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Lim, C. S. "Plastic limit pressures for pressure vessels with defects at openings." Thesis, Cardiff University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234339.
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Kianbakhsh, Pejman. "Recycling polymer composite hydrogen pressure vessels." Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546472.
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By 2002 the world market for polymer composites was 7.2 Million Tons. The automotive and industrial vehicle industry consumes 25% of the world's composite material output. Composite materials benefit the automotive industry in multiple ways. Regulatory pressure that encourages recyclablity and reduction of energy consumption pushes automotive manufacturers to consider new technologies to meet these environmental standards. The work being undertaken in this research is part of an ED integrated Project under the "Sixth Framework of Research and Development Funding". The project title is "Hydrogen Storage Systems for Automotive Application (StorHy)". Within this project, the Recycling Work Package (WP5) aims to develop recycling techniques for glass and carbon fibre reinforced polymer composite pressure vessels that were proposed for hydrogen storage. This thesis describes the development of a SIze reduction technique for the carbon/epoxy and glass/PP pressure vessels with respect to the particle size and investigates ways of preparing the granulated fractions for subsequent processing. An image analysis technique was successfully developed for the characterisation of the reground material from the carbon/epoxy pressure vessel. The same image analysis technique could not be used to analyse the reground material produced from the thermoplastic vessel. Alternatively, the reground material from the thermoplastic vessel were characterised through a sieve analysis technique. The reground material from the thermoset vessel produced in this work could be processed in a fluidized bed rig which is mentioned in a number of publications. In this work, the reground material from the thermoplastic vessel was successfully processed using an injection moulding machine, with mechanical properties as good as comparable to commercial composites. In this study micro mechanical models available in the short fibre composite literature such as Halpin-Tsai and the rule of mixtures were used to predict the stiffness of the injection moulded composites. The trend observed for the Halpin-Tsai model appeared not to be in a good agreement with the experimental data but the rule of mixtures model was found to predict the experimental data more accurately.
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Tenace, Michael A. "Optimal design of fibre composite pressure vessels." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5819.
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Fibre composite pressure vessels are replacing conventional metallic vessels because of their higher efficiencies (stored energy/unit weight). In this study, multi-layered fibre composite pressure vessels have been designed using a Direct Search method to simultaneously determine the optimal design parameters of layer thickness and wind angle (based upon maximum vessel efficiency according to an interactive failure theory). It was shown that the ability of the fibre composite pressure vessel to resist the internal pressure without failure increased with increasing total wall thickness, up to a certain limit, after which little or no increase in failure pressure was possible. It was also shown that an improved design of a fibre composite pressure vessel can be accomplished by increasing the number of individual equal thickness layers in the vessel wall. Additional improvement in the design can be obtained by allowing the thickness of each individual layer to vary, especially for thicker vessels. Peak vessel efficiency generally occurred at the same wall thickness, implying the efficiency is mostly affected by the type of fibre/matrix combination selected. A slight improvement in efficiency was noticed by increasing the number of individual layers and allowing their thicknesses to vary. Finally, the manufacturing and testing aspects are described.
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Little, Andrew P. F. "The performance of corrugated carbon fibre pressure vessels under external pressure." Thesis, University of Portsmouth, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323284.
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Setlock, Robert J. "Hydrostatic pressure retainment." Ohio : Ohio University, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1091108803.
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Hovsepian, Sarah. "Digital material skins : for reversible reusable pressure vessels." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/72807.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 50-51).
Spacecraft missions have traditionally sacrificed fully functional hardware and entire vehicles to achieve mission objectives. Propellant tanks are typically jettisoned at different stages in a spacecraft mission and left to burn in the atmosphere after one use, creating a substantial amount of waste and redundancy which leads to high operational costs. Spaceflight programs cannot continue to rely on current methods of discarding hardware, since the cost to transport materials from Earth is extremely high. Significant improvements need to be made in recovery and reuse of valuable hardware, to be able to lower costs per mission and increase the number of missions. Strategies need to focus on avoiding complete loss of hardware. This thesis proposes a new class of materials called digital material skins, that will revolutionize the fabrication and assembly of everyday functional objects to spacecraft structural applications, by embedding the intelligence not in the fabrication tools but in the materials themselves, to create reusable and recyclable materials. A workflow for digital material skins is also demonstrated, based on existing fabrication tools to rethink the entire lifecycle of functional skins from design to fabrication to disassembly. When a child builds a structure out of Legos, precision lies not in the human assembler but in the material, component geometry, and linking mechanism to dictate how and where each material interlocks within the larger material system. A digital material skin is made of discrete units with a finite set of parts and joints used to construct a functional structural skin for airtight,waterproof, high or low pressure applications.The surface is enclosed or the surface is open. Digital material skins are used to construct any shape or interior volume that is regular or amorphous. A digital material skin is an exterior structure which relies on an interior digital material structure for support, or a digital material skin is self-supported with few or no interior support. Parts and links are arranged and configured in a regular pattern to create a surface larger than the units themselves. The skin is part of a larger assembly or part of a single unitary structure of any size or shape. The skin may have a thickness that is smaller or larger than any dimension. The skin is made of one or more layers of one material or multi-material units. The joints are reversible, allowing transfer of forces from one unit to adjacent units to create a continuous bulk material. The work will develop a prototype of a digital material skin concept for pressure vessel skins, and adumbrate a new design methodology that considers the entire lifecycle of digital material skins.
by Sarah Hovsepian.
S.M.
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Kandaz, Murat. "Computer Aided Design And Structural Analysis Of Pressure Vessels." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607261/index.pdf.
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This study is conducted for the design and analysis of pressure vessels and associated pressurized equipment using various codes and methods. A computer software is developed as the main outcome of this study, which provides a quick and comprehensive analysis by using various methods utilized in codes and standards together with theoretical and empirical methods which are widely accepted throughout the world.
Pressure vessels are analyzed using ASME Boiler and Pressure Vessel Code, whereas auxiliary codes, especially ASCE and AISC codes are utilized for structural analyses of these equipment. Effect of wind, seismic, and other types of loadings are also taken into consideration in detail, with dynamic analyses. Support structures and their auxiliary components are also items of analysis.
Apart from pressure vessels, many pressurized process equipments that are commonly used in the industy are also included in the scope of the study. They include safety valves which are an integral part of those kinds of pressurized or enclosed systems, two of the heat exchanger components with great importance -tubesheets and expansion joints-, and API 650 tanks for oil or water storage.
The computer software called as VESSELAID is written in Microsoft Visual Basic 6.0 using SI units. Design and analysis methods of VESSELAID are based on various code rules, recommended design practices and alternative approaches.
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Rohrauer, Greg. "Ultra-high-pressure composite vessels with efficient stress distributions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0015/NQ43586.pdf.
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CASTRO, ARISTAGORAS MORAES DE. "STRESS ANALYSIS NOZZLES IN PRESSURE VESSELS WITH CONICAL CAPS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1992. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=25613@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORO presente trabalho tem por objetivo o estudo de tensões críticas em bocais cilíndricos soldados a vasos de pressão, também cilíndricos, com tampas de geometria cônica submetidos a pressão interna e a um carregamento axial externo. O problema é atacado analiticamente através da teoria de cascas de revolução, particularizada para cascas finas axissimétricas. É utilizado o método de flexibilidade para imposição da continuidade dos esforços e deslocamentos nas junções bocal/tampa e tampa/vaso. Foi desenvolvido um programa de computador que fornece as tensões máximas que ocorrem no bocal, bem como as resultantes de tensão, momentos, deslocamentos e rotações ao longo da estrutura. Observou-se que para uma dada configuração do sistema (diâmetros do bocal e vaso, e ângulos da tampa cônica) existe uma relação ótima entre as espessuras do bocal e da tampa, para a qual o fator de concentração de tensões é mínimo. Esta relação é independente da rasão entre os carregamentos axial e a pressão.
The present work is concerned whit critical stresses due to the combined affect of axial loads and intornal pressure in nossles welded to cilindrical pressure vessels whit conical hoads. The problem is treatod analytically through, axisimetric, thin ahell theory. The method of flexibility is employed to enforce the continuity of loads, moments, displacements and rotations at the junctions. A computer code has been developed for the calculation of the critical atresses in the nozzle, as well as the stresses resultants, moments, displacements, and the rotations along the atracture. It has been observed that for a griven configuration (nozzle and vessel diameters and angle of the conical head), there is an optimum between the nozzle and head thickness for which the stress concentration factor is minimum. This ratio is independent of the relation between the axial hoad and internal pressure.
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Zhao, Yingzi, and 趙瑩子. "Acute and chronic impact of pressure on vascular responsiveness." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/207185.
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Hypertension leads to vascular complications including endothelial dysfunction, heart failure and stroke. The purpose of the present studies was to investigate the chronic and acute impact of high pressure on vascular responsiveness.
In Study I, isometric tension measurements demonstrated that contractions to phenylephrine, in the presence of indomethacin (inhibitor of cyclooxygenase), were smaller in aortae of spontaneously hypertensive rats (SHR) with, than in those without, endothelium, while they were comparable in such preparations of normotensive Wistar-Kyoto rat (WKY); the difference in SHR aortae was not affected by L-NAME [inhibitor of nitric oxide synthase (NOS)]. This endothelium-dependent, NOS-independent inhibition of phenylephrine-induced contraction was greater in older SHR (36 versus 18 weeks), and abolished by NO scavengers and ODQ (inhibitor of soluble guanylyl cyclase). It was observed not only in the presence of indomethacin but also apocynin (antioxidant), but inhibited by diphenyleneiodonium (inhibitor of cytochrome P450 reductase). These results suggest that the endothelium-dependent, eNOS-independent inhibition is caused by NO produced by cytochrome P450 reductase in the endothelium of the SHR aorta.
Study II investigated the mechanisms underlying the reduced contractions to prostaglandin E2 [agonist of prostaglandin E2 and thromboxane-prostanoid (TP) receptors] by a previous exposure to phenylephrine (agonist of α1-adrenoceptor) in the aortic smooth muscle of the SHR. This inhibition induced by the pre-activation of α1-adrenoceptor was augmented in aortae of older SHR (36 versus 18 weeks) and was not present in WKY preparations. Pre-exposure to the protein kinase C (PKC) activator, phorbol 12,13-dibutyrate, also inhibited subsequent contractions to prostaglandin E2 in SHR aortae. Inhibition of PKC by calphostin C abolished the effect of pre-exposure to phenylephrine. The mRNA expressions of PKC isoforms differed in WKY and SHR smooth muscle. These experiments suggest that in the SHR but not the WKY aorta, α1-adrenergic activation causes heterologous desensitization of TP receptor through activation of a specific PKC isoform(s).
In Study III, experiments were performed in a pressure myograph to determine whether or not acute elevation of transmural pressure in the isolated carotid artery of adult mouse (10-12 weeks) impairs endothelium-dependent dilatation by increasing angiotensin II expression or by directly activating AT1 receptors. Transient exposure of arteries to increased pressure (150 mmHg, three hours) inhibited endothelium-dependent, NO-mediated dilatations to acetylcholine, but did not affect responses to the NO donor DETA-NONOate. Inhibiting angiotensin II signaling or angiotensin converting enzyme prevented the impairment of endothelium-dependent dilatation by elevated pressure. Elevated pressure increased the expression of angiotensinogen [precursor of angiotensin II]. Thus, exposure of carotid arteries to elevated pressure leads to local release of angiotensin II, which activates AT1 receptors to cause endothelial dysfunction.
In summary, chronic increased pressure increased the endothelial NO release produced by cytochrome P450 reductase from nitrate and developed the heterologous desensitization of TP receptor caused by PKC in SHR aorta. Acute increased pressure impaired endothelium-dependent NO-mediated vasodilatation by activation of local angiotensin system in adult mouse carotid artery. These processes likely contribute to the pathogenesis of hypertension-induced vascular dysfunction and organ injury.published_or_final_version
Pharmacology and Pharmacy
Doctoral
Doctor of Philosophy
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Nadarajah, Chithranjan. "A design study of nozzles and attachments in pressure vessels." Thesis, University of Strathclyde, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338935.
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Charles, Ian David. "Ratchetting strains in pressurised pipes." Thesis, Coventry University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302999.
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Ellis, M. B. D. "Fracture mechanics in a 2.25Cr-1Mo pressure vessel steel." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382220.
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Hu, Jianbing. "Modeling and simulation of high pressure composite cylinders for hydrogen storage." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Hu_09007dcc805d8846.pdf.
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Thesis (Ph. D.)--Missouri University of Science and Technology, 2009.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 9, 2009) Includes bibliographical references.
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King, Benjamin. "Welding and post weld heat treatment of 2.25%Cr-1%Mo steel." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060404.095844/index.html.
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Soboyejo, Winston Oluwole. "The propagation of defects under fatigue loading." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257906.
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Fowler, Hamish. "The influence of warm prestressing and proof loading on the cleavage fracture toughness of ferritic steels." Thesis, University of Bristol, 1998. http://hdl.handle.net/1983/39f337c6-2760-4f16-99bf-85fa841d63b1.
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This thesis presents a combination of numerical and experimental studies performed to assess the influence of the warm prestress effect on the cleavage fracture toughness of two ferritic pressure vessel steels. The aims of the research are to gain a detailed knowledge of the materials low temperature response under uniaxial and fracture conditions; to examine, using the finite element method, crack tip stress fields during warm prestress LUCF load cycles; and provide a clear and consistent method of classifying the warm prestress effect. An experimental programme investigated the room temperature and low temperature response of two candidate steels, A533B and BS1501. These steels were tested uniaxially under monotonic and cyclic conditions, and in the cracked condition in the as-received and warm prestressed conditions. Application of a three parameter statistical model to the experimental data showed that the distribution of data in the as received and warm prestressed conditions can be described accurately. The shift in the cleavage toughness distribution following warm prestressing was predicted by combining the statistical model with a validated analytical model of the warm prestress effect. Repeated proof loading was shown to increase cleavage toughness in A533B steel, providing the loading was load controlled. There were negligible effects of repeated proof loading on BS1501 steel. Some further enhancement of cleavage fracture toughness was observed when sub critical crack extension was introduced following warm prestressing, although the results were highly scattered. The finite element method was employed to simulate experimental fracture events. It was found from these simulations that fracture occurs following warm prestressing, when the reloaded crack tip stress distribution matches the as-received fracture crack tip stress distribution. The stress matching was observed to occur well into the elastic stress field ahead of the crack tip. This fracture criterion was employed to provide predictions of cleavage toughness following varying applied preload levels. The results were compared to experimental data sets and various analytical models. The Chell model of the warm prestress effect was observed to provide the best agreement with the finite element predictions. Crack tip blunting during the preload steps was found to have no influence on the predictions of cleavage fracture toughness. Differences in hardening response of the material was also shown to have little influence of the predictions of cleavage toughness. Simulations incorporating sub critical crack extension prior to reloading to fracture demonstrated that cleavage 'toughness can be enhanced further by limited crack extension. Large increments of crack growth were shown to reduce the warm prestress effect. The finite element predictions were validated against the appropriate analytical solution proposed by Chell and experimental results.
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Sidorenko, Igor. "Pressure effects on fluidized bed behaviour." Monash University, Dept. of Chemical Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/9541.
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Watt, Gerald. "An investigation of the use of metal matrix composites for pressure vessels." Thesis, University of Surrey, 2018. http://epubs.surrey.ac.uk/845776/.
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Continuous reinforcement metal matrix composites (MMCs) have yet to become widely used within the aerospace industry. Despite the high stiffness and strength of unidirectional MMCs, the complexity and inherent cost of manufacture are major factors that have prevented the widespread uptake of these advanced materials. Furthermore, the relatively poor mechanical performance of unidirectional MMCs subjected to transverse loads has largely precluded their use in structures which experience complex loading (with the notable exception of bladed compressor discs in gas turbines). Recently, TISICS has been involved in projects with two major aerospace companies to investigate the use of titanium and aluminium matrix composites. In both projects it was necessary to examine the properties of less conventional cross-ply composites and the work undertaken by the author in conjunction with these projects forms the basis of this EngD thesis. A range of MMC layups were tested in tension, compression and shear and detailed microscopy was undertaken to investigate the failure processes. A simple rule-of-mixtures approach was found to show good agreement with the unidirectional tensile test results. Subsequently, a more complex approach taking ‘weighted’ averages for biaxial and multiaxial laminates at a ply level was developed and this enabled full tensile response of the composites to be modelled, albeit with some limitations in low strain response. Part of the work which was conducted to increase the understanding of cross-ply composites involved the determination of residual stresses. Although cross-ply MMCs were thought to have greater axial residual stresses than unidirectional MMCs, the variation of residual stresses throughout the eight ply laminates was found to change significantly (from 0.37% in the innermost to 0.23% in the outermost plies) depending on the sub-laminate sequence. Finite element modelling predictions were compared to the experimental residual stress determination techniques and it was found that the FE modelling underestimated the strains in cross-ply composites. Both aluminium and titanium pressure vessels were manufactured and tested; the mechanical data from pressurisation was compared to simple analytical modelling and macroscale FEA. Metallographic samples studied from the failed vessels showed deficiencies in manufacture and a rudimentary form of acoustic emission showed that damage was incurred at relatively low strains, but did not propagate to failure during the proof test cycles. This suggests that with adequate provisions, the development of damage within a cross-ply layup does not need to rule out its use in a non-critical tank application.
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Dyess, Mark Vernon. "OPTIMIZATION OF THE MATERIAL SELECTION PROCESS FOR CRYOGENIC COMPOSITE OVERWRAPPED PRESSURE VESSELS." MSSTATE, 2008. http://sun.library.msstate.edu/ETD-db/theses/available/etd-03272008-163646/.
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The objective of this research was to develop a test methodology for the evaluation of materials for possible use in cryogenic composite overwrapped pressure vessels (COPVs). This paper investigates various micromechanical and macromechanical techniques to test the interaction between fibers and resins. Uniaxial tension testing was performed at ambient and cryogenic temperatures on neat resin samples, straight-sided composite specimens, and NOL ring specimens. COPVs were constructed and burst tested to provide a performance comparison. Results show resins suitable for use at cryogenic conditions display a LN2 temperature elongation to failure greater than 2% and an ambient temperature elastic modulus less than 35 MPa. NOL rings were determined to be the preferred composite test method rather than straight-sided specimens. Mechanical performance of the NOL rings compares well with actual COPV performance.
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Balasubramaniam, Krishna. "A finite element procedure for assessing continuous flaws in clad pressure vessels." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/11800.
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Durrant, J. C. "The design and analysis of pressure vessels using the finite element method." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368008.
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Masu, Leonard Mbevi. "The effect of cross bore geometry on the strength of pressure vessels." Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369175.
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Ong, L. S. "The effect of high internal pressure on cylindrical vessels with geometric imperfections." Thesis, University of Strathclyde, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371964.
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Viehrig, Hans-Werner, Eberhard Altstadt, Mario Houska, Gudrun Mueller, Andreas Ulbricht, Joerg Konheiser, and Matti Valo. "Investigation of decommissioned reactor pressure vessels of the nuclear power plant Greifswald." Helmholtz-Zentrum Dresden - Rossendorf, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-235681.
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The investigation of reactor pressure vessel (RPV) material from the decommissioned Greifswald nuclear power plant representing the first generation of Russian-type WWER-440/V-230 reactors offers the opportunity to evaluate the real toughness response. The Greifswald RPVs of 4 units represent different material conditions as follows:
• Irradiated (Unit 4),
• irradiated and recovery annealed (Units 2 and 3), and
• irradiated, recovery annealed and re-irradiated (Unit1).
The recovery annealing of the RPV was performed at a temperature of 475° for about 152 hours and included a region covering ±0.70 m above and below the core beltline welding seam.
Material samples of a diameter of 119 mm called trepans were extracted from the RPV walls. The research program is focused on the characterisation of the RPV steels (base and weld metal) across the thickness of the RPV wall. This report presents test results measured on the trepans from the beltline welding seam No. SN0.1.4. and forged base metal ring No. 0.3.1. of the Units 1 2 and 4 RPVs. The key part of the testing is focussed on the determination of the reference temperature T0 of the Master Curve (MC) approach following the ASTM standard E1921 to determine the facture toughness, and how it degrades under neutron irradiation and is recovered by thermal annealing. Other than that the mentioned test results include Charpy-V and tensile test results. Following results have been determined:
• The mitigation of the neutron embrittlement of the weld and base metal by recovery annealing could be confirmed.
• KJc values of the weld metals generally followed the course of the MC though with a large scatter.
• There was a large variation in the T0 values evaluated across the thickness of the multilayered welding seams.
• The T0 measured on T-S oriented SE(B) specimens from different thickness locations of the welding seams strongly depended on the intrinsic structure along the crack front.
• The reference temperature RT0 determined according to the “Unified Procedure for Lifetime Assessment of Components and Piping in WWER NPPs - VERLIFE” and the fracture toughness lower bound curve based thereon are applicable on the investigated weld metals.
• A strong scatter of the fracture toughness KJc values of the recovery annealed and re-irradiated and the irradiated base metal of Unit 1 and 4, respectively is observed with clearly more than 2% of the values below the MC for 2% fracture probability. The application of the multimodal MC-based approach was more suitable and described the temperature dependence of the KJc values in a satisfactory manner.
• It was demonstrated that T0 evaluated according to the SINTAP MC extension represented the brittle fraction of the data sets and is therefore suitable for the nonhomogeneous base metal.
• The efficiency of the large-scale thermal annealing of the Greifswald WWER 440/V230 Unit 1 and 2 RPVs could be confirmed.
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Olsen, Gregory Dana. "Experimental investigation into catastrophic failure of pressure vessels due to hypervelocity impact /." Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3008411.
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Sterjovski, Zoran. "Investigation of postweld heat treatment of quenched and tempered pressure vessel steels." Access electronically, 2003. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20031127.160623/index.html.
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Jones, Daniel Thomas. "The advanced winding patterns and analysis for dome-ended filament wound pressure vessels." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362907.
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ADAME, WALLACE MOREIRA. "ON THE ANALYSIS BEHAVIOUR OF CYLINDRICAL PRESSURE VESSELS CONSIDERING PLATE TO SHELL JUNCTION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2018. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=36065@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Este trabalho apresenta a análise numérica de vasos de pressão cilíndricos modelados por cascas e placas axissimétricas submetidas a carregamento de pressão interna uniformemente distribuída, utilizando-se a técnica de elementos finitos. São consideradas análises de junções entre superfícies com diferentes espessuras, tais como paredes finas (razão entre o raio e a espessura superior a 10) e moderadamente espessas (razão entre o raio e a espessura inferior a 5). Os campos de deslocamento considerados são os referentes aos elementos planos axissimétricos. A partir deste modelo são avaliadas as tensões na transição entre as superfícies e os resultados comparados com soluções analíticas simplificadas. Conclui-se que a solução analítica aproximada é aceitável para uma grande faixa de valores envolvendo placas e cascas de espessuras moderadamente espessas, enquanto que, para paredes finas, a análise por elementos finitos é necessária para verificação do comportamento das tensões na junção. Testes numéricos utilizando o programa ANSYS são apresentados para demonstrar o desempenho de análises lineares axissimétricas, empregando elementos quadráticos em comparação com as soluções analíticas e avaliando também as limitações do modelo analítico na região da descontinuidade geométrica do modelo proposto.
This work presents the numerical analysis of cylindrical pressure vessels, modeled using axisymmetric shells and plates elements under internal pressure loads. The numerical analysis considers surface joints for various surface thickness ratios, from thin (ratio between radius and thickness greater than 10) to thick (ratio between radius and thickness less than 5) shells. Element displacement fields of axisymmetric plane elements are used to evaluate the stress state at the surfaces junctions, and the obtained results are compared to simplified analytical solutions. It is concluded that analytical approximate results present an acceptable solution for a large range of plates to shells geometries up to moderately thick shells, whereas for thin shells the finite element solution is necessary to be considered in order to accurately verify the stresses at plate to shell junction. Numerical tests applying ANSYS program are presented to demonstrate the performance of linear axisymmetric analysis applying quadratic elements in comparison to the analytical solutions also evaluating the limitations of the analytical model in the region of the geometric discontinuity of the proposed model.
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Rojek, Jan. "Effect of voids in thick-walled pressure vessels : Experimental observations and numerical modelling." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLM015.
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Dans cette thèse, on analyse l'effet de la porosité sur le comportement mécanique d'un matériau composite à fibres de carbone utilisé dans le cadre d'applications à hautes performances. Les réservoirs hyperbare destinés au stockage de l'hydrogène en sont un exemple. Du fait de leur fabrication par enroulement filamentaire, ces structures à parois épaisses présentent des taux de porosité parfois très élevés. La conséquence de telles porosités sur la durabilité des réservoirs et plus largement sur des structures composites chargées de manière multi-axiale est très peu documentée. Les travaux présentés ici s'inscrivent par ailleurs dans le développement d'un modèle existant à MINES ParisTech et ayant fait ses preuves pour prédire la résistance de composites unidirectionnels. Il s'agit ici de perfectionner ce modèle en intégrant de nouveaux facteurs comme les porosités. Des observations (tomographie aux rayons X et microscopie optique) d'un réservoir sont réalisées afin de caractériser les vides et leur distribution au sein de la structure. En parallèle, une étude expérimentale est conduite sur des éprouvettes à différents taux de porosité. La résistance de ces éprouvettes, chargées simultanément en traction longitudinale et compression transverse, est évaluée grace à un système expérimental spécialement conçu. A des échelles encore plus fines, des essais sont réalisés sur des échantillons d'époxy entaillés pour caractériser la croissance des cavités microscopiques et le comportement mécanique de la résine sous un état des contraintes multi-axial. Toutes ces données expérimentales sont ensuite exploitées et intégrées dans le modèle numérique afin de simuler le comportement à rupture d'un réservoir à parois épaissesThe topic of this thesis is the influence of voids on the mechanical properties of carbon fibre reinforced polymers used in high performance applications, such as pressure vessels for hydrogen storage. Manufactured through filament winding, these thick-walled structures can show a significant void content. The effect of these voids on the strength of pressure vessels and, more in general, on the strength of composite structures subjected to multiaxial loads, is not thoroughly understood. The work presented in this thesis is carried out in the context of an existing model of tensile failure of unidirectional composites developed at MINES ParisTech. The objective of the work presented here is to take into account additional factors, such as void content. X-ray tomography and optical microscopy observations are carried out to characterize voids in a carbon-epoxy pressure vessel. In another experimental study, mechanical tests are performed on carbon-epoxy specimens with different levels of void content. The influence of a biaxial load (longitudinal tension and through-thickness compression) is evaluated using a custom-designed experimental setup.At the microscopic scale, tests on notched epoxy specimens are carried out to investigate microscopic void growth and the mechanical behaviour of the resin under a multiaxial stress state. Finally, a numerical approach to modelling failure of a thick-walled cylinder is proposed in the framework of the multiscale fibre break model, taking into account the experimental observations
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Shum, Pak W. "A critical analysis of the acoustic emmission technique for NDE of pressure vessels." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-09192009-040341/.
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Endersby, Stephen. "Numerical analysis of a thick cylinder in the presence of cracked crossbore and axial holes." Thesis, Northumbria University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245277.
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Chapman, Benjamin James. "Continuous fibre reinforced thermoplastic pipes." Thesis, University of Newcastle Upon Tyne, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285377.
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Bagshaw, Nick. "A study of leak rates through narrow cracks." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366150.
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SILVA, MARIA C. A. T. da. "Introducao a analise de vasos de pressao em concreto protendido multicavidade." reponame:Repositório Institucional do IPEN, 1986. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9867.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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OLIVEIRA, CARLOS A. de. "Um modelo para a analise estrutural de flanges de vasos de pressao nucleares." reponame:Repositório Institucional do IPEN, 1987. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9871.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Rogers, Craig A. "An axisymmetric linear/high-order finite element for filament wound composite structures." Diss., Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/52316.
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The development of an axisymmetric linear by high-order finite element to model filament-wound structures is presented. The primary objective of this work was to develop a ’design code' to analyze filament wound spherical pressure vessels. In order to develop a design-oriented analysis capability which can produce accurate results rather quickly with reduced input-data requirements, the total number of system equations must be reduced. To accomplish this task, a linear by high-order element was formulated which uses a single high-order displacement field finite element to model the total thickness of an axisymmetric composite structure. The displacement order for the in-plane direction remains linear, while the transverse order is user selectable. Numerical integration for stiffnesses is evaluated with respect to varying material properties and lamirna thicknesses in each individual element. Results from a computational economy study are presented showing potential time savings of 40 percent when compared to the conventional modeling scheme of using bi-linear elements. Actual test cases indicate that computation time savings may be as great as 55 percent when using linear by fourth-order elements and 45 percent when using linear by sixth-order elements. The accuracy of the element was evaluated by comparing the finite element results to elasticity solutions for isotropic, orthotropic, and filament-wound cylindrical pressure vessels. Most of the finite element results indicated a ±3 percent maximum error of the stresses compared to the elasticity results. The new linear by high order element stress results were nominally within ±2 percent of stresses calculated with conventional bilinear elements. Comparisons of finite element results for an actual filament-wound spherical pressure vessel slowed that linear by third- or fourth-order elements may be adequate for preliminary design purposes while the higher-order elements generally correlated better with the conventional bi-linear elements. Also presented is an outline of the design code and sample results for spherically wound pressure vessels.Ph. D.
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Harris, David Malcolm. "The effect of pre-exposing the microbial population on gas production using the Pressure Transducer Technique." Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242337.
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Manu, Christopher Corneliu. "Finite element analysis of stress rupture in pressure vessels exposed to accidental fire loading." Thesis, Kingston, Ont. : [s.n.], 2008. http://hdl.handle.net/1974/1295.
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Grigorian, H. "Nonlinear sensitivity analysis and its application to the optimal shape design of pressure vessels." Thesis, Swansea University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637180.
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A method of calculating design sensitivities for non-linear continuum systems is presented. The sensitivity process is established through operating on the converged solution of a set of non-linear equations which have been solved by the finite element method. The method is applied to structural elasto-plastic problems with particular emphasis being placed on the load sensitivities with respect to geometry. Comparisons are made using forward and backward approximations on the two results. Furthermore this thesis is concerned with the development and application of a numerical design model for shape optimization of pressure vessel structures under internal pressure. The main objective is the minimisation of the maximum plastic strains such that optimal designs can be produced.
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Milososka, Katarina, and Louise Nylander. "Value Stream Mapping of GKN Aerospace Applied Composites production of pressure vessels and radomes." Thesis, Linköpings universitet, Kommunikations- och transportsystem, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-119939.
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Examensarbete är utfört på GKN Aerospace Applied Composites (ACAB) där produktionsflödet för fyra produkter har kartlagts. Idag upplever företaget svårigheter med att hålla leveranstiden för dessa produkter, dessutom upplevs verkstäderna som ostrukturerade. GKN Aerospace Applied Composites tillverkar idag flertalet produkter i komposit till både den civila och militära marknaden. För detta examensarbete har flödet av tre stycken radomer och en storlek av tryckkärl kartlagts. Tryckkärl är en produkt som tillverkas i större volymer och har ett flödesorganiserat produktionsupplägg. Radomerna är kundorderspecifika produkter som endast tillverkas i enstyck eller mindre volymer. Detta innebär att radomverkstaden är funktionellt organiserad. Med ett varierande och växande produktsortiment ökar kraven på produktionsplaneringen och hantera kombinationen av de två olika produktionsuppläggen. För att kunna ta fram förbättringsförslag för framtiden har en analys genomförts av produktionen. Förbättringsförslagen resulterar i studiens rekommendationer och förbättringsplan till ACAB. Den metod som använts är Value Stream Mapping (VSM), som är en metod i Lean filosofin. Denna metod används för att eliminera alla former av slöseri genom att identifiera värdeskapande och icke värdeskapande tid. För att sammanställa en VSM för respektive produkt genomfördes en datainsamling som bestod av intervjuer, observationer och uppmätningar av flödenas avstånd. För varje produkt identifierades problemområden med tillhörande förbättringsförslag, dessa förslag på åtgärder och rekommendationer resulterade i ett framtida alternativt flöde för produktionen. Historisk data har analyserats av genomloppstider, en medeltid för varje process har beräknats ur äldre order för respektive produkt. Som en riktlinje för dagens produktion har ACAB idag standardtider som de planerar leveransdatum efter. Beräknade medeltider har satts i förhållande till standardtiderna för att kunna urskilja vilka processtider som överstiger eller understiger dagens riktlinjer. I de alternativa flödena presenteras åtgärdsförslag för att kunna förbättra verkstädernas layout genom att förkorta de uppmätta avstånden. Utöver jämförelse av tider och avstånd presenteras övergripande åtgärder som 5S och kontinuerlig utbildning av personal. Generellt för båda produktionerna har jämförelsen mellan medeltider och standardtider visat att standardtiderna behöver korrigeras. Korrigeringen av tider medför inte kortare genomloppstider utan bidrar till en bättre planering av leveransdatum. Däremot förväntas de förändringar av layout och organisering som föreslagits för respektive verkstad reducera genomloppstiderna.
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Myles, John Robert. "Electronic Speckle Pattern Interferometry (ESPI) NDE of cracks in pressure vessels with FEA modelling." Master's thesis, University of Cape Town, 1997. http://hdl.handle.net/11427/6922.
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Includes bibliographical references.This dissertation describes the results of an attempt to simulate the Electronic Speckle Pattern Interferometric fringe patterns observed around a crack or combination of cracks in a pressure vessel by finite element methods. Electronic Speckle Pattern Interferometry (ESPI) is a coherent optical measurement technique that produces a contour map of the surface displacement of an object when it is stressed. The sensitivity of the techniques is of the order of half the Wavelength of light. The objective of the study was to determine a procedure for the modelling of interferometric fringes by finite elements. The finite element model may then be used to study the effects of crack geometry on fringe patterns and produce a library of reference fringe patterns for comparison with experimental fringe patterns found for unknown flaws. The approach to the problem was to simulate the fringe patterns for a crack free cylinder and compare these with these observed experimentally. The FE model modulus of elasticity was than to be calibrated to minimise uncertainty in the exact value of the elastic modulus. Once the model was calibrated, various cracks and combinations of cracks were introduced into both the physical cylinders and the FE model and fringe patterns obtained were compared. The experimental results for the cracks and combinations of cracks were compared with the finite element predictions at a range of loads.
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Pierola, Javier. "Three dimensional stress intensity factor for large arrays of radial internal surface cracks in a cylindrical pressure vessel." FIU Digital Commons, 1993. http://digitalcommons.fiu.edu/etd/2514.
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The objective of this study is to present the mode I stress intensity factor distribution (SIF) along the crack-front for a wide array of semicircular and semi-elliptical surface cracks inside of a pressurized thick-walled cylinder. A three-dimensional finite element package ANSYS is used to evaluate the SIF for multicracked cylinder with number of cracks from n=1 to 128, the ratio of crack-depth to the wall thickness a/t=0.05 to 0.6, the ellipticity of the crack (the crack-depth to the semi-crack length) a/c=0.2 to 1.5, the ratio of the outer to the inner radius ro/ ri=2.
A substructuring technique is introduced which solved a coarse model meshed with ten-node isoparametric elements and applied the resulting displacements in the boundary surface of a submodel which is built employing singular elements along the crack-front to produce the 1/√r singularity . The SIF is evaluated using nodal-displacement method.
To validate the modeling and analysis procedure of the present results various configurations were solved using this method and compared to other finite element solutions. The present results were in very good agreement: less than 5 % comparing with Raju and Newman's results and within 8 % of Kirkhope's results.
An empirical equation to calculate the maximum SIF, was developed in this study. The equation was obtained by nonlinear fitting of the finite element results and the error was within ± 5.7 %.
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Vecchi, Rodrigo de. "Regulamentos tecnicos de apoio para atendimento a NR 13." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264073.
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Orientador: Caio Glauco SanchezDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Procurou-se neste trabalho, reunir uma grande quantidade de normas técnicas de inspeção, de projeto e de ensaios não destrutivos a fim de serem sugeridos e principalmente fornecer dados e critérios necessários para a realização segura e apropriada dos exames e testes tidos como mandatórios ou alternativos na NR13. Para isto foi necessária uma pesquisa detalhada do acervo de normas técnicas existentes em nosso país e também em outros países, a fim de obter informações que pudessem ser confrontadas com casos específicos e reais, cujos dados foram coletados com profissionais qualificados e certificados. Três aspectos foram analisados: os requisitos da norma NR13, que é compulsória e tem abrangência geral, critérios específicos utilizados por normas de enfoque singular, ou seja, para uma única linha de equipamento, de teste ou de inspeção e a experiência prática que trouxe a realidade encontrada em muitos estabelecimentos através do resultado de inspeções realizadas para garantir a segurança na operação de vasos de pressão e caldeiras. Vale frisar que tais inspeções fazem parte de nosso acervo técnico pessoal e estão devidamente registradas no CREA através de mais de 600 ART's recolhidas em 8 diferentes estados brasileiros. Também foram apresentados alguns acidentes gerados, talvez, pela execução errônea de testes e inspeções, seguidos por sugestões que poderiam evitar a ocorrência dos mesmos. Os resultados desse trabalho são de grande importância nos futuros estudos e revisões normativas.
Abstract: It was intended to group a large amount of technical standards that treat about Boilers and Pressure Vessel design and inspections and also non destructive examinations in order to suggest and supply data and criteria to perform appropriate and safe inspections and examinations mentioned as mandatory or alternative at NR13. It was necessary an extensive research into Brazilian and foreign standards to collect information which could be confronted with real and specific cases described by qualified and certificated professionals. Three aspects have been analyzed: NR13 requirements which are mandatory and have only a global sight, criteria used in specific situations for unique kind of equipment, test or examination and practical experience that brought the reality of many companies through the result of inspections performed to guarantee a safe operation of pressure vessels and boilers. It is important to emphasize that these inspections belong to a personal technical performance and are registered at CREA through more than 600 ART's paid in 8 different Brazilian states. It was also presented some accidents probably caused by wrong execution of tests and inspections, followed by suggestions which could avoid them. The results obtained from this job are very important in future studies and revisions of normative standards.
Mestrado
Termica e Fluidos
Mestre em Engenharia Mecânica
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Ramirez, G. "Monitoring and prediction of damage in filament wound composite pipes under pressure loading /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Edgar, Christopher Austin. "Improvements to the pool critical assembly benchmark using 3-D discrete ordinate transport with adaptive difference." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49087.
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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.
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Penso, Jorge A. "Fundamental study of failure mechanisms of pressure vessels under thermo-mechanical cycling in multiphase environments /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486399451963218.
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Heath, Melissa. "Heat Transfer Regimes during Charging of Pressure Vessels with Compressed Gas at Low Reynolds Numbers." Thesis, Griffith University, 2018. http://hdl.handle.net/10072/378153.
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Over the past decade signi cant interest in heat transfer during lling of pressure
vessels has arisen due to overheating and under- lling when utilizing compressed
hydrogen gas as a practical storage solution for clean energy sources. The problem
is most clearly evident when hydrogen is stored as compressed gas for use in the
automotive industry since carbon bre reinforced plastic (CFRP) vessels are used
for their low weight. The low thermal conductivity of the plastic component of the
vessel wall has an insulating e ect on the stored gas. During lling, the gas undergoes
heating due to compression work, particularly during lling rates comparable to that
of a traditional vehicle. As the CFRP material can be damaged by overheating, it
is important to be able to predict the temperature of the gas, and the temperature
distribution in the vessel wall. Key to this is understanding the heat transfer between
the gas and the wall during lling. While signi cant progress has been made with
larger vessels, few studies have considered the lower Reynolds number regimes.
The aim of the PhD is to ll the gap in the literature for lower Reynolds number
regimes by providing knowledge and fundamental data required for accurately
predicting heat transfer during lling of gas pressure vessels. The methodologies
being used include experimental work, numerical simulation and analytical methods.
The thesis addresses understanding the heat transfer by experimentally producing
benchmark quality temperature measurements for validation. Experiments
have been undertaken which provide detailed measurements of thermal elds and
heat transfer and the thermal response in the vessel. Computational
uid dynamics
(CFD) is used to determine local Nusselt numbers and understand the development
of boundary layers within the vessel. An analytical solution has been developed
by neglecting convection, essentially treating the vessel as a solid with and evenly
distributed heat source. This model has provided an upper limit on the temperature
rise within the vessel and lower limit on the heat transfer.
The developed analytical solution elucidates the e ect of near wall compression
heating and provides a theoretical limit for the minimum Nusselt number and maximum gas temperature rise in the vessel. The minimum Nusselt number limit is
approached in the case of low Reynolds number. Taking the limit of small Reynolds
number for a vessel being lled with compressed gas, the energy equation was found
to asymptote to the unsteady heat conduction equation with heat generation and
variable density. This equation was solved analytically for cylindrical and spherical
geometry. Assuming the density changes linearly with time, a solution is obtained
which can become identical in form to the constant density solution if the Fourier
number is de ned using a log-mean density rather than the instantaneous density.
For a constant energy input rate the Nusselt number was found to approach a
constant value after an initial transient period. At such 'steady state' conditions, the
Nusselt number based on the diameter for cylinders with aspect ratios larger than 1
rapidly approaches an integer solution of NuD = 8. For cylinders with aspect ratios
less than 1, the Nusselt number based on the cylinder length (height) characteristic
dimension rapidly approaches NuL = 6. It is shown experimentally and numerically
that during compression lling, the heat transfer asymptotically approaches this
analytical solution at low Reynolds numbers.
Four distinct regimes were identi ed during the lling of the vessel. At the
very beginning of lling, heat transfer is dominated by heat conduction and can be
described by the analytical solution. Following this there is a period dominated by
forced convection from the jet of gas entering the vessel. A signi cant temperature
di erence and increased density of the gas causes natural convection currents to
develop as the Rayleigh number increases. Both free and forced convection play an
important role for a period of time which can be described as a mixed convection
regime. As the lling rate and jet penetration into the
ow eld decays forced
convection e ects diminish leaving only free convection which continues after gas
has stopped entering the vessel until thermal equilibrium is reached.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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Bradley, Frederick Joseph. "Thermal shock resistance parameters for the industrial lining problem." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25568.
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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
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Garza, Tanya Cruz. "Single crystal silicon as a macro-world structural material : application to compact, lightweight high pressure vessels." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/62875.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 163-166).
Single crystal silicon has promising inherent structural properties which are attractive for weight sensitive applications. Single crystal silicon, however, is a brittle material which makes the usable strength that can be obtained from silicon devices dependent on flaws or cracks that can arise during fabrication in a sample that begins relatively free of defects. This research explores the use of micro-machined, single crystal silicon (Si) for high-strength macro-scale application and determines its practical advantages when compared to conventional approaches. The major contributions of this thesis includes evaluation of wafer-scale silicon for macro-world applications, identification of cellular pressure vessels as a promising wafer-scale silicon device, identification of design criteria for brittle pressure vessels and quantified metrics for a competitive silicon pressure vessel design, identification of DRIE failure mechanisms, elucidation of the role of wafer-level strength variation related to surface morphology variation in wafer-scale structures, and identification of promising strength recovery techniques and promising avenues to explore for further strength improvements. High pressure vessels for aerospace applications with volumes of 10's of cc's were designed under the premise that the superior strength-to-density ratio of Si and post- processing strength recovering techniques can compensate for fabrication technology limitations that constrain the vessel shape and for the brittle nature of the material. A combination of literature review, analysis, and numerical simulations suggest that there are single crystal silicon fabrication technology compromised pressure vessel designs that can have lower structural mass to pressurant mass ratios than conventional pressure vessel designs at design pressures above about 6000 psi. A honeycomb geometry offered the best results of those studied. The honeycomb silicon pressure vessel offers the possibility of integrated micro-valves, regulators and sensors. Such vessels would be useful for nano and pico satellites and for launch vehicles. Fabrication processes and strength recovering techniques were explored experimentally to understand and improve the usable strength of microfabricated single crystal silicon macro-structures. It was found that silicon strength will vary across a DRIE etched wafer as a result of submicron sidewall roughness variation independent 3 of larger geometric parameter variation. Secondary anisotropic SF6 plasma etching and surface migration were shown to be a promising combination for recovery of microfabricated silicon strength while oxidation and oxide removal offer less promise. Long SF6 smoothing etches revealed significantly varied sidewall roughness from that hidden by overhanging silicon which affects correlations of surface morphology to device strength. An analytical model was developed that correlates silicon strength data found experimentally to the silicon pressure vessel design. The model predicts that reasonable improvements to usable silicon strength need to be made to make a silicon pressure vessel design competitive with conventional designs. Further work on strength uniformity across wafer and strength recovery is recommended to improve the usable strength of wafer-scale, DRIE single crystal silicon devices.
by Tanya Cruz Garza.
Ph.D.