams have been established. We have found that Van der Waals attractive interactions between gold nanobeads incorporated into hybrid colloids favor formation of Smectic-B like fibrils in which virus particles are organized in periodic layers separated by layers of gold nanobeads. Finally, we have studied the effect of introducing a weak asymmetry into hybrid virus-based colloids and investigated the possible segregation of their respective blocks through the formation of the lamellar Smectic-A phase.Overall, we have demonstrated an efficient way to control self-organization of virus-based colloids by varying interactions between them, which results in formation of various original self-assembled morphologies
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Speck, Kerstin. "Beton unter mehraxialer Beanspruchung." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1216628091575-43714.
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Diese Arbeit basiert auf der Untersuchung von hochfesten und ultrahochfesten Betonen mit und ohne Fasern unter zwei- und dreiaxialer Druckbeanspruchung. Die Auswirkung der unterschiedlichen Betonzusammensetzung ist für verschiedene Beanspruchungen nicht gleich ausgeprägt, dennoch konnten grundlegende Zusammenhänge herausgearbeitet werden. Anhand der Bruchbilder konnten die drei Versagensmechanismen Druck-, Spalt- und Schubbruch identifiziert werden, deren Charakteristik über die Kalibrierung an vier speziellen Versuchswerten direkt in das Bruchkriterium einfließen. Dieses stellt eine Erweiterung der Formulierung von OTTOSEN dar, so dass das spröde und z. T. anisotrope Verhalten von Hochleistungsbeton berücksichtigt wird. Die beobachteten Spannungs-Dehnungs-Verläufe korrelieren mit den Versagensformen. Deshalb wird ein Stoffgesetz getrennt für den Druck- und den Zugmeridian aufgestellt, dessen Parameter sich mit zunehmendem hydrostatischen Druck verändern. In die Anfangswerte fließen die Betonzusammensetzung und herstellungsbedingte Anisotropien ein. Die lastinduzierte Anisotropie infolge einer gerichteten Mikrorissbildung wird in dem vorgestellten Stoffgesetzt über richtungsabhängige Parameter ebenfalls berücksichtigt.
25
Speck, Kerstin. "Beton unter mehraxialer Beanspruchung: Ein Materialgesetz für Hochleistungsbetone unter Kurzzeitbelastung." Doctoral thesis, Technische Universität Dresden, 2007. https://tud.qucosa.de/id/qucosa%3A23705.
Full textAbstract:
Diese Arbeit basiert auf der Untersuchung von hochfesten und ultrahochfesten Betonen mit und ohne Fasern unter zwei- und dreiaxialer Druckbeanspruchung. Die Auswirkung der unterschiedlichen Betonzusammensetzung ist für verschiedene Beanspruchungen nicht gleich ausgeprägt, dennoch konnten grundlegende Zusammenhänge herausgearbeitet werden. Anhand der Bruchbilder konnten die drei Versagensmechanismen Druck-, Spalt- und Schubbruch identifiziert werden, deren Charakteristik über die Kalibrierung an vier speziellen Versuchswerten direkt in das Bruchkriterium einfließen. Dieses stellt eine Erweiterung der Formulierung von OTTOSEN dar, so dass das spröde und z. T. anisotrope Verhalten von Hochleistungsbeton berücksichtigt wird. Die beobachteten Spannungs-Dehnungs-Verläufe korrelieren mit den Versagensformen. Deshalb wird ein Stoffgesetz getrennt für den Druck- und den Zugmeridian aufgestellt, dessen Parameter sich mit zunehmendem hydrostatischen Druck verändern. In die Anfangswerte fließen die Betonzusammensetzung und herstellungsbedingte Anisotropien ein. Die lastinduzierte Anisotropie infolge einer gerichteten Mikrorissbildung wird in dem vorgestellten Stoffgesetzt über richtungsabhängige Parameter ebenfalls berücksichtigt.
26
Rolo, Reinaldo. "The anisotropic stress-strain-strength behaviour of brittle sediments." Thesis, Imperial College London, 2004. http://hdl.handle.net/10044/1/8239.
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Huber, Marius. "Dynamique des grands glissements de terrain rocheux, modélisation numérique et études de cas en Himalaya." Electronic Thesis or Diss., Université de Lorraine, 2024. https://docnum.univ-lorraine.fr/ulprive/DDOC_T_2024_0083_HUBER.pdf.
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Les glissements de terrain sont un phénomène courant à la surface de la Terre. Ils représentent à la fois un risque naturel majeur pour les populations et les infrastructures, et un processus dominant dans l’érosion des pentes montagneuses et dans l'évolution des surfaces continentales. Les facteurs qui conditionnent et préparent les pentes avant de les conduire à s’effondrer sont multiples et comprennent, entre autres, les caractéristiques du matériau constitutif du versant ainsi que des facteurs externes tels que le climat et la sismicité. L’étude de ces facteurs est fondamentale pour pouvoir comprendre l’apparition des mouvements gravitaires et leur dynamique. Cela inclut notamment la compréhension des déformations de grande ampleur, qui bien que se produisant rarement ou avec un faible taux d'activité, ont un fort impact en termes d’aléas naturels et de développement des reliefs. Cette thèse de doctorat se concentre sur les glissements de terrain profonds qui se produisent au sein du substrat rocheux des versants. La première partie de cette thèse s’intéresse à deux phénomènes gravitaires majeurs se produisant dans le massif de l'Annapurna en Himalaya (Népal central) : les écroulements rocheux géants (volume de débris > 0,1 km3) et les déformations gravitaires non- catastrophiques de versants (DSGSD en anglais). Des mesures d'âge d’exposition basées sur les nucléides cosmogéniques (isotopes 10Be et 36Cl) et d’âge d’enfouissement (14C) nous ont permis de dater l'âge de 3 écroulements géants en flanc nord des Annapurnas, et de reconstruire la paléo-activité d'un grand DSGSD en flanc sud. Combinés avec la reconstruction des volumes, nos résultats indiquent que les écroulements géants se sont produits pendant l'optimum climatique de l'Holocène (EHCO) et l’optimum climatique médiéval, c'est-à-dire principalement à la fin de périodes plus chaudes et plus humides qu’ait connu la Terre. Ce synchronisme suggère un forçage climatique sur le déclenchement des effondrements géants. Nous identifions également une plus grande activité du DSGSD à la fin de l'EHCO, soulignant de même le rôle du forçage climatique sur la déstabilisation des versants himalayens. Dans la deuxième partie de la thèse, un modèle numérique aux éléments discrets est utilisé pour étudier comment l'anisotropie mécanique de la roche affecte la rupture d'un versant de pente uniforme. Après avoir défini un matériau à isotropie transverse et aux caractéristiques mécaniques proches de celles d'un gneiss, nous explorons de manière systématique et en deux dimensions (0 - 180°), l’influence sur la rupture de l’orientation relative du plan d'isotropie par rapport à celle du versant. Nos résultats indiquent que si le plan d'isotropie est légèrement moins incliné que la pente topographique (configuration cataclinale), la stabilité de la pente n’est assurée qu’avec une résistance du substrat beaucoup plus élevée que dans une configuration où le plan d'isotropie est perpendiculaire à la pente (configuration anaclinale). De plus, comme constaté sur le terrain en Himalaya, les modes d’effondrement des versants dépendent fortement de l'orientation du plan d'isotropie. Nous observons : pour les pentes cataclinales, un glissement parallèle au plan d’isotropie ou sinon un flambage, si le versant est plus ou respectivement moins raide que le plan d’isotropie ; pour les pentes anaclinales, un basculement/fléchissement ou l'éboulement par blocs, suivant que le plan d'isotropie est à fort ou à faible pendage. Contredisant, pour les montagnes actives, la vision simplifiée de versants aux pentes uniformes et proches de l'angle de frottement interne des roches, notre travail met en évidence une diversité de pentes critiques et de processus de glissement de terrain qui dépendent à la fois de facteurs internes (e.g. l'anisotropie) et de facteurs externes (contexte tectono-climatique)Landslides are a common phenomenon on the Earth’s surface. They come in many forms as a wide range of environmental conditions determine the characteristics of slope failure. They are a threat to human society and play an important role in the denudation of hillslopes and thus in the evolution of the Earth's surface. Factors that precondition and prepare slopes to failure are diverse and include the characteristics of the failure material as well as external factors such as climate and seismicity. A conceptually coherent understanding of these factors is required to better assess landslides, especially their large representatives which occur with low frequency and activity rates, but are however critical in terms of natural hazards and development of reliefs. This PhD-thesis is focused on bedrock landslides, which are slope failures that occur in rock masses. In the first part of the thesis, two subtypes of bedrock landslides located in the Annapurna Massif of central Nepal are investigated: Giant rock avalanches (> 0,1 km3 failure volume) and non-catastrophic Deep-Seated Gravitational Slope Deformations (DSGSDs). Absolute dating techniques, including cosmogenic nuclide exposure measurements (10Be and 36Cl isotopes) and 14C carbon burial dating were used to determine the age and volumes of 3 giant rock avalanches and reconstruct the paleo- activity of a DSGSD. Our results indicate that the giant rock avalanches occurred predominantly at the end of Holocene periods with warmer and wetter climatic conditions, i.e. during the Early Holocene Climatic Optimum (EHCO) and the Medieval Warm Period (MWP). This highlights the role of climatic forcing on slope failure. We also identified a higher activity of the DSGSD at the end of the EHCO, further emphasizing the role of climatic forcing on slope destabilization. Besides their implications for natural hazards, our results offer new perspectives on mountain-scale erosion fluxes and landscape denudation in the region. In the second part of the thesis, a discrete element model is used to investigate how rock strength anisotropy affects the failure of a 1 000 m high slope with constant slope angle. After setting up the transverse isotropic material with the mechanical characteristics of a gneiss, the whole range of possible isotropy plane orientations with respect to the slope face is systematically explored in two dimensions (0 – 180°). Our results indicate that if the isotropy plane is slightly less inclined than the topographic slope (i.e. cataclinal overdip configuration), slope stability requires a material strength one order of magnitude higher than in a configuration where the isotropy plane is perpendicular to the slope (i.e. anaclinal configuration). Moreover, as expected from field observations, slope failure modes are directly constrained by the isotropy plane orientation: sliding is observed for cataclinal overdip slopes, buckling for cataclinal underdip slopes, toppling for anaclinal slopes with steeply dipping isotropy planes, and crumbling for anaclinal slopes with less steeply dipping isotropy planes. By analysing the south-facing slopes of the Annapurna Massif (Nepal), we were able to evidence the role of material anisotropy in landscape shaping in the area. The relative orientation of the anisotropy with respect to the topography is an important precondition of slope failure, controlling both the stability and the failure mode. The systematic investigation performed in this thesis contributes to slope stability analysis in general as well as to a better understanding of landscape shaping by slope failure. Our work highlights a diversity of critical slopes and landslide processes that depend on both internal factors (in this case, anisotropy) and external factors (tectono-climatic context)
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Karpuz, Pinar. "Investigation Of The Effects Of Equal Channel Angular Extrusion On Light Weight Alloys." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614036/index.pdf.
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Severe plastic deformation methods are of great interest in industrial forming applications, as they give rise to significant refinement in microstructures and improvements in mechanical and physical properties. In the &ldquoEqual Channel Angular Extrusion (ECAE)&rdquo
, which is the most common method for production of ultrafine grained bulk samples, very high plastic strains are introduced into the bulk material without any change in cross section. This study is composed of two main parts. Part I focuses on the plastic deformation behavior of Al alloys by modeling ECAE with Msc. Marc finite element software. A series of numerical experiments were carried out for the die angles of 90°
, 120°
, and 150°
, different friction conditions, and different round corners. Besides, the effects of strain hardening characteristics of the material, strain hardening coefficient (K) and exponent (n) of Hollomon&rsquo
s law, on corner gap formation and strain homogeneity in equal channel angular pressing process were investigated quantitatively. The results were compared and verified with those of the upper bound analysis. The numerical results showed that the process performance can be improved by modifying the die corner curvature accordingly, without running time consuming simulations. On the other hand, the aim of Part 3 is to investigate the texture evolution, mechanical response and the corresponding mechanisms, in terms of the flow stress anisotropy and tension-compression asymmetry in the ZK60 Mg alloy. The alloy was processed using ECAE, with different processing routes and temperatures, in order to produce samples with a wider variety of microstructures and crystallographic textures. Several mechanical tests and microstructure examinations were carried out
and the flow stress anisotropy and tension-compression asymmetry of the as-received and processed samples were measured. It was found that the initial texture has a strong effect on the resulting textures
and the textures, combined with the microstructure effect, define the mechanical properties of processed samples. Thus, the tension-compression asymmetry and the flow stress anisotropy variations in the processed samples are attributed to the generated textures and it is possible to control these properties by controlling the processing route and temperature.
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Solas, Denis. "Anisotropie des propriétés mécaniques et endommagement des alliages Al-Zn-Mg-Cu." Grenoble INPG, 1997. http://www.theses.fr/1997INPG0226.
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Les toles fortes en alliage d'aluminium de la serie 7000 peuvent presenter une anisotropie des proprietes mecaniques (limite d'elasticite, ecrouissage et endommagement). Ces toles sont obtenues apres laminage a chaud, mise en solution, trempe, detensionnement et traitement de revenu. Dans un premier temps, nous avons caracterise la microstructure du materiau (structure granulaire, texture cristallographique, microstructure des joints de grains. . . ). L'anisotropie des proprietes mecaniques est determinee pour differents traitements de revenu par essai de traction. L'anisotropie de la limite d'elasticite est simulee a l'aide d'un modele autocoherent elastoplastique. Ce modele permet de prevoir et de prendre en compte les contraintes residuelles du deuxieme ordre generees par le detensionnement. En ce qui concerne l'endommagement et la rupture, plusieurs mecanismes ont ete identifies en fonction du traitement de revenu et de la direction de traction. En particulier, la rupture intergranulaire se produit pour une contrainte critique qui depend du mode de sollicitation des joints de grains (traction et cisaillement) et de leur microstructure.
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Todeschini, Rodrigo. "Ensaios uniaxiais e biaxiais para avalição de criterio de resistencia de materiais anisotropicos aplicado a madeira." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257676.
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Orientador: Nilson Tadeu MasciaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: A realização de ensaios uniaxiais e biaxiais permite uma melhor compreensão do comportamento mecânico de um material que possui direções principais de resistência e é sem dúvida uma forma que pesquisadores encontraram para obter resultados condizentes com a situação real que uma determinada estrutura apresenta. O presente trabalho teve como objetivo o estudo do critério de resistência proposto por Tsai e Wu, realizando-se ensaios uniaxiais e biaxiais. A avaliação do critério ficou restrita ao ensaio de compressão, devido às dificuldades de se realizar ensaios biaxiais de tração. Com o ensaio biaxial de compressão, tensões em duas direções principais foram simultaneamente desenvolvidas, utilizando-se um equipamento de ensaio tradicional para uma direção e na direção perpendicular um equipamento tipo alicate desenvolvido para este fim. O parâmetro estudado foi o 12 F , parâmetro este que designa a possibilidade da superfície de ruptura ser aberta ou fechada, considerando-se que para a segurança de um projeto é imprescindível obter uma superfície fechada para o critério de resistência adotado. Observa-se, além disso, que o parâmetro 12 F foi obtido no ensaio biaxial de compressão de forma direta. Para as espécies de madeira Pinus elliottii e Goupia glabra (Cupiúba), obtiveram-se valores experimentais satisfatórios, sendo algumas inconsistências observadas em função da heterogeneidade do material.
Abstract: The completion of the uniaxial and biaxial tests permits a better understanding of the mechanical behavior of a material that has main failure directions and it is undoubtedly a method that researchers identified to achieve consistent results with the actual situation that a particular structure presents. This study aimed at studying the strength criterion proposed by Tsai and Wu, performing uniaxial and biaxial tests. The evaluation of this criterion was restricted to compression biaxial tests due to the difficulties presented by tension biaxial tests. With a compression biaxial test, the stresses in two main directions were simultaneously carried out, using a standard equipment test for one direction and for the perpendicular direction an equipment type pliers especially developed for this purpose. The failure parameter studied was 12 F , which evaluates the possibility of failure surface to be opened or closed, also considering that for the safety of design it is essential to obtain a closed surface for the failure criterion adopted. Furthermore, it was noted that in the compression biaxial test the parameter 12 F was obtained directly. For the species of wood Pinus elliottii and Goupia glabra (Cupiúba), the experimental values obtained were satisfactory with some inconsistencies observed in the light of the heterogeneity of the material.
Mestrado
Estruturas
Mestre em Engenharia Civil
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Fourmeau, Marion. "Characterization and Modelling of the Anisotropic Behaviour of High-Strength Aluminium Alloy." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for konstruksjonsteknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23979.
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The purpose of the present study is to describe and characterize the anisotropic flow and fracture behaviour of a high-strength aluminium alloy. To this end, thick plates of AA7075-T651 aluminium alloy have been tested. Different specimen geometries were used to investigate various stress states. Each specimen was machined in different directions of the plate to enlighten the anisotropy of the material. For all tests, the plastic flow exhibited a slight anisotropy while the failure strain and failure modes showed a very important dependence to the loading direction. A microstructure analysis of the virgin material was performed by scanning electron microscope (SEM) and electron back-scatter diffraction to identify its texture, grain shape and particle distribution. A transmission electronic microscope analysis gave information of the precipitate free zones and their composition. Tensile tests were performed on smooth axisymmetric specimens under uniaxial tension. Tensile tests were also conducted on notched axisymmetric specimens of notch radii and to obtain higher stress triaxiality states. Shear tests were performed on butterfly specimens and compression tests were performed on cylindrical specimens. Fracture surface analyses were carried out by SEM to identify the failure modes, supported by the microstructure analysis. Based on the plastic anisotropy observed experimentally, the Yld2004-18p anisotropic yield function proposed by Barlat et al. (2005) was chosen to model the elasto-plastic behaviour of the AA7075-T651 alloy. The plastic parameters were calibrated using seven in-plane uniaxial tensile tests, a compression test in the normal direction of the plate and a shear test in the rolling direction. Numerical simulations of all the experimental tests were performed using the anisotropic elasto-plastic model. Predicted stress-strain curves were in very good agreement with the experimental curves for all tests including the tensile tests on notched specimens, which were not used in the calibration of the model. The overestimation of predicted stress level, generally observed (e.g. by Wilson, 2002) with notched specimens and isotropic pressure independent yield function, was significantly decreased when taking into account anisotropy. The stress and strain states on elements where failure is experimentally observed were evaluated. The establishment of a failure locus (relation between failure strain and stress triaxiality) was also discussed. Analytical approaches were used to gain some insight of the failure process. First, the void growth approach proposed by Rice and Tracey (1969) was extended to an anisotropic matrix. Then, the usual localization criterion (Rice, 1976) was developed with various constitutive characteristics to account for the shape of the yield function, non-associative plastic flow, large deformations and thermo-mechanical couplings. For industrial applications, a phenomenological failure criterion based on “plastic work”, called the anisotropic extended Cockcroft-Latham (AECL), was proposed. The criterion was calibrated using the seven uniaxial in-plane tensile tests and the shear test performed in the rolling direction. Numerical simulations of all tests were, once again, performed accounting for plastic anisotropy. A parameter study was carried out to enlighten the influence of parameters such as the plastic anisotropy and the failure anisotropy. The predicted failure strain and failure modes were not accurate enough to give predictive capability to this failure criterion in all material tests. Finally, this anisotropic failure criterion was also used in numerical simulations of some impact tests on AA7075-T651 plates with ogival and blunt projectiles. A thermoelasto-thermoviscoplastic model with anisotropic yielding was used and as for the material tests, a parameter study was performed. Ballistic limits were predicted and compared with the experimental results obtained by Børvik et al. (2010). It was found that the anisotropy of plastic flow and failure had almost no influence at very high impact velocities, while it had a substantial effect at impact velocities close to the ballistic limit. The introduced anisotropy was not found to improve the ballistic limit prediction for all cases, and also other parameters (e.g. yield shape, temperature coefficients and contact algorithms) have a prominent influence on the predicted ballistic limit. However, supported by experimental observations of non-axisymmetric failure modes (Pedersen et al., 2011), both the plastic anisotropy and the failure anisotropy are believed to be important ingredient of the constitutive model.
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Yung, See Yuen. "Determination of shear wave velocity and anisotropic shear modulus of an unsaturated soil /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202004%20YUNG.
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Schwenk-Ferrero, Aleksandra [Verfasser]. "Verfahren zur numerischen Loesung der Neutronentransportgleichung mit strenger Behandlung der anisotropen Streuung / Aleksandra Schwenk-Ferrero." Karlsruhe : KIT-Bibliothek, 2018. http://d-nb.info/1197077944/34.
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Idier, Jonathan. "Utilisation de nanomatériaux anisotropes pour l'élaboration d'électrodes transparentes conductrices." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0314/document.
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Ce travail de thèse est principalement dédié à la mise en forme et à l’utilisation de nano-objets unidimensionnels comme matériaux d’électrodes transparentes. Les nanofils d’argent font partie des candidats les plus prometteurs pour le remplacement de l’oxyde d’indium-étain, actuellement le plus répandu dans les dispositifs commerciaux. La forte instabilité des nanofils d’argent à l’oxydation est néanmoins un problème critique puisque les électrodes deviennent moins performantes en peu de temps. En premier lieu, la triphénylphosphine a été utilisée comme agent inhibant l’oxydation. Contrairement aux électrodes non modifiées, celles-ci sont stables pendant plus de trois mois. Une deuxième partie est consacrée à l’utilisation de l’électrofilage pour élaborer des électrodes transparentes à base de nanofibres de matériaux conducteurs (nanofibres de cuivre, nanotubes de carbone, oxyde de graphène réduit). Enfin, une dernière partie concerne l’étude des propriétés mécaniques de nanofibres d’alcool polyvinylique par l’écoulement d’un fluide porteur dans une constriction réalisée en impression 3D. Cette méthode permet une analyse et une évaluation simple et rapide de la contrainte à la rupture des nanofibres, propriété difficilement accessible par des mesures mécaniques traditionnellesThis PhD work deals mainly with the high scale organization and use of unidimensional nano-objects for making transparent electrodes. Among the candidates of choice for the replacement of indium tinoxide, the main material used in commercial devices, silver nanowires (Ag NW) are among the most promising. However, the tendency of silver nanowires to be quickly oxidized can severely affect their performances. Firstly, this drawback is circumvented through the use of triphenylphosphine (PPh3)as a protective agent. Unlike bare Ag NW electrodes, the PPh3 modified Ag NW electrodes are stable over three months. A second part is dedicated to the production of transparent electrodes via the electrospinning technique. Materials such as copper nanofibers, carbon nanotubes and reduced graphene oxide are investigated. The last part of the manuscript deals with the measurement of the mechanical properties of poly(vinyl alcohol) (PVA) nanofibers. To do so, the flowing of a fluid in a3D-printed constriction is used. Usually determined with difficulty, the fracture strength of the nanofibers can be evaluated quickly at ease
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Simpson, Nathaniel Denis John. "An analysis of tensile strength, fracture initiation and propagation in anisotropic rock (gas shale) using Brazilian tests equipped with high speed video and acoustic emission." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for petroleumsteknologi og anvendt geofysikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-24284.
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This study attempts to further our knowledge of fracture behaviour by establishing an experimental system that links tensile strength, fracture initiation and propagation of an anisotropic rock (Mancos Shale) using an integrated Brazilian Test Setup equipped with Acoustic Emission and High Speed Video. The unique experimental conguration was applied to an anisotropic gas shale (Mancos Shale) in addition to other petroleum related reservoir rocks (such as sandstone and chalk). The variation in tensile strength, fracture initiation location, propagation time and the failure pattern are examined as a function between the layer plane and the loading direction. A time shift was shown to exist between the time at ultimate tensile stress and the time at fracture initiation. This phenomenon has been dubbed the Naet Shift.
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Baumgarten, Lars. "Gesteinsmechanische Versuche und petrophysikalische Untersuchungen – Laborergebnisse und numerische Simulationen." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2016. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-202612.
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Dreiaxiale Druckprüfungen können als Einstufenversuche, als Mehrstufenversuche oder als Versuche mit kontinuierlichen Bruchzuständen ausgeführt werden. Bei der Anwendung der Mehrstufentechnik ergeben sich insbesondere Fragestellungen hinsichtlich der richtigen Wahl des Umschaltpunktes und des optimalen Verlaufs des Spannungspfades zwischen den einzelnen Versuchsstufen. Fraglich beim Versuch mit kontinuierlichen Bruchzuständen bleibt, ob im Versuchsverlauf tatsächlich Spannungszustände erfasst werden, welche die Höchstfestigkeit des untersuchten Materials repräsentieren. Die Dissertation greift diese Fragestellungen auf, ermöglicht den Einstieg in die beschriebene Thematik und schafft die Voraussetzungen, die zur Lösung der aufgeführten Problemstellungen notwendig sind. Auf der Grundlage einer umfangreichen Datenbasis gesteinsmechanischer und petrophysikalischer Kennwerte wurde ein numerisches Modell entwickelt, welches das Spannungs-Verformungs-, Festigkeits- und Bruchverhalten eines Sandsteins im direkten Zug- und im einaxialen Druckversuch sowie in dreiaxialen Druckprüfungen zufriedenstellend wiedergibt. Das Festigkeitsverhalten des entwickelten Modells wurde in Mehrstufentests mit unterschiedlichen Spannungspfaden analysiert und mit den entsprechenden Laborbefunden verglichen.
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Zhai, Jinyuan. "Modeling Ductile Damage of Metallic Materials." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1466471348.
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Mehrapour, Mohammad Hadi, and Mohammad Hadi Mehrapour. "Development of a Failure Criterion for Rock Masses Having Non-Orthogonal Fracture Systems." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625679.
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Two new three-dimensional rock mass strength criteria are developed in this dissertation by extending an existing rock mass strength criterion. These criteria incorporate the effects of the intermediate principal stress, minimum principal stress and the anisotropy resulting from these stresses acting on the fracture system. In addition, these criteria have the capability of capturing the anisotropic and scale dependent behavior of the jointed rock mass strength by incorporating the effect of fracture geometry through the fracture tensor components. Another significant feature of the new rock mass strength criterion which has the exponential functions (equation 6.7) is having only four empirical coefficients compared to the existing strength criterion which has five empirical coefficients; if the joint sets have the same isotropic mechanical behavior, the number of the empirical coefficients reduces to two in this new strength criterion (equation 6.10).
The new criteria were proposed after analyzing 452 numerical modeling results of the triaxial, polyaxial and biaxial compression tests conducted on the jointed rock blocks having one or two joint sets by the PFC3D software version 5. In this research to have several samples with the same properties a synthetic rock material that is made out of a mixture of gypsum, sand and water was used. In total, 20 joint systems were chosen and joint sets have different dip angles varying from 15 to 60 at an interval of 15 with dip directions of 30 and 75 for the two joint sets. Each joint set also has 3 persistent joints with the joint spacing of 42 mm in a cubic sample of size 160 mm and the joints have the same isotropic mechanical behavior. The confining stress combination values were chosen based on the uniaxial compressive strength (UCS) value of the modeled intact synthetic rock. The minimum principal stress values were chosen as 0, 20, 40 and 60 percent of the UCS. For each minimum principal stress value, the intermediate principal stress value varies starting at the minimum principal stress value and increasing at an interval of 20 percent of the UCS until it is lower than the strength of the sample under the biaxial loading condition with the same minimum principal stress value.
The new rock mass failure criteria were developed from the PFC3D modeling data. However, since the joint sets having the dip angle of 60 intersect the top and bottom boundaries of the sample simultaneously, the joint systems with at least one of the joint sets having the dip angle of 60 were removed from the database. Thus, 284 data points from 12 joint systems were used to find the best values of the empirical coefficients for the new rock mass strength criteria. λ, p and q were found to be 0.675, 3.16 and 0.6, respectively, through a conducted grid analysis with a high R2 (coefficient of determination) value of 0.94 for the new criterion given by equation 6.9 and a and b were found to be 0.404 and 0.972, respectively, through a conducted grid analysis with a high R2 value of 0.92 for the new criterion given by equation 6.10.
The research results clearly illustrate how increase of the minimum and intermediate principal stresses and decrease of the joint dip angle, increase the jointed rock block strength. This dissertation also illustrates how different confining stress combinations and joint set dip angles result in different jointed rock mass failure modes such as sliding on the joints, failure through the intact rock and a combination of the intact rock and joint failures.
To express the new rock mass strength failure criteria, it was necessary to determine the intact rock strengths under the same confining stress combinations mentioned earlier. Therefore, the intact rock was also modeled for all three compression tests and the intact rock strengths were found for 33 different confining stress combinations. Suitability of six major intact rock failure criteria: Mohr-Coulomb, Hoek-Brown, Modified Lade, Modified Wiebols and Cook, Mogi and Drucker-Prager in representing the intact rock strength was examined through fitting them using the aforementioned 33 PFC3D data points. Among these criteria, Modified Lade, Modified Mogi with power function and Modified Wiebols and Cook were found to be the best failure criteria producing lower Root Mean Square Error (RMSE) values of 0.272, 0.301 and 0.307, respectively. Thus, these three failure criteria are recommended for the prediction of the intact rock strength under the polyaxial stress condition.
In PFC unlike the other methods, macro mechanical parameters are not directly used in the model and micro mechanical parameter values applicable between the particles should be calibrated using the macro mechanical properties. Accurate calibration is a difficult or challenging task. This dissertation emphasized the importance of studying the effects of all micro parameter values on the macro mechanical properties before one goes through calibration of the micro parameters in PFC modeling. Important effects of two micro parameters, which have received very little attention, the particle size distribution and the cov of the normal and shear strengths, on the macro properties are clearly illustrated before conducting the said calibration. The intact rock macro mechanical parameter values for the Young’s modulus, uniaxial compression strength (UCS), internal friction angle, cohesion and Poisson's ratio were found by performing 3 uniaxial tests, 3 triaxial tests and 5 Brazilian tests on a synthetic material made out of a mixture of gypsum, sand and water and the joint macro mechanical parameter values were found by conducting 4 uniaxial compression tests and 4 direct shear tests on jointed synthetic rocks with a horizontal joint. Then the micro mechanical properties of the Linear Parallel Bond Model (LPMB) and Modified Smooth Joint Contact Model (MSJCM) were calibrated to represent the intact rock and joints respectively, through the specific procedures explained in this research. The similar results obtained between the 2 polyaxial experiments tests of the intact rock and 11 polyaxial experimental tests of the jointed rock blocks having one joint set and the numerical modeling verified the calibrated micro mechanical properties and further modification of these properties was not necessary.
This dissertation also proposes a modification to the Smooth Joint Contact Model (SJCM) to overcome the shortcoming of the SJCM to capture the non-linear behavior of the joint closure varying with the joint normal stress. Modified Smooth Joint Contact Model (MSJCM) uses a linear relation between the joint normal stiffness and the normal contact stress to model the non-linear relation between the joint normal deformation and the joint normal stress observed in the compression joint normal stiffness test. A good agreement obtained between the results from the experimental tests and the numerical modeling of the compression joint normal test shows the accuracy of this new model. Moreover, another shortcoming associated with the SJCM application known as the interlocking problem was solved through this research by proposing a new joint contact implementation algorithm called joint sides checking (JSC) approach. The interlocking problem occurs due to a shortcoming of the updating procedure in the PFC software related to the contact conditions of the particles that lie around the intended joint plane during high shear displacements. This problem increases the joint strength and dilation angle and creates unwanted fractures around the intended joint plane.
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Svensson, Erik, and Marcus Wiechert. "Abrasiv nötning av polymerer tillverkade genom 3D-skrivning." Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-11124.
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Volvo Cars in Skövde manufacture and assemble Volvo engines. When attaching the ignition coil to all 4-cylinder engines, a special mounting tool is required. This mounting tool is currently manufactured from injection-molded polyoxymethylene (POM), a thermoplastic. It has been noted that the life span of the tool is shortened as a result of abrasive wear that occurs during the attachment process of the ignition coil. An investigation of the possibility of manufacturing the mounting tool with a 3D-printer is undertaken in cooperation with ÅF, a consultant to Volvo Cars. A literature study is first presented to introduce broader knowledge on the subject. The abrasive wear and other material characteristics such as tensile strength, compressive strength and elongation of POM and an alternative material for 3D-printing, Ultem™, an amorphous thermoplastic polyetherimide are discussed. These material characteristics are studied further and considered in tandem with both a theoretical analysis and a wear experiment, based on the pin-on-disc method. It is shown in the theoretical analysis that the wear is approximately six times larger for Ultem™ when compared to POM. The wear resistance of Ultem™ is highest when wear occurs parallel to the direction of the printed layers. In contrast, the experiment shows that the wear is about three times larger in Ultem™ than in POM. The highest tensile strength of Ultem™ is also found in the direction of the printed layers. Some issues with the small elongation of the 3D-printed material are presented. It is recommended that ÅF apply the 3D-printing technique with Ultem™ only for construction details with complex geometries and where the material elongation will not exceed 5%. It is also recommended that ÅF both support and contribute to this innovative technique in order to develop leading edge competence in the subject.Volvo Cars i Skövde tillverkar och monterar Volvomotorer. Vid monteringen av tändspolen till alla 4-cylindriga motorer behövs ett monteringsverktyg. Detta monteringsverktyg tillverkas för närvarande från formsprutad termoplast polyoximetylen (POM). Det har noterats att livslängden av verktyget förkortas på grund av abrasiv nötning som uppkommer under monteringsprocessen av tändspolen. Möjligheterna att tillverka monteringsverktyget med en 3D-skrivare utvärderas i samverkan med ÅF, en konsult till Volvo Cars. En litteraturstudie presenteras för att introducera en bredare kunskap i ämnet. Den abrasiva nötningen och materialegenskaper såsom draghållfasthet, tryckhållfasthet samt töjning hos POM och ett alternativt material för 3D-skrivning, Ultem™, en amorf termoplast polyeterimid, behandlas. Dessa materialegenskaper studeras vidare och tas i beaktning med både en teoretisk analys och ett nötningsexperiment, baserat på pin-on-disc metoden. Enligt den teoretiska analysen är nötningen hos Ultem™ approximativt 6 gånger större vid jämförelsen med POM. Nötningsbeständigheten hos Ultem™ är högst då nötning sker parallellt med 3D-skrivningsriktningen av lagren. Nötningsexperimenten visar att nötningen hos Ultem™ är ungefär 3 gånger större vid jämförelsen med POM. Den högsta draghållfastheten hos Ultem™ uppkommer också parallellt med 3D-skrivningsriktningen av lagren. Problem med den låga töjningen hos det 3D-skrivna materialet behandlas. ÅF rekommenderas att tillämpa 3D-skrivning med materialet Ultem™ främst för detaljer med komplexa geometrier med en töjning som inte överskrider 5 %. ÅF rekommenderas även att både stödja och bidra till denna innovativa teknik för att kunna skapa en ledande expertis i ämnet.
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Мартиненко, Володимир Геннадійович. "Розробка методів розрахунку елементів конструкцій із в'язкопружних композиційних матеріалів." Thesis, НТУ "ХПІ", 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/37543.
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Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.02.09 – динаміка та міцність машин. Національний технічний університет "Харківський політехнічний інститут", Харків, 2018 р.
Дисертацію присвячено створенню нових методів опису та моделювання анізотропної в'язкопружності композиційних елементів конструкцій і машин. На підставі аналізу актуальних методик встановлено, що на даний момент не існує комплексного підходу до встановлення параметрів анізотропної в'язкопружності полімерних армованих композиційних матеріалів, а також моделювання їхньої механічної поведінки. З метою визначення властивостей в'язкопружного композиту був розроблений чисельний метод гомогенізації ядер ортотропної в'язкопружності ортогонально армованого композиційного матеріалу. Спланований та реалізований експеримент зі знаходження параметрів анізотропної в'язкопружності склотекстоліту кількісно та якісно підтвердив результати чисельних розрахунків, що продемонструвало необхідність врахування в'язкопружних властивостей із загальним ступенем анізотропії при моделюванні механіки елементів конструкцій і машин, виконаних із полімерних армованих композиційних матеріалів. Запропонований в роботі метод накладених сіток надав до цього моменту відсутні можливості моделювання будь якого ступеня анізотропії в'язкопружних властивостей в програмних комплексах скінченно-елементного. Цей метод в роботі був застосований до моделювання контакту ділянки пружного трубопроводу із ортотропним в'язкопружним ремонтним бандажем за допомогою тривимірної в'язкопружної скінченно-елементної моделі, що в порівнянні із розробленими аналітичною та чисельно-аналітичною моделями плоского вісесиметричного напружено-деформованого стану такої конструкції показало його адекватність та високу точність.Thesis for granting the Degree of Candidate of Technical sciences in speciality 05.02.09 – Dynamics and Strength of Machines. – National Technical University "Kharkiv Politechnical Institute", 2018. The thesis is dedicated to a creation of new methods for describing and modeling the anisotropic viscoelasticity of composite structural elements. Basing on an analysis of actual methods it is established that at the moment there is no a complex approach for determining anisotropic viscoelastic parameters of polymer reinforced composite materials and modeling their mechanical behavior. With a purpose of finding the quantitative and qualitative properties of a viscoelastic composite, a numerical method for homogenizing orthotropic viscoelastic kernels of orthogonally reinforced composite material, that are dependent on a fiber volume fraction, time and temperature, was developed. The time dependencies of these kernels were approximated by Prony series, whereas the temperature ones were approximated by Williams-Landel-Ferry shift function. This approach allowed to indicate that the viscoelasticity of fiber reinforced polymeric composite materials is of orthotropic nature for an orthogonal reinforcement scheme, that the relaxation curves of viscoelastic parameters are not similar to each other, which contradicts the classical engineering viscoelastic models, and that the temperature dependency of these properties coincide with the ones of the composite polymeric matrix. The planned and realized experiment on finding the parameters of anisotropic viscoelasticity of a fiber-glass with a woven reinforcement scheme has confirmed the results of numerical calculations, which demonstrated the need to take into account viscoelastic properties with a general degree of anisotropy when modeling the mechanics of structural elements and machines made of fiber reinforced polymeric composite materials. The experiment rig was improved during the research in order to satisfy the requirements for carrying out tests on plane polymeric composite samples. The method of super-imposed meshes proposed in the work provided the possibilities of modeling any degree of anisotropy of viscoelastic properties in commercial finite-element codes without a necessity to create additional material user subroutines using only the standard tools of these codes. The convergence of the method was also proved in the work. This method was applied to modeling a contact behavior of an elastic pipeline section with an orthotropic viscoelastic repair bandage using a three-dimensional viscoelastic finite element model that in comparison with the developed analytical and numerical-analytical models of a plane axisymmetric stress-strain state of such a design showed its adequacy and accuracy. In addition, proposed analytical and numerical-analytical methods allowed to take into account mounting features of repair band-age assembled on unloaded or loaded pipeline with or without tension, that enabled to indicate a relaxation of contact stresses for different repair regimes.
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Мартиненко, Володимир Геннадійович. "Розробка методів розрахунку елементів конструкцій із в'язкопружних композиційних матеріалів." Thesis, НТУ "ХПІ", 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/37542.
Full textAbstract:
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.02.09 – динаміка та міцність машин. Національний технічний університет "Харківський політехнічний інститут", Харків, 2018 р.
Дисертацію присвячено створенню нових методів опису та моделювання анізотропної в'язкопружності композиційних елементів конструкцій і машин. На підставі аналізу актуальних методик встановлено, що на даний момент не існує комплексного підходу до встановлення параметрів анізотропної в'язкопружності полімерних армованих композиційних матеріалів, а також моделювання їхньої механічної поведінки. З метою визначення властивостей в'язкопружного композиту був розроблений чисельний метод гомогенізації ядер ортотропної в'язкопружності ортогонально армованого композиційного матеріалу. Спланований та реалізований експеримент зі знаходження параметрів анізотропної в'язкопружності склотекстоліту кількісно та якісно підтвердив результати чисельних розрахунків, що продемонструвало необхідність врахування в'язкопружних властивостей із загальним ступенем анізотропії при моделюванні механіки елементів конструкцій і машин, виконаних із полімерних армованих композиційних матеріалів. Запропонований в роботі метод накладених сіток надав до цього моменту відсутні можливості моделювання будь якого ступеня анізотропії в'язкопружних властивостей в програмних комплексах скінченно-елементного. Цей метод в роботі був застосований до моделювання контакту ділянки пружного трубопроводу із ортотропним в'язкопружним ремонтним бандажем за допомогою тривимірної в'язкопружної скінченно-елементної моделі, що в порівнянні із розробленими аналітичною та чисельно-аналітичною моделями плоского вісесиметричного напружено-деформованого стану такої конструкції показало його адекватність та високу точність.Thesis for granting the Degree of Candidate of Technical sciences in speciality 05.02.09 – Dynamics and Strength of Machines. – National Technical University "Kharkiv Politechnical Institute", 2018. The thesis is dedicated to a creation of new methods for describing and modeling the anisotropic viscoelasticity of composite structural elements. Basing on an analysis of actual methods it is established that at the moment there is no a complex approach for determining anisotropic viscoelastic parameters of polymer reinforced composite materials and modeling their mechanical behavior. With a purpose of finding the quantitative and qualitative properties of a viscoelastic composite, a numerical method for homogenizing orthotropic viscoelastic kernels of orthogonally reinforced composite material, that are dependent on a fiber volume fraction, time and temperature, was developed. The time dependencies of these kernels were approximated by Prony series, whereas the temperature ones were approximated by Williams-Landel-Ferry shift function. This approach allowed to indicate that the viscoelasticity of fiber reinforced polymeric composite materials is of orthotropic nature for an orthogonal reinforcement scheme, that the relaxation curves of viscoelastic parameters are not similar to each other, which contradicts the classical engineering viscoelastic models, and that the temperature dependency of these properties coincide with the ones of the composite polymeric matrix. The planned and realized experiment on finding the parameters of anisotropic viscoelasticity of a fiber-glass with a woven reinforcement scheme has confirmed the results of numerical calculations, which demonstrated the need to take into account viscoelastic properties with a general degree of anisotropy when modeling the mechanics of structural elements and machines made of fiber reinforced polymeric composite materials. The experiment rig was improved during the research in order to satisfy the requirements for carrying out tests on plane polymeric composite samples. The method of super-imposed meshes proposed in the work provided the possibilities of modeling any degree of anisotropy of viscoelastic properties in commercial finite-element codes without a necessity to create additional material user subroutines using only the standard tools of these codes. The convergence of the method was also proved in the work. This method was applied to modeling a contact behavior of an elastic pipeline section with an orthotropic viscoelastic repair bandage using a three-dimensional viscoelastic finite element model that in comparison with the developed analytical and numerical-analytical models of a plane axisymmetric stress-strain state of such a design showed its adequacy and accuracy. In addition, proposed analytical and numerical-analytical methods allowed to take into account mounting features of repair band-age assembled on unloaded or loaded pipeline with or without tension, that enabled to indicate a relaxation of contact stresses for different repair regimes.
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Ismael, Mohamed. "Inherent strength and stiffness anisotropy of laminated rocks." Doctoral thesis, 2018. http://tubaf.qucosa.de/id/qucosa%3A32251.
Full textAbstract:
The variation of rock strength and stiffness, known as mechanical anisotropy, is expected at different scales: large (rock mass) - or small (intact rock) - scales. It is always mandatory for engineering applications built either on or in anisotropic rock masses to investigate the strength and deformation behavior of those masses. To achieve this goal, continuum-based constitutive models are presented to analyze the mechanical anisotropy. One of both implemented models is named ‘Transubi model’ which considers the transverse isotropic elasticity into bi-linear Mohr-Coulomb strain hardening/softening plastic framework. Experimental investigations and numerical simulations focused mainly on the influence of the mechanical anisotropy on the plastic zoning around excavated openings in laminated rocks. Later, the Transubi model was applied to a tunnel excavated in a shaly facies formation of bedded argillaceous Opalinus clay in an URL (FE-tunnel) to obtain the short-term stability insights. Overall, the research outcomes may have a prospective impact regarding the understanding of anisotropy of laminated, bedded and foliated rocks which improves the deformation behaviour predictability using continuum-based numerical modeling tools.
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"EFFECT OF DISCONTINUITY ROUGHNESS AND ANISOTROPY ON SHEAR STRENGTH." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12604948/index.pdf.
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Chang, Hao-Ting, and 張浩庭. "The Study of Perpendicular Magnetic Anisotropy, Annealing Effect, Coupling Strength in MgO/CoFeB/Nb/CoFeB/MgO." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/99253624247953377618.
Full textAbstract:
碩士大葉大學
電機工程學系
101
In this study, we deposited MgO / CoFeB / Nb, Nb / CoFeB / MgO and MgO / CoFeB / Nb / CoFeB / MgO by sputtering and grew synthetic antiferromagnetic structure. These three structures were changed ferromagnetic or non-magnetic layer thickness of the material, and in the hysteresis curves measured after annealing to explore the perpendicular anisotropy and magnetic coupling. Studies have shown that the structure after annealing, which found that the perpendicular magnetic anisotropy (PMA) of the top structure only exist in a CoFeB thickness range from 1.2 to 1.6 nm. Squarness, coercivityfield(Hc)and magnetic anisotropy field (Hk) were decreased when thickness increases. In the top structure showing that thickness of the CoFeB structure for perpendicular anisotropy has a great influence. But, in the bottom structure which after annealing, almost all thicknesses are perpendicular anisotropy, and in addition to the value of the coercive field increases with Nb thickness, squareness and anisotropic magnetic field is extremely stable, Nb infer the structure changes in the thickness of the perpendicular anisotropy has little effect. In full structures, perpendicular magnetic anisotropy weredecreases when thickness increases. Nb = 1.0nm, 1.5nm, m1 and m2 trends are consistent with results showing both the upper and lower CoFeB layers produce magnetic dead CoFeB layer is very similar. Nb = 2.0nm, annealing temperature in between 255oC and 345oC, m1 increase with temperature increase, but m2 decrease as temperature increase, as shown in the hysteresis curve of this annealing temperature is different to Nb = 1.0 and 1.5nm. Our experimental data are compared with the reference literature, we found that coupling energy, anisotropy energy and annealing temperature value to Nb as spacer layer synthetic antiferromagnetic structure are lower than with Ru as the spacer layer synthetic antiferromagnetic structure .
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LU, ZHONG-CHENG, and 呂仲誠. "An investigation of the strength anisotropy for the stratified compacted laterite and its influence on the slope stability." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/16218079774058323308.
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Dai, Feng Jr. "Dynamic Tensile, Flexural and Fracture Tests of Anisotropic Barre Granite." Thesis, 2010. http://hdl.handle.net/1807/26141.
Full textAbstract:
Granitic rocks usually exhibit strongly anisotropy due to pre-existing microcracks induced by long-term geological loadings. The understanding of anisotropy in mechanical properties of rocks is critical to a variety of rock engineering applications. In this thesis, the anisotropy of tension-related failure parameters involving tensile strength, flexural strength and Mode-I fracture toughness/fracture energy of Barre granite is investigated under a wide range of loading rates.
Three sets of dynamic experimental methodologies have been developed using the modified split Hopkinson pressure bar system; Brazilian test to determine the tensile strength; semi-circular bend method to determine the flexural strength; and notched semi-circular bend method to determine the Mode-I fracture toughness and fracture energy. For all three tests, a simple quasi-static data analysis is employed to deduce the mechanical properties; the methodology is assessed critically against the isotropic Laurentian granite. It is shown that if dynamic force balance is achieved in SHPB, it is reasonable to use quasi-static formulas. The dynamic force balance is obtained by the pulse shaper technique.
To study the anisotropy of these properties, rock blocks are cored and labeled using the three principal directions of Barre granite to form six sample groups. For samples in the same orientation group, the measured strengths/toughness shows clear loading rate dependence. More importantly, a loading rate dependence of the strengths/toughness anisotropy of Barre granite has been first observed: the anisotropy diminishes with the increase of loading rate.
The reason for the strengths/toughness anisotropy can be understood with reference to the preferentially oriented microcracks sets; and the rate dependence of this anisotropy is qualitatively explained with the microcracks interaction. Two models abstracted from microscopic photographs are constructed to interpret the rate dependence of the fracture toughness anisotropy in terms of the crack/microcracks interaction. The experimentally observed rate dependence of the anisotropy is successfully reproduced.
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"A Study on an In-Process Laser Localized Pre-Deposition Heating Approach to Reducing FDM Part Anisotropy." Master's thesis, 2016. http://hdl.handle.net/2286/R.I.40335.
Full textAbstract:
abstract: Material extrusion based rapid prototyping systems have been used to produceprototypes for several years. They have been quite important in the additive manufacturing field, and have gained popularity in research, development and manufacturing in a wide field of applications. There has been a lot of interest in using these technologies to produce end use parts, and Fused Deposition Modeling (FDM) has gained traction in leading the transition of rapid prototyping technologies to rapid manufacturing. But parts built with the FDM process exhibit property anisotropy. Many studies have been conducted into process optimization, material properties and even post processing of parts, but were unable to solve the strength anisotropy issue. To address this, an optical heating system has been proposed to achieve localized heating of the pre- deposition surface prior to material deposition over the heated region. This occurs in situ within the build process, and aims to increase the interface temperature to above glass transition (Tg), to trigger an increase in polymer chain diffusion, and in extension, increase the strength of the part. An increase in flexural strength by 95% at the layer interface has been observed when the optical heating method was implemented, thereby improving property isotropy of the FDM part. This approach can be designed to perform real time control of inter-filament and interlayer temperatures across the build volume of a part, and can be tuned to achieve required mechanical properties.Dissertation/Thesis
Masters Thesis Mechanical Engineering 2016
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Singh, Jagdeep. "Strength prediction of anisotropic rocks." Thesis, 1988. http://localhost:8080/iit/handle/2074/5836.
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Shu-Cheng, Hsu, and 徐書政. "Determination of tensile strength of anisotropic rocks." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/48442721119682106407.
Full textAbstract:
碩士國立成功大學
資源工程學系
88
Abstract The tensile strength of anisotropic rocks is an important factor to control the failure of rock mass. Laboratory techniques to measure the tensile strength of rocks include the direct tensile test and indirect tensile tests. The direct tensile test is an appropriate method for determining the behavior of rocks under tension. However, the greatest difficulty in the direct tensile test is the gripping of the rock specimens. As a result, a number of indirect methods have been developed for determining the tensile strength of rocks. The most commonly used method is the Brazilian test. The Brazilian test suffers from the disadvantage that not only tensile stresses are developed in the disc but also hight shear stresses are set up close to the loading platens. To limit the shearing stresses developed in the disc in Brazilian test, the method of ring test has been developed where a disc with a central hole. This paper uses the Brazilian test and the equation to determine the tensile strength of anisotropic marble from Hualien. Another, this paper presents a combination of the ring test and the BEM method for determining the tensile strength of anisotropic marble, and presents an anisotropic tensile strength equation, , for the ring test. Finally, compare the failure model and tensile strength between the Brazilian test and the ring test. As shown by the results, the tensile strength of marble decreases with the increase of the inclination angle for both methods. In ring test, the tensile strength for different inclination angle decreases with the increase of the hole diameter, and is 3 ~ 5 times as great as the results of Brazilian test.
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Su, Shi-Fon, and 蘇世豐. "ANISOTROPIC UNDRAINED STRESS-STRAIN-STRENGTH BEHAVIOR OF IVE SOILS." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/23491290234178947130.
Full textAbstract:
碩士國立臺灣科技大學
營建工程技術學系
81
A semi-empirical constitutive model is proposed in this paper for the undrained stress-strain-strength behavior of the cohesive soils in terms of the consolidation history, the anisotropy, the general stress state, and the simplicity to needed parameters. Totally, only three parameters are required this model namely, the shear strength in compression(S), the strength in extension(S), and the initial Young''s modulus(E). The accuracy of this model has been satisfactorily validated with the published experimental data.