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1
Jones, Kimberly A. „The creep behavior of aluminum alloy 8009“. Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/19630.
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Hamilton, Benjamin Carter. „Creep crack growth behavior of aluminum alloy 2519-T87“. Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/20500.
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3
Flaig, Alexander. „Thermal cycling creep of a fiber reinforced aluminum alloy“. [S.l. : s.n.], 2000. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB9386071.
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4
Hamilton, Benjamin Carter. „Creep behavior of aluminum alloys C415-T8 and 2519-T87“. Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/20497.
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5
Taylor, David Wayne. „The Lithium concentration dependence of creep in binary Aluminum-Lithium alloys“. Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26044.
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6
Allen, Benjamin William. „Creep and Elevated Temperature Mechanical Properties of 5083 and 6061 Aluminum“. Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/52630.
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With the increasing use of aluminum in naval vessels and the ever-present danger of fires, it is important to have a good understanding of the behavior of aluminum at elevated temperatures. The aluminum samples 5083-H116 and 6061-T651 were examined under a variety of loading conditions and temperatures. Tensile testing was completed on both materials to measure strength properties of elastic modulus, yield strength, and ultimate strength as well as reduction of area from room temperature to 500 deg C taking measurements every 50 deg C. These tests showed how much the material weakened as temperature increases. Low temperatures had a minimal effect on strength while exposure to temperatures between 200 and 300 deg C had the most significant impact. Creep testing was also completed for these materials. These tests were completed at temperatures between 200 and 400 deg C in 50 deg C increments. Stresses for these tests were in the range of 13 to 160MPa for 5083 aluminum and between 13 to 220MPa for 6061 aluminum. These tests showed a significant relationship between stress and temperature and how changes to one can cause a very different resulting behavior. In addition to the creep testing, three creep models were examined as a means of predicting creep behavior. These models included a power law, exponential, and hyperbolic-sine versions and were able to predict creep results with decent accuracy depending on the stress used in the model.Master of Science
7
Yang, Haoliang. „Creep age forming investigation on aluminum alloy 2219 and related studies“. Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/39352.
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By the middle of the 20th Century, traditional mechanical metal forming methods were showing to be inadequate for producing components comprising of large high strength aluminium alloy panels with complex curvatures, such as those used in modern aircraft and aerospace metal structures. To deal with this problem, a new forming method was conceived by Textron, which has proven to be very useful for forming components with these shape characteristics and good mechanical properties. The method is called Creep Age Forming (CAF). The research described in this thesis is a study of CAF of a 2219 aluminium alloy, which is used for fabricating the isogrid structure for fuel tanks of launch vehicles. The main aim of the research is to develop experimental and modelling tools for CAF of AA2219 sheet structures. A series of creep-ageing tests and stress-relaxation tests have been conducted on AA2219 at 175 °C. The age-hardening, creep deformation and stress relaxation behaviour of AA2219 have been investigated. Based on the experimental investigation, a novel set of physically based, unified creep constitutive equations has been established. A small scale CAF test rig was designed to validate the springback prediction from FE simulation. The experimental result and simulation are in good agreement. Development of FE procedures for simulating creep-ageing behaviour of the material and springback has been performed to predict and assess the springback behaviour of metal sheet in typical forming tools.
8
Afrin, Nasima. „An investigation of deformation behaviour and creep properties of micron sized Ni3Al columns“. Thesis, Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37005467.
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9
Mezni, Fadi. „Étude de l'influence de la température sur le fluage des conducteurs aériens de lignes de transport d'énergie électrique“. Mémoire, Université de Sherbrooke, 2018. http://hdl.handle.net/11143/11903.
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Le fluage est l'un des phénomènes qui influencent le comportement des conducteurs aériens de transport d'énergie électrique. Il s'agit d'une déformation irréversible qui apparaît dans les structures soumises à des charges mécaniques permanentes. Ce phénomène commence à l'instant où la charge est appliquée et continue, à un taux décroissant, aussi longtemps que la charge et la température sont maintenues.
Dans les conducteurs en portée, le fluage se manifeste par l'augmentation de la flèche et la réduction des distances sécuritaires entre les lignes et le sol. D'autre part, la température moyenne des conducteurs, transportant en continue un courant électrique important, peut être largement supérieure à la température ambiante, ce qui influence le phénomène de fluage des câbles. Dans ce cadre, s'inscrit ce projet de maîtrise qui consiste à évaluer l'effet de la température sur le comportement en fluage des conducteurs en mesurant l'allongement des fils qui les constituent.
Pour ce faire, un banc d'essai de fluage des câbles a été conçu pour étudier le fluage sur les conducteurs et un banc d'essai de fluage des brins a été utilisé pour déterminer le comportement en fluage des fils. Pour les conducteurs, un essai préliminaire de fluage, de 400 heures, a été effectué sur un conducteur de type AAC (Orchid) pour valider le montage expérimental et vérifier l'effet de la mise en place des brins sur le fluage. Le câble a été testé à 38°C et à 25% de sa résistance à la traction assignée (RTA). Pour les essais sur les brins, les fils d'aluminium 1350-H19 et d'almélec ont été testés en fluage pendant 1000 heures. Les fils ont été soumis à quatre niveaux de température d'opération : 20°C, 38°C, 55°C et 70°C et à quatre niveaux de contrainte : 15%, 25%, 35% et 47% RTA pour l'aluminium et 8%, 15%, 25% et 35% RTA pour les fils en almélec. De plus, des essais de traction sur des fils en aluminium et en alliage d'aluminium ont été effectués pour évaluer l'effet du fluage et de la température sur le comportement mécanique des fils isolés.
Ces résultats ont permis d'étudier l'effet de la température et de la contrainte sur le fluage des conducteurs à travers le fluage des fils. À partir des données expérimentales, une loi d'évolution de fluage a été établie et tient compte du taux de chargement et de la température.
10
Rippe, Christian M. „Burnthrough Modeling of Marine Grade Aluminum Alloy Structural Plates Exposed to Fire“. Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/64154.
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Current fire induced burnthrough models of aluminum typically rely solely on temperature thresholds and cannot accurately capture either the occurrence or the time to burnthrough. This research experimentally explores the fire induced burnthrough phenomenon of AA6061-T651 plates under multiple sized exposures and introduces a new burnthrough model based on the near melting creep rupture properties of the material.
Fire experiments to induce burnthrough on aluminum plates were conducted using localized exposure from a propane jet burner and broader exposure from a propane sand burner. A material melting mechanism was observed for all localized exposures while a material rupture mechanism was observed for horizontally oriented plates exposed to the broader heat flux. Numerical burnthrough models were developed for each of the observed burnthrough mechanisms. Material melting was captured using a temperature threshold model of 633 deg C. Material rupture was captured using a Larson-Miller based creep rupture model.
To implement the material rupture model, a characterization of the creep rupture properties was conducted at temperatures between 500 and 590 deg C. The Larson-Miller curve was subsequently developed to capture rupture behavior. Additionally, the secondary and tertiary creep behavior of the material was modeled using a modified Kachanov-Rabotnov creep model. Thermal finite element model accuracy was increased by adapting a methodology for using infrared thermography to measure spatially and temporally varying full-field heat flux maps. Once validated and implemented, thermal models of the aluminum burnthrough experiments were accurate to 20 deg C in the transient and 10 deg C in the steady state regions.
Using thermo-mechanical finite element analyses, the burnthrough models were benchmarked against experimental data. Utilizing the melting and rupture mechanism models, burnthrough occurrence was accurately modeled for over 90% of experiments and modeled burnthrough times were within 20% for the melting mechanism and 50% for the rupture mechanism. Simplified burnthrough equations were also developed to facilitate the use of the burnthrough models in a design setting. Equations were benchmarked against models of flat and stiffened plates and the burnthrough experiments. Melting mechanism burnthrough time results were within 25% of benchmark values suggesting accurate capture of the mechanism. Rupture mechanism burnthrough results were within 60% of benchmark values.Ph. D.
11
Seaton, Robert Leonard. „The influence of temperature and composition on the activation energy for creep in binary aluminum lithium alloys“. Thesis, Monterey, California: Naval Postgraduate School, 1990. http://hdl.handle.net/10945/27666.
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Approved for public release; distribution is unlimited.With the fast pace of technology in the aerospace industry, there are increasing demands for higher strength and stiffness in structural materials but with reduced weight and improved formability. Aluminum alloys have been widely used in the construction of aerospace vehicles because of their high strength to weight ratio, forming characteristics and corrosion resistance. An investigation was conducted to determine the temperature and composition dependence on the activation energy for creep of A1-0.5wt.pct.lithium, A1-1.Owt.pct.Li, and A1-2. Owt.pc+.Li alloys. A series of isothermal tests were conducted utilizing constant true stress creep tests, with nominal temperatures ranging from 300 C to 500 C. Temperature cycling tests involved a range of 10 C for each test. Experimental results indicate all three alloys behave as a class II alloy (pure metal class) with a stress exponent, n, approximately equal to 5. In addition, subgrain formation was observed in association with the primary stage of creep. The activation energy for creep of the A1-0.5wt.pct.Li and A1-1.Owt.pct.Li alloys was observed to b essentially the same as that for pure Aluminum.
12
Seaton, Robert L. „The influence of temperature and composition on the activation energy for creep in binary aluminum lithium alloys“. Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA242299.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 1990.Thesis Advisor(s): McNelley, Terry R. ; Kalu, Peter N. "December 1990." Description based on title screen as viewed on April 2, 2010. DTIC Identifier(s): Aluminum alloys, lithium, creep, binary alloys, strength weight ratio, stress tests, stress strain relations, microstructure, aerospace craft, isothermal tests, theses. Author(s) subject terms: Temperature, composition, activation energy, creep binary aluminum lithium alloys. Includes bibliographical references (p. 89-90). Also available in print.
13
Taminger, Karen M. B. „Analysis of Creep Behavior and Parametric Models for 2124 Al and 2124+SiC Composite“. Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/31399.
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The creep behavior of unreinforced 2124 aluminum and 2124 aluminum reinforced with 15 w/o silicon carbide whiskers was studied at temperatures from 250 F to 500 F. Tensile tests were conducted to determine the basic mechanical properties, and microstructural and chemical anyalyses were performed to characterize the starting materials. The creep, tensile, and microstructural data for the 2124+SiC composite were compared with a similarly processed unreinforced 2124 aluminum alloy. Applying the basic theories for power law creep developed for common metals and alloys, the creep stress exponents and activation energies for creep were determined from the experimental data. The results were used to identify creep deformation mechanisms and compared to predicted values based on a parametric approach for creep analysis. The results demonstrate the applicability of traditional creep analysis on non-traditional materials.Master of Science
14
Wang, Jianfeng. „Principles of the draw-bend springback test“. Columbus, Ohio : Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1080227128.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xvii, 167 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Robert H. Wagoner, Dept. of Materials Science and Engineering. Includes bibliographical references (p. 158-167).
15
Jianfeng, Wang. „Principles of the draw-bend springback“. The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1080237228.
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Ribeiro, Fábio Cruz. „Modelagem numérica da manufatura de painéis aeronáuticos pelo processo de conformação por fluência com envelhecimento“. Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/3/3151/tde-11072014-120238/.
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Esta dissertação tem como objetivo modelar numericamente a manufatura de painéis aeronáuticos de ligas AA7XXX com dupla curvatura variáveis sem reforçadores por meio do processo de conformação por fluência com envelhecimento (CFE). A fundamentação dos fenômenos processo CFE foram estudadas com ensaios de tração à quente, fluência e microscopia eletrônica de transmissão (MET) em amostras de AA7050. Utilizou-se a liga AA7010 e ensaios de fluência da literatura para a aplicação de modelos uniaxiais tanto simplificados quanto unificados para predição do comportamento de fluência com envelhecimento. Um modelo uniaxial unificado foi implementado programa de método dos elementos finitos MSC.Marc por meio de uma sub-rotina codificada em FORTRAN. Em seguida, construiu-se uma metodologia para se simular a fabricação de um revestimento feito de AA7475. Comparou-se a geometria obtida com a de um experimento real. Os resultados da modelagem uniaxial mostram que o modelo obtido é 46% mais exato que o modelo da literatura utilizado como referência e podem ser melhorados caso a influência do envelhecimento na fluência seja mais adequadamente quantificado. O método de simulação do processo CFE se mostrou aderente ao comportamento do material e pode ser mais exato conforme se melhore a modelagem do material.This dissertation aims to model numerically the manufacture of aircraft wing panels with double variable curvature and without stringers by creep age forming (CAF) process. The phenomena fundamentals were studied using AA7050 alloy samples through hot tensile, creep tests and transmission electron microscopy (TEM).The modeling of creep behavior under uniaxial and aging condition was performed using both simplified and unified models and compared with literature data for the alloy AA7010. A unified model was implemented in MSC.Marc finite elements method program through a subroutine coded in FORTRAN. Then, it was built a methodology to simulate an AA7475 panel forming. The obtained geometry was compared with a real experiment. The uniaxial modeling results show that the obtained simplified model is 46% more exact that the literature model, utilized as reference. These results can be improved if the ageing influence on creep is better quantified. The simulation method has described the material behavior, but there are limitations due to the power law material model.
17
Swaroop, N. R. Sathya. „Processing And High Temperature Deformation Of Pure And Magnesia Doped Alumina“. Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/180.
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Creep resistance is an important design criterion at high temperatures especially when continuous attempts are made to increase the efficiencies by increasing the operating temperatures. Alumina is an important high temperature material and in addition to that it is used in wide variety of applications such as substrates for electronic packaging, spark plugs, envelopes for sodium vapour lamps, cutting tools (when reinforced with silicon carbide) and in artificial joint prostheses.
Studies on creep in alumina. have started as early as 1961. There are differing mechanisms proposed to explain the creep behaviour of alumina in the literature, but until now there is no any unanimous decision as to what the rate controlling mechanism is. Magnesia doped at ppm levels can produce significant changes in the microstructure of alumina, the most important consequence of that being the grain growth inhibition, which renders alumina superplastic. However, in a stoichiometric oxide like alumina, small impurities can create extrinsic defects which would change the diffusivities and creep rates. Therefore the background impurities in alumina should be kept to a minimum, if small dopant effects have to be studied. The present study was undertaken making use of high purity alumina powder and comparing the grain growth and creep properties of pure and magnesia doped alumina, especially since no such investigation was carried out in the recent past with high purity alumina.
Pure alumina was processed by cold compaction followed by cold isostatic pressing (CIP) and pressureless sintering in air at 1773 K for 1 hour. Magnesia doped alumina was prepared by calcining a mixture of alumina and magnesium nitrate at 973 K for 2 hours followed by cold compaction, CIPing and pressureless sintering in air at 1773 K. Both pure and magnesia doped alumina were further annealed at 1873 K for various times to get grain sizes in the ranges of 1-5 μm.
Grain growth kinetics of pure and magnesia doped alumina were studied at 1823 and 1873 K. The parameter Kg which quantifies the mobility of the grain boundary was got. It was found that Kg had decreased in the magnesia doped alumina (in comparison with pure alumina) by a factor of about 3 to 4 which was marginal and insignificant. The grain sizes followed a log normal distribution in both the cases, indicative of normal grain growth.
Creep studies were conducted on pure and magnesia doped alumina in three modes, namely, constant stress, temperature jump and stress jump test. The temperature range used was 1673 to 1773 K and the stress range used was 10 to 100 MPa. The creep parameters were found to be n~1.6, p~3.7 and Q-545 kJ mol"1 for pure alumina and n~l .3, p~3.0 and Q~460 kJ mol-1 for magnesia doped alumina. The creep rates in the case of magnesia doped alumina were found to have increased by a factor of 2 to 3, in comparison with pure alumina. The increase in creep rates were found to be insignificant. The creep data were analyzed and the possibility of the dislocation and interface reaction controlled creep mechanisms were ruled out since they were inconsistent with the data. It was found, from creep parameters and the comparison of theoretical Coble and Nabarro-Herring creep rates with the experimental rates, that Coble creep might be rate controlling. The activation energy values suggested that aluminium ion diffusing along grain boundary might be the rate controlling species. However, when the theoretical creep rates considering various species were compared, the rate controlling species turned out to be oxygen ion diffusing along the grain boundary.
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Pearce, I. „Creep rupture and creep life prediction of aluminium airframe alloys“. Thesis, Swansea University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638435.
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Aluminium alloys 2419-T851, 2124-T851 and 7010-T7351 are candidates to succeed the current airframe alloy, RR58. In the present work, high precision constant stress creep curves have been obtained for alloys 2419-T851 and 7010-T7351 over an approximate stress range 100-400MPa at 373-463K. In the case of alloy 2419-T851, the creep curves recorded were predominantly primary in nature, alloy 7010-T7351 exhibited predominantly tertiary curves, while creep curves reported (2) for 2124-T851 showed an intermediate curve shape. These results have been analysed to allow comparisons to be made between conventional methods of creep data representation and a new approach, termed the theta Projection Concept.
19
Furness, Justin Albert George. „Thermal cycling creep of aluminium based composites“. Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239618.
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O'Dwyer, John Gerard. „Creep performance of SiCp reinforced aluminium alloy 2618A“. Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313719.
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Flaig, Alexander. „Thermal cycling creep of a fiber reinforced aluminium alloy /“. [S.l. : s.n.], 2000. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB9334241.
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Przydatek, Jan. „The elevated temperature deformation of aluminium alloy 2650“. Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287577.
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Durman, Mehmet. „The creep behaviour of pressure diecast zinc-aluminium based alloys“. Thesis, Aston University, 1989. http://publications.aston.ac.uk/11881/.
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The creep behaviour of three pressure diecast commercial zinc-aluminium based alloys: Mazak 3, corresponding to BS 1004A, and the new alloys ZA.8 and ZA.27 with a series of alloys with compositions ranging from 0% to 30% aluminium was investigated. The total creep elongation of commercial alloys was shown to be well correlated using an empirical equation. Based on this a parametrical relationship was derived which allowed the total creep extension to be related to the applied stress, the temperature and the time of test, so that a quantitative assessment of creep of the alloys could be made under different conditions. Deviation from the normal creep kinetics occurred in alloys ZA.8 and ZA.27 at very low stresses, 150°C, due to structural coarsening combined with partial transformation of ε -phase into T' phase. The extent of primary creep was found to increase with aluminium content, but secondary creep rates decreased in the order Mazak 3, ZA.8 and ZA.27. Thus, based on the above equation, ZA.8 was found to have a substantially better total creep resistance than ZA.27, which in turn was marginally better than Mazak 3 for strains higher than 0.5%, but inferior for smaller strains, due to its higher primary creep extension. The superior creep resistance of ZA.8 was found to be due to the presence of strictly-orientated, thin plate-like precipitates of ε(CuZn4) phase in the zinc matrix of the eutectic and the lamellarly decomposed β phase, in which the precipitation morphology and orientation of ε in the zinc matrix was determined. Over broad ranges of temperature and stresses, the stress exponents and activation energies for creep were found to be consistent with some proposed creep rate mechanisms; i.e. viscous glide for Mazak 3, dislocation climb over second phase particles for ZA.8 and dislocation climb for ZA.27, controlled by diffusion in the zinc-rich phase. The morphology of aluminium and copper-rich precipitates formed from the solid solution of zinc was clearly revealed. The former were found to further increase the creep rate of inherently low creep resistant zinc, but the latter contributed significantly to the creep resistance. Excess copper in the composition, however, was not beneficial in improving the creep resistance. Decomposition of β in copper-containing alloys was found to be through a metastable Zn-Al phase which is strongly stabilised by copper, and the final products of the decomposition had a profound effect on the creep strength of the alloys. The poor creep resistance of alloy ZA.27 was due to the presence of particulate products derived from decomposed β-phase and a large volume of fine, equiaxed products of continuously decomposed α-dendrites.
24
Wang, Le-Min. „Microstructure and properties of certain 2000 series aluminium alloys“. Thesis, Imperial College London, 1999. http://hdl.handle.net/10044/1/8801.
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Garcia-Granada, Andres-Amador. „The effect of creep and mechanical load on cold expanded fastener holes“. Thesis, University of Bristol, 2000. http://hdl.handle.net/1983/4740bd70-cca6-4bca-8a3f-86724e04559e.
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Madgwick, Alexander. „Creep and damage in an A359 aluminium alloy/SiC metal matrix composite“. Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620311.
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Mir, Arshad A. „The creep properties of a series of zinc-rich zinc-aluminium alloys“. Thesis, Aston University, 1998. http://publications.aston.ac.uk/13277/.
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The compressive creep behaviour of six sand cast zinc-rich alloys: No3 and No5, corresponding to BS 1004A and BS 1004B, respectively, alloy No2, ILZRO,.16 and two newer alloys ACuZinc5 and ACuZinc10 was investigated. The total creep contraction of the alloys was found to be well correlated using an empirical equation. On the basis of this equation, a parametrical relationship was derived which allowed the total creep contraction to be related to the applied stress, the temperature and the time of test, so that a quantitative assessment of compressive creep of the alloys could be made under different testing conditions. The primary creep and secondary creep rates were found for the alloys at different temperatures and stresses. Generally, the primary creep contraction was found to increase with copper content, whereas secondary creep rates decreased in the order No3, ACuZinc10, ACuZinc5 and No2. ILZRO.16 was tested only at the highest stress and two higher temperatures. The results showed that ILZRO.16 had higher creep resistance than all the other alloys. Thus, based on the above empirical equation, alloy No2 was found to have a substantially better total creep resistance than alloys No3 and No5, and slightly better than ACuZinc5 and ACuZinc10 for strains up to 1%. Both ACuZinc alloys had higher creep strength than commercial alloys No3 and No5. Alloy No5 had much higher creep resistance than alloy No3 under all conditions. The superior creep resistance of alloy No2 was considered to be due to the presence of small precipitates of -phase in the zinc matrix and a regular eutectic morphology. The stress exponents and activation energies for creep under different testing conditions were found to be consistent with some established creep-controlling mechanisms; i.e. dislocation climb for alloy No3, dislocation climb over second phase particles for alloys No5, No2, ACuZinc10, controlled by lattice diffusion in the zinc-rich phase. The lower creep resistance of alloy No3 was mainly due to the lower creep strength of copper-free primary particles having greater volume than eutectic in the microstructure. Alloys No5, ACuZinc5 and ACuZinc10 showed much better creep resistance than alloy No3, based on the precipitation-hardening due to the presence of small -phase precipitates. The primary dendrites in both ACuZinc alloys however were not of much benefit in improving the creep resistance of the alloys.
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Ham-Su, Rosaura. „Processing and creep behaviour of silicon carbide-platelet reinforced alumina“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0005/NQ42741.pdf.
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Caneo, Cartagena Eliseo Antonio. „Creep de compuestos de A16061/Nano A1203 fabricados por proceso de stir casting“. Tesis, Universidad de Chile, 2017. http://repositorio.uchile.cl/handle/2250/145899.
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Ingeniero Civil MecánicoEl aluminio y sus aleaciones son materiales con una elevada demanda en los campos industrial, aeroespacial y automotriz, debido a su amplia variedad de propiedades mecánicas y sobre todo por su elevada proporción de resistencia-peso, y gran resistencia a la corrosión. Para mejorar aún más las propiedades de estos materiales, se han creado los materiales compuestos de matriz metálica, los cuales tienen excelentes propiedades mecánicas y por lo tanto motiva su investigación. El objetivo general de este trabajo es estudiar el efecto de la cantidad de refuerzo de 〖Al〗_2 O_(3 ) sobre el creep y módulo elástico, en una matriz de aluminio 6061. También, se busca medir los términos del exponente del esfuerzo (n) y la energía de activación (Q) de la ecuación fundamental del creep. Para llevar esto acabo, se tienen muestras del compuesto con distintos porcentajes de 〖Al〗_2 O_3 como refuerzo. Luego, se implementa la técnica de creep por impresión con el fin de aprovechar las ventajas de este en comparación al creep por compresión. Las ventajas radican principalmente en la optimización del uso del material y en la disminución de error en los resultados. Se realizan análisis de vibraciones mediante excitación por impulso. A continuación, se realizan tratamientos térmicos de endurecimiento por solución y envejecimiento, y en paralelo se hacen mediciones de dureza Vickers después de cada uno de estos tratamientos. Se realizan ensayos de creep a temperaturas entre los 220°C y 280°C a diferentes esfuerzos constantes, para obtener varias curvas características de estas y mejorar el análisis de las mismas. Los resultados muestran que el refuerzo de alúmina aumenta el módulo de elasticidad de estas, obteniéndose valores cercanos a los 63 [GPa]. No se comprueba una relación lineal directa entre la cantidad de refuerzo con la deformación en creep y módulo elástico. Se incorpora el término de umbral de tensión que ayuda a explicar los mecanismos de creep existentes en los MMC de forma análoga a las aleaciones sólidas. Finalmente en los ensayos de creep, las muestras se comportan como si fuesen aleaciones de solución sólida. No se encuentra un valor certero para n ni Q debido a errores en mediciones, pero se logra ver una leve tendencia del mecanismo de creep por deslizamiento viscoso de dislocaciones.
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Djakovic, Aleksander. „Creep behaviour of aluminium alloy 2650-T8 : damage identification and physically based modelling“. Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404559.
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Anwar, Muhammad. „The compressive creep and load relaxation properties of a series of high aluminium zinc-based alloys“. Thesis, Aston University, 1997. http://publications.aston.ac.uk/13271/.
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A new family of commercial zinc alloys designated as ZA8, ZA12, and ZA27 and high damping capacity alloys including Cosmal and Supercosmal and aluminium alloy LM25 were investigated for compressive creep and load relaxation behaviour under a series of temperatures and stresses. A compressive creep machine was designed to test the sand cast hollow cylindrical test specimens of these alloys. For each compressive creep experiment the variation of creep strain was presented in the form of graphs plotted as percentage of creep strain () versus time in seconds (s). In all cases, the curves showed the same general form of the creep curve, i.e. a primary creep stage, followed by a linear steady-state region (secondary creep). In general, it was observed that alloy ZA8 had the least primary creep among the commercial zinc-based alloys and ZA27 the greatest. The extent of primary creep increased with aluminium content to that of ZA27 then declined to Supercosmal. The overall creep strength of ZA27 was generally less than ZA8 and ZA12 but it showed better creep strength than ZA8 and ZA12 at high temperature and high stress. In high damping capacity alloys, Supercosmal had less primary creep and longer secondary creep regions and also had the lowest minimum creep rate among all the tested alloys. LM25 exhibited almost no creep at maximum temperature and stress used in this research work. Total creep elongation was shown to be well correlated using an empirical equation. Stress exponent and activation energies were calculated and found to be consistent with the creep mechanism of dislocation climb. The primary and phases in the as-cast structures decomposed to lamellar phases on cooling, with some particulates at dendrite edges and grain boundaries. Further breakdown into particulate bodies occurred during creep testing, and zinc bands developed at the highest test temperature of 160°C. The results of load relaxation testing showed that initially load loss proceeded rapidly and then deminished gradually with time. Load loss increased with temperature and almost all the curves approximated to a logarithmic decay of preload with time.
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Srivastava, Vivek. „Low stress creep of copper and some aluminium and magnesium alloys at high and intermediate homologous temperatures“. Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398484.
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D'Ascenzo, Marco. „Analisi del comportamento a caldo dell'acciaio AISI - H11 per la stima della vita utile di matrici per estrusione“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amslaurea.unibo.it/508/.
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The effect of process parameters on the creep-fatigue behavior of a hot-work tool steel for aluminum extrusion die was investigated through a technological test in which the specimen geometry resembled the mandrel of a hollow extrusion die. Tests were performed on a Gleeble thermomechanical simulator by heating the specimen using jouleâs effect and by applying cyclic loading up to 6.30 h or till specimen failure. Displacements during the tests at 380, 490, 540 and 580°C and under the average stresses of 400, 600 and 800 MPa were determined. In the first set of test a dwell time of 3 min was introduced during each of the tests to understand the creep behavior. The results showed that the test could indeed physically simulate the cyclic loading on the hollow die during extrusion and reveal all the mechanisms of creep-fatigue interaction. In the second set a pure fatigue laod were induced and in the third set a static creep load were induced in the specimens. Furher type of tests, finite element and microstructural analysis were presented.
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Regensburger, Jochen. „Nichtlineares Deformationsverhalten von Karosserie-Außenhautbauteilen aus Aluminium im Lacktrocknungsprozess“. Universitätsverlag der Technischen Universität Chemnitz, 2017. https://monarch.qucosa.de/id/qucosa%3A21182.
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In dieser Arbeit wird die Berechenbarkeit des Deformationsverhaltens von Aluminiumaußenhautbauteilen in einem für die Automobilindustrie typischen Lacktrocknungsprozess um den irreversiblen Kriecheffekt erweitert. Untersucht wird dabei die in Europa oft für Außenhautbauteile eingesetzte Legierung AA6016 mit Hilfe von Zug- und Biegetests, aus denen ein geeignetes Werkstoffmodell für die numerische Simulation abgeleitet wird. Dabei wird auch der Einfluss des Umformgrades im Blechbauteil aus dem Herstellprozess untersucht und bewertet. Die seriennahe Validierung des Werkstoffmodells findet anhand einer eigens ausgelegten Baugruppe statt, die nach dem Wärmeprozess optisch sichtbare Formabweichungen aufweist. Mittels optischer Messungen wird die Baugruppe dabei vor, im und nach dem Wärmeprozess analysiert und die berechneten Formänderungen validiert. Im Ergebnis kann mit dem Werkstoffmodell die Auswirkung thermisch induzierter Spannungen unterhalb der klassischen Streckgrenze auf die Formänderung von Aluminiumblech in der frühen Produktentwicklungsphase prognostiziert werden.In this work, the computability of the deformation behaviour of aluminium car body panels in a typical automotive paint drying process is enhanced by the irreversible creep effect. The alloy AA6016, which is often used in Europe for aluminium car body panels, is examined with the aid of tensile and bending tests from which a suitable material model for numerical simulation is derived. The influence of the plastic deformation in the sheet metal component due to the manufacturing process is also examined and evaluated. The near-series validation of the material model takes place on the basis of a specially designed assembly which shows optically visible shape deviations after the heating process. Using optical measurements, the assembly is analyzed before, during and after the heating process and the calculated shape changes are validated. As a result, the material model can be used to predict the effect of thermally induced stresses below the classic yield strength on the deformation of aluminium sheet in the early product development phase.
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Khan, Kirity Bhusan. „Processing And Characterization Of B4C Particle Reinforced Al-5%Mg Alloy Matrix Composites“. Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/182.
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Metal matrix composites (MMCs) are emerging as advanced engineering materials for application in aerospace, defence, automotive and consumer industries (sports goods etc.). In MMCs, a metallic base material is reinforced with ceramic fiber, whisker or particulate in order to achieve a combination of properties not attainable by either constituent individually. Aluminium or its alloy is favoured as metallic matrix material because of its low density, easy fabricability and good engineering properties. In general, the benefits of aluminium metal matrix composites (AMCs) over unreinforced aluminium alloy are increased specific stiffness, improved wear resistance and decreased coefficient of thermal expansion. The conventional reinforcement materials for AMCs are SiC and AI2O3.
In the present work, boron carbide (B4C) particles of average size 40μm were chosen as reinforcement because of its higher hardness (very close to diamond) than the conventional reinforcement like SiC, AI2O3 etc. and of its density (2.52 g cm"3) very close to Al alloy matrix. In addition, due to high neutron capture cross-section of 10B isotope, composites containing B4C particle reinforcement have the potential for use in nuclear reactors as neutron shielding and control rod material. Al-5%Mg alloy was chosen as matrix alloy to utilize the beneficial role of Mg in improving wettability between B4C particles and the alloy melt. (Al-5%Mg)-B4C composites containing 10 and 20 vol% B4C particles were fabricated. For the purpose of inter-comparison, unreinforced Al-5%Mg alloy was also prepared and characterized. The Stir Cast technique, commonly utilized for preparation of Al-SiC, was adapted in this investigation.The Composites thus prepared was subsequently hot extruded with the objective of homogenization and healing minor casting defects. Finally the unreinforced alloy and its composites were characterized in terms of their microstructure, mechanical and thermo-physical properties, sliding wear behaviour and neutron absorption characteristics.
The microstructures of the composites were evaluated by both optical microscope and scanning electron microscope (SEM). The micrographs revealed a relatively uniform distribution of B4C particles and good interfacial integrity between matrix and B4C particles.
The hot hardness in the range of 25°C to 500°C and indentation creep data in the range of 300°C to 400°C show that hot hardness and creep resistance of Al-Mg alloy is enhanced by the presence of B4C particles. Measurement of coefficient of thermal expansion (CTE) of composites and unreinforced alloy upto 450°C showed that CTE values decrease with increase in volume fraction of reinforcement.
Compression tests at strain rates, 0.1, 10 and 100 s-1 in the temperature range 25 - 450 °C showed that the flow stress values of composites were, in general, greater than those of unreinforced alloy at all strain rates. These tests also depicted that the compressive strength increases with increase in volume fraction of reinforcements. True stress values of composites and unreinforced alloy has been found to be a strong function of temperature and strain rate. The kinetic analysis of elevated temperature plasticity of composites revealed higher stress exponent values compared to unreinforced alloy. Similarly, apparent activation energy values for hot deformation of composites were found to be higher than that of self-diffusion in Al-Mg alloy.
Tensile test data revealed that the modulus and 0.2% proof stress of composites increase with increase in volume fraction of the reinforcements. Composites containing 10%BUC showed higher ultimate tensile strength values (UTS) compared to unreinforced alloy. However, composites with 20%B4C showed lower UTS compared to that of the unreinforced alloy. This could be attributed to increased level of stress concentration and high level of plastic constraint imposed by the reinforcing jparticles or due to the presence solidification-induced defects (pores and B4C agglomerates ).
Sliding wear characteristics were evaluated at a speed of 1 m/s and at loads ranging from 0.5 to 3.5kg using a pin-on-disc set up. Results show that wear resistance of Al-5%Mg increases with the addition of B4C particles. Significant improvement in wear resistance of Al-5%Mg is achieved with the addition of 20% B4C particles. SEM examination of worn surfaces showed no pull-out of reinforcing particles even at the highest load of 3.5 kg, thus confirming good interfacial bonding between dispersed B4C particles and Al alloy matrix.
The neutron radiography data proved that (Al-5%Mg)-B4C composites possess good neutron absorbing characteristics.
From the experimental data evaluated in the "study, it may be concluded that (Al-5%Mg)-B4C composites could be a candidate material for neutron shielding and control rod application.
The enhanced elevated temperature-strength and favourable neutron absorption characteristics of these composites are strong points in favour of this material.
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Silva, Carlos Henrique da. „Degradação de UHMWPE e de POM devido à ação tribológica contra aço inoxidável e alumina“. Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/3/3132/tde-24122013-114021/.
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O presente trabalho tem como objetivo estudar o efeito da carga normal aplicada, da velocidade de deslizamento, do acabamento superficial e do tipo de contra-corpo, na degradação dos materiais poliméricos POM e UHMWPE, resultante do contato deslizante contra corpos rígidos. Para tanto, foram realizados ensaios de desgaste em um tribômetro do tipo pino-contra-disco, com os pinos de materiais poliméricos e os discos de alumina e aço inoxidável. Nos ensaios de desgaste, utilizou-se 3 valores de carga, 3 velocidades de deslizamento e 3 níveis de acabamento superficial do contra-corpo. Para cada condição de ensaio, foram realizadas 3 repetições. Durante os ensaios, foram monitoradas a temperatura na interface dos materiais, a força de atrito e a posição vertical do pino. O deslocamento vertical do pino devido ao desgaste foi utilizado para a determinação da taxa de desgaste do polímero. A distância percorrida pelos pinos sobre o disco foi de 3.500 metros. Os ensaios foram realizados em ambiente com umidade relativa controlada em 50 ± 5 %. As análises por microscopia eletrônica de varredura das superfícies de desgaste dos pinos e dos discos indicaram a ocorrência de três tipos de mecanismos de desgaste: a abrasão, a fadiga e a transferência de filme (adesão). Para analisar o comportamento do desgaste mediante as influências estudadas, um parâmetro de severidade global (PVR/DD) é proposto. No parâmetro PVR/DD, considerou-se a relação entre um fator mecânico (condição de pressão e velocidade, PV), um fator topográfico (rugosidade do contra-corpo, R) e um fator térmico (difusividade térmica dos materiais em contato, DD). Verificou-se que os níveis de desgaste dos materiais poliméricos são influenciados pela condição de severidade global do contato; entretanto, o efeito preponderante foi devido ao tipo de material do contracorpo. Como foi observado que o deslocamento vertical ocorre devido não somente ao desgaste, mas também à fluência do polímero, à atuação de diferentes mecanismos de desgaste e ao fenômeno da fusão, os resultados de cada material de polímero estudado foram organizados na forma de mapas em função da severidade global, salientando as regiões de atuação de cada fenômeno.The present investigation aims to study the degradation of polymeric materials resulting from the sliding contact against rigid bodies. The effect of some tribological influences, such as the applied load, the sliding velocity, the surface roughness and the counter-face material, were investigated. Experimental sliding wear tests were performed through a pin-on-disc tribometer, with the pins of polymeric material and the discs of alumina and stainless steel. The testing conditions of the wear tests encompassed three values of load (normal pressure) and three values of sliding velocity, or PV values, and three ranges of disc surface roughness. Three tests were performed in each condition. The interface temperature between the specimens, the friction force and the vertical position of the pin were monitored along the tests. The vertical displacement of the pin, resulting from the wear, was used for the determination of the polymer wear rate. The total sliding distance was of 3,500 meters. During the tests, the relative humidity of the environment was controlled to 50 ± 5 %. Analyses on the worn surfaces of pins and discs performed through scanning electronic microscopy indicated the occurrence of three wear mechanisms: abrasion (scratches), fatigue (waves) and adhesion (transfer film). In order to analyze the wear behavior of the polymer, a parameter of global severity of the contact (PVR/DD) was proposed. This parameter comprised a mechanical factor (the PV values), a topographic factor (the disc roughness) and a thermal factor (the thermal diffusivity of the materials in contact). It was possible to verify that the polymer wear depended on the level of global severity of the contact, where the major effect was due to the counterface material. It was also observed that the vertical displacement of the pin occurred not only due to the wear phenomena, but also due to the creep and the melting of the polymer, both depending on the testing condition. The creep and the melting phenomena were considered in the polymer degradation behavior, organizing the results of polymeric pin displacement in degradation maps, showing the boundaries of each observed phenomena, in function of the contact global severity.
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Perrière, Loïc. „Élaboration par solidification dirigée et comportement mécanique de céramiques eutectiques à base d’oxydes réfractaires : rôle de la microstructure sur la fissuration et la déformation plastique à haute température“. Thesis, Paris Est, 2008. http://www.theses.fr/2008PEST0048/document.
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Dans le contexte général lié aux économies d’énergie, l’amélioration sensible du rendement des turbines à gaz (aéronautiques ou terrestres), nécessitera d’augmenter notablement la température des gaz de combustion. Cela implique l’emploi de matériaux stables au-delà de 1 500°C. Les céramiques eutectiques préparées par solidification dirigée, à partir des systèmes Al2O3 - Ln2O3 (où Ln représente un élément lanthanide ou l’yttrium) sont une solution envisageable. En effet, leur microstructure, constituée d’un réseau interpénétré 3D de deux phases monocristallines, et exempte de pores, de colonies et de joints de grains, confère à ces systèmes eutectiques des propriétés mécaniques d’un bon niveau, et quasi-constantes jusqu’à des températures proches de leur température eutectique (> 1 700°C). Nos travaux ont consisté à élaborer plusieurs systèmes eutectiques binaires et ternaires, par ajout d’une phase ZrO2 renforçante. Les six systèmes présentant les microstructures les plus prometteuses (3 binaires : Al2O3 - Y3Al5O12, Al2O3 - Er3Al5O12, Al2O3 - GdAlO3, et 3 ternaires : Al2O3 - Y3Al5O12 - ZrO2, Al2O3 - Er3Al5O12 - ZrO2, Al2O3 - GdAlO3 - ZrO2) ont été retenus pour étudier certaines de leurs propriétés mécaniques. Plusieurs modes de fissuration, allant dans le sens de l’augmentation de ténacité détectée dans ces systèmes, ont été décelés après des essais de flexion biaxiale. Ces modes de fissuration ont été corrélés aux caractéristiques microstructurales et à la distribution des contraintes résiduelles, déterminées par le calcul et mesurées par une méthode piézo-spectroscopique. Enfin, l’étude du comportement en fluage à haute température a permis de mettre en évidence une évolution des mécanismes de déformation en fonction des conditions de sollicitation. L’étude MET post mortem a également souligné l’influence marquée du caractère interconnecté de la microstructure sur le comportement en fluageIn the general context of energy savings at a global scale, the improvement of the thermal efficiency of both terrestrial and aeronautical gas turbines will require to increase the turbine inlet gas temperature. The development of new materials, stable up to 1 500°C, is thus necessary. In this context, Directionally Solidified Eutectic Ceramics (DSEC), prepared from Al2O3 and Ln2O3-based systems, could be a potential solution. Their microstructure consists of two single-crystal phases continuously entangled in a threedimensional interpenetrating network without grain boundaries, pores or colonies. The outstanding stability of these microstructures gives rise to a high strength and creep resistance at high temperature. Our research consisted first in obtaining, by directional solidification, several eutectic systems, either binary or ternary (with addition of a toughening third ZrO2 phase). The six most promising DSEC (3 binary systems: Al2O3 - Y3Al5O12, Al2O3 - Er3Al5O12, Al2O3 - GdAlO3, and 3 ternary systems: Al2O3 - Y3Al5O12 - ZrO2, Al2O3 - Er3Al5O12 - ZrO2, Al2O3 - GdAlO3 - ZrO2) have then been selected to study some of their mechanical properties. Several crack propagation patterns have been detected after biaxial flexure testing, and partially explain the toughening which has been proven for DSEC. Attention has been paid to the possibility of crack deflection in the various phases and in the phase boundaries, a phenomenon which may markedly improve the toughness of these eutectic ceramics. These observations have been correlated to internal stress calculations and piezo-spectroscopic measurements. Finally, the study of the creep behavior showed that the deformation mechanisms evolve with the macroscopic solicitation (temperature and stress). microstructure. Moreover, post mortem TEM observations exhibited that creep mechanisms are strongly dependant on the entangled microstructure
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Blugan, Gurdial Sing. „A systematic study of the effects of alumina, yttria and zirconia sintering additives on the microstructure and high temperature creep properties of silicon nitride“. Thesis, Queen Mary, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271817.
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Stanislav, Filip. „Tváření hliníkových slitin při stárnutí“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-400501.
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The diploma thesis is focused on the description and the verification of a relatively young creep age forming method. This method is based on a relaxation of stress and a creep of material, which occur by forming a part in the clamping tool during the artificial precipitation heat treatment at elevated temperature. After removing from the tool, the spring back and the residual stresses in the part are smaller compared to the conventional forming methods. This is mainly reflected in the increased fatigue resistance of the structure. The creep aging is only applicable to the precipitation heat treatable alloys. This thesis is focused on aluminium alloys, which are typical for the aerospace industry. The first part of the thesis describes principles of technology, its use in the aviation and material processes in the aluminium precipitation heat treatable alloys during the creep age forming. In the second part, there is a methodology of the verification of technology on samples made of the aluminium alloys ČSN EN AL-P 7075 and ČSN 424203 (approximate equivalent of ČSN EN AL-P 2024). Furthermore, a forming tool is designed, and experiments are performed according to the proposed methodology. At the end of the thesis, the experiments are evaluated and changes in the spring back of the samples are compared for three different methods of forming: the conventional cold clamping forming, the creep age forming and the creep age forming with an overaging.
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Facco, Antoine. „Développement d'un nouvel alliage austénitique résistant en fluage à forte teneur en Al : Relation microstructure/propriétés mécaniques/vieillissement“. Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR130.
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Les alliages austénitiques réfractaires Fe-Ni-Cr sont utilisés pour la fabrication des tubes coulés par centrifugation constituant les fours de vapocraquage. Ces tubes sont soumis à de très hautes températures (950-1150°C) sous quelques bars dans un environnement sévère (oxydation, carburation, cokage, …). Les développements actuels portent sur des alliages alliés avec de l’Al afin d’améliorer leur résistance à l’environnement via la formation d’une couche d’alumine protectrice. Cependant l'ajout d'Al diminue les propriétés en fluage. La problématique majeure de ce travail est de comprendre l’influence de la composition chimique et plus particulièrement de l’Al sur la microstructure et les propriétés en fluage dans l’optique de proposer une nouvelle nuance à forte teneur en Al (>3.5%m) résistante en fluage. Dans cette étude, plusieurs alliages aluminoformeurs (AFA) ont été testés en fluage et caractérisés microstructuralement après solidification, après vieillissement thermique et après fluage dans l’optique de faire le lien entre leurs propriétés en fluage et leurs microstructures. Ce travail a montré que : - La nature des carbures primaires de Cr conditionne la résistance en fluage des alliages dans le régime haute contrainte. - La précipitation secondaire de carbures M23C6 est déterminante concernant les propriétés en fluage dans le régime haute contrainte mais a peu d’effet dans le régime basse contrainte. - L’addition de teneur élevée en Y empêche le développement de la précipitation secondaire de M23C6 malgré la transformation des M7C3 primaires en M23C6. - L’ajout de fortes teneurs en Al associé à de fortes teneurs en Cr stabilise les phases ductiles NiAl et α’ aux températures de service. La phase NiAl a été identifiée comme étant néfaste en fluage. Toutes ces conclusions ont permis de développer une méthode d’optimisation de la composition chimique d’alliages austénitiques à forte teneur en Al résistant en fluage. L’objectif industriel consistant à développer des alliages à forte teneur en Al (>3.5%m d’Al) alliant de bonnes propriétés en fluage et une bonne résistance à l’environnement a été rempli et s’est concrétisé par le développement de la Manaurite® XAl4 actuellement commercialisée par Manoir IndustriesHeat resistant Fe-Ni-Cr austenitic stainless alloys are used in centrifugally cast tubes for cracking furnaces. These tubes undergo high temperatures (950-1150°C), low pressure (few bars) in a harsh environment (oxidation, carburization, coking, …). The current developments are focused on alloys with high Al-content in order to improve the environmental resistance thanks to the formation of a protective alumina scale. Nevertheless, Al is known to decrease the creep properties. The main goal is to understand the influence of the chemical composition especially the Al-content on the microstructure and the creep properties in order to propose a new creep-resistant alloy with high Al-content (>3.5wt.%). In this study, several aluminaforming austenitic alloys (AFA) were tested in creep and their microstructures characterized after solidification, after thermal ageing and after creep in order to make the link between creep properties and microstructures. This work showed: - The nature of primary Cr-carbides determines the creep resistance of these alloys in the high stress regime. - The secondary precipitation of M23C6 is crucial regarding the creep properties in the high stress regime but has low impact in the low stress regime. - The addition of high level of Y prevents the secondary precipitation of M23C6 despite the M7C3 transformation into M23C6. - The addition of high Al and Cr contents stabilizes the NiAl and α’ ductile phases at service temperature. The NiAl phase was identified as deleterious for the creep properties. These conclusions allowed to develop a method for chemical composition optimization of creep resistant austenitic alloy with high Al-content. The industrial aim consisting to develop alloys with high Al-content (>3.5wt.%) with good environment resistance while keeping good creep properties was filled and resulted in the development of the Manaurite® XAl4 currently commercialized by Manoir Industries
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Verrelli, D. I. „Drinking water treatment sludge production and dewaterabilityф“. D. I. Verrelli, 2008. http://repository.unimelb.edu.au/10187/3521.
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The provision of clean drinking water typically involves treatment processes to remove contaminants. The conventional process involves coagulation with hydrolysing metal salts, typically of aluminium (‘alum’) or trivalent iron (‘ferric’). Along with the product water this also produces a waste by-product, or sludge. The fact of increasing sludge production — due to higher levels of treatment and greater volume of water supply — conflicts with modern demands for environmental best practice, leading to higher financial costs. A further issue is the significant quantity of water that is held up in the sludge, and wasted.One means of dealing with these problems is to dewater the sludge further. This reduces the volume of waste to be disposed of. The consistency is also improved (e.g. for the purpose of landfilling). And a significant amount of water can be recovered. The efficiency, and efficacy, of this process depends on the dewaterability of the sludge.In fact, good dewaterability is vital to the operation of conventional drinking water treatment plants (WTP’s). The usual process of separating the particulates, formed from a blend of contaminants and coagulated precipitate, relies on ‘clarification’ and ‘thickening’, which are essentially settling operations of solid–liquid separation.WTP operators — and researchers — do attempt to measure sludge dewaterability, but usually rely on empirical characterisation techniques that do not tell the full story and can even mislead. Understanding of the physical and chemical nature of the sludge is also surprisingly rudimentary, considering the long history of these processes.
The present work begins by reviewing the current state of knowledge on raw water and sludge composition, with special focus on solid aluminium and iron phases and on fractal aggregate structure. Next the theory of dewatering is examined, with the adopted phenomenological theory contrasted with empirical techniques and other theories.The foundation for subsequent analyses is laid by experimental work which establishes the solid phase density of WTP sludges. Additionally, alum sludges are found to contain pseudoböhmite, while 2-line ferrihydrite and goethite are identified in ferric sludges.
A key hypothesis is that dewaterability is partly determined by the treatment conditions. To investigate this, numerous WTP sludges were studied that had been generated under diverse conditions: some plant samples were obtained, and the remainder were generated in the laboratory (results were consistent). Dewaterability was characterised for each sludge in concentration ranges relevant to settling, centrifugation and filtration using models developed by LANDMAN and WHITE inter alia; it is expressed in terms of both equilibrium and kinetic parameters, py(φ) and R(φ) respectively.This work confirmed that dewaterability is significantly influenced by treatment conditions.The strongest correlations were observed when varying coagulation pH and coagulant dose. At high doses precipitated coagulant controls the sludge behaviour, and dewaterability is poor. Dewaterability deteriorates as pH is increased for high-dose alum sludges; other sludges are less sensitive to pH. These findings can be linked to the faster coagulation dynamics prevailing at high coagulant and alkali dose.Alum and ferric sludges in general had comparable dewaterabilities, and the characteristics of a magnesium sludge were similar too.Small effects on dewaterability were observed in response to variations in raw water organic content and shearing. Polymer flocculation and conditioning appeared mainly to affect dewaterability at low sludge concentrations. Ageing did not produce clear changes in dewaterability.Dense, compact particles are known to dewater better than ‘fluffy’ aggregates or flocs usually encountered in drinking water treatment. This explains the superior dewaterability of a sludge containing powdered activated carbon (PAC). Even greater improvements were observed following a cycle of sludge freezing and thawing for a wide range of WTP sludges.
Further aspects considered in the present work include deviations from simplifying assumptions that are usually made. Specifically: investigation of long-time dewatering behaviour, wall effects, non-isotropic stresses, and reversibility of dewatering (or ‘elasticity’).Several other results and conclusions, of both theoretical and experimental nature, are presented on topics of subsidiary or peripheral interest that are nonetheless important for establishing a reliable basis for research in this area.
This work has proposed links between industrial drinking water coagulation conditions, sludge dewaterability from settling to filtration, and the microstructure of the aggregates making up that sludge. This information can be used when considering the operation or design of a WTP in order to optimise sludge dewaterability, within the constraints of producing drinking water of acceptable quality.
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Himbeault, Donald Denis. „Creep of aluminum (rich)-nickel eutectic“. 1985. http://hdl.handle.net/1993/28891.
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Chang, Wen-Hsiung, und 張文雄. „The study of 6061 aluminum alloys and aluminum matrix composites on the high temperture creep properties“. Thesis, 1996. http://ndltd.ncl.edu.tw/handle/52826426625448272047.
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碩士國立臺灣大學
材料科學(工程)研究所
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The goal of this experiment is to study the creep properties of 6061 aluminum matrix composites (AMCs) reinforced with SiC rein- forcement using powder metallurgy (P/M) route. The material for the experiment were 6061 Al and 6061 Al+10vol%SiC, with rein- forcement sizes 0.53 and 7μm respectively. Two different types of extrusion technique, namely traditional and reciprocating extrusion, were employed in the P/M method. The effects of processing parameters, as well as the effects of reinforcement size, on the creep resistance of the composites have been evalu- ated. In the first part of the study the two methods of extrusion have been compared. In the reciprocating extrusion method, the powders after blending were hot-pressed and then directly subjected to reciprocating extrusion. On the other hand, for the composites undergone the traditional extrusion, the powders were cold-isostatic pressed, liquid phase sintered and then extruded in the conventional way. The creep behaviors of the composite were the subject of research in the second part of the study. Threshold stress was detected for all materials tested , and this threshold stress increased as the size of reinforcement decreased. The creep resistance of AMC reinforced with 0.53μm SiC was significantly improved over that of the AMC with 7μm SiC reinforcement. In addition,the sub- micron SiC reinforced AMCs showed a higher stress exponent and a higher creep activation energy as compared to those of AMC rein- forced with 7μm reinforcement. If the method of extrusion taken was introduced by reciprocating extrusion method, in terms of stable creep rate and the span of creep rupture life, was found to be superior to that produced by conventional method.
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Nimityongskul, Aaron. „Creep and relaxation in die-cast aluminum alloys at elevated temperature“. 2005. http://catalog.hathitrust.org/api/volumes/oclc/64386988.html.
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Cho, Junghyun. „Role of rare-earth dopants on the improved creep properties of aluminum oxide /“. Diss., 1998. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9919142.
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Flaig, Alexander [Verfasser]. „Thermal cycling creep of a fiber reinforced aluminum alloy / vorgelegt von Alexander Flaig“. 2000. http://d-nb.info/962022152/34.
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McMahon, Michael E. „The variation of subgrain misorientation in aluminum with large steady-state creep strain“. Thesis, 1986. http://hdl.handle.net/10945/22179.
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High purity aluminum was torsionally deformed to various strains up to 16.33 at a temperature of 644 K in this study. The variation in the dislocation substructure was determined with increasing strain. Recent work revealed that both the subgrain size and density of dislocations not associated with subgrain boundaries remained constant over the range of steady-state strains examined. However, transmission electron microscopy in this work revealed that subgrain boundaries remained constant over the range of steady-state strains examined. However, transmission electron microscopy in this work revealed that subgrain boundaries undergo two types of basic changes during steady-state creep. At the onset of steady-state behavior (epsilon = 0.20) all subgrain boundaries had small misorientations, typically, 0.6. The misorientation across boundaries formed as a result of dislocation accumulation continued to increase well past steady-state up to a strain of about 1.2, where a maximum average value of 1.2 was observed. This suggests that the dislocation spacing in subgrain boundaries is not principally responsible for the creep resistance during five power-law creep. At strains greater than about four, nearly a third of the subgrain boundaries were determined to be high angle boundaries (HAB)
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Gobien, Jeremy Michael. „Creep properties of a zinc-aluminum die-casting alloy as a function of grain size“. 2010. http://www.lib.ncsu.edu/theses/available/etd-03302010-121610/unrestricted/etd.pdf.
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Mieszczanski, Paul P. „The variation in the subgrain size in aluminum deformed to large steady-state creep strains“. Thesis, 1985. http://hdl.handle.net/10945/21615.
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Wetter, Timothy Scott. „The variation of the dislocation density in aluminum deformed to large steady-state creep strains“. Thesis, 1986. http://hdl.handle.net/10945/22178.
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