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1
Smith, Jansen A., Daniel A. Auerbach, Karl W. Flessa, Alexander S. Flecker et Gregory P. Dietl. « Fossil clam shells reveal unintended carbon cycling consequences of Colorado River management ». ROYAL SOC, 2016. http://hdl.handle.net/10150/622496.
Texte intégralRésumé :
Water management that alters riverine ecosystem processes has strongly influenced deltas and the people who depend on them, but a full accounting of the trade-offs is still emerging. Using palaeoecological data, we document a surprising biogeochemical consequence of water management in the Colorado River basin. Complete allocation and consumptive use of the river's flow has altered the downstream estuarine ecosystem, including the abundance and composition of the mollusc community, an important component in estuarine carbon cycling. In particular, population declines in the endemic Colorado delta clam, Mulinia coloradoensis, from 50-125 individuals m(-2) in the pre-dam era to three individualsm-2 today, have likely resulted in a reduction, on the order of 5900-15 000 tCyr(-1) (4.1-10.6 mol Cm-2 yr(-1)), in the net carbon emissions associated with molluscs. Although this reduction is large within the estuarine system, it is small in comparison with annual global carbon emissions. Nonetheless, this finding highlights the need for further research into the effects of dams, diversions and reservoirs on the biogeochemistry of deltas and estuaries worldwide, underscoring a present need for integrated water and carbon planning.
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Lawrence, Ursula. « The engineering geology of the clay-with-flints : (as shown on the British Geological Survey 1:50 000 New Series Geological sheets) ». Thesis, University of Surrey, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420056.
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Kaparulina, E. (Ekaterina). « Eurasian Arctic ice sheets in transitions:consequences for climate, environment and ocean circulation ». Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526217765.
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Abstract In this Ph.D. thesis sediment cores from the central Arctic Ocean, southwestern Barents Sea and sediment exposures from the Kola Peninsula were investigated in order to reveal interactions between the late middle Pleistocene and late Pleistocene Arctic ice sheets, between Marine Isotope Stages 6 and 1 (MIS 6 and MIS 1). One of the main objectives of this work is to establish provenance areas for the sediments studied in the central Arctic, the southwestern (SW) Barents Sea and the Kola Peninsula, their transport mechanisms and through that their relationship to glaciations in the Arctic and to development in the Kola Peninsula during the late middle and late Pleistocene. Mineralogical and geochemical data from the core 96/12-1pc on the Lomonosov Ridge, central Arctic Ocean was studied to evaluate ice transport from circum-Arctic ice sheets and variability in sediment drainage systems associated with their decay. SW Barents Sea sediments contain important information on Late Glacial and Holocene sediment provenance characteristics in relation to ice flow patterns and ice rafting from different regional sectors. The studied SW Barents Sea sediment cores show that sediments were most likely derived from a combination of far-field Fennoscandian sources, local subcropping Mesozoic strata below the seafloor and sea ice transport. The investigation carried out on the Kola Peninsula indicates that the Eemian (MIS 5e) marine environment in the White Sea Basin and onshore coastal areas gradually changed into a glaciolacustrine environment during MIS 5d to MIS 5a. Subsequently, the Scandinavian Ice Sheet (SIS) covered the Kola Peninsula, most probably during MIS 4. The final deglaciation of the SIS on the Kola Peninsula took place, however, during the late Weichselian (MIS 2) between 16–12 kaTiivistelmä Tässä väitöstutkimuksessa tutkittiin sedimenttikairanäytteitä keskeiseltä Jäämereltä ja Lounais-Barentsinmereltä sekä tarkasteltiin sedimenttiseurantoja Kuolan niemimaalla tarkoituksena selvittää myöhäisen keskipleistoseeni- ja myöhäispleistoseeniajan Arktisten jääkenttien keskinäiset vuorovaikutukset erityisesti merellisten isotooppivaiheiden 6 ja 1 (MIS 6 ja MIS 1) välillä. Tämän työn yhtenä päätavoitteena on määritellä sedimenttien lähdealueet keskeisellä Arktiksella, lounaisella Barentsinmerellä ja Kuolan niemimaalla, sedimenttien kuljetusmekanismit ja näiden perusteella riippuvuudet Arktisiin jäätiköihin ja Kuolan niemimaalla tapahtuneeseen myöhäiskeski- ja myöhäispleistoseenin kehitykseen. Mineraloginen ja geokemiallinen tieto Lomonosovin harjanteen kairauksesta 96/12-1pc, keskeisellä Jäämerellä on perusta arvioitaessa jääkuljetusmekanismeja ympäröiviltä sirkum-Arktisilta jäätiköiltä ja arvioitaessa valuma-alueiden osuutta suhteessa näiden jäätiköiden häviämiseen. Lounaisen Barentsinmeren sedimentit sisältävät tärkeätä tietoja viimeisen jäätiköitymisen loppuvaiheen ja holoseeni-ajan sedimenttien lähdealueista ja suhteista jäävirtauksiin ja jääkuljetukseen eri aluesektoreilta. Tutkitut Lounais-Barentsinmeren sedimentit osoittavat, että sedimentit olivat todennäköisimmin peräisin suhteellisen kaukaisilta Fennoscandian lähdealueilta, paikallisista mesotsoosista merenpohjan kerrostumista ja merijään kuljettamasta materiaalista. Kuolan niemimaalla tehty tutkimus osoittaa, että Eem-kauden (MIS 5e) meriympäristö Vienanmeren altaassa ja rannikkoalueilla vähitellen muuttui glaciolakustriseksi ympäristöksi MIS 5d:n ja MIS 5a:n välisenä aikana. Sen jälkeen Skandinavian jääkenttä (SIS) peitti Kuolan niemimaan, todennäköisimmin koko MIS:n 4 ajanjakson. SIS:n lopullinen deglasiaatio alkoi Kuolan niemimaalla kuitenkin myöhäisen Veiksel-jääkauden (MIS 2) aikana noin 16–12 ka sitten
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Jara, Heiner Lopez, Brandon Bravo Barrionuevo et Carlos Fernández Díaz. « Application of glass and fan shells to a clay soil to increase its mechanical properties ». IOP Publishing Ltd, 2021. http://hdl.handle.net/10757/655956.
Texte intégralRésumé :
Improving the mechanical properties of a clayey soil is one of the best options to avoid future structural failures in buildings and is cheaper than replacing all the material. Therefore, this article proposes the use of recycled glass and fan shells as reinforcement materials. This article presents an experimental study to evaluate the mechanical properties of a pure and mixed soil. The clay soil was mixed with 7% of glass (PV) and with 3%, 6%, 10%, 12% and 15% of Fan Shells (PCA) duly crushed and passed through sieve #100. Tests of sieve granulometry, sedimentation granulometry, Atterberg limits, modified proctor and drained consolidated direct cut were performed. This allowed comparing all the data obtained and defining the optimal percentage of the mixture in which the clay improves its mechanical properties. According to the tests carried out, the proportion that has 7% glass and 6% Fan Shells has better results because there is an improvement in its dry density from 1,784 g / cm3 to 1,847 g / cm3, its moisture content increases from 9.4% to 12.1%. In addition, its friction angle improves from 28.9 °to 32 °and cohesion from 0.05 kg / cm2 to 0.1 kg / cm2. These results verify that the properties of the clay soil are improved.
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Patterson, Shelley M. « The effects of ballistic impact of littorinid shells on the erosion of a cohesive clay bed ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58430.pdf.
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Arias, Ruiz Camilo. « High resolution climate records from modern and last interglacial periods derived from giant clam shells (Tridacnidae) in Sulawesi, Indonesia ». Thesis, Nantes, 2017. http://www.theses.fr/2017NANT4081/document.
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Des coquilles de bénitiers géants (Famille Tridacnidae) ont étés utilisées pour reconstruire des conditions climatiques au cours des dernières périodes interglaciaires dans l’ île de Sulawesi , en Indonésie. Des analyses géochimiques sur des coquilles modernes, ont montré que ces organismes enregistrent effectivement la variation de l ’environnement dans lequel ils habitent , en termes de : température, salinité, précipitations et apports en nutriments . Le s résultat s principaux ont été la reproductibilité du signal géochimique dans deux espèces différentes et l’enregistrement des anomalies climatiques liées au phénomène La Niña en 2010. La datation à travers l’Uranium - Thorium a mis en évidence des récifs formés lors du début de la dernière période interglaciaire (MIS - 5) et de l’avant dernière interglaciaire ou MIS - 7. La comparaison entre reconstructions modernes et fossiles a donné comme résultats : 1) des conditions de température en moyenne plus froides et avec une saisonnalité réduite pour ces deux périodes (début du MIS - 5 et MIS - 7), liée à des conditions plus sèches.2) Ces paramètres répondent systématiquement aux variations du niveau marin et témoignent la forte interaction entre la circulation atmosphérique et océanique dans la région .3) La variabilité interannuelle SST/SSS présente des oscillations dans la même amplitude qu’aujourd’hui pour la période du MIS - 5, cependant pour le MIS 7, ces oscillations sont réduites autour de 50 % par rapport à l’actuelle . 4) Le Mg/Ca présente une forte variation taxonomique, des études complémentaires sont nécessaires pour enlever le facteur biologique du signal géochimique. 5) Le Ba/Ca et le 13C sont potentiellement liées aux processus d’upwelling et/ou variations de salinitéGiant clam shells (Tridacnidae family) were used to reconstruct climatic conditions during the last interglacial periods in Indonesia's Sulawesi Island. Geochemical analyzes on modern shells have shown that these organisms actually record the variation of the environment in which they live, in terms of: temperature, salinity, precipitation and nutrient inputs. The main results were the reproducibility of the geochemical signal in two different species, as well as the recording of the climatic anomalies related to the La Niña phenomenon in 2010. Uranium-series dating revealed reefs formed at the beginning of the last interglacial period (MIS-5) and the penultimate interglacial or MIS-7. The comparison between modern and fossil reconstructions gave the following main results: 1) colder average temperature conditions with reduced seasonality for both periods (beginning of MIS-5 and MIS-7) due to drier conditions.2) These parameters respond systematically to a decrease / increase of the sea level and testify the strong interaction between the atmospheric and ocean circulation in the region3) The interannual variability of SST / SSS presents oscillations in the same amplitude as today for the MIS-5 period, however for MIS 7, these oscillations are reduced around 50% compared to the current interglacial4) The Mg/Ca ratio has a strong taxonomic variation, additional studies are needed to remove the biological factor related to geochemical signal. 5) Ba/Ca present a potential use as tracers of upwelling processes and/ or variations in salinity. Giant clam shells (Tridacnidae family) were used to reconstruct climatic conditions during the last interglacial periods in Indonesia's Sulawesi Island. Geochemical analyzes on modern shells have shown that these organisms actually record the variation of the environment in which they live, in terms of: temperature, salinity, precipitation and nutrient inputs. The main results were the reproducibility of the geochemical signal
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Acaba, Joseph Michael. « Primary Sediment Production from Granitic Rocks in Southeastern Arizona ». Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/231212.
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Isolated granitic rock bodies (granites, granodiorites, quartz monzonites) in the vicinity of Benson in southeastern Arizona were studied to trace the behavior of rock weathering. Thin sections of fresh granites were examined to characterize the original mineralogy which consisted mainly of quartz, feldspars, and micas. The weathering products show up on the granites as grus and soil profiles as well as down slope in the basin deposits. X -ray diffraction studies of the < 2 micrometers fraction of the weathering products proved illite, smectite, illite-smectite mixed layer, and kaolinite to be the dominant clays; quartz and feldspar also persisted into this size fraction. Silt sized material produced similar results. The quartz monzonite of Texas Canyon afforded a special study of the initial weathering stages of feldspars and micas. In the < 2 micrometers fraction obtained from granitic material placed in an ultra sonic bath, the feldspars weathered to a Na-montmorillinite while biotite weathered to vermiculite.
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Edkvist, Kristin, et Linnéa Powell. « Lerstensskiva med armering av fårull : Undersökning av böjhållfasthet, ånggenomsläpplighet, brandtålighet,värmekonduktivitet och praktisk användning ». Thesis, Högskolan i Gävle, Avdelningen för bygg- energi- och miljöteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-27393.
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The focus of this study is aimed at the traditional building material; clay, together withsheep’s wool to act as reinforcement. The combination of the two materials created thebasis for an alternative board material. Soil-based building materials were used to alarge extent in the past. The oldest clay houses found were built as early as 8000 yearsBC. During the Middle Ages in Central Europe, soil and clay were used as fillers in timberframe structures. As new building materials evolved, clay based building methodshave suffered a more secluded position in the western world. New building materialshave caused the characteristics of traditional building materials to be forgotten. Sheep’swool, unlike clay, has previously not been classified as a building material, but ismostly used for textiles. Sheep are bred generally for two purposes; meat productionand wool production. The wool that comes from sheep that are in the meat productionbecomes a by-product that is usually reckoned as waste.The study presented below involves a product development of a board material containingclay and sheep’s wool. Nine different compositions were made in different series.Focus on the three different series was places on variety of sheep’s wool, amountof sheep’s wool and the viscosity of the clay. The manufacturing of the product wasmade by hand with own thought out and manufactured aids.The lack of aggregated material properties complicates the use of clay and sheep’swool. A performance based declaration and the CE marking of a product are requiredfor a building material to become an accepted product in the construction market.Building engineering research was carried out in the laboratory environment, and basedon standardized methods calculations were made on the Clay-wool board such as flexuralstrength, vapour permeability, thermal conductivity, fire resistance and practicaluse.The result shows that the Clay-wool board is comparable to other board materials. Thetechnical characteristics of the Clay-wool board regarding flexural strength reportedvalues between 118 N and 550 N, depending on the composition of clay and wool. Allthe boards showed that the point of breaking was viscous, since the wool held the clayslabs together. When calculation vapour permeability, the result showed values between2,289 x 106 m2/s and 3,571 x 106 m2/s.The thermal conductivity was measured on one single board, the one containing thelargest amount of wool, where the value was established to 0,218 W/m*K. It was noticedthat the thermal conductivity increased when wool was clay–dipped.Denna studie fokuserar på det traditionella byggmaterialet lera tillsammans medfårull som ska agera som armering. Kombinationen av de två materialen skapadegrunden för ett alternativt skivmaterial. Jordbaserade byggmaterial användes förri tiden i stor utsträckning. De äldsta lerhusen som hittats är byggda så tidigt sompå 8000 – talet f.Kr. I medeltidens Centraleuropa användes jord och lera till utfackningari ramverkskonstruktioner av trä. I takt med att nya byggmaterial utvecklatsfick lerbaserade byggmetoder en undanskymd ställning i västvärlden.Nya byggmaterial har gjort att det traditionella byggmaterialets egenskaper generellthar glömts bort. Fårull har tidigare inte klassats som ett byggmaterial, liktlera, utan används till största del till textilier. Får avlas generellt för två syften;köttproduktion och ull produktion. Ullen som kommer från får i köttproduktionenblir en biprodukt som vanligen räknas som avfall.Studien som presenteras omfattar en produktutveckling av ett skivmaterial innehållandelera och fårull. Nio olika kompositioner gjordes i tre olika serier. Fokuspå de tre olika serier lades på fårullssort, ullmängd och lerviskositet. Tillverkningav lerullsskivorna gjordes för hand med egna uttänkta och tillverkade hjälpmedel.Bristen på sammanställda materialegenskaper komplicerar användningen av leraoch fårull. Det krävs en prestandadeklaration och CE-märkning av en vara för attett byggmaterial ska bli en accepterad produkt på byggmarknaden. Byggnadstekniskforskning gjordes i laboratorisk miljö och utifrån standardiserade metoderhar beräkningar gjorts på lerullskivorna gällande, böjhållfasthet, ånggenomsläpplighet,värmekonduktivitet, brandtålighet samt praktisk användning.Resultatet visar på att lerullsskivan är jämförbar med andra skivmaterial. Lerullsskivornastekniska egenskaper gällande böjhållfasthet redovisade värden mellan118 N och 550 N, beroende på komposition av lerullsskiva. Alla skivor visade påsega brott, eftersom ullen höll ihop lerullsskivorna. Vid beräkning av ångpermeabilitetvisade resultaten på värden mellan 2,289 x 106 m2/s och 3,571 x 106m2/s. Värmeledningsförmågan beräknades endast på lerullsskivan med störstmängd ull, där värdet blev 0,218 W/m*K. Det uppdagades att värmeledningsförmåganökade när ullen dränktes i lervälling.
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Souto, Esperanza. « Effet des échanges ioniques sur la stabilité des milieux poreux argileux ». Vandoeuvre-les-Nancy, INPL, 1994. http://docnum.univ-lorraine.fr/public/INPL_T_1994_SOUTO_E.pdf.
Texte intégralRésumé :
Cette étude est consacrée à l'effet des échanges cationiques sur la stabilité des milieux poreux argileux. Elle allie résultats expérimentaux et modélisation. Le milieu poreux étudié est un grès argileux naturel riche en illite, originaire des Vosges. Les expériences, menées en réacteur fermé et en écoulement sur des carottes de grès naturellement consolidées, ont permis de relier les réductions de perméabilité du milieu poreux aux compositions transitoires, engendrées par échange cationique, lors du remplacement de la solution en place par une solution de salinité plus faible. Pour des solutions aqueuses de chlorure de cation alcalin, à pH neutre ou basique, la diminution de la salinité injectée provoque un échange cationique entre les cations alcalins et les protons de l'eau. Il en résulte une composition transitoire déstabilisante, caractérisée par une salinité faible et un pH élevé. Les variations transitoires de pH sont modélisées en tenant compte d'une capacité d'échange cationique variable avec le pH et de l'échange cationique avec les protons. Pour les mélanges de chlorure de cation alcalin et de chlorure de calcium, à pH neutre, la stabilité du milieu poreux dépend du niveau global de la salinité et de la fraction ionique de cations divalents calcium en solution. En écoulement, l'échange cationique entre les cations monovalents alcalins et les cations divalents calcium peut conduire à une diminution transitoire de la concentration de calcium en solution, et donc à un endommagement du milieu
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Дегерменджі, Анастасія Всеволодівна. « Ливарний комплекс АТ ”Полтавський турбомеханічний завод” з розробкою технології лиття ». Master's thesis, Київ, 2018. https://ela.kpi.ua/handle/123456789/26676.
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Об’єкт проектування – чавуноливарний цех з розробленням технологічних процесів виготовлення виливків різної маси литтям у разові піщано-глинясті форми.
Метою проекту є визначення технологічних параметрів та складання опису виробництва виливка; розроблення і обґрунтування етапів приготування рідкого сплаву; технологічне планування і проектування ливарного цеху.
Розроблений технологічний процес виготовлення виливка може бути рекомендований як типовий при виробництві чавуних виливків середньої складності в умовах дрібносерійного і великосерійного виробництва.
Попередніми розрахунками економічних показників прийнятих проектних рішень установлено економічну доцільність використання запропонованих процесів.
Розроблено організаційну схему роботи ливарного цеху та заходи, спрямовані на усунення небезпечних та шкідливих чинників.The design object is an iron foundry with the development of technological processes for the production of castings of various masses by casting into one-off sand-clay forms. The aim of the project is to determine the technological parameters and compile a description of the production of the casting; development and justification of the stage of preparation of the liquid alloy; technological planning and design of a foundry. The technological process of casting manufacturing has been developed can be recommended as typical for the production of iron castings of medium complexity in small-scale and large-scale production. Preliminary calculations of the economic indicators of the adopted design decisions established the economic feasibility of using the proposed processes. An organizational chart of the foundry’s work and measures aimed at eliminating dangerous and harmful factors have been developed.
Объект проектирования - чугунолитейный цех с разработкой технологических процессов изготовления отливок различной массы литьем в разовые песчано-глинистые формы. Целью проекта является определение технологических параметров и составления описания производства отливки; разработка и обоснование этапе приготовлении жидкого сплава; технологическое планирование и проектирование литейного цеха. Разработан технологический процесс изготовления отливки может быть рекомендован как типичный при производстве чугунных отливок средней сложности в условиях мелкосерийного и крупносерийного производства. Предварительным расчетам экономических показателей принятых проектных решений установлено экономическую целесообразность использования предложенных процессов. Разработана организационная схема работы литейного цеха и меры, направленные на устранение опасных и вредных факторов.
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Lošáková, Jana. « Porovnání nákladů výstavby rodinného domu z klasických materiálů a z materiálů přírodních ». Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240414.
Texte intégralRésumé :
This diploma thesis is focused on a comparison of construction cost of the house made of classic materials with the equivalent made of natural building materials and consequently on comparison of both construction variants. In order to perform those tasks, the used natural building materials were defined. Furthermore, the specific options of usage of these natural building materials as well as the used composition structures were introduced. The thesis concludes with a price calculation of the constructions made of natural building materials which were not available in the common budgetary software. The appendix of the thesis contains budgets for the first variant, where the house is made of natural building materials, and also for the second variant, where the house is made of classic materials.
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Svoboda, Jan. « Sportovní centrum Polička ». Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240241.
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This thesis deals with the design and elaboration process of a project documentation of a sports centre. The designed sports centre building is situated in the southern part of the town of Polička, in the area determined for sports and free time activities complexes and areas. It is a two-floor, non-cellar, flat-roof building. It is based on plain concrete strip foundations and reinforced concrete foundation footing. The bearing, peripheral and partition walls are designed from POROTHERM hollow clay blocks. Reinforced concrete columns are designated in open disposition areas. The ceiling construction is made from SPIROLL pre-stressed concrete floor slabs and point-supported reinforced concrete slabs. The peripheral walls of the first aboveground floor are insulated with external thermal insulation system with a protective gabion facade. The peripheral wall thermal insulation in a bowling restaurant and gym halls extension is designed from a ventilated facade with CEMBRIT METRO facade cladding panels. The building is functionally divided into two main parts with a shared entrance. The sports centre with gyms and other sports facilities form the first part. Three squash courts, a mini-football piste, a special room for spinning and alpinning, a room for group exercising and cloakrooms with sanitary facilities are designed within one part of the sports centre. A restaurant with a bowling area and a kitchen with storerooms and other facilities for employees form the second part. The designed complex is barrier-free. There is aimed to be a car park for fifty cars, four motorbikes and a bus in front of the building. Three parking places are for disabled people.
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Tseng, Huang-Chi, et 曾煌& ;;#26826. « Analysis on cold roll-bonding and sheet hydroforming process of clad metal sheets ». Thesis, 2010. http://ndltd.ncl.edu.tw/handle/76117279319989548657.
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博士國立交通大學
機械工程學系
99
This study comprises three sections that include cold roll-bonding, forming limit diagrams (FLDs), and sheet hydroforming (SHF). First, the bonding performance of Al/Cu clad metal sheet with different initial thickness and reduction rate were discussed. The heat flux calculation with thermal conduction, plastic heat and friction consideration were adopted in finite element analysis (FEA). The temperatures of clad metal sheet at maximum reduction region were obtained by rigid-plastic FE code (DEFORM-2D), and then the temperature distribution of Al/Cu clad metal sheets with different combinations of process parameter were determined. The simulation results pointed out that higher rotation speed, higher reduction rate, and asymmetrical rotation are positive to improve the bonding performance for clad metal sheets. The possibility of applying FLDs to fracture prediction of clad metal sheets is examined. The forming limits of Al/Cu clad metal sheets with different thickness reduction are investigated via FLD test. Moreover, deep drawing tests are carried out to compare the numerical results. The results pointed out that the fractures of clad metal sheets are predicated by experimental FLDs. For clad metal sheet application, the SHF was adopted to improve the formability of Ti/Al clad metal sheet used in 3C product housings. Some significant process parameters were analyzed for improving formability of clad metal sheet by FEA. In numerical simulation, a virtual film technique was proposed to realistically approach the hydraulic loading for SHF. And pre-bulging and tool modification are proposed to reduce thinning ratio of Ti/Al clad metal sheet, operation stage, and tooling cost.
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KUMAR, SHARMA PANKAJ. « EXPERIMENTAL AND NUMERICAL STUDIES ON SPRINGBACK OF 2-PLY AND 3-PLY LAMINATE COMPOSITES OF ALUMINIUM AND STAINLESS STEEL ». Thesis, 2023. http://dspace.dtu.ac.in:8080/jspui/handle/repository/20390.
Texte intégralRésumé :
To meet the requirement of materials having higher tensile strength to weight ratio
along with corrosion resistance, the 2-ply and 3-ply clad sheets of aluminium and
stainless steel are being utilized in domestic applications, manufacturing of automotive
sheet metal parts, shipbuilding, and other industries. Metal clad sheet composites are a
different kind of composite material where alternating metal layers are bonded together
with inter-metallic bond.
The sheet metal components manufactured by forming processes may undergo some
geometrical changes due to the phenomenon of springback. The behaviour of
springback during bending of 2-ply and 3-ply clad sheet metals is very complex due to
the combination of sheets of different mechanical properties and thicknesses.
Accurate prediction of springback in clad sheets in a bending operation will help in
improving the die design by involving springback compensation. It would facilitate the
optimum selection of materials, blank design, and other design variables so as to
manufacture parts with minimum springback. In the present work, an analytical method
has been developed that predicts the amount of springback in bending of clad sheet
using input parameters from stress-strain diagrams of sheet materials like tensile
properties, strain hardening exponent and anisotropy of parent sheets. The total bending
moment in the analytical model at a cross sectional plane is calculated from the bending
stresses for different layers. Springback is calculated by superimposing the effect of a
negative bending moment of the same magnitude so as to simulate the unloading
phenomenon. Numerical simulations have also been done for the simulation of V bending of clad sheet using Abaqus software based on FEM (finite element method).
Experimental work has also been carried out and compared with the simulation and
vii
analytical results. The data from stress-strain plots for the parent and clad sheets was
generated using computerized UTM. The parent and clad sheets are characterized using
tensile properties, strain hardening exponent and anisotropy. The typical yield strengths
(0.2% offset) of clad sheets for the tensile specimens oriented at 0°, 45° and 90° are
observed to be 115MPa, 117MPa and 114MPa for a 2-ply and 153.5MPa, 174MPa and
176 MPa for a 3-ply sheet, respectively. A set of three punch profile radii was used to
conduct V-bending experiments for the measurement of springback on a computerized
UTM. The results from the analytical model and FEM simulation are seen found to be
in close agreement with the experimental results. It is observed that an increase in punch
profile radius causes a significant increase in springback for both 2-ply and 3-ply clad
sheets. For a 2-ply clad sheet, the bend samples (with AA1050 as inner layer ) which
are oriented at 45° to the rolling direction, the experimental values of springback, higher
than the other two orientations, are observed to be 4.12 and 4.88 with punch profile
radii of 15mm and 20mm, respectively. In case of a 3-ply clad sheet, the bend samples
(with SS304 as inner layer) oriented at 90° to the rolling direction, the experimental
values of springback higher than the other two orientations, are found to be 5.15° and
6.10° with punch radii of 15mm and 20mm, respectively. Similar trend of results is
obtained with analytical and simulation techniques. FE simulation results are closer to
the values of experimental results than the analytical model results. The analytical
model assumes a plane strain condition and neglects the neutral axis shift. These
assumptions are not made for the simulation. Also, a more robust material model is
used in FE simulations.
The effect of sheet setting on the die is also investigated in this work. Effect of the
position of aluminium sheet at both inner and outer layers is studied. Sheet setting
viii
conditions affect the values of springback due to the tensile strength variations and
different bending radii during V-bending operations. For both the sheet settings, the
residual stresses as predicted Abaqus simulations are in good agreement with the
experimental results except for a few cases.
15
Wei, Chih, et 黃智威. « Analysis on Flow Behavior and Mechanical property of Lap Joint Friction Stir Weld of Aluminum-Clad 2024-T3 Aluminum Alloy Sheets ». Thesis, 2010. http://ndltd.ncl.edu.tw/handle/48713916385854171097.
Texte intégralRésumé :
碩士國立中正大學
機械工程所
98
The objective of this research is to study the friction stir welding of lap joint of the Aluminum-Clad 2024-T3 sheet metal. Friction stir welding was conducted process at different parameters such as tool rpm, tool revolution direction, feeding rate, and tool geometris. During the welding process, dynamic load and temperature history use recorded, to observe the flow behavior at the stir zone. The appearance of the weld surface, macro-and microstructure of the weld cross section were observed to understand the flow behavior of the friction stir weld, the joining mechanisms of the lap joints, and the weld metal characteristics of the Aluminum-Clad 2024-T3 lap joints. The tool or probe geometries play an dominant role in the flow behavior of the friction stir lap joint. Probes with cylindrical thread caused a vertical flow in the stir zone at the interface of the pure aluminum layer in between the upper and lower plate. The vertical material flow resulted in a reduction of the effective sheet thickness. On the other hand, probes with eccentric triangular geometry to a horizontal flow behavior of the material, so that the aluminum surface coating remained maximal horizontal at the interface. With this tool effective sheet thickness in the stir zone is achieved. Rewelding on the same weld bead with different feeding rates resulted in an accumulative effect of the material flow. Four types of failure modes were concluded from the fracture analysis and tensile strength : fracture at efftective sheet thickness, the defect on which tensile stress concentrates, of the stir zone, HAZ, interface peeling. Material welded by FT13-2 tool revealed the best tensile stress. The fracture mode was the HAZ fracture. Dynamic load measurement was also combined to analyze the effects caused by different process parameters and the tool geometry. The T15.5 tool resulted in a horizontal material flow in the stir zone. Successive friction stir welding on the same plate resulted in temperature rise of the material, which had a negative effect in the tensile stress and fracture mode.
16
Yu, Teng Hsiang, et 鄧翔宇. « Study on Compression Forming of Clad Sheet ». Thesis, 2008. http://ndltd.ncl.edu.tw/handle/80258250063013410254.
Texte intégralRésumé :
碩士國立屏東科技大學
機械工程系所
96
The study proposes three analysis methods to explore the plastic deformation behaviour and characteristics of two-layer and three-layer bounded clad sheet ; one is Slab Method ,the second one is Upper Bound Method , and the third is Finite Element Method. The frictions of top and bottom dies are assumed as constant sheet friction. And coulomb friction , and those can be different. The shape of outer surface and the compression force can be obtained by the upper bound method , however the stress distributions can not be found , those are able to get by the slab method. The mathematical models based on the slab method and upper bound method are established to investigate the effects of various compression conditions such as clad thickness ratio, shear yield stress ratio, and reduction on various stress distributions and compression forces. Using the FEM simulation and Taguchi method to explore the compression forming of clad sheet ; and to carry out the experimental plan by L9(34) orthogonal array which includes four various. Control factors the clad thickness ratio, the shear yield stress ratio, the frictional factor ratio or frictional coefficient ratio and the width thickness ratio to explore the effects of the compression characteristics of clad sheet. For the optimization of compression forming of clad sheet, the SUPERFORM commercial software is used to perform the FEM simulation with constant shear friction and Coulomb friction. The shape of outer surface of clad sheet, the equivalent stress, the equivalent strain, the velocity field, the pressure distribution and the compression force can be simulated by the FEM. With a view to verifying the results of FEM simulation, the results can be compared to those based on the slab method and the upper bound method. The acceptance of FEM simulation can be verified by the comparisons of compression forces. Adjusting effectively various compression conditions to control the shape of outer surface to be uniform, the clad sheet is apt to perform the second forming. The analysis results can be offered to the forging industries at the reference.
17
Yang, Ching-Yin, et 楊清印. « Analysis Of Compression Forming of Bounded Three-Layer Clad Sheet ». Thesis, 2006. http://ndltd.ncl.edu.tw/handle/99723276014156499194.
Texte intégralRésumé :
碩士國立高雄第一科技大學
機械與自動化工程所
94
Abstract This study proposes two analysis methods to investigate the plastic behavior and characteristics of three-layer clad sheet of compression forming. The friction can be assumed as constant shear friction, the frictions for the upper and lower dies can be different. The outer surface shape, the effective strain distribution, the compression force can be obtained from the upper bound method (UBM), but the stress distribution cannot be found from UBM, it can be found from the slab method (SM). With a view to exploring the plastic behavior of the three-layer clad sheet compression forming, the mathematical models based on the slab method and upper bound method are respectively established to investigate effects of the various compression conditions, such as the clad thickness ratio, the shear yield stress ratio, the frictional factor ratio, the width thickness ratio, frictional factor ratio, and reduction ratio, on various stress distributions and compression force. The compression forces based on both the models are compared to prove the feasibility of the two models, and the analysis results can offer to the forging industries.
18
Chang, Chiu Yi, et 邱義彰. « FEM Analysis of Asymmetrical Rolling of Bounded Double-Layer Clad Sheet ». Thesis, 2010. http://ndltd.ncl.edu.tw/handle/67904288343371903234.
Texte intégralRésumé :
碩士高苑科技大學
機械與自動化工程研究所
98
This study assumes constant shear friction to perform FEM simulation of asymmetrical rolling of double-layer bounded clad sheet using Deform 2D commercial software The effects of characteristics of the rolling conditions such as roll speed ratio, clad sheet thickness ratio, shear yield stress ratio, roll radius ratio, equivalent roll radius thickness ratio, frictional factor ratio, frictional factor between roll and clad sheet, and reduction ratio etc on the rolling characteristics. The FEM analysis model is compared with various rolling characteristics from the slab method to verify the acceptance of FEM model. The FEM analysis results obtained can be used as the reference of rolling industry. Keywords: Constant Shear Friction, Roll Speed Ratio, Shear Yield Stress Ratio, Frictional Factor Ratio, Reduction Ratio.
19
Wu, Fan-Yi, et 巫凡逸. « FEM Simulation Analysis of Deep Drawing of Double-Layer Bounded Clad Sheet ». Thesis, 2009. http://ndltd.ncl.edu.tw/handle/62262354020695672429.
Texte intégralRésumé :
博士國立屏東科技大學
機械工程系所
97
The clad plate of pressure vessel with large dimension and thick thickness can be produced by the spinning forming, but that with small dimension and thin thickness then can be used by the deep drawing forming process. For the deep drawing process, it can be divided into two types, the first is a deep drawing with the blank holder, the second is a deep drawing without blank holder. In the study, 2D and 3D clad sheet deep drawing simulation analysis without the blank holder is performed, and the effective stress, the effective strain, the punch force, the minimum thickness, the reduction ratio of thickness, and the shape of product in the deep drawing process are investigated. The effects of the forming conditions such as the arc of die, the gap between punch and die, the frictional coefficient ratio, the minimum of thickness or the reduction ratio of thickness are explored systematically. Moreover, the differences between 2D and 3D analysis are compared to be more complete for the clad sheet deep drawing forming. Furthermore, actually performing the manufacture of the clad plate of pressure vessel in order to realize the acceptance of deep drawing without blank holder.
20
Tsai, Sung-chi, et 蔡松基. « A Study of Different Volume Fraction of Cu-Al Clad Sheet Metal in Drawing Property ». Thesis, 2007. http://ndltd.ncl.edu.tw/handle/63988759321722721982.
Texte intégral
21
Tu, Yu-Sheng, et 塗育昇. « To Analysis and Experiment the Bending Deformation of Cu-Al Clad Metal Sheet with Marc ». Thesis, 2007. http://ndltd.ncl.edu.tw/handle/83514236192325027915.
Texte intégral
22
Li, Chih-Ting, et 李致廷. « Studies on Antioxidative Activity of Water Extracts and Bactericidal Effects of Calcinated Powders of Hard Clam and Freshwater Clam Shells ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/72819811026319089079.
Texte intégralRésumé :
碩士國立臺灣海洋大學
食品科學系
101
The composition of bivalve shells includes about 96% - 98% inorganic compounds (mainly CaCO3) and 2% - 3% organic compounds. The purpose of this study was to investigate the antioxidative activities of water soluble extracts and the bactericidal effects of calcinated powders from the most abundant freshwater bivalve, freshwater clam (Corbicula fluminea), and seawater bivalve, hard clam (Meretrix lusoria), in Taiwan. In the first part of this study, first of all, the shells of hard clam and freshwater clam were cleaned-up and then crushed to a powder. An equal weight of deionized water was added to the powder and extracted at 130℃ and 1.5 atm for 60 min. The extract solution was filtered and dialyzed. Finally, the solution was lyophilized and employed as the water extract of freshwater clam shells (FSE) and hard clams (HSE). The protein content of HSE and FSE was about 17.37% and 12.43%, respectively. The peptide (&;lt; 6 kDa) content of HSE and FSE was about 11.78% and 9.11%, respectively. Either FSE or FSE didn’t contain carbohydrates and polyphenols. Both HSE and FSE solutions were weak basic. The amino acid composition of FSE and HSE was mainly glycine. Aspartic acid, tyrosine and phenylalanine were also rich. In the antioxidant activity study, the IC50 (half maximal inhibitory concentration) value of DPPH (1,1-diphenyl-2- picrylhydrazyl) scavenging activity of FSE was about 124.70 μg/ml. HSE didn’t have DPPH radical scavenging activity. The IC50 values of Fe2+-inhibition of FSE and HSE were 1.36 and 0.25 mg/ml, respectively. The reducing power of FSE was five times more than HSE. There was no significant difference of ABTS+ scavenging activity between FSE and HSE at low concentrations. In the cell experiments, the cell viability of CCD966SK cells was not affected by FSE or HSE treatment. Furthermore, H2O2-induced oxidative stress in CCD966SK cells was reduced by FSE treatment, but not by HSE treatment. In the second part of this study, freshwater clam shell powder (FSP) and hard clam shell powder (HSP) was calcinated at 1,050℃ for 24 hr, and the yields of calcinated FSP (CFSP) and calcinated HSP (CHSP) were both about 45%. The main composition of CFSP and CHSP was converted to CaO from CaCO3. On the other side, the particle sizes were also decreased. Both of CFSP and CHSP was strong basic (pH 11.5-12.4). After 6 days storage, the pH of CFSP and CHSP suspended solutions were not changed significantly. Bacterial counts of Proteus vulgaris and Bacillus subtilis were reduced about 7 log CFU/ml by either 0.1% (w/v) CFSP or CHSP for 3 min immersion. Bacterial counts of Staphylococcus capitis were reduced about 7 log CFU/ml by 0.5% (w/v) either CFSP or CHSP for 3 min immersion. Finally, bacterial counts of Listeria monocytogenes were reduced about 6.25-7.42 log CFU/ml by either 1% (w/v) CFSP or CHSP for 3 min immersion. Oppositely, neither HSP nor FSP had no bactericidal effect. Hence, antioxidant activities were found in both HSE and FSE, which can be used for skin protection materials. Bactericidal effects were found in both CFSP and CHSP solutions, which can be used as food cleaners.
23
Lin, Chien-Yu, et 林建佑. « Development of less-polluting incense : addition of Oyster and Asiatic clam shells in incense prepartion ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/18934807614010425779.
Texte intégralRésumé :
碩士嘉南藥理科技大學
環境工程與科學系
101
Particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs) emissions of burning incense have been investigated on the quality of surrounding air. However, the reduction of PM and PAHs from burning incense has received little attention. In the present study, two types of incense were made in the laboratory. Five to thirty percent of Oyster (OS) and Asiatic Clam Shells (ACS) was added to Sin-shan, Lao-shan, Liao and Chen wood flours, which are popular incense materials. Experimental results indicate that the reduction of emissions of PM and PAHs from burning incense increased with increasing amount of OS and ACS additive. Mean PM reductions for 30.0% of OS and ACS were 35% and 34%, respectively. Mean PAH reductions were 21% and 20% for particle-phase PAHs, respectively, and 37% and 21% for benzo[a]pyrene equivalent concentration, respectively. These results may be attributed to OS and ACS acted as filler in the burning incense. OS and ACS was substituted for organic material in the incense reducing PM and PAHs emissions from the smolder. The findings of this study may serve as a guide to producing safer and less-polluting incense.
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Wang, Ting-Hsuan, et 王廷軒. « Preparation of calcium organic salts and submicron composite calcium from hard clam shells and Gracilaria polysacchrides ». Thesis, 2011. http://ndltd.ncl.edu.tw/handle/01161030696108267274.
Texte intégralRésumé :
碩士國立臺灣海洋大學
食品科學系
99
Abstract In this study, we used hard clam and freshwater clam to prepare organic calcium salts, to prepare submicron composite calcium by mixing organic calcium salts with Gracilaria polysaccharide extracts, and to analyze the characteristics of calcium polysaccharide submicron particles and their antioxidant capacity. Hard clam shells and freshwater clam shells contain calcium carbonate 93.91% and 92.15%, respectively. The decomposition was performed by immersing clam shells in different concentrations and solid-liquid ratios of hydrochloric acid, acetic acid or formic acid. As the molar concentration of acid increased from 1 M increased to 6 M, the decomposition rate increased from 53.02 %, 49.33% and 49.99% to 95.49, 98.07% and 99.77%, respectively. Varying the solid-liquid ratio acid had no significant effect on the decomposition rate and reaction rate. Raising reaction temperature significantly reduced decomposition time. It took 12 hours for 6 M acetic acid at room temperature to decompose 95.49% calcium carbonate in shells. When heated to 60oC, similar acid solution only needed 3 hours to break down 98.9% calcium carbonate in shells. The decomposition product of calcium carbonate was mixed with citric acid (CA), malic acid (MA), vitamin C or citric-malic acid (CMA) solution to prepare calcium organic salts. By using calcium acetate solution with increasing levels of organic acid, the yield of calcium citrate (CC) raised to 91.15%, the yield of calcium malate (CM) and calcium citrate-malate (CCM) increased to 89.3% and 87.0%, respectively. After the addition of vitamin C for 48 hours, no organic salt was formed. Calcium citrate showed the highest solubility of 0.92 g / 100 mL in deionized water at pH 1.2. The solubility of calcium malate was 0.68 g / 100 mL. Atomic Absorption Spectrophotometry (AAS) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) were used to analyze CC, CM and CCM for heavy metals and trace elements. The results are in compliance with food safety and hygiene standards. CC, CM and CCM in scanning optical microscopy showed the appearance of long rod-shaped sticks, tiles, and porous spherical shape, respectively. Calcium and Gracilaria polysaccharide extract (GPE) were used to prepare particles of chitosan-GPE-calcium submicron composite and analyze their composition, stability and antioxidant capacity. The particles prepared without chitosan were unstable, resulting in a wider range of particle size distribution, but it had a higher TEAC and DPPH radical scavenging capacity (61.12 - 66.6%, 40.35 - 57.85%). The addition of chitosan resulted in a narrower particle size distribution, indicating chitosan formed stronger interactions with Gracilaria polysaccharide and calcium. However, the TEAC and DPPH radical scavenging effects of chitosan-GPE-calcium particles were significantly lower (25.15 - 34.17%, 37.06 - 37.59%).
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Huang, Long-Jhong, et 黃仲隆. « Preparation and release profile of calcium carbonate submicron particles encapsulating L-ascorbic acid from freshwater clam shells ». Thesis, 2012. http://ndltd.ncl.edu.tw/handle/44990014829584573844.
Texte intégralRésumé :
碩士國立臺灣海洋大學
食品科學系
100
Freshwater clam shells contain about 92.01% CaCO3. The objectives of this study were to use freshwater clam to prepare calcium carbonate particles, to prepare submicron composite calcium by mixing calcium carbonate with L-ascorbic acid and chitosan, and to analyze the characteristics of calcium carbonate particles and their release capacity. The decomposition was performed by immersing clam shells in different concentrations and solid-liquid ratios of acetic acid. As the molar concentration of acid increased from 1 M to 2 M, the decomposition rate increased from 81.78% to 89.47%. Varying the solid-liquid ratio acid had significant effect on the decomposition rate and reaction rate. Raising reaction temperature significantly reduced the decomposition time. It took 14 hours for 1 M acetic acid at room temperature to decompose 91.80% of calcium carbonate in shells. When the solution was heated to 90oC, it took only 6 hours to break down 96.40% of calcium carbonate in shells. The decomposition product of calcium carbonate was mixed with sodium carbonate solution to prepare calcium carbonate, as confirmed by Fourier transmission infrared spectrometer (FTIR). In the solubility test, calcium carbonate particles showed the highest solubility of 0.72 g / 100 mL in deionized water at pH 1.2. Atomic Absorption Spectrophotometry (AAS) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) were used to analyze calcium carbonate particles for heavy metals and trace elements. The results are in compliance with food safety and hygiene standards. Calcium carbonate particles in scanning optical microscopy showed the appearance of rough porous spherical shape. Higher ascorbic acid concentration results in more acidic solution during the preparation of nanoparticles. Lower pH increased the diameter and polydispersity (PDI) of nanoparticles. Dissolution testing at different pH environments indicated that calcium carbonate particles could reduce the release rate of ascorbic acid. The antioxidative activity was determined by comparing the DPPH scavenging ability of before and after encapsulation. Test results confirmed the component was unchanged after the encapsulation process.
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Friedrich, Christine. « Untersuchungen zur Bedeutung und Quantifizierung der Klauenqualität und Moderhinkeresistenz beim Schaf ». Doctoral thesis, 2011. http://hdl.handle.net/11858/00-1735-0000-0006-AB47-D.
Texte intégral