Dans le cadre de cette étude, l'influence de la pré-déformation sur l'anisotropie du comportement plastique et sur la ténacité d'un acier API X100 pour pipeline a été abordée. Une étude expérimentale approfondie de la microstructure, des propriétés mécaniques et de l'endommagement du matériaux a été mise en oeuvre. Un modèle phénoménologique anisotrope combinant les écrouissagesisotrope et cinématique a été développé dans l'objectif de rendre compte du comportement ductile de cet acier à haute résistance. De plus, un modèle d'endommagement anisotrope a été établi pour représenter l'effet de pré-déformation sur la ductilité et la ténacité de cet acier. L'application des modèles à la flexion sous contrainte illustre, par exemple, l'effet négatif de la pré-déformation sur la charge limite (Moment de flexion maximum) supportée avant flambement du pipe.

This thesis is on the transformation of Turco-Georgian relations since the early 1990s. In recent years, these relations have been taken to a next level in light of the trans-national cooperation that resulted in the construction of the Baku-Tbilisi-Ceyhan (BTC) pipeline. With a narrow focus on the Turco-Georgian border, this study attempts to understand the trajectory of the improving relations between the two countries through a reconceptualised understanding of the border. By emphasising both the horizontal and vertical dimensions of borders, this thesis tries to steer away from the zero-sum approaches and understand the nature of Turco-Georgian as a complex multiplicity.

Linear assets are among the largest and most important engineered systems; their reliability is of the utmost importance. This thesis presents an overview of the reliability estimation methods used for the various types of linear assets, both observation- and statistically-based. While observation-based reliability monitoring and estimation methods are necessarily particular to a certain type of asset, statistically-based methods developed for one type can potentially inform those used for another. Therefore, this thesis looks to point out commonalities in the methods for the statistical evaluation of the reliability of various types of linear assets, develop and extend reliability models and methods with this knowledge, and suggest how maintenance strategies may be improved. To help illustrate and test the models described in this paper a case study was conducted with a utility operator; this thesis shows the modelling results from the study, and demonstrates the model’s use in a maintenance decision model.

Linear assets are among the largest and most important engineered systems; their reliability is of the utmost importance. This thesis presents an overview of the reliability estimation methods used for the various types of linear assets, both observation- and statistically-based. While observation-based reliability monitoring and estimation methods are necessarily particular to a certain type of asset, statistically-based methods developed for one type can potentially inform those used for another. Therefore, this thesis looks to point out commonalities in the methods for the statistical evaluation of the reliability of various types of linear assets, develop and extend reliability models and methods with this knowledge, and suggest how maintenance strategies may be improved. To help illustrate and test the models described in this paper a case study was conducted with a utility operator; this thesis shows the modelling results from the study, and demonstrates the model’s use in a maintenance decision model.

Thesis (Ph.D)--Geosystems, Georgia Institute of Technology, 2010. / Committee Chair: Frost, J. David; Committee Member: Burns, Susan E.; Committee Member: Gokhale, Arun; Committee Member: Mayne, Paul W.; Committee Member: Rix, Glenn J. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 355-372).

Thesis (M. of Strategic Studies)--U.S. Army War College, 2007. / "USAWC program research paper." "DDE research project"--P. [iii]. Title from PDF title screen. Includes bibliographical references (p. 21-26). Also available online via the STINET website (http://stinet.dtic.mil/).

Ο κεραυνός είναι μία ηλεκτρική εκκένωση ατμοσφαιρικής προέλευσης απλή ή πολλαπλή μεταξύ νέφους και γης. Αποτελεί ένα φυσικό φαινόμενο με επικίνδυνα αποτελέσματα για την ασφάλεια των ανθρώπων, των κτιρίων και των ηλεκτρικών συστημάτων. Αν και είναι τόσο παλιό όσο και ο πλανήτης μας, μπόρεσε να εξηγηθεί μόνο κατά τους τελευταίους δύο αιώνες. Από το 1753 όπου ο B. Franklin απέδειξε την ύπαρξη ατμοσφαιρικού ηλεκτρισμού μέχρι σήμερα, με πολλές μοντέρνες μεθόδους και πειράματα έχει αποκτηθεί αρκετή γνώση επάνω στο φαινόμενο αυτό και κατά συνέπεια έχουν αναπτυχθεί αρκετά ασφαλείς τρόποι προστασίας από τους κινδύνους ενός κεραυνού. Όταν ένας κεραυνός πλήξει το έδαφος, το ρεύμα του εκφορτίζεται στη μάζα της γης. Η τελική κατανομή του ρεύματος εξαρτάται κατά πολύ από την ανομοιογένεια του εδάφους, επειδή το ρεύμα θα ρέει όπου είναι πιο εύκολο δηλαδή κατά μήκος αγώγιμων κοιτασμάτων ή γεωλογικών σφαλμάτων που είναι διάχυτα σε έδαφος με μικρή αγωγιμότητα. Εξ αιτίας αυτού του γεγονότος, όταν υπάρχει ένας μεταλλικός αγωγός μεγάλου μήκους , η μεταλλική του επιφάνεια θα βραχυκυκλώσει τμήμα του ηλεκτρικού πεδίου που δημιουργείται στο έδαφος από πλήγμα κεραυνού. Το ρεύμα του κεραυνού συγκεντρώνεται στην επιφάνεια του αγωγού, ενώ το βάθος διείσδυσης του κεραυνού είναι κυρίως συνάρτηση της επικρατούσας ειδικής αντίστασης του εδάφους. Επίσης, ένας κεραυνός που πλήττει το έδαφος παράγει ένα μεταβαλλόμενο ηλεκτρομαγνητικό πεδίο, το οποίο επάγει τάσεις σημαντικού ύψους στους υπόγειους μεταλλικούς αγωγούς που βρίσκονται σε γειτνιάζουσα περιοχή με το σημείο του πλήγματος, οι οποίες θα καταπονήσουν τους υπόγειους αγωγούς προκαλώντας ακαριαία καταστροφή ή ισχυρή καταπόνηση οδηγώντας σε βαθμιαία φθορά. Σκοπός αυτής της διπλωματικής εργασίας είναι η μελέτη και η ανάλυση των επαγόμενων υπερτάσεων οι οποίες εμφανίζονται σε υπόγειους μεταλλικούς αγωγούς λόγω των κεραυνικών πληγμάτων. Για αυτούς τους λόγους κάνουμε μια εκτενή ανάλυση της δημιουργίας κεραυνών καθώς και των επιπτώσεών τους στη γήινη επιφάνεια. Ακόμη γίνεται αναφορά στο είδος των υπερτάσεων που δημιουργούνται από τους κεραυνούς καθώς και στο τρόπο με τον οποίο προστατεύονται οι υπόγειοι αγωγοί από τις υπερτάσεις. Στη συνέχεια με την χρήση του λογισμικού ATP-EMTP γίνεται ανάλυση των υπερτάσεων που δημιουργούνται στους αγωγούς όταν ένας κεραυνός πλήξει μια γειτονική γραμμή μεταφοράς. Η εργασία ολοκληρώθηκε με παρατηρήσεις επάνω στα αποτελέσματα των εξομοιώσεων. / Lightning is an electrical discharge atmospheric origin single or multiple between cloud and earth. It is a natural phenomenon with dangerous results for the safety of people, buildings and electrical systems. Although it is as old as our planet, could be explained only in the last two centuries. Since 1753 when the B. Franklin proved the existence of atmospheric electricity up to today, with many modern methods and experiments has been acquired enough knowledge on this phenomenon and accordingly have been developed several safe ways to protect against the risks of lightning. When a lightning struck the ground, his current discharged to the mass of earth. The final distribution of current depends by far from the heterogeneity of the soil, because the current flows where it is easier, that is to say at length of conductive deposits or geological faults that are diffuse in the soil with low conductivity. Because of this, when there is a long metal pipeline, his metal surface will fuse department of electric field that is created in the ground by hurt of lightning. The lightning current is concentrated on the surface of the pipeline, while the depth of infiltration of lightning is mainly a function of the prevailing soil resistivity. Also, a lightning that affects the ground produces a altered electromagnetic field, which induces voltages considerable amount of underground metallic pipelines located in nearby locations to point to the shock, which stresses the underground pipes, causing immediate destruction or high stress leading to a gradual deterioration. Aim of this work is the study and analysis of induced voltages that occur in underground metallic pipelines due to lightning strikes. For these reasons, we do an extensive analysis of the creation of lightning and its impact on the earth's surface. Also refers to the type of over voltages caused by lightning and the way protect underground pipes from the over voltages. Afterwards, with the use of ATP-EMTP software becomes analysis of the over voltages that are created in the pipelines when a lightning struck a nearby transmission line. The work was completed with observations on the results of the simulation.

As oportunidades do processo de digestão anaeróbia, em aterros sanitários, controlados e sistemas de compostagem, são ligadas à formação de biogás através da biodegradação da matéria orgânica (MO) em ambiente predominantemente anaeróbio. O aterro da Caturrita, localizado na cidade de Santa Maria, possui cerca de 467.929 toneladas de resíduos depositados em uma de suas células. A recuperação total do CH4 desta quantidade de resíduo entre 2013 e 2033, considerando um rendimento na captação de gases de 70%, foi calculada em 17.529.657 m3. O total da receita estimada para o mesmo período, admitindo uma comercialização conservadora de créditos de carbono e energia elétrica, foi de USD 2.131.458 , isto é, um faturamento mensal de USD 8.881. No caso da compostagem, onde podem ocorrer ambientes anaeróbios, o sistema de ponteiras horizontais em camadas utilizado experimentalmente apresentou indícios de diminuição da geração de CH4 com vantagem em relação à compostagem com ponteiras verticais. Para isso, utilizaram-se taxas de aeração de 0,557 m³ ar.d-1.kg-1 de MO em peso seco (PS), com o monitoramento da temperatura interna e da umidade das leiras. As variações das perdas de cargas calculadas para as tubulações da leira experimental com ponteiras horizontais ficaram entre 1,56% e 2,56%, com a temperatura interna máxima em 70,8°C, diferentemente da leira com ponteiras verticais que atingiu uma máxima de 47,1°C, ambas para umidades superiores a 50%. O custo por metro para a implantação em escala real equivale a USD 21,22, considerando o uso de materiais alternativos, mas com resistência mecânica e térmica adequados. Observou-se na leira experimental com ponteiras horizontais proposta a diminuição do NH4 + concomitantemente à elevação do NO3 em menor tempo que na leira com ponteiras verticais. Além disso, com a proposta do sistema de aeração alternativo, a emissão de CH4 seria pouco significativa, pois o processo é basicamente aeróbio. Para a compostagem com ponteiras verticais utilizado na empresa, considerando apenas a emanação de CH4, estima-se o custo ambiental entre USD 2.059 e USD 75.841 por ano para uma quantidade processada de 50.000 t de resíduos agroindustriais. Para o aterro da Caturrita, o custo ambiental pode ser estimado entre USD 7.733 e USD 52.287 por ano. Com uma recuperação de 70% de CH4, através de queima ou conversão em energia elétrica, o custo ambiental máximo estimado cairia para USD 15.686 para a quantidade estimada e disposta no aterro da Caturrita entre 1999 e 2008 de 467.929 toneladas. / The anaerobic digestion process opportunities, about controlled landfills and composting systems, are related to a biogas formation process through the biodegradation of organic substances in a predominantly anaerobic environment. The Caturrita’s landfill, located in Santa Maria – RS - Brazil, has around 467,929 tons of deposited residues in one of its cells. The recovery of methane between 2013 and 2033, considering an availability of 70%, was estimated at 17,529,657 m³. Admitting the carbon credits and electric energy commercialization, during the same period, was estimated and would result in USD 2,131,438, that is, a monthly profits of USD 8,881. In a composting system, where anaerobic environments may occur, the horizontal pipelines system used showed that the CH4 production decreased with advantage in relation to vertical pipelines. For this experiment, Organic matter (OM) was aerated at a rate of 0.557 m3 air·d-1·kg-1, as determined by dry weight (DW), and the internal temperature and humidity of the windrows were monitored. The calculated variation of the pressure loss for the pipelines in the experimental widrow with horizontal pipelines proposal was between 1.56% and 2.56% at a maximum internal temperature of 70.8°C, unlike the windrow with vertical pipelines, which reached a maximum temperature of 47.1°C. In both systems, the humidity was greater than 50%. The cost per metre for commercial scale implementation is equivalent to USD 21.22, considering the use of alternative materials with the necessary mechanical and thermal resistance values. It was observed in the experimental pile with horizontal pipelines proposal the reduction of NH4 + simultaneously to the elevation of NO3 in less time than in the pile with vertical pipelines. Furthermore, with the alternative aeration system, the CH4 emission would be insignificant, because the process is essentially aerobic. For composting system with vertical pipelines used in the company, considering only the emanation of CH4, the environmental cost can be estimated between USD 2,059 and USD 75,841 per year for an amount of 50,000 t of processed agribusiness residues. For Caturrita’s landfill, the environmental cost can be estimated between USD 7,733 and USD 52,287 per year. With a CH4 recovery of 70%, by burning or conversion into electrical energy, the maximum estimated environmental cost would fall to USD 15,686 for the estimated quantity and disposed of in landfill Caturrita between 1999 and 2008 of 467,929 tons.

[pt] No processo de transporte e produção de petróleo e seus derivados em linhas submarinas, o controle da transferência de calor entre o produto quente e o mar frio, é fundamental para a garantia do escoamento. Se a temperatura do produto cair abaixo de determinados valores críticos, problemas como formação de hidratos ou deposição de parafina nas paredes da tubulação podem ocorrer, levando ao bloqueio da linha e interrupção de produção, demandando altos custos. A perda de calor para o ambiente é minimizada, através de isolantes térmicos projetados para operações em regime permanente. Nestes casos, devido às altas velocidades do escoamento axial, o qual é tipicamente turbulento, o processo de transferência de calor dominante é o de convecção forçada. Porém, durante uma operação de manutenção de algum equipamento, a produção pode ser interrompida e o fluido ficando parado no interior da linha, tende a resfriar-se podendo atingir uma temperatura crítica. Durante este resfriamento, na ausência de bombeio, o processo de convecção natural passa a dominar. O presente trabalho analisa o processo de transferência de calor após a parada de bombeio, considerando os efeitos da convecção natural no resfriamento do produto, assim como a influência da capacidade térmica da parede do duto e das camadas de revestimento no transiente térmico. Inicialmente, considera-se que o escoamento axial é rapidamente levado ao repouso e utiliza-se um modelo bidimensional da seção transversal do duto, utilizando três produtos típicos: um óleo leve, um óleo pesado, e um gás. Os campos de velocidade e temperatura são obtidos numericamente utilizando o software FLUENT, considerando a hipótese de Boussinesq para avaliar a convecção natural. A taxa de resfriamento obtida é comparada com a previsão de um modelo unidimensional na direção axial, que utiliza correlações empíricas para avaliar a transferência de calor entre o fluido a parede da tubulação, em função do regime de escoamento. Boa concordância entre as simulações para a seção central da linha é obtida. No entanto, como as variações axiais para o caso do gás são maiores, para este produto, um modelo tridimensional também foi analisado, onde se considerou os efeitos combinados da convecção forçada e natural. Adicionalmente, a hipótese de Boussinesq foi eliminada, e a equação de gás ideal foi considerada. / [en] Heat transfer control is crucial for flow assurance in transport as well as production operations of oil and its derivatives in subsea lines. If the product temperature falls below certain critical values, problems such as hydrate formation or wax deposition in the pipelines walls can occur, inducing line blockage and interruption of production, demanding high costs. The heat loss to the environment is minimized by employing thermal insulation, which are designed for stead state operations. For these cases, due to high axial velocities, the flow is typically turbulent, and the dominant heat transfer mechanism is due to convection forced. However, during maintenance operation of some equipment, the production can be interrupted and the stagnant fluid in the interior of the line tends to cool down and it can reach a critical temperature. During this cooling, in the absence of pumps, the process of natural convection begins to dominate. The present work analyzes the heat transfer process after flow shutdown, considering the effect of the natural convection, as well as the influence in the thermal transient of the thermal capacity of the duct wall and insulation layers. Initially, it is considered that the axial flow is set to rest very quickly and a two-dimensional model of the transversal section of the duct is employed, using three typical products: light oil, heavy oil and pressurized gas. The velocity and temperature filed are obtained using the numerical software FLUENT, considering the hypothesis of Boussinesq to evaluate the natural convection. The cooling rate is compared with the forecast of a unidimensional model in the axial direction based on empirical correlations, function of the flow regime, to evaluate the heat transfer between the fluid and the duct wall. Good agreement is obtained between the solutions of the 2-D model and the pipeline central cross section of the 1-D model. However, as the axial variations for the gas case are significant, for this product, a three-dimensional model also was analyzed, where it was considered the effects of the forced and natural convection. Additionally, the hypothesis of Boussinesq was eliminated, and the ideal gas equation was considered.