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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Thermo-mechanically Coupled Numerical And Experimental Study On 7075 Aluminum Forging Process And Dies

Ozcan, Mehmet Cihat 01 September 2008 (has links) (PDF)
Combination of high strength with light weight which is the prominent property of aluminum alloy forgings has led aluminum forgings used in rapidly expanding range of applications. In this study, to produce a particular 7075 aluminum alloy part, the forging process has been designed and analyzed. The forging process sequence has been designed by using Finite Volume Method. Then, the designed process has been analyzed by using Finite Element Method and the stress, strain and temperature distributions within the dies have been determined. Five different initial temperatures of the billet / 438, 400, 350, 300 and 250 degree Celsius have been considered in the thermo-mechanically coupled simulations. The initial temperatures of the dies have been taken as 200 degree Celsius for all these analyses. Finite volume analysis and finite element analysis results of the preform and finish part have been compared for the initial billet temperature of 400 oC. Close results have been observed by these analyses. The experimental study has been carried out for the range of the initial billet temperatures of 251&amp / #8211 / 442 degree Celsius in METU-BILTIR Center Forging Research and Application Laboratory. It has been observed that the numerical and the experimental results are in good agreement and a successful forging process design has been achieved. For the initial die temperature of 200 degree Celsius, to avoid the plastic deformation of the dies and the incipient melting of the workpiece, 350 degree Celsius is determined to be the appropriate initial billet temperature for the forging of the particular part.
12

Slope Stability Assessment Along The Bursa-inegol-bozuyuk Road At Km: 72+000-72+200

Oztepe, Damla Gaye 01 September 2009 (has links) (PDF)
The purpose of this study is to determine the most suitable remediation technique via geotechnical assessment of the landslide that occurred during the construction of Bursa-ineg&ouml / l-Boz&uuml / y&uuml / k Road at KM: 72+000-72+200 in an ancient landslide area. For this purpose, the geotechnical parameters of the mobilized soil along the slide surface was determined by back analyses of the landslide at four profiles by utilizing the Slope/W software. The landslide was then modeled using coupled analyses (with the Seep/W and Slope/W softwares) along the most representative profile of the study area by considering the landslide mechanism, the parameters determined from the geotechnical investigations, the size of the landslide and the location of the slip circle. In addition, since the study area is located in a second degree earthquake hazard region, pseudo-static stability analyses using the Slope/W software were performed incorporating the earthquake potential. The most suitable slope remediation technique was determined to be a combination of surface and subsurface drainage, application of rock buttress at the toe of the slide and unloading of the landslide material. A static and dynamic analyses of the landslide was also performed through utilizing finite element analyses. The static analyses were calibrated using the inclinometer readings in the field. After obtaining a good agreement with the inclinometer readings and finite element analyses results, the dynamic analyses were performed using acceleration time histories, which were determined considering the seismic characteristics of the study area.
13

Behavior of Gas Hydrate-Bearing Soils during Dissociation and its Simulation / ガスハイドレート含有地盤の分解時における挙動及びその解析

Iwai, Hiromasa 23 March 2015 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18933号 / 工博第3975号 / 新制||工||1612(附属図書館) / 31884 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 木村 亮, 教授 勝見 武, 准教授 木元 小百合 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM
14

Evaluation of a computational method for natural fiber-reinforced plastics / Bedömning av en beräkningsmetod för naturfiberförstärkta plaster

Lim, Anna January 2023 (has links)
The importance of using natural fiber composites (NFCs) has been addressed as a substitution for synthetic fibers, such as glass and carbon fibers. This substitution contributes significantly to reducing greenhouse gas emissions, aligning with the environmental responsibilities of engineering industries. Wood fiber(WF) is one of the natural fibers (NFs) dominating the market in various businesses. As an excellent alternative to non-renewable sources, the demand for injection-molded applications using natural fiber-reinforced plastics has expanded across various sectors. Despite extensive prior research on the mechanical properties of WFs, there remains a need for a deeper understanding of the connection between fiber orientation and mechanical characteristics. This understanding is essential for developing computational methods aimed at ensuring structural integrity, cost-efficiency, and sustainability in real-world components. This study aims to evaluate coupled injection molding simulation to finite element method with mapping of fiber orientation tensor for a wood fiber composite (WFC). To achieve this, WFC’s mechanical properties and behavior under tensile loading conditions are investigated. The research methodology involves conducting uniaxial tensile testing on dog bone-shaped specimens at different fiber orientations (0 degrees, 45 degrees, and 90 degrees). Experimental data is collected, analyzed, and compared with the obtained results with numerical simulations to validate the accuracy of the models used. Additionally, the aspect ratio and volume fraction of the WFs are measured through both mathematical calculations and image analysis using MATLAB. The main contribution of this study can be summarized in two key observations. Firstly, the investigation of mechanical characteristics across different fiber orientations has revealed distinct patterns. Specimens aligned at 0 degrees exhibit noticeable differences in behavior compared to those at 45 and 90 degrees, highlighting the material's anisotropic nature. Secondly, the comparison between experimental data and computational simulations exhibits the effectiveness of the developed models. The close agreement between the two validates the accuracy of the predictive approach. Moreover, the consistent aspect ratio, volume fraction, and fiber orientation value obtained through both mathematical calculations and image analysis add credibility to the reliability of our measurements. Notably, the comparison with glass fibers (GFs) reveals that WFs exhibit considerably less breakage, highlighting their durability and potential suitability for various applications. / Betydelsen av att använda naturfiberkompositer har behandlats som en ersättning för syntetiska fibrer, såsom glas- och kolbaserade fibrer. Denna substitution bidrar betydligt till att minska utsläpp av växthusgaser och överensstämmer med ingenjörsbranschens miljöansvar. Träfiber är en av de naturfibrer som dominerar marknaden inom olika branscher. Som ett utmärkt alternativ till icke-förnybara källor har efterfrågan på formsprutade applikationer med naturfiberförstärkta plaster ökat inom olika sektorer. Trots omfattande tidigare forskning om träfibrers mekaniska egenskaper finns det fortfarande ett behov av en djupare förståelse för sambandet mellan fiberns orientering och dess mekaniska egenskaper. Denna förståelse är avgörande för att utveckla beräkningsmetoder som syftar till att säkerställa strukturell integritet, kostnadseffektivitet och hållbarhet i komponenter i den verkliga världen. Denna studie syftar till att utvärdera kopplad formsprutningssimulering med ändelementmetod och kartläggning av fibrernas orienteringstensor för en träfiberkomposit. För att uppnå detta undersöks träfiberkompositens mekaniska egenskaper och beteende under dragbelastningsförhållanden. Forskningsmetodiken innefattar genomförande av enaxlig dragprovning på hundbenformade provkroppar vid olika fibrers orientering (0 grader, 45 grader och 90 grader). Experimentella data samlas in, analyseras och jämförs med de erhållna resultaten från numeriska simuleringar för att validera modellernas noggrannhet. Dessutom mäts träfibrernas aspektratio och volymfraktion genom både matematiska beräkningar och bildanalys med hjälp av MATLAB. Huvudbidraget från denna studie kan sammanfattas i två centrala iakttagelser. För det första har undersökningen av mekaniska egenskaper vid olika fibrers orienteringar avslöjat tydliga mönster. Prover som är riktade i 0 grader uppvisar märkbara skillnader i beteende jämfört med de vid 45 och 90 grader, vilket understryker materialets anisotropa natur. För det andra visar jämförelsen mellan experimentella data och beräkningsmässiga simuleringar effektiviteten hos de utvecklade modellerna. Den nära överensstämmelsen mellan de båda validerar noggrannheten i den prediktiva metoden. Dessutom lägger de konsekventa värdena för aspektratio, volymfraktion och fibrernas orientering som erhållits genom både matematiska beräkningar och bildanalys trovärdighet till våra mätningar. Det bör noteras att jämförelsen med glasfiber visar att träfibrer uppvisar betydligt mindre brytning, vilket betonar deras hållbarhet och potentiella lämplighet för olika tillämpningar.
15

[en] A FORMULATION OF DYNAMIC DAMPING OF SOILS IN THE LIGHT OF POROMECHANICS / [pt] UMA FORMULAÇÃO DO AMORTECIMENTO DINÂMICO DE SOLOS À LUZ DA POROMECÂNICA

KARL IGOR MARTINS GUERRA 15 April 2021 (has links)
[pt] A natureza física do amortecimento nos solos e sua formulação matemática têm sido objeto de intensa pesquisa ao longo do último meio século. Estes vários ensaios para explicar os mecanismos de perda de energia durante os episódios de vibração surgem da importância do amortecimento no problema de propagação de ondas para fins de engenharia. O objetivo deste estudo é propor uma maneira alternativa de analisar o fenômeno do amortecimento em solos, considerando o problema de vibração como um problema matemático poromecânico acoplado onde deslocamentos relativos e velocidades entre as duas fases que compõem o material geológico, fluido e sólido, gera forças de interação nas interfaces e pode desempenhar um papel importante na perda de energia vibracional dos solos. Presume-se que o problema seja resolvido na escala de poros, concentrando-se nas condições cinéticas e dinâmicas na interface entre o esqueleto sólido e o fluido de saturação. Variáveis adimensionais que misturam propriedades fluidas e sólidas permitem o acoplamento do problema, resultando no surgimento de uma massa aparente, coeficientes de amortecimento e rigidez que serão introduzidos posteriormente nas equações de movimento. A equação proposta de amortecimento será então justaposta a testes de laboratório e uma comparação com os modelos mais importantes da literatura será feita usando o software DEEPSOIL para análise de propagação de ondas para verificar sua validade. / [en] The physical nature of damping in soils and its mathematical formulation attempts have been the subject of intensive researches along the last half century. These several trials to explain the mechanisms of energy loss during vibration episodes arise from the importance of damping in the wave propagation problem for engineering purposes. The aim of this study is to propose an alternative way to analyze the damping phenomenon in soils by looking at the vibration problem as a coupled poromechanical mathematical problem where relative displacements and velocities in between the two phases that compose the geological material, fluid and solid, generates interaction forces at the interfaces and can play an important role in the vibrational energy loss of soils. The problem is assumed to be solved at the pore scale, focusing on the kinetic and dynamic conditions at the interface in between the solid skeleton and the saturating fluid. Dimensionless variables that mixes fluid and solid properties allows the coupling of the problem, resulting on the rising of an apparent mass, damping and stiffness coefficients that will be introduced later in the equations of motion. The proposed equation of damping will thus be juxtaposed to laboratory tests data and a comparison with the most important models in the literature will be done further using the software DEEPSOIL for wave propagation analysis to check its validity.
16

Structural Health Monitoring Of Composite Structures Using Magnetostrictive Sensors And Actuators

Ghosh, Debiprasad 01 1900 (has links)
Fiber reinforced composite materials are widely used in aerospace, mechanical, civil and other industries because of their high strength-to-weight and stiffness-to-weight ratios. However, composite structures are highly prone to impact damage. Possible types of defect or damage in composite include matrix cracking, fiber breakage, and delamination between plies. In addition, delamination in a laminated composite is usually invisible. It is very diffcult to detect it while the component is in service and this will eventually lead to catastrophic failure of the structure. Such damages may be caused by dropped tools and ground handling equipments. Damage in a composite structure normally starts as a tiny speckle and gradually grows with the increase in load to some degree. However, when such damage reaches a threshold level, serious accident can occur. Hence, it is important to have up-to-date information on the integrity of the structure to ensure the safety and reliability of composite components, which require frequent inspections to identify and quantify damage that might have occurred even during manufacturing, transportation or storage. How to identify a damage using the obtained information from a damaged composite structure is one of the most pivotal research objectives. Various forms of structural damage cause variations in structural mechanical characteristics, and this property is extensively employed for damage detection. Existing traditional non-destructive inspection techniques utilize a variety of methods such as acoustic emission, C-scan, thermography, shearography and Moir interferometry etc. Each of these techniques is limited in accuracy and applicability. Most of these methods require access to the structure.They also require a significant amount of equipment and expertise to perform inspection. The inspections are typically based on a schedule rather than based on the condition of the structure. Furthermore, the cost associated with these traditional non-destructive techniques can be rather prohibitive. Therefore, there is a need to develop a cost-effective, in-service, diagnostic system for monitoring structural integrity in composite structures. Structural health monitoring techniques based on dynamic response is being used for several years. Changes in lower natural frequencies and mode shapes with their special derivatives or stiffness/ exibility calculation from the measured displacement mode shapes are the most common parameters used in identification of damage. But the sensitivity of these parameters for incipient damage is not satisfactory. On the other hand, for in service structural health monitoring, direct use of structural response histories are more suitable. However, they are very few works reported in the literature on these aspects, especially for composite structures, where higher order modes are the ones that get normally excited due to the presence of flaws. Due to the absence of suitable direct procedure, damage identification from response histories needs inverse mapping; like artificial neural network. But, the main diffculty in such mapping using whole response histories is its high dimensionality. Different general purpose dimension reduction procedures; like principle component analysis or indepen- dent component analysis are available in the literature. As these dimensionally reduced spaces may loose the output uniqueness, which is an essential requirement for neural network mapping, suitable algorithms for extraction of damage signature from these re- sponse histories are not available. Alternatively, fusion of trained networks for different partitioning of the damage space or different number of dimension reduction technique, can overcome this issue efficiently. In addition, coordination of different networks trained with different partitioning for training and testing samples, training algorithms, initial conditions, learning and momentum rates, architectures and sequence of training etc., are some of the factors that improves the mapping efficiency of the networks. The applications of smart materials have drawn much attention in aerospace, civil, mechanical and even bioengineering. The emerging field of smart composite structures offers the promise of truly integrated health and usage monitoring, where a structure can sense and adapt to their environment, loading conditions and operational requirements, and materials can self-repair when damaged. The concept of structural health monitoring using smart materials relies on a network of sensors and actuators integrated with the structure. This area shows great promise as it will be possible to monitor the structural condition of a structure, throughout its service lifetime. Integrating intelligence into the structures using such networks is an interesting field of research in recent years. Some materials that are being used for this purpose include piezoelectric, magnetostrictive and fiber-optic sensors. Structural health monitoring using, piezoelectric or fiber-optic sensors are available in the literature. However, very few works have been reported in the literature on the use of magnetostrictive materials, especially for composite structures. Non contact sensing and actuation with high coupling factor, along with other prop- erties such as large bandwidth and less voltage requirement, make magnetostrictive materials increasingly popular as potential candidates for sensors and actuators in structural health monitoring. Constitutive relationships of magnetostrictive material are represented through two equations, one for actuation and other for sensing, both of which are coupled through magneto-mechanical coefficient. In existing finite element formulation, both the equations are decoupled assuming magnetic field as proportional to the applied current. This assumption neglects the stiffness contribution coming from the coupling between mechanical and magnetic domains, which can cause the response to deviate from the time response. In addition, due to different fabrication and curing difficulties, the actual properties of this material such as magneto-mechanical coupling coefficient or elastic modulus, may differ from results measured at laboratory conditions. Hence, identification of the material properties of these embedded sensor and actuator are essential at their in-situ condition. Although, finite element method still remains most versatile, accurate and generally applicable technique for numerical analysis, the method is computationally expensive for wave propagation analysis of large structures. This is because for accurate prediction, the finite element size should be of the order of the wavelength, which is very small due to high frequency loading. Even in health monitoring studies, when the flaw sizes are very small (of the order of few hundred microns), only higher order modes will get affected. This essentially leads to wave propagation problem. The requirement of cost-effective computation of wave propagation brings us to the necessity of spectral finite element method, which is suitable for the study of wave propagation problems. By virtue of its domain transfer formulation, it bypasses the large system size of finite element method. Further, inverse problem such as force identification problem can be performed most conveniently and efficiently, compared to any other existing methods. In addition, spectral element approach helps us to perform force identification directly from the response histories measured in the sensor. The spectral finite element is used widely for both elementary and higher order one or two dimensional waveguides. Higher order waveguides, normally gives a behavior, where a damping mode (evanescent) will start propagating beyond a certain frequency called the cut-off frequency. Hence, when the loading frequencies are much beyond their corresponding cut-off frequencies, higher order mo des start propagating along the structure and should be considered in the analysis of wave propagations. Based on these considerations, three main goals are identified to be pursued in this thesis. The first is to develop the constitutive relationship for magnetostrictive sensor and actuator suitable for structural analysis. The second is the development of different numerical tools for the modelling the damages. The third is the application of these developed elements towards solving inverse problems such as, material property identification, impact force identification, detection and identification of delamination in composite structure. The thesis consists of four parts spread over six chapters. In the first part, linear, nonlinear, coupled and uncoupled constitutive relationships of magnetostrictive materials are studied and the elastic modulus and magnetostrictive constant are evaluated from the experimental results reported in the literature. In uncoupled model, magnetic field for actuator is considered as coil constant times coil current. The coupled model is studied without assuming any explicit direct relationship with magnetic field. In linear coupled model, the elastic modulus, the permeability and magnetostrictive coupling are assumed as constant. In nonlinear-coupled model, the nonlinearity is decoupled and solved separately for the magnetic domain and mechanical domain using two nonlinear curves,’ namely the stress vs. strain curve and magnetic flux density vs. magnetic field curve. This is done by two different methods. In the first, the magnetic flux density is computed iteratively, while in the second, artificial neural network is used, where a trained network gives the necessary strain and magnetic flux density for a given magnetic field and stress level. In the second part, different finite element formulations for composite structures with embedded magnetostrictive patches, which can act both as sensors and actuators, is studied. Both mechanical and magnetic degrees of freedoms are considered in the formulation. One, two and three-dimensional finite element formulations for both coupled and uncoupled analysis is developed. These developed elements are then used to identify the errors in the overall response of the structure due to uncoupled assumption of the magnetostrictive patches and shown that this error is comparable with the sensitivity of the response due to different damage scenarios. These studies clearly bring out the requirement of coupled analysis for structural health monitoring when magnetostrictive sensor and actuator are used. For the specific cases of beam elements, super convergent finite element formulation for composite beam with embedded magnetostrictive patches is introduced for their specific advantages in having superior convergence and in addition, these elements are free from shear locking. A refined 2-node beam element is derived based on classical and first order shear deformation theory for axial-flexural-shear coupled deformation in asymmetrically stacked laminated composite beams with magnetostrictive patches. The element has an exact shape function matrix, which is derived by exactly solving the static part of the governing equations of motion, where a general ply stacking is considered. This makes the element super convergent for static analysis. The formulated consistent mass matrix, however, is approximate. Since the stiffness is exactly represented, the formulated element predicts natural frequency to greater level of accuracy with smaller discretization compared to other conventional finite elements. Finally, these elements are used for material property identification in conjunction with artificial neural network. In the third part, frequency domain analysis is performed using spectrally formulated beam elements. The formulated elements consider deformation due to both shear and lateral contraction, and numerical experiments are performed to highlight the higher order effects, especially at high frequencies. Spectral element is developed for modelling wave propagation in composite laminate in the presence of magnetostrictive patches. The element, by virtue of its frequency domain formulation, can analyze very large domain with nominal cost of computation and is suitable for studying wave propagation through composite materials. Further more, identification of impact force is performed form the magnetostrictive sensor response histories using these spectral elements. In the last part, different numerical examples for structural health monitoring are directed towards studying the responses due to the presence of the delamination in the structure; and the identification of the delamination from these responses using artificial neural network. Neural network is applied to get structural damage status from the finite element response using its mapping feature, which requires output uniqueness. To overcome the loss of output uniqueness due to the dimension reduction, damage space is divided into different overlapped zones and then different networks are trained for these zones. Committee machine is used to co ordinate among these networks. Next, a five-stage hierarchy of networks is used to consider partitioning of damage space, where different dimension reduction algorithms and different partitioning between training and testing samples are used for better mapping fro the identification procedure. The results of delamination detection for composite laminate show that the method developed in this thesis can be applied to structural damage detection and health monitoring for various industrial structures. This thesis collectively addresses all aspects pertaining to the solution of inverse problem and specially the health monitoring of composite structures using magnetostric tive sensor and actuator. In addition, the thesis discusses the necessity of higher order theory in the high frequency analysis of wavw propagation. The thesis ends with brief summary of the tasks accomplished, significant contribution made to the literature and the future applications where the proposed methods addressed in this thesis can be applied.
17

Estudo e implantação numérica da teoria de Biot para meios elastoplásticos e uso de estratégias de otimização para o processamento / Study and implementation of Biot s theory for media elastoplastic and use of optimization strategy for the processing

Costa, Joseanderson Augusto de Caldas 03 May 2012 (has links)
This work presents a strategy for the coupled poro-elasto-plastic formulation. The Finite Element Method (FEM) is used to solve the differential equations, interpolating displacement and pore pressure fields. This problem is solved fully coupled, based on an only one system of equations. The nonlinear problem is globally solved by the Newton-Raphson procedure, and the Closest Point algorithm is implemented for the returning map in the elasto-plastic models. Based on a computational module that has already been developed (PORO), which is written using C++ language and Object-Oriented Programming (OOP), this work expands this program creating new classes for different elasto-plastic constitutive models. The program is verified by classical examples in the literature such as the poro-elastic column and the problem of Schiffman. Some strategies for optimization the computational cost are presented, which use specialized math libraries (MKL) and code parallelization (OpenMP). / Este trabalho apresenta, discute e implementa a formulação poro-elastoplástica fortemente acoplada. A discretização espacial das equações diferenciais governantes é realizada através do Método dos Elementos Finitos (MEF), com interpolação do campo de deslocamento e da poropressão. O problema poro-mecânico é resolvido de forma totalmente acoplada, com base em um único sistema de equações. O método iterativo de Newton-Rhapson é empregado para a solução global do problema não linear, tendo ainda o algoritmo implícito iterativo Closest Point para a integração local das equações da plasticidade. Baseando-se em um programa computacional pré-existente denominado PORO, escrito na linguagem C++ e que utiliza o paradigma de Programação Orientada a Objetos (POO), faz-se a adaptação desse código através da criação de novas classes para permitir o uso de modelos constitutivos elastoplásticos e lei de fluxo associada no acoplamento poro-mecânico. Para verificação do programa são analisados problemas clássicos da literatura, a exemplo da coluna poro-elástica e o caso de Schiffman. Descrevem-se ainda algumas estratégias de otimização do custo computacional, implementando-se o uso de bibliotecas matemáticas (MKL) e paralelização do código (OpenMP).
18

[pt] AVALIAÇÃO DE ESQUEMAS DE ACOPLAMENTO NA SIMULAÇÃO DE RESERVATÓRIOS DE PETRÓLEO / [en] EVALUATION OF COUPLING SCHEMES IN THE SIMULATION OF PETROLEUM RESERVOIRS

NIURKA PATRICIA RODRIGUEZ YAQUETTO 04 July 2013 (has links)
[pt] Os estudos entre a interação do fluxo de fluido e a deformação do meio poroso têm sido realizados com o objetivo de explicar alguns fenômenos que ocorrem ao longo da produção/injeção de fluidos, e assim obter uma simulação de reservatórios cada vez mais precisa. A solução ideal para o problema é implementar um esquema, onde as leis que governam o fluxo e analise de tensões sejam obedecidas simultaneamente em cada intervalo de tempo. Este trabalho apresenta os resultados de um código (programado em C positivo positivo) que permite acoplar um simulador de fluxo convencional (ECLIPSE) e um programa que permite analisar tensões e deslocamentos (Abaqus /CAE). O objetivo deste trabalho é validar varias soluções para resolver um problema usando os diferentes tipos de acoplamento, que juntamente com uma filosofia empregada nas principais formulações permite dar respostas similares aquelas do acoplamento total. São apresentadas as formas de acoplamento e a formulação empregada em cada um dos esquemas usados. Os resultados obtidos pelos esquemas são comparados em termos de fluxo e tensões e deslocamentos a partir de modelos tridimensionais. / [en] Studies between the interaction of fluid flow and deformation of porous media have been carried out with the aim of explaining some phenomena that occur along the production/injection of fluids, thereby obtaining a more accurate reservoir simulation. The ideal solution for this problem is to implement a scheme where laws governing the flow and stress analysis are met simultaneously at each time interval. This dissertation presents the results of a computer code (programmed in C positive positive) that allows the coupling of a conventional reservoir simulator (ECLIPSE) and a stress-displacement finite element based program (Abaqus /CAE). This work presents the use of various coupling schemes for the solution of a synthetic case, in particular the use of a methodology that generates results very close to the ones predicted from the use of fully coupled methods. The results obtained by the different coupling schemes are compared in terms of fluid pressure, stress and displacement responses for synthetic three-dimensional models.
19

Model komory reaktoru pro mikrovlnný ohřev / Model of the reactor chamber for microwave heating

Kříž, Tomáš January 2008 (has links)
The diploma thesis deals with the concept of a high-frequency chamber which serves for desiccation of emulsion consisted of oil and water where the contents of water is over 30% of the emulsion capacity. The high-frequency chamber works on frequency 2,45 GHz. The task was to design a numerical model in which a high-frequency thermic conjugated problem is solved. The design of a high-frequency chamber is made up considering the heat distribution in inhomogeneous environment as well as chemical and physical changes. The proportions of the high-frequency chamber can guarantee the biggest output transmitted from the source to the chamber with the emulsion desiccated and uniform layout of electromagnetic field. These criteria are necessary for smooth heating of the emulsion desiccated. In this diploma thesis, there were several numerical models with various proportions made up. Finally, the one with the shortest time of heating the emulsion in reference to emulsion capacity was chosen.
20

Estudo de viabilidade do sistema de ancoragem de uma unidade flutuante de produção e armazenamento \"FPSO\" acoplada a um sistema de completação seca \"TLWP\". / Mooring system feasibility study of a floating production and storage unit \"FPSO\" coupled to a dry tree system \"TLWP\".

Rampazzo, Fabiano Pinheiro 29 March 2011 (has links)
A produção de petróleo e gás em campos brasileiros é cada vez mais proveniente de regiões com águas profundas e situadas longe da costa, chegando a distâncias de mais de 100 km, como, por exemplo, na Bacia de Campos ou de Santos. Devido à falta de infra-estrutura e às características do petróleo desses campos, a cadeia de abastecimento e o sistema de exportação da produção possuem grande importância para a indústria offshore. Uma maneira usual para a exportação da produção é através de dutos submarinos, onde o óleo e/ou a gás flui das plataformas diretamente para o continente. Com esta infra-estrutura é possível a utilização de sistemas de produção sem capacidade de armazenamento e, conseqüentemente, torna-se desnecessário o uso de navios para o alívio da produção. No entanto, devido à qualidade do óleo e às distâncias entre os poços e a costa em alguns campos brasileiros, a utilização dos oleodutos mostra-se uma solução pouco viável. Por este motivo, é bastante comum o uso de FPSOs ou semi-submersíveis conectadas a sistemas auxiliares, como o FSO (Floating Storage and Offloading). Nas plataformas, outra característica importante e desejada é tornar viável o uso de um sistema de completação seca (árvore de Natal acima da linha dágua) com o objetivo de diminuir, significativamente, os custos operacionais envolvidos. Esse tipo de completação é utilizado, com excelência, por unidade do tipo TLWP ou Spar, devido ao baixo nível dos movimentos e acelerações observadas nestas plataformas. Entretanto, as condições ambientais severas amplificam as dificuldades para encontrar um sistema com grande capacidade de armazenamento e que permita o uso de completação seca. Neste contexto, pesquisadores e engenheiros estão sendo obrigados a desenvolver novos conceitos capazes de atender a essa demanda. Desta forma, uma nova solução, considerando um FPSO e uma TLWP operando a uma curta distância e trabalhando de forma acoplada com a conexão garantida por cabos sintéticos vem sendo estudada. Essencialmente, o grande atrativo deste conceito é o fato de que toda a produção e o armazenamento são concentrados no FPSO e a TLWP é responsável pela perfuração e extração dos hidrocarbonetos através de risers verticais. Assim o sistema trabalhando de forma conjunta possui capacidade de armazenamento e permite o uso da completação seca. Nesta dissertação, foi realizado um estudo sobre a evolução deste novo conceito, dividido em três fases. A primeira focada no dimensionamento do sistema de conexão e ancoragem das unidades e em uma investigação da interação hidrodinâmica entre as unidades de forma a mostrar a viabilidade do sistema. A segunda fase, focada na validação dos resultados por meio da comparação com os testes realizados no modelo em escala do NMRI (National Maritime Research Institute - Japão). Finalmente, a terceira fase, com foco no redimensionamento do sistema de amarração e no sistema de conexão, com base nos resultados obtidos na segunda fase. / The oil and gas production in Brazilian fields are commonly found in deep water and situated far away from the coast, reaching distances of more than 100 km as, for example, in the Campos Basin or Santos Basin. Due to the heavy oil and lack of pipeline infrastructure found in these fields, not only subsea equipments that must support high pressure but also logistics problems such as supply chain and production exportation system play an important role for the offshore industry. A usual way to export the production is to concentrate it in hubs of submarine pipelines which flows the oil or gas from the platforms to the continent. This infrastructure makes possible the use of no storage production systems and, consequently, releases the use of the shuttle tanks employment. However, due to the quality of the oil and the distances between the wells and the coast, some Brazilian fields do not allow the use of the pipelines to export their production. For this reason, is quite common to use FPSO and semi-submersible aided by auxiliary systems such as the FSO (Floating Storage and Offloading) units. Another important and desired characteristic of production platforms is to make it feasible to install a dry Christmas tree system aiming to decrease, significantly, operational costs involved. This feature is performed, with excellence, by TLWP and Spar units due to the low level of motions and accelerations observed in these platforms. Harsh environmental conditions can bring difficulties to find a solution of a system with both storage and dry tree system capability. In this context, researchers and engineers are being forced to develop new technological systems capable to support this demand. In this way, a new solution considering a FPSO and a TLWP coupled in a short distance by synthetic ropes has being studied. Essentially, the attractive feature of this concept is the fact that the production is performed by the FPSO whereas the TLWP is responsible to support the risers and drilling facilities turning the system coupled, equipped with a dry Christmas tree and with the possibility to storage the production. By now, the concept evolution has been divided in three phases. The first phase concerned about an advanced research focusing on the connection and mooring system development and the hydrodynamic interaction between the units and having in mind the verification of the concept feasibility. The second phase, concerned about the results validation by a comparison with scale model tests performed in the NMRI (National Maritime Research Institute Japan). Finally, the third phase, has the focus in the mooring and connection system resizing based on the results obtained on second phase.

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