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1
Calmunger, Mattias. "On High-Temperature Behaviours of Heat Resistant Austenitic Alloys." Doctoral thesis, Linköpings universitet, Konstruktionsmaterial, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-122945.
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Advanced heat resistant materials are important to achieve the transition to long term sustainable power generation. The global increase in energy consumption and the global warming from greenhouse gas emissions create the need for more sustainable power generation processes. Biomass-fired power plants with higher efficiency could generate more power but also reduce the emission of greenhouse gases, e.g. CO2. Biomass offers no net contribution of CO2 to the atmosphere. To obtain greater efficiency of power plants, one option is to increase the temperature and the pressure in the boiler section of the power plant. This requires improved material properties, such as higher yield strength, creep strength and high-temperature corrosion resistance, as well as structural integrity and safety. Today, some austenitic stainless steels are design to withstand temperatures up to 650 °C in tough environments. Nickel-based alloys are designed to withstand even higher temperatures. Austenitic stainless steels are more cost effective than nickel-based alloys due to a lower amount of expensive alloying elements. However, the performance of austenitic stainless steels at the elevated temperatures of future operation conditions in biomass-red power plants is not yet fully understood. This thesis presents research on the influence of long term high-temperature ageing on mechanical properties, the influence of very slow deformation rates at high-temperature on deformation, damage and fracture, and the influence of high-temperature environment and cyclic operation conditions on the material behaviour. Mechanical and thermal testing have been performed followed by subsequent studies of the microstructure, using scanning electron microscopy, to investigate the material behaviours. Results shows that long term ageing at high temperatures leads to the precipitation of intermetallic phases. These intermetallic phases are brittle at room temperature and become detrimental for the impact toughness of some of the austenitic stainless steels. During slow strain rate tensile deformation at elevated temperature time dependent deformation and recovery mechanisms are pronounced. The creep-fatigue interaction behaviour of an austenitic stainless steel show that dwell time gives shorter life at a lower strain range, but has none or small effect on the life at a higher strain range. Finally, this research results in an increased knowledge of the structural, mechanical and chemical behaviour as well as a deeper understanding of the deformation, damage and fracture mechanisms that occur in heat resistant austenitic alloys at high-temperature environments. It is believed that in the long term, this can contribute to material development achieving the transition to more sustainable power generation in biomass-red power plants.
2
Nam, Jae-Do. "Polymer matrix degradation : characterization and manufacturing process for high temperature composites /." Thesis, Connect to this title online; UW restricted, 1991. http://hdl.handle.net/1773/9867.
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Moricca, Maria del Pilar. "High temperature oxidation characteristics of Nb-10W-XCr alloys." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Liu, Yi Johnson R. Wayne. "Packaging of silicon carbide high temperature, high power devices processes and materials /." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Spring/doctoral/LIU_YI_31.pdf.
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Mignanelli, Paul Michael. "The design of new nickel-base superalloys with high niobium contents." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709110.
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Fox, Bronwyn Louise. "The manufacture, characterization and aging of novel high temperature carbon fibre composites." View thesis entry in Australian Digital Theses Program, 2001. http://thesis.anu.edu.au/public/adt-ANU20011207.114246/index.html.
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Khattab, Ahmed. "Exploratory development of VARIM process for manufacturing high temperature polymer matrix composites." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4186.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (month day, year) Vita. Includes bibliographical references.
8
Garimella, Narayana. "Multicomponent interdiffusion in austenitic Ni-, Fe-Ni-base alloys and L1₂-Ni₃Al intermetallic for high-temperature applications." Orlando, Fla. : University of Central Florida, 2009. http://purl.fcla.edu/fcla/etd/CFE0002521.
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Pang, Lisa Yee San. "Thin film diamond : electronic devices for high temperature, high power and high radiation applications." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313317.
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Callender, Chad M. "Refractory metal to nickel-based alloy joining technologies for high temperature applications." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Summer/Theses/CALLENDER_CHAD_35.pdf.
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Talekar, Anjali S. "Oxidation behavior of Ni-base superalloys and high strength low alloy (HSLA) steels at elevated temperatures." abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3316371.
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Shi, Shu. "Repair weldability of heat-resistant stainless steel casings-HP45NB, HP50NB and 20-32NB alloys." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1140490923.
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Ventura, Julieta Angelica. "High temperature oxidation behavior of Nb-20Mo-15Si-5B-20Cr alloy." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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14
Liu, Qiang. "Microstructure Evaluation and Wear-Resistant Properties of Ti-alloyed Hypereutectic High Chromium Cast Iron." Doctoral thesis, KTH, Tillämpad processmetallurgi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-128532.
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High chromium cast iron (HCCI) is considered as one of the most useful wear resistance materials and their usage are widely spread in industry. The mechanical properties of HCCI mainly depend on type, size, number, morphology of hard carbides and the matrix structure (γ or α). The hypereutectic HCCI with large volume fractions of hard carbides is preferred to apply in wear applications. However, the coarser and larger primary M7C3 carbides will be precipitated during the solidification of the hypereutectic alloy and these will have a negative influence on the wear resistance. In this thesis, the Ti-alloyed hypereutectic HCCI with a main composition of Fe-17mass%Cr-4mass%C is studied based on the experimental results and calculation results. The type, size distribution, composition and morphology of hard carbides and martensite units are discussed quantitatively. For a as-cast condition, a 11.2μm border size is suggested to classify the primary M7C3 carbides and eutectic M7C3 carbides. Thereafter, the change of the solidification structure and especially the refinement of carbides (M7C3 and TiC) size by changing the cooling rates and Ti addition is determined and discussed. Furthermore, the mechanical properties of hypereutectic HCCI related to the solidification structure are discussed. Mechanical properties of HCCI can normally be improved by a heat treatment process. The size distribution and the volume fraction of carbides (M7C3 and TiC) as well as the matrix structure (martensite) were examined by means of scanning electron microscopy (SEM), in-situ observation by using Confocal Laser Scanning Microscope (CLSM), Transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD). Especially for the matrix structure and secondary M7C3 carbides, EBSD and CLSM are useful tools to classify the fcc (γ) and bcc (α) phases and to study the dynamic behavior of secondary M7C3 carbides. In conclusion, low holding temperatures close to the eutectic temperature and long holding times are the best heat treatment strategies in order to improve wear resistance and hardness of Ti-alloyed hypereutectic HCCI. Finally, the maximum carbides size is estimated by using statistics of extreme values (SEV) method in order to complete the size distribution results. Meanwhile, the characteristic of different carbides types will be summarized and classified based on the shape factor.QC 20130913
15
Sharpe, Heather Joan. "Effect of Microstructure on High-Temperature Mechanical Behavior of Nickel-Base Superalloys for Turbine Disc Applications." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16255.
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Engineers constantly seek advancements in the performance of aircraft and power generation engines, including, lower costs and emissions, and improved fuel efficiency. Nickel-base superalloys are the material of choice for turbine discs, which experience some of the highest temperatures and stresses in the engine. Engine performance is proportional to operating temperatures. Consequently, the high-temperature capabilities of disc materials limit the performance of gas-turbine engines. Therefore, any improvements to engine performance necessitate improved alloy performance.
In order to take advantage of improvements in high-temperature capabilities through tailoring of alloy microstructure, the overall objectives of this work were to establish relationships between alloy processing and microstructure, and between microstructure and mechanical properties. In addition, the project aimed to demonstrate the applicability of neural network modeling to the field of Ni-base disc alloy development and behavior.
A full program of heat-treatment, microstructural quantification, mechanical testing, and neural network modeling was successfully applied to next generation Ni-base disc alloys. Mechanical testing included hot tensile, hot hardness, creep deformation, creep crack growth, and fatigue crack growth. From this work the mechanisms of processing-structure and structure-property relationships were studied. Further, testing results were used to demonstrate the applicability of machine-learning techniques to the development and optimization of this family of superalloys.
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Lipke, David William. "Novel reaction processing techniques for the fabrication of ultra-high temperature metal/ceramic composites with tailorable microstructures." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/43750.
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Ultra-high temperature (i.e., greater than 2500°C) engineering applications present continued materials challenges. Refractory metal/ceramic composites have great potential to satisfy the demands of extreme environments (e.g., the environments found in solid rocket motors upon ignition), though general scalable processing techniques to fabricate complex shaped parts are lacking. The work embodied in this dissertation advances scientific knowledge in the development of processing techniques to form complex, near net-shape, near net-dimension, near fully-dense refractory metal/ceramic composites with controlled phase contents and microstructure.
Three research thrusts are detailed in this document. First, the utilization of rapid prototyping techniques, such as computer numerical controlled machining and three dimensional printing, for the fabrication of porous tungsten carbide preforms and their application with the Displacive Compensation of Porosity process is demonstrated. Second, carbon substrates and preforms have been reactively converted to porous tungsten/tungsten carbide replicas via a novel gas-solid displacement reaction. Lastly, non-oxide ceramic solid solutions have been internally reduced to create intragranular metal/ceramic micro/nanocomposites. All three techniques combined have the potential to produce nanostructured refractory metal/ceramic composite materials with tailorable microstructure for ultra-high temperature applications.
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Middlemas, Michael Robert. "A Nitride-Based Reaction for the Formation of a Three-Phase Molybdenum-Silicon-Boron Intermetallic Alloy." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7190.
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The alloy Mo-3Si-1B (wt%) may have the fracture toughness and oxidation resistance required for use as jet turbine engine blades. Mo-3Si-1B (wt%) forms a three-phase mixture of and #945;-Moss, A15 (Mo3Si) and T2 (Mo5SiB2). It has been observed that at high-temperatures, the A15 and T2 intermetallics form a oxidation resistant borosilicate glass coating. To achieve the proper combination of mechanical and thermal properties, the material must have a molybdenum matrix with a fine dispersion of intermetallics to produce a continuous protective layer. In this project, reactive sintering of molybdenum, Si3N4 and BN powders was used to create a semi-continuous molybdenum matrix with a fine dispersion of the A15 and T2 intermetallics. Sintering of the materials was further enhanced by the use of submicron-sized reactants. X-ray diffraction analysis was used verify the desired phases were formed. It was determined that formation of the A15 intermetallic phases begins as low as 1200?nd formation of T2 begins at 1300? The reactions are complete by 1400? Samples with bulk densities as high as 95% of theoretical were produced. Scanning electron microscopy images reveal a microstructure with dispersed intermetallics in a semi-continuous molybdenum matrix with grain sizes on the order of 1-4 and #956;m. It was found that by varying parameters such as mixing method and heating rates, it is possible to engineer the final microstructure, changing the level of dispersion of the intermetallics and continuity of the matrix.
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Saillard, Audric. "Modeling and simulation of stress-induced non-uniform oxide scale growth during high-temperature oxidation of metallic alloys." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33898.
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The metallic alloys employed in oxidizing environment at high temperature rely on the development of a protective oxide scale to sustain the long-term aggressive exposition. However, the oxide scale growth is most of the time coupled with stress and morphological developments limiting its lifetime and then jeopardizing the metallic component reliability. In this study, a mechanism of local stress effect on the oxidation kinetics at the metal/oxide interface is investigated. The objective is to improve the understanding on the possible interactions between stress generation and non-uniform oxide scale growth, which might result in a precipitated mechanical failure of the system. Two different oxides are studied, alumina and chromia, in two different industrial systems, thermal barrier coatings and solid oxide fuel cell interconnects. A specific thermodynamic treatment of local oxide phase growth coupled with stress generation is developed. The formulation is completed with a phenomenological macroscopic framework and a numerical simulation tool is developed allowing for realistic analyses. Two practical situations are simulated and analyzed, concerning an SOFC interconnect and a thermal barrier coating system, for which oxide scale growth and associated stress and morphological developments are critical. The consequence of the non-uniform oxide growth on the system resistance to mechanical failure is investigated. Finally, the influences of material-related properties are studied, providing optimization directions for the design of metallic alloys which would improve the mechanical lifetime of the considered systems.
19
Rockett, Chris H. "Flexural Testing of Molybdenum-Silicon-Boron Alloys Reacted from Molybdenum, Silicon Nitride, and Boron Nitride." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16293.
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MoSiB alloys show promise as the next-generation turbine blade material due to their high-temperature strength and oxidation resistance afforded by a protective borosilicate surface layer. Powder processing and reactive synthesis of these alloys has proven to be a viable method and offers several advantages over conventional melt processing routes. Microstructures obtained have well-dispersed intermetallics in a continuous matrix of molybdenum solid-solution (Mo-ss). However, bend testing of pure Mo and Mo-ss samples has shown that, while the powder processing route can produce ductile Mo metal, the hardening effect of Si and B in solid-solution renders the matrix brittle. Testing at elevated temperatures (200°C) was performed in order to determine the ductile-to-brittle transition temperature of the metal as an indication of ductility. Methods of ductilizing the Mo-ss matrix such as annealing and alloying additions have been investigated.
20
Nguyen, QuynhGiao N. "High Temperature Volatility and Oxidation Measurements of Titanium and Silicon Containing Ceramic Materials." Abstract only. Full text release has been delayed at the author's request until December 31, 2010, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=csu1239291812.
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Thesis (Ph.D.)--Cleveland State University, 2008Abstract. Includes bibliographical references (p. 110-111). Electronic full text release has been delayed at the author's request until December 31, 2010.
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Gockel, Brian Timothy. "Developing the capability to examine environmental effects on small fatigue crack growth." Dayton, Ohio : University of Dayton, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1271184488.
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Thesis (M.S. in Mechanical Engineering) -- University of Dayton.Title from PDF t.p. (viewed 06/22/10). Advisor: Robert Brockman. Includes bibliographical references (p. 42-44). Available online via the OhioLINK ETD Center.
22
Morata, Royes Joan. "Wear resistance of heat-treated Advanced High Strength Steels and casting." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80526.
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The necessity to improve the durability of the machinery used in the milling industry has lead to several types of research. One study is focused on the plates that are located in the stationary and moving jaws of crushers to diminish particles sizes of Gneiss and Diabase rocks. Thus, one type of approach to increase its durability is by reducing the material loss of the plates. Amongst all the parameters to reduce the wear ratio that includes inputs from geometry to load, just the hardness input of the material can be in constant development. Consequently, there are two well-known types of heat treatment that can produce this change in hardness and are named Carbide Free Bainite (CFB) and Quenching and Partitioning (QP). In this master thesis the topic is to perform the QP heat treatments for two compositions A and B to obtain the microstructure of the steels that consist in a mix of austenite, bainite and martensite which considerably increase the hardness while the toughness is not drastically reduced due to the austenite soft phase. Five samples have been studied at four different partitioning temperatures: QP250 A, QP180 B, QP210 B, QP240 B and Mn Steel as it is the composition most used nowadays in the industry. In order to characterise both mechanical properties and microstructural features, different analysis had been performed with Micro-indentations, Charpy-V, Gouging Abrasion Tests, Optical Microscopy, Scanning Electron Microscopy and X-Ray Diffraction. These analysis had been done in the samples before and after wear as a result in change of the microstructure. As the abrasive-impact of the rocks collide with the sample, austenite transforms to martensite by induced plasticity called TRIP effect. Thus, the surface of the alloy is harder than the bulk material as no austenite is found and the wear ratio is seen to be improved. The results have shown several behaviours. Austenite transforms in its majority to fresh martensite which is an unstable martensitic phase but harder than tempered martensite that is the stable martensitic phase. Moreover, the difference in hardness between the bulk and the surface produce an affected depth layer as a consequence of the abrasive-impact penetration of rocks in which the microstructure has fully transformed to martensite on the surface and the austenite phase increases as it goes further inside the steel. The thinner this layer is, the better wear ratio presents the alloy. From all the samples, the best combination of hardness and toughness is for QP210 B.
23
Rodriguez, Patrick. "Apparent Total Evaporative Resistance for Clothing Ensembles at High Heat Stress Levels." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3318.
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Donning protective clothing for mitigation of hazard from chemical agents poses a problem in the form of heat stress. When choosing protective clothing, many factors must be taken into account including insulative properties and evaporative resistance. This study calculated and compared Re,T,a for three clothing ensembles at levels of heat stress past the level of compensation for heat gain to determine if Re,T,a values varied or remained the same with changes in heat stress level. A three-way mixed model analysis of variance demonstrated significant differences for estimated Re,T,a values among ensembles, heat stress levels and interactions among ensembles and heat stress levels (p < 0.0001). A significant interaction between heat stress levels and ensembles was identified (p<0.05). The results of the study indicated that Re,T,a values are affected by levels of heat stress such that increasing levels were associated with lower values of Re,T,a. The study also helped to illustrate that Re,T,a values are not a constant associated with clothing, walking speed, and air speed.
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Allo, Justine. "Mécanismes fondamentaux et cinétiques d'oxydation d'alliages réfractaires de nouvelle génération pour la prétrochimie." Thesis, Normandie, 2021. http://www.theses.fr/2021NORMR005.
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Magee, Michael P. "Thermal boundary resistance in a high temperature thin-film superconductor under varying heat flux." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1996. http://handle.dtic.mil/100.2/ADA326312.
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Thesis (M.S. in Mechanical Engineering) Naval Postgraduate School, December 1996."December 1996." Thesis advisor(s): Matthew Kelleher, Pat E. Phelan. Includes bibliographical references (p. 73-75). Also available online.
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Shimizu, H., Y. Yokomizu, T. Matsumura, and N. Murayama. "Proposal of flux flow resistance type fault current limiter using Bi2223 high T/sub c/ superconducting bulk." IEEE, 2002. http://hdl.handle.net/2237/6785.
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Liu, Qiang. "Control of Wear-Resistance Properties in Ti-added Hypereutectic High Chromium Cast Iron." Licentiate thesis, KTH, Tillämpad processmetallurgi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-105854.
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High chromium cast iron (HCCI) is considered as one of the most useful wear resistance materials and their usage are widely spread in industry. The wear resistance and mechanical properties of HCCI mainly depend on type, size, number, morphology of hard carbides and the matrix structure (γ or α). The Hypereutectic HCCI with large volume fractions of hard carbides is preferred to apply in wear applications. However, the coarser and larger primary M7C3 carbides will be precipitated during the solidification of the hypereutectic alloy and these will have a negative influence on the wear resistance. In this thesis, the Ti-added hypereutectic HCCI with a main composition of Fe-17mass%Cr-4mass%C is quantitatively studied based on the type, size distribution, composition and morphology of hard carbides and martensite units. A 11.2μm border size is suggested to classify the primary M7C3 carbides and eutectic M7C3 carbides. Thereafter, the change of the solidification structure and especially the refinement of carbides (M7C3 and TiC) size by changing the cooling rates and Ti addition is determined and discussed. Furthermore, the mechanical properties of hypereutectic HCCI related to the solidification structure are discussed. Mechanical properties of HCCI can normally be improved by a heat treatment process. The size distribution and the volume fraction of carbides (M7C3 and TiC) as well as the matrix structure (martensite) were examined by means of scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). Especially for the matrix structure, EBSD is a useful tool to classify the fcc (γ) and bcc (α) phases. In conclusion, low holding temperatures close to the eutectic temperature and long holding times are the best heat treatment strategies in order to improve wear resistance and hardness of Ti-alloyed hypereutectic HCCI.QC 20121130
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Демченко, М. В. "Дослідження жаростійкості високоентропійних сплавів системи АlСгFеСоNi, легованих міддю." Thesis, Сумський державний університет, 2018. http://essuir.sumdu.edu.ua/handle/123456789/67472.
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Löbel, Martin, Thomas Lindner, Thomas Mehner, and Thomas Lampke. "Microstructure and Wear Resistance of AlCoCrFeNiTi High-Entropy Alloy Coatings Produced by HVOF." Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-230210.
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The investigation of high-entropy alloys (HEAs) has revealed many promising properties. HEAs with a high share of Al and Ti are suitable for the formation of lightweight materials. Investigations of the alloy system AlCoCrFeNiTi showed high strength, hardness, ductility, and wear resistance, which makes this special alloy interesting for surface engineering and particularly for thermal spray technology. In this study, the suitability of inert gas-atomised HEA powder for high-velocity-oxygen-fuel (HVOF) thermal spray is investigated. This process allows for high particle velocities and comparatively low process temperatures, resulting in dense coatings with a low oxidation. The microstructure and phase composition of the atomised powder and the HVOF coating were investigated, as well as the wear behaviour under various conditions. A multiphase microstructure was revealed for the powder and coating, whereas a chemically ordered bcc phase occurred as the main phase. The thermal spray process resulted in a slightly changed lattice parameter of the main phase and an additional phase. In comparison with a hard chrome-plated sample, an increase in wear resistance was achieved. Furthermore, no brittle behaviour occurred under abrasive load in the scratch test. The investigation of wear tracks showed only minor cracking and spallation under maximum load.
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Rahmanian, Ima. "Thermal and mechanical properties of gypsum boards and their influences on fire resistance of gypsum board based systems." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/thermal-and-mechanical-properties-of-gypsum-boards-and-their-influences-on-fire-resistance-of-gypsum-board-based-systems(d8eb4bf5-706a-4264-911f-9584ebfbbc83).html.
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Gypsum board assemblies are now widely used in buildings, as fire resistant walls or ceilings, to provide passive fire protection. The fire resistance of such systems is fundamentally due to the desirable thermal properties of gypsum. Yet there is wide variability in reported values of thermal properties of gypsum at high temperatures and a lack of understanding of its integrity in fire. To evaluate the fire protection performance of gypsum board assemblies, it is essential to quantify its thermal properties and obtain information on its mechanical properties at high temperatures. Gypsum boards shrink and crack at high temperatures, and this leads to collapse of parts of the gypsum boards in fire. Fall-off of gypsum in fire affects the fire resistance of the assembly considerably, and cannot be overlooked when evaluating the fire resistance of gypsum board assemblies. The current research proposes a model to define the temperature-dependent thermal properties of gypsum boards at high temperatures. Thermal conductivity of gypsum is considered as the most influential parameter in conduction of heat through gypsum, and a hybrid numerical-experimental method is presented for extracting thermal conductivity of various gypsum board products at elevated temperatures. This method incorporates a validated one-dimensional Finite Difference heat conduction program and high temperature test results on small samples of gypsum boards. Moreover, high temperature mechanical tests have been performed on different gypsum board products; thermal shrinkage, strength and stress-strain relationships of gypsum products at elevated temperatures are extracted for use in numerical mechanical analysis. To simulate the structural performance of gypsum boards in fire, a two-dimensional Finite Element model has been developed in ABAQUS. This model successfully predicts the complete opening of a through-thickness crack in gypsum, and is validated against medium-scale fire tests designed and conducted as part of this research. Gypsum fall-off in fire is a complex phenomenon; however, it is believed that delaying the formation of through-thickness cracking will delay falling off of gypsum in fire, and hence improve the fire resistance of gypsum board assemblies. Finally, a study has been performed on the effects of various detailing parameters in gypsum board wall assemblies, and recommendations are offered for improving the fire resistance of such systems.
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Dhakal, Shankar. "Circuit Level Reliability Considerations in Wide Bandgap Semiconductor Devices." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1532703747534188.
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Kempe, Andreas, Christoph Neinhuis, and Thea Lautenschläger. "Adansonia digitata and Adansonia gregorii fruit shells serve as a protection against high temperatures experienced during wildfires." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-234853.
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The thick and woody shell of the fruit of Adansonia species cannot be explained solely by adaptation to zoochory or hydrochory. Since the trunks of Adansonia possess a thick and fire-resistant bark and wildfires occur regularly in its habitat (savannah), we examined with the African Adanonia digitata and the Australian Adansonia gregorii whether the fruit offers protection against high heat typically experienced in wildfires. Heat-resistance tests were conducted by applying a simple heat test based on known temperature and temperature residence times occurring in savannah fires and complemented by tests to reveal the impact of heat on germination since long-term seed dormancy is known for Adansonia. Germination tests with acid treated and heat treated seeds were performed to establish if heat also increased germination rate as effectively as acid treatments have been found to do. Heat was found to increase germination rate, but not as effectively as treatment with acid, therefore fruits exposed to high temperatures experienced in wildfires may have a better chance of germination than fruits that were not exposed to wildfires. The ability of the investigated fruits to protect seeds from high temperatures suggests that wildfires may have played a role in the evolution of the hard-shell structure typically found in Adansonia.
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Müller, Jiří. "Kotevní silikátový expanzní materiál se zvýšenou teplotní odolností." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392344.
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This master thesis deals with the development of an expansive anchor material. This material is intended especially for the engineering and power industry where the operating conditions cause thermal stresses of the anchor. In order to meet the requirements for a firm and secure connection of the anchored part, it is necessary to achieve excellent physical-mechanical properties of the developed material such as high compressive strength, high tensile strength based on the base, and resistance to thermal stresses till 200 ° C. All of these processes must be achieved after the ageing of the cement material. Due to the current trend of modern materials that are environmentally friendly, the use of partial replacements for Portland cement is used as a substitute for a primary binder.
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Loizou, Andreas. "Modelling and simulation of themo-mechanical phenomena at the friction interface of a disc brake.An empirically-based finite element model for the fundamental investigation of factors that influence the interface thermal resistance at the friction interface of a high energy sliding pair in a disc brake." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5489.
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The fundamental theories of heat generation and transfer at the friction interface of a
brake assume either matching or not matching surface temperatures by having a
varying or uniform heat partition ratio respectively. In the research presented the
behaviour of heat partition has been investigated in a fundamental study based on
experimental measurements of temperature and the associated modelling and
simulation of heat transfer in a brake friction pair. For a disc brake, an important
parameter that was identified from the literature study is the interface tribo-layer
(ITL), which has been modelled as an equivalent thermal resistance value based on its
thickness and thermal conductivity. The interface real contact area was also an
important parameter in this investigation, and it has been found to affect heat
partitioning by adding its own thermal resistance.
A 2-dimensional (2D) coupled-temperature displacement Finite Element (FE) model is
presented, based on which a novel relationship which characterises the total thermal
resistance (or conductance) at the friction interface has been characterised based on
the ITL thermal properties, the contact area, and the contact pressure at the interface.
Using the model the effect of friction material wear on the total thermal resistance (or
conductance) at the friction interface was predicted and a comparison of the Archard
and Arrhenius wear laws in predicting the wear of a resin bonded composite friction
material operating against a cast iron mating surface is presented.
A 3-dimensional (3D) model is also presented. This model has represented a small
scale disc brake test rig which has been used in parallel with the simulation for
validation in a drag braking scenario. Two simulation conditions with different pad
surface states were investigated, the first having a nominally flat surface, and the
second an adjusted (worn) pad surface based on bedding-in data. The Arrhenius wear
model was applied to significance of including wear on the total thermal resistance at
the friction interface over a short brake application.
A sensitivity analysis on the interface thermal conductance, the location of heat
generation, and the magnitude of contact pressure has identified the importance of
each factor in determining the total thermal resistance (or conductance) at the friction
interface during any friction brake application. It is concluded that the heat
partitioning is insensitive on the location of heat generation, and that the most
sensitive parameter is the contact pressure.Institution of Mechanical Engineers (IMechE)
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Loizou, Andreas. "Modelling and simulation of themo-mechanical phenomena at the friction interface of a disc brake : an empirically-based finite element model for the fundamental investigation of factors that influence the interface thermal resistance at the friction interface of a high energy sliding pair in a disc brake." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5489.
Full textAbstract:
The fundamental theories of heat generation and transfer at the friction interface of a brake assume either matching or not matching surface temperatures by having a varying or uniform heat partition ratio respectively. In the research presented the behaviour of heat partition has been investigated in a fundamental study based on experimental measurements of temperature and the associated modelling and simulation of heat transfer in a brake friction pair. For a disc brake, an important parameter that was identified from the literature study is the interface tribo-layer (ITL), which has been modelled as an equivalent thermal resistance value based on its thickness and thermal conductivity. The interface real contact area was also an important parameter in this investigation, and it has been found to affect heat partitioning by adding its own thermal resistance. A 2-dimensional (2D) coupled-temperature displacement Finite Element (FE) model is presented, based on which a novel relationship which characterises the total thermal resistance (or conductance) at the friction interface has been characterised based on the ITL thermal properties, the contact area, and the contact pressure at the interface. Using the model the effect of friction material wear on the total thermal resistance (or conductance) at the friction interface was predicted and a comparison of the Archard and Arrhenius wear laws in predicting the wear of a resin bonded composite friction material operating against a cast iron mating surface is presented. A 3-dimensional (3D) model is also presented. This model has represented a small scale disc brake test rig which has been used in parallel with the simulation for validation in a drag braking scenario. Two simulation conditions with different pad surface states were investigated, the first having a nominally flat surface, and the second an adjusted (worn) pad surface based on bedding-in data. The Arrhenius wear model was applied to significance of including wear on the total thermal resistance at the friction interface over a short brake application. A sensitivity analysis on the interface thermal conductance, the location of heat generation, and the magnitude of contact pressure has identified the importance of each factor in determining the total thermal resistance (or conductance) at the friction interface during any friction brake application. It is concluded that the heat partitioning is insensitive on the location of heat generation, and that the most sensitive parameter is the contact pressure.
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Eisel, Thomas. "Cooling of electrically insulated high voltage electrodes down to 30 mK." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-77442.
Full textAbstract:
The Antimatter Experiment: Gravity, Interferometry, Spectroscopy (AEGIS) at the European Organization for Nuclear Research (CERN) is an experiment investigating the influence of earth’s gravitational force upon antimatter. To perform precise measurements the antimatter needs to be cooled to a temperature of 100 mK. This will be done in a Penning trap, formed by several electrodes, which are charged with several kV and have to be individually electrically insulated. The trap is thermally linked to a mixing chamber of a 3He-4He dilution refrigerator.
Two link designs are examined, the Rod design and the Sandwich design. The Rod design electrically connects a single electrode with a heat exchanger, immersed in the helium of the mixing chamber, by a copper pin. An alumina ring and the helium electrically insulate the Rod design. The Sandwich uses an electrically insulating sapphire plate sandwiched between the electrode and the mixing chamber. Indium layers on the sapphire plate are applied to improve the thermal contact. Four differently prepared test Sandwiches are investigated. They differ in the sapphire surface roughness and in the application method of the indium layers.
Measurements with static and sinusoidal heat loads are performed to uncover the behavior of the thermal boundary resistances. The thermal total resistance of the best Sandwich shows a temperature dependency of T-2,64 and is significantly lower, with roughly 30 cm2K4/W at 50 mK, than experimental data found in the literature. The estimated thermal boundary resistance between indium and sapphire agrees very well with the value of the acoustic mismatch theory at low temperatures.
In both designs, homemade heat exchangers are integrated to transfer the heat to the cold helium. These heat exchangers are based on sintered structures to increase the heat transferring surface and to overcome the significant influence of the thermal resistance (Kapitza resistance). The heat exchangers are optimized concerning the adherence of the sinter to the substrate and its sinter height, e.g. its thermal penetration length.
Ruthenium oxide metallic resistors (RuO2) are used as temperature sensors for the investigations. They consist of various materials, which affect the reproducibility. The sensor conditioning and the resulting good reproducibility is discussed as well.
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OBADIA, BAROGHEL SYLVIA. "Frittage de melanges al::(2)o::(3) + sio::(2) gel pour moules de fonderie : developpement des microstructures et deformation a chaud." Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0079.
Full textAbstract:
Etude du frittage reactif de melanges prepares a partir de la silice colloidale et l'alumine alpha entrant dans la composition des moules. Influence du temps, de la temperature et de la composition initiale sur l'affaissement des moules carapaces de fonderies pour la coulee/solidification dirigee des aubes de turbine des reacteurs d'avions
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Juřička, Viktor. "Vývoj polymerních správkových hmot s využitím druhotných surovin." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-372189.
Full textAbstract:
The diploma thesis deals with the development of polymeric repair mortars in two qualitative levels ECONOMY and PREMIUM, designed especially for heavy engineering plants and the energy industry. In order to effectively withstand difficult industrial conditions, the developed materials should meet the highest requirements such as increased chemical and heat resistance, excellent adhesion to the concrete substrate, minimal shrinkage and other physical and mechanical properties. The PREMIUM level is aimed to achieve maximum physical and mechanical properties. Within the economy version, the emphasis is placed not only on very good properties, but also the possibility capability of reducing price of the resulting material. The partial aim of this work is the efficient use of secondary raw materials, mainly based on industrial waste in the form of fillers to the developed polymeric repair mortars.
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Harmouch, Khaled. "Conception et réalisation d’un moteur piézoélectrique pour application automobile haute température." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC007.
Full textAbstract:
L’objectif de cette thèse est deconcevoir et de réaliser un moteurpiézoélectrique destiné à une application derécupération de chaleur du gaz d’échappement.Cette application nécessite un couplerelativement élevé, une compacité importante,une endurance thermique et un coût acceptable.Afin d’atteindre ce but, la conception du moteurpasse par le choix de son mode defonctionnement. Ce choix est fait en se basantsur des critères comme bas coût, fort couple etcompacité importante.Après la détermination de l’architecture dumoteur piézoélectrique, la modélisation estabordée. Le but du modèle est de calculer lescaractéristiques couple/vitesse connaissantses dimensions et ses matériaux, l’état desurface du contact, la précontrainte et la tensiond’alimentation.La modélisation développée était validée pardes mesures expérimentales.Dans la dernière partie, le moteur dimensionnéest réalisé et testé. Son comportementdynamique et ces caractéristiquescouple/vitesse étaient mesurés. A l’exceptiondu couple à l’arrêt et celui de blocage, toutes lesperformances requises par l’application étaientremplies.Finalement, les résultats de modèle sontcomparés aux mesures faites sur le prototype.Le comportement dynamique était bienreproduit par la modélisation. Néanmoins, uneimprécision du calcul des déplacements dustator était constatée. Cela implique uneimprécision du calcul des caractéristiquesmoteur. Il s’avère que cette imprécision est liéeà l’absence du coefficient d’amortissement decontactThe goal of this thesis is to designand build a piezoelectric motor for an exhaustgas heat recovery application. This applicationrequires relatively high torque, highcompactness, thermal endurance and acceptablecost.In order to achieve this goal, the design of theengine passes by the choice of its mode ofoperation. This choice is made based on criteriasuch as low cost, high torque and compactness.After the determination of the architecture ofthe piezoelectric motor, the modelling isaddressed. The purpose of the model is tocompute the torque/speed characteristicsknowing the motor dimensions and materials,the surface state of the contact, the precompressionforce and the supply voltage.The modeling developed was validated byexperimental measurements.In the last part, the motor is build and tested. Itsdynamic behavior and torque/speedcharacteristics were measured. With theexception of the peak and blocking torque, allthe performances required by the applicationwere fulfilled.Finally, the model results are compared to themeasurements done on the prototype. Thedynamic behavior is well predicted by themodel. However, the model is not able tocompute accurately the stator displacements.This implies inaccuracy in the motorcharacteristics computation. It turns out thatthey are related to the absence of the coefficientof contact damping
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Hamasaiid, Anwar. "Transferts thermiques interfaciaux en fonderie en moules métalliques d'alliages légers." Toulouse 3, 2007. http://www.theses.fr/2007TOU30249.
Full textAbstract:
L'objectif de ce projet est d'étudier les transferts thermiques interfaciaux pendant la solidification des alliages légers dans les procédés de fonderie par gravité et sous pression. Pour cela, nous avons développé des méthodes expérimentales et des capteurs appropriés permettant d'effectuer les mesures de température dans le moule et en surface de la pièce pendant le remplissage et la solidification. Nous avons également enregistré les paramètres procédés sur une installation de fonderie sous pression particulièrement bien instrumentée. Pour la mesure de température de surface de la pièce coulée, nous avons adapté une technique pyrométrique utilisant un pyromètre et une fibre optique auxquels nous avons ajouté un crystal de saphir transparent dans la gamme de longueur d'onde du pyromètre. Ainsi, nous avons effectué plusieurs centaines de cycles pendant lesquels trois alliages ASG03, AS9U3 et AZ91D ont été coulés par ces deux procédés. Les mesures de température ont été exploitées par une méthode inverse pour évaluer le coefficient d'échange thermique et la densité de flux de chaleur à l'interface pièce/moule pour chaque cycle effectué. Les résultats obtenus ont été comparés entre les diverses conditions de coulée et avec les microstructures des pièces produites. Nous avons proposé deux modèles analytiques pour la Résistance Thermique de Contact (RTC) à l'interface liquide/solide pour les deux conditions de contact rencontrées dans les deux procédés étudiés. .The present investigation is about the interfacial heat transfer during the solidification of light alloys in Gravity (GDC) and High Pressure (HPDC) Die Casting processes. The study consists of three principle fields, experimental, analytical and modelling. The Experimental activity involves measuring the temperature around the casting-die interface, in the mould and at the surface of the castings and other process parameters during die filling and solidification. For this purpose, suitable experimental methods and sensors have been developed. Particularly a pyrometric measurement method has been adapted to measure the casting surface temperature during its solidification. Hundredths of trials were performed using Al-7Si-0. 3Mg, A-9Si-3Cu and AZ91 D alloys during the two investigated processes. From the temperature measurements, interfacial heat transfer coefficient and heat flux density have been evaluated using an inverse method. The obtained results have been analysed with regards to the various process parameters and to the microstructure of the castings. .
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SACHAN, RADHA. "STUDIES ON HIGH HEAT RESISTANT ACRYLIC ADHESIVE." Thesis, 2018. http://dspace.dtu.ac.in:8080/jspui/handle/repository/16403.
Full textAbstract:
Acrylic copolymer was prepared by solution polymerisation technique using water as a solvent. The Cloisite 30B/Acrylic Copolymer nanocomposites with different loading of nanoclay (0.5-3.0%) were prepared by In-situ method. For compositional analysis fourier transform infrared spectroscopy (FTIR), Proton nuclear magnetic resonance (1H NMR) and Isothermal thermal gravimetric analysis have been studied and results show that a suitable copolymer has been formed with four monomers that are acrylic acid, methacrylic acid, butyl acrylate, methyl methacrylate.
Different parameters like solid content, solubility, appearance, acid value and pH values were checked for each nanofilled copolymer. Rheology was tested for pure and 0.5% filled copolymer and increase in viscosity with shear thickening behaviour at high shear rate was observed. All compositions were checked for thermal stability by thermal gravimetric analysis (TGA) analysis and found that 50 % wt. at 398 °C for 2.0% filled Cloisite 30B/ Acrylic nanocomposite. Epoxy resin was added as tackifier with curing agent with acrylic system. Peel strength was checked for two substrate: corona treated metallised biaxially-oriented polypropylene (bopp) and nylon cloth. Peel strength was increasing with nanofiller loading upto 2.0%.
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HUNG, SHIH-CHIEH, and 洪士傑. "The development of high- heat-resistant aluminum alloy bonding wire." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/enmex7.
Full textAbstract:
碩士國立高雄應用科技大學
模具系碩士在職專班
104
Aluminum bonding wire is currently used as material for large-current semiconductors such as power devices. Recently, however, increased power density requirements for aerospace, automotive and deep well drilling applications mean that higher junction temperatures are to be encountered in power electronics. Wide band gap semiconductors like SiC and GaN can operate at much higher temperatures and are currently being introduced to applications, such as MOSFETs and IGBTs. There have been demands for development of high heat resistant materials as power devices have higher density, become more compact and have higher output, high purity aluminum bonding wire can contribute to improve heat resistance temperature of packages. In this study, the main research projects are development of high purity aluminum alloy bonding wire as the power module , this experiment selected 4N aluminum ingot, with iron , copper and other metals to enhance the strength and heat resistance , Al-Fe-Cu alloy ingot through appropriate deployment under , extruded , and other steps can be cold drawn wire diameter 0.378 mm, breaking load ≧ 900g, elongation ≧ 18%, electrical conductivity ≧ 62% IACS, and its composition is Fe: 0.7%, Cu: 0.1-0.2%, Al: bal. Keywords: semiconductor package, power module, heat-resistant aluminum bonding wire
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DeFazio, Christian F. "High temperature/high strength discrete fiber reinforced composites." 2007. http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.13462.
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Sung, Wei-Chung, and 宋偉忠. "The study of heat-resistant mg alloy''s deformation mechanism for high temperature." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/01324656518357995458.
Full textAbstract:
碩士逢甲大學
機械工程學所
93
In order to probe into magnesium alloy characteristics of deformation mechanism for high temperature. We use MRI 153M and MRI 230D magnesium alloy. This study carries on the high-temperature tensile test and compression test at room temperature to 400 degrees Centigrade and we use three different strain rate. Then we use proceed accelerate creep test at custom degree and load. From above we can understand the deformation mechanism of high temperature through the behaviors of these materials. In observing the fracture part, tensile strength in low temperature side shows cleavage; The experiment shows that(400℃,7.4×10-4 s-1 ), we will obtain great elongation because of the function of the dynamic recrystallization under high temperature. In addition, we obtain the characteristics of deformation of compression by the compression testing (RT to 400 degrees Centigrade). When observing the SEM photograph, it tells us that the fracture of material will propagate along the grain boundary. Because of the higher Ca content in MRI 230D,the Al2Ca formes and result in lowing the average tensile strength but it also reduces the strength sensitivity to temperature.
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WANG, JIAN-XIANG, and 王建翔. "Mechanical Properties and Microstructure Analysis of High Ni-Cr Alloy Heat-Resistant Tube." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/6c7kan.
Full textAbstract:
碩士明志科技大學
機械工程系機械與機電工程碩士班
106
The work focuses on mechanical properties and microstructural compar-sions for new and ten years service heat-resistant tubes of HP40. HP40 Ni-Cr al-loys (ASTM A297 HP40). HP40 Ni-Cr alloys have been widely used in oil and chemi-cal industries due to their heat-resistance at high-temperature environment. In this work, we compared new and old tubes by conducting high-temperature tensile tests, microstructural analyses, and passive layer exploration. The correlation of mechanical strength and microstructures is evaluated in the thesis. According to tensile tests, the tensile strength and elongation of new heat-resistant tubes are higher than old ones at room temperatures and 600℃. Based on the precipitated phase observation, new heat-resistant tube in precipitated phases show a dis-persing state at the grain boundary, while the old heat-resistant tube exhibit a continuous precipitated phase, which caused the differences of the tensile strength and elongation between new and old heat-resistant tubes. Besides, the tensile strength of new and old heat-resistant tubes is nearly the same at 800℃ and 990℃. According to microstructure observations, the similar grain size and precipitated phase exist in new and old heat-resistant tubes, which is responsi-ble for new and old tubes with the same tensile strength. As temperature up to 990℃, old tubes causes grain boundary sliding and tube failure, which ex-plained the elongation of new tube is lower than old tube at 990℃. From passive layer observations, the outer passive layer of old tube shows ferric oxide (FeO、Fe2O3、Fe3O4), chrome oxide (Cr2O3), and metal nickel (Ni). The inner passive layer also shows chromium oxide (Cr2O3) and metal nickel. The ASTM A297 HP40 tube contains iron (Fe), chromium (Cr) and nickel (Ni). After heating, the iron and chromium of old tube was oxidized and then nickel was precipitated due to its higher free energy of oxide state.
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Arafa, Mohamed Danish. "High strength-high temperature laminated sandwich beams." 2007. http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.15782.
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Chen, Yan-Chih, and 陳彥志. "The Effect of Graphite Morphology and Matrix Structure on the High Temperature Oxidation Resistant of Heat Resistant Cast Iron." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/47652878782649729909.
Full textAbstract:
碩士逢甲大學
機械工程學系
87
Heat Resistant Cast Irons have been used extensively and have substantial practical value in the industry. The objective of this study is to investigate the high temperature oxidation and thermal shock phenomenon of the heat resistant cast irons. The effects of matrix structure (ferrite, pearlite and austenite) , various graphite morphology (flake, compacted / vermicular , spheroidal) and various alloy additions (Cr,Ni,Si) on the oxidation resistant (weight increasement , oxidation rate)and thermal shock resistant (crack numbers , crack length ) at different temperatures(1073 K, 873 K and 673 K) of cast irons have been evaluated in this study by using the specimen size of 20mm×30mm for the oxidation test and 50mm×20mm×15mm for the thermal shock test . Meanwhile, we observed the microstructural changes caused by the high temperature oxidation by the metallurgical microscope and used the EDS and XRD to make sure the kinds of the oxidation layers. According to the results of study know that , as a whole , the order of oxidation resistant for various alloy addations is that 20%Ni-2%Cr＞0.5%Cr＞no alloy addition . The order of oxidation resistant for the matrix strcutures is that austenite＞pearlite＞ferrite. The order of oxidation resistant for various graphite morphology is that spheroidal＞c / v＞flake . The changes of weight for various specimens after high temperature oxidation by regression analysis are known that oxidation resistance of cast iron is better , the regression functions are near logarithm or cubic curve regularity. For thermal shock of cast irons , the order of thermal shock resistance for graphite morphology of cast iron is that spheroidal＞c / v＞flake.The order of crack length in the matrix is pearlite＞austenite＞ferrite , and the 20%Ni-2%Cr specimen has more crack number than the others . Moreover , the effect of graphite morphology , martix structure and alloy additions on the thermal shock resistant of heat resist cast iron , the graphite morphology shows has most obvious affect and economic benefit .
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Cress, Catherine Marion. "Using elastic energy considerations to explain rafting in Ni-based superalloys with a high gamma volume fraction." Thesis, 1993. https://hdl.handle.net/10539/24291.
Full textAbstract:
A Dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, for the Degree of Master of ScienceA simple three-dimensional model of a high y' volume fraction Ni-based alloy is developed. The model is based on the idea that a unit volume in the superalloy can be represented by a cuboidal precipitate with thin 'slabs' of matrix material 'stuck' onto its faces in such a way that coherency is maintained. Rafting is investigated by considering the changes in total energy whon the cuboidal precipitates start to flatten into plate shapes or lengthen into rod shapes. It is assumed that inelastic effects are negligible. Internal and external stresses and strains are determined. Expressions for the derivative of the total energy with respect to a shape parameter are then calculated in the absence of applied stress and in the presence of applied stress. Predictions of rafting behaviour are made for six alloys. Excellent agreement is found with experimental evidence but it is suggested that the agreement is fortuitous.
AC 2018
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Yu, Chih-Chien, and 余志堅. "Study on Thermal Shock and High Temperature Strength Property of Heat Resistant Cast Iron." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/04070021880059143853.
Full textAbstract:
碩士逢甲大學
機械工程學系
88
Heat Resistant Cast Irons have been used in high temperature environment, so it must have excellent high temperature properties, such as high temperature tensile strength, high temperature fatigue strength and thermal shock resistance . The objective of this study is to investigate the high temperature strength property and thermal shock resistance of the heat resistant cast irons. The effects of matrix structure (ferrite, pearlite and austenite) , graphite morphology (flake, compacted / vermicular , spheroidal) and alloying element (Cr,Ni) on the high temperature tensile strength, the high temperature fatigue strength, and thermal shock resistant at different temperatures(1073 K, 873 K and 673 K) of cast irons have been evaluated in this study. We expect to find the quality index apply to themal shock resistance. According to the results of study know that , as a whole , the order of high temperature tensile strength for alloying element is that 0.5%Cr＞20%Ni-2%Cr＞none alloy addition at R.T., 673K, and 873K ; but the order is that 20%Ni-2%Cr＞0.5%Cr＞none alloy addition at 1073K. The order of high temperature tensile strength for the matrix strcutures is that pearlite＞austenite＞ferrite; but the order is that austenite＞pearlite＞ferrite at 1073K. The order of high temperature tensile strength for various graphite morphology is that spheroidal＞c / v＞flake at vaious test temperature. The order of high temperature fatigue strength for Heat Resistant Cast Irons of austenite matrix strcutures is that spheroidal＞c / v＞flake at 673K. For thermal shock resistance of cast irons , the order of thermal shock resistance for graphite morphology of cast iron is that spheroidal＞c / v＞flake.The order of thermal shock resistance for matrix is austenite＞pearlite＞ferrite . The order of thermal shock resistance for alloying element is that 20%Ni-2%Cr＞0.5%Cr＞none alloy addition. Quality Index of High Temperature Strength Property (QHTSP) is obtained for evaluating the high temperature property of the heat resistant cast iron by analysis and evaluation. It is showed has high accurcy and can be used as an important index and reference.
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Huang, Meng-Shun, and 黃盟舜. "Synthesis and Manufacture of high-performance heat-resistant resins / Copper Foil composites without Adhesive." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/21287938125239144493.
Full textAbstract:
博士國立臺灣科技大學
高分子工程系
93
Three kinds of polyurethane-urea-imide (PUUI) were synthesized. The Polyurethane prepolymer was synthesized from 4,4'-diphenylmethane diiso-cyanate (MDI) and polyethylene glycol (PEG-400), after which the pre-polymer was reacted with 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA) to form polyimide prepolymer, after which the prepolymer was reacted respectively with p-phenylenediamines (PPD), 4,4'-oxydianiline (4,4'-ODA), and 4,4'-methylenedianiline (MDA) to form PUUI-1, PUUI-2, and PUUI-3. Three kinds of polyurea-imide (PUI) and three kinds of polyamide-imide (PAI) were synthesized. The polyimide prepolymer was synthesized from MDI and PMDA, after which the prepolymer was reacted respectively with PPD, 4,4'-ODA, and MDA to form PUI-1, PUI-2, and PUI-3. The prepolymer was reacted respectively with terephthalic acid (TPA), isophthalic acid (IPA), and 4,4'-oxybisbenzonic acid (OBBA) to form PAI-1, PAI-2, and PAI-3. Amide-containing bismaleimide (ACBI) resins were prepared using four monomer reactants : 3,4'-oxydianiline (3,4'-ODA), trimellitic anhydride (TMA), maleic anhydride (MA), and 4-aminobenzoic acid. The PAI and polyurea-amide-imide (PUAI) resins were polymerized from five reactants : 4,4'-ODA, 4-nitrobenzoyl chloride, MDI, PMDA, and 3,3'-4,4'-benzophenone tetracar-boxylic dianhydride (BTDA). Their chemical structures were characterized using elemental analysis (EA), Fourier transform infrared spectrometry (FTIR) and nulclear magnetic resonance (NMR). The thermal properties, electrical properties, solubility, and mechanical properties of these resins were measured, and the optimal hot-press conditions, electrical properties, chemical resistance, peel strength, and heat resistance of resins / copper foil composites were studied. The experimental results show that the optimal hot-press conditions for PAI-1, PAI-2 and PAI-3 were respectively 235 oC / 5.88 MPa, 235 oC / 6.86 MPa, and 245 oC / 4.90 MPa. For PAI-4, PUAI and ACBI were respectively 380 oC / 4.90 MPa, 250 oC / 4.90 MPa, and 320 oC / 4.90 MPa. The glass transition temperatures of PUI-1, PUI-2 and PUI-3 films occurred respectively at 276 oC, 272 oC and 258 oC, the PAI-1, PAI-2, PAI-3 and PAI-4 films occurred respectively at 232 oC, 233 oC, 236 oC and 360 oC and PUAI films occurred at 229 oC. The dielectric constants of resins / copper foil composites were lower than 5.5 and the dissipation factors were lower than 0.035, those electrical properties in this study met the industrial requirements. These PAI / copper foil composites exhibited peel strength higher than 2.30 kN/m under normal circumstances and higher than 2.15 kN/m after heating. The order of peel strength was PAI-1 > PAI-3 > PAI-2. The chemical resistancetests showed that the peel strength retention values of the resins / copper foil composites were respectively more than 94 % and more than 92 % after immersing in 10 % H2SO4 solution at 70 oC for 1 h. The ACBI / copper foil composites treating with 0.2% coupling agent NZ97 had the highest peel strength of 2.097 kN/m. The peel strength was 1.57 kN/m after 1h at 300 oC. After treating in 10 % H2SO4 solution at 60 oC for 30 minutes, ACBI composites maintained 88% of their original peel strength.