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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.
41

Tensoes termicas no vaso de pressao de um reator a agua pressurizada (PWR)

BASSEL, WAGEEH S. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:26:08Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:10:21Z (GMT). No. of bitstreams: 1 00653.pdf: 2722544 bytes, checksum: 26bcce3d962be5c281c69fd5f50fca70 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
42

Tensoes termicas no vaso de pressao de um reator a agua pressurizada (PWR)

BASSEL, WAGEEH S. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:26:08Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:10:21Z (GMT). No. of bitstreams: 1 00653.pdf: 2722544 bytes, checksum: 26bcce3d962be5c281c69fd5f50fca70 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
43

Caractérisation et modélisation de l'endommagement des composites bobinés. Application à la prédiction de l'éclatement des réservoirs bobinés hyperbares / Wound composites damage modelling and characterization. Application to burst prediction of hyperbaric wound composite pressure vessels

Berro Ramírez, Juan Pedro 28 November 2013 (has links)
Un modèle d’endommagement dédié aux composites bobinés est développé à partir des outils de lamécanique de l’endommagement continu, de la thermodynamique des processus irréversibles et dela théorie de représentation des fonctions tensorielles. La particularité de ce modèle est l’utilisationd’une approche à directions fixes de l’endommagement qui associe à chaque mode de dégradationdes variables internes scalaires et des tenseurs directionnels. La rupture des fibres (considéréecomme probabiliste), les fissurations tant matricielles, que hors – plan ou provoquées par lecisaillement sont ainsi prises en compte. Le modèle est capable de reproduire, dans un contextetridimensionnel imposé par les fortes épaisseurs de composite, la perte de rigidité, l’interaction entreanisotropies initiale et induite, la non linéarité du comportement, les déformations résiduelles et laviscosité en cisaillement. Afin de valider cette approche, le comportement thermomécaniqued’éprouvettes issues de structures bobinées a été caractérisé grâce à des essais de traction multi –instrumentés (vidéo – traction, émission acoustique,...). On montre que le modèle est capable nonseulement de simuler la réponse mécanique macroscopique de ces échantillons, mais également dereproduire l’émission acoustique enregistrée, de distinguer les différentes formesd’endommagement et de prédire précisément l’éclatement des réservoirs hyperbares. / A damage model dedicated to wound composite is developed by using the tools of continuousdamage mechanics, irreversible processes thermodynamics and the representation theory of tensorfunctions. The particularity of this model is the use of a fixed directions approach of damage whichassociates each degradation mode to internal scalar variables and directional tensors. Fiber breakage(considered probabilistic), matrix cracking (transverse, out-of-plane or caused by shear) are thustaken into account. The model is able to reproduce, in a three-dimensional context imposed bythick composite layers, loss of strength, interaction between initial and induced anisotropy, nonlinearitybehavior, residual strain and shear viscosity. To validate this approach, thermo mechanicalbehavior of specimens from the wound structures was characterized by tensile multi - instrumentedtests (video - traction, acoustic emission, ...). We show that the model is able to simulate not onlythe macroscopic mechanical response of these samples, but also to reproduce the recorded acousticemission to distinguish the various forms of damage and to accurately predict the burst ofhyperbaric tanks.
44

Thermal shock resistance parameters for the industrial lining problem

Bradley, Frederick Joseph January 1985 (has links)
A two-dimensional constant heating rate thermoelastic model has been used to develop design and selection criteria for refractory components of linings of high-temperature furnaces and process vessels. The criteria are in the form of resistance to fracture initiation and resistance to damage parameters which account for the influence of thermal and mechanical properties, geometry, and temperature range, while distinguishing between the heating and cooling cases. The resistance to fracture initiation parameter ɸs is the maximum rate at which a shape can be heated or cooled through a specified temperature range without causing fracture. The damage resistance parameter Rd is expressed as the ratio of surface energy per unit area to the elastic strain energy available for crack propagation. Both parameters can be quickly estimated for arbitrary conditions with the aid of tabulated solutions for the maximum principal tensile stress and total strain energy Thermoelastic analyses were used to interpret published results of a variety of thermal shock experiments. Thermal conditions associated with water quenching, radiative furnace heating, gas burners, and controlled heating were simulated using appropriate analytical solutions. Finite element analysis was used to compute maximum principal tensile stresses and elastic strain energy. A simple procedure was developed to invert the stress solution and thereby determine the instant of fracture. Good agreement between thermoelastic predictions and published experimental results with regard to strength retained versus thermal shock relationships, location of fracture, and safe heating rates provided justification for a thermoelastic approach to the thermal shock. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate
45

Improvements to the pool critical assembly benchmark using 3-D discrete ordinate transport with adaptive difference

Edgar, Christopher Austin 20 September 2013 (has links)
The internationally circulated Pool Critical Assembly (PCA) Pressure Vessel Benchmark was analyzed using the PENTRAN Parallel SN code system for the geometry, material, and source specifications as described in the PCA Benchmark documentation. Improvements to the benchmark are proposed through the application of more representative flux and volume weighted homogenized cross sections for the PCA reactor core, which were obtained from a rigorous heterogeneous modeling of all fuel assembly types in the core. A new source term definition is also proposed based on calculated relative power in each core fuel assembly with a spectrum based on the Uranium-235 fission spectra. This research focused on utilizing the BUGLE-96 cross section library and accompanying reaction rates, while examining both adaptive differencing on a coarse mesh basis, as well as the sole use of Directional Theta-Weighted (DTW) SN differencing scheme in order to compare the calculated PENTRAN results to measured data. The results show good comparison with the measured data, which suggests PENTRAN is a viable and reliable code system for calculation of light water reactor neutron shielding and dosimetry calculations. Furthermore, the improvements to the benchmark methodology resulting from this work provide a 6 percent increase in accuracy of the calculation (based on the average of all calculation points), when compared with experimentally measured results at the same spatial location in the PCA pressure vessel simulator.
46

Optimal strength of carbon fibre overwrapped composite high-pressure vessels

Numbi, M. N. 08 December 2021 (has links)
M. Tech. (Mechanical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / The purpose of this study was to design a composite overwrapped pressure vessel by combining the best optimal structural options. This study investigated the effects of constituents such as fibre and shell thickness, on the bursting strength. Thereafter, these constituents were combined in order to achieve optimization of strength for an improved sustainable composite pressure vessel. The analytical method was carried out using the Tsai-wu failure theorem. The developed analytical equations were solved with Matlab 2016 software to determine composite fibre and shell thickness. With variation of the vessel’s liner, a total of 56 parts were created on two different profiles with purpose of generating of vessels resistant to bursting failure. Henceforth, the structural integrity of fibre imparted into the design was optimally analyzed at an angle of 55⁰, through the negative and positive directions. The shell thickness overwrapping the liner, being as well an influential factor to this optimization, was, therefore, analyzed on symmetrical and asymmetrical lamination patterns. The optimal fibre and shell thickness range were thereafter determined on a first ply failure and hoop stress threshold approach. Additionally, the identified optimal range of pressure vessel constituents were numerically validated, on Abaqus/CAE software, to have a degree of reassurance on the result generated, using Hashin failure criteria. Optimal design with improved strength and weight factor was therefore achieved by combining the generated optimal vessel constituents yielded from Minitab software version 2016. The generated results of the study revealed no change on the fibre thickness determined with respect to direction. For shell thickness on the other hand, asymmetrical pattern was identified as the desired sequence of lamination. In addition, with two profiles considered in the research, the composite constituents were found for a p value of 0.066, to be optimal on profile 1 at 0.0048 mm of liner, 0.0005 mm of fibre and 0.0027 mm of shell. The profile 2 on the other hand, revealed optimization of liner at 0.0095 mm, fibre at 0.0021 mm and shell at 0.0055 mm. Through combination of these ultimate constituents the response optimizer on Minitab software generated optimal bursting strength with factor of 4% improvement with a weight reduction of 33% compared to the stainless steel vessel. It was, therefore, concluded that profile 1 was the most optimal with hoop strength of 123.43 MPa, Von Mises of 178.56 MPa and Tresca of 179.48 MPa.
47

Initiation of subcooled pool boiling during pressure transients

Schmidt, Don. January 1985 (has links)
Call number: LD2668 .T4 1985 S337 / Master of Science
48

Accounting for proof test data in Reliability Based Design Optimization

Ndashimye, Maurice 03 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Recent studies have shown that considering proof test data in a Reliability Based Design Optimization (RBDO) environment can result in design improvement. Proof testing involves the physical testing of each and every component before it enters into service. Considering the proof test data as part of the RBDO process allows for improvement of the original design, such as weight savings, while preserving high reliability levels. Composite Over-Wrapped Pressure Vessels (COPV) is used as an example application of achieving weight savings while maintaining high reliability levels. COPVs are light structures used to store pressurized fluids in space shuttles, the international space station and other applications where they are maintained at high pressure for extended periods of time. Given that each and every COPV used in spacecraft is proof tested before entering service and any weight savings on a spacecraft results in significant cost savings, this thesis put forward an application of RBDO that accounts for proof test data in the design of a COPV. The method developed in this thesis shows that, while maintaining high levels of reliability, significant weight savings can be achieved by including proof test data in the design process. Also, the method enables a designer to have control over the magnitude of the proof test, making it possible to also design the proof test itself depending on the desired level of reliability for passing the proof test. The implementation of the method is discussed in detail. The evaluation of the reliability was based on the First Order Reliability Method (FORM) supported by Monte Carlo Simulation. Also, the method is implemented in a versatile way that allows the use of analytical as well as numerical (in the form of finite element) models. Results show that additional weight savings can be achieved by the inclusion of proof test data in the design process. / AFRIKAANSE OPSOMMING: Onlangse studies het getoon dat die gebruik van ontwerp spesifieke proeftoets data in betroubaarheids gebaseerde optimering (BGO) kan lei tot 'n verbeterde ontwerp. BGO behels vele aspekte in die ontwerpsgebied. Die toevoeging van proeftoets data in ontwerpsoptimering bring te weë; die toetsing van 'n ontwerp en onderdele voor gebruik, die aangepaste en verbeterde ontwerp en gewig-besparing met handhawing van hoë betroubaarsheidsvlakke. 'n Praktiese toepassing van die BGO tegniek behels die ontwerp van drukvatte met saamgestelde materiaal bewapening. Die drukvatontwerp is 'n ligte struktuur wat gebruik word in die berging van hoë druk vloeistowwe in bv. in ruimtetuie, in die internasionale ruimtestasie en in ander toepassings waar hoë druk oor 'n tydperk verlang word. Elke drukvat met saamgestelde materiaal bewapening wat in ruimtevaartstelsels gebruik word, word geproeftoets voor gebruik. In ruimte stelselontwerp lei massa besparing tot 'n toename in loonvrag. Die tesis beskryf 'n optimeringsmetode soos ontwikkel en gebaseer op 'n BGO tegniek. Die metode word toegepas in die ontwerp van drukvatte met saamgestelde materiaal bewapening. Die resultate toon dat die gebruik van proeftoets data in massa besparing optimering onderhewig soos aan hoë betroubaarheidsvlakke moontlik is. Verdermeer, die metode laat ook ontwerpers toe om die proeftoetsvlak aan te pas om sodoende by ander betroubaarheidsvlakke te toets. In die tesis word die ontwikkeling en gebruik van die optimeringsmetode uiteengelê. Die evaluering van betroubaarheidsvlakke is gebaseer op 'n eerste orde betroubaarheids-tegniek wat geverifieer word met talle Monte Carlo simulasie resultate. Die metode is ook so geskep dat beide analitiese sowel as eindige element modelle gebruik kan word. Ten slotte, word 'n toepassing getoon waar resultate wys dat die gebruik van die optimeringsmetode met die insluiting van proeftoets data wel massa besparing kan oplewer.
49

Implementação de rotinas computacionais para o cálculo de trajetórias geodésicas no processo de filament winding / Computational routines for the calculation of geodesic paths in filament winding process

Gomes, Edgar dos Santos 18 May 2009 (has links)
Materiais compósitos são conhecidos pela alta resistência mecânica e baixo peso, desempenho superior, resistência à corrosão e baixa densidade. A produção de um material composto possui vários processos com particularidades diferentes. O enrolamento filamentar (Filament Winding) é um processo no qual fibras de reforço contínuas são posicionadas de maneira precisa e de acordo com um padrão predeterminado para compor a forma do componente desejado. As fibras, submetidas à tração, são enroladas continuamente ao redor de um mandril que tem a forma do produto final, em geral utilizando equipamentos automáticos. No final do processo, após a cura da resina, o mandril é geralmente removido. Desta forma, é de fundamental importância que o projetista disponha de recursos computacionais adequados para o cálculo das trajetórias e sequenciamento de posicionamento das fibras. Esse trabalho tem como objetivo o desenvolvimento de procedimentos matemáticos para cálculo de trajetórias geodésicas no processo de \"Filament Winding\" e implementá-los em um ambiente computacional em linguagem de alto nível Java, considerando-se os casos de revestimento circunferencial, helicoidal e polar. São desenvolvidos dois estudos de caso: tubos cônicos e vasos de pressão, e os resultados apresentados e discutidos, validando os procedimentos e ambiente implementado. / Composite materials are well known by the high strength and low weight, superior performance, resistance to the corrosion and low density. The production of a composite material part involves some processes with different requirements. The filament winding process is an automated process in which continuous reinforcement fibers are lay down in prescribed paths on the surface of a mandrel, which is generally removed after the cure of the resin. In such a way, it is fundamental that the designer uses computational resources for the calculation of the paths and sequence of the fibers. In this work is developed the mathematical procedures for calculation of geodesic trajectories in the Filament Winding process and implements them in a computational environment in high level language Java, considering the circumferential, helical and polar strategies. Two case studies are developed successfully: conical pipes and pressure vessels, and the results presented and discussed, validating the procedures and implemented environment.
50

Desenvolvimento de metodologia para parametrização de equipamentos mecânicos pressurizados / Development of methodology for parameterization of pressurized mechanical equipments

Santos, Alan Garcia 07 October 2011 (has links)
Trata do desenvolvimento de uma metodologia para parametrização de equipamentos mecânicos pressurizados. Objetiva criar sistemas para geração de famílias de equipamentos petroquímicos e reduzir o tempo total de elaboração do projeto, desenhos e listas de materiais em até 80%, diminuir em até 70% o tempo consumido na geração de fichas de corte e mapas de solda na execução de roteiros de fabricação e ainda aprimorar a aquisição de materiais e componentes devido à padronização das entradas de projeto. Relata que os sistemas CAD (Computer-Aided Design) tridimensionais paramétricos têm papel cada vez mais destacado no desenvolvimento de equipamentos, porém alguns setores tradicionais da indústria brasileira apresentam ainda certa resistência ao emprego desta tecnologia. Demonstra que diante dos desafios impostos pela exploração de petróleo na camada do Pré-Sal e o grande volume de investimentos da PETROBRAS na expansão do setor produtivo ligado à extração e refino de petróleo, as empresas fornecedoras de equipamentos para o setor petroquímico são obrigadas a se modernizar e buscar novos paradigmas de projeto e fabricação para atender à demanda. Explica que o emprego produtivo de sistemas CAD 3D paramétricos se torna essencial neste cenário. Aplica a metodologia que foi desenvolvida baseada na abordagem top-down para modelagem de montagens, e afirma esta metodologia pode ser adaptada a qualquer sistema CAD 3D paramétrico comercial, com baixo consumo de recursos computacionais. Apresenta para validação um exemplo de aplicação passo a passo da metodologia para um equipamento. Mostra que a metodologia foi aplicada também para a construção de uma família de vasos de pressão verticais suportados por saia, com o intuito de avaliar o desempenho, com a obtenção de resultados significativos. Discute os problemas e dificuldades enfrentados na implantação do sistema paramétrico, juntamente com as alterações que este sistema trás na estrutura organizacional tradicional de empresas de bens de capital. Conclui que a metodologia desenvolvida apresentou resultados dentro dos objetivos estabelecidos e é uma alternativa viável para projetos mecânicos, que possibilita ganho de produtividade significativo. / This work addresses a methodology for the parameterization of pressurized mechanical equipments. It focuses on creating systems to generate an assembly of petrochemical equipments, hence reducing the total time of project designs, layouts and bill of material until 80%, decreasing until 70% the time consumed for executing manufacturing instructions and also improving materials and components acquisition due to the standardization of project entries. The study reports that three-dimensional parametric CAD systems (Computer-Aided Design) have an increasingly prominent role in the development of equipments, however some traditional sectors in the Brazilian industry are still somewhat resistant to using this technology. This work shows that with the challenges posed by oil exploration in the pre-salt layer and PETROBRAS large investments in the productive expansion sector for oil extraction and refining, the equipment supply companies servicing the petrochemical industry are forced to modernize and seek new design and manufacturing paradigms to meet the demands. It explains that the productive use of 3D parametric CAD systems are essential in this scenario. The methodology that was developed based on the top-down approach for assembly modeling is applied, thereby showing that this methodology can be adapted to any commercial 3D parametric CAD system, with low computational consumption of resources. For validation, it shows a step by step application example of the methodology in one equipment. It shows that the methodology was also applied to the construction of a family of skirt supported vertical pressure vessels, in order to evaluate the performance, with significant results. This work discusses the problems and difficulties faced in implementing the parametric system, along with the changes this system brings in the traditional organizational structure of capital goods companies. It concludes that this methodology presented results within the stated objectives and that it is a viable alternative for mechanical designs, hence enabling significant productivity gains.

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