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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

Estudo da hidrogenação para pulverização de ligas à base de terras raras com Nb para eletrodos de hidreto metálico / Study of hydrogenation for pulverization of rare earth alloys with nb for metal hydride electrodes

FERREIRA, ELINER A. 22 June 2016 (has links)
Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-06-22T13:51:24Z No. of bitstreams: 0 / Made available in DSpace on 2016-06-22T13:51:24Z (GMT). No. of bitstreams: 0 / Neste trabalho foram estudadas as series de ligas La0,7Mg0,3Al0,3Mn0,4Co(0,5-x)NbxNi3,8 (x =0 a 0,5) e La0,7Mg0,3Al0,3Mn0,4Nb(0,5-x)Ni(3,8-x) (x =0,3; 0,5 e 1,3), como eletrodo negativo de baterias de Níquel Hidreto Metálico. A pulverização das ligas foi realizada com duas pressões de H2 (2 bar e 9 bar). A capacidade de descarga das baterias de níquel hidreto metálico foi analisada pelo equipamento de testes elétricos Arbin BT-4. As ligas, no estado bruto de fusão, foram analisadas por microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva (EDS) e difração de raios-X. Com o aumento da concentração de nióbio nas ligas nota-se a diminuição da estabilidade cíclica das baterias e da capacidade máxima de descarga. A capacidade de descarga máxima obtida foi para a liga La0,7Mg0,3Al0,3Mn0,4Co0,5Ni3,8 (45,36 mAh) e a bateria que apresentou a melhor performance foi a liga La0,7Mg0,3Al0,3Mn0,4Co0,4Nb0,1Ni3,8 (44,94 mAh). / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
162

Estudos das Propriedades de Termoluminescência (TL), Ressonância Paramagnética (EPR) e Absorção Ótica (AO) para caracterização do mineral Monticelita / Study of the Properties Thermoluminescence (TL), Electron Paramagnetic Resonance (EPR) and Optical Absorption for characterization of mineral Montecillite

QUINA, ANTONIO de J.A. de 22 December 2016 (has links)
Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2016-12-22T12:40:27Z No. of bitstreams: 0 / Made available in DSpace on 2016-12-22T12:40:27Z (GMT). No. of bitstreams: 0 / Foram estudados as propriedades de absorção ótica, de termoluminescência e de ressonância paramagnética eletrônica do mineral natural de silicato de nome MONTICELITA do grupo Olivina, para caracterização desse mineral, cuja formula química é CaMgSiO4. A absorção ótica mostrou que há três bandas de absorção em 450 nm, 660 nm e 1050 nm. As duas primeiras bandas, a primeira no azul e a segunda no amarelo-vermelho são responsáveis pela cor verde da Monticelita. Essas duas bandas são consequência do elemento cromo contido no mineral absorver fótons do feixe universal no visível de frequências centradas em 450 nm e 660 nm. A banda em 1050 nm é devido ao Fe2+. As curvas de emissão de uma amostra de Monticelita irradiada com raios gama de doses entre 10 e 1000 Gy apresenta três picos em 150 °C , 270 °C e 370 °C . Pelo método da deconvolução e de várias taxas de aquecimento foram obtidos energia E1=1,35 eV e fator de frequência s1=4,98x1011 s-1 para o pico 270 °C e E2=1,70 eV e s2=1,88x1011 s-1 para pico 370 °C . A irradiação com raios gama de doses entre 5 kGy e 50 kGy produziram pico TL de 380 °C com intensidade TL em função da dose linear e crescente. Este resultado e importante para dosimetria da radiação de altas doses. O espectro EPR de uma amostra natural, mostrou um resultado não esperado e interessante. Além dos sinais típicos de interação hiperfina do Mn2+, um sinal avantajado de g =6,34 indica que o ferro formou moléculas de hematita, Fe2O3. Esse sinal desaparece com aquecimento acima de 800 °C de recozimento, dando origem dipolos magnéticos de Fe3+, que dá origem a um sinal típico em g =2. Esta descrição mostra bem a caracterização do mineral Monticelita. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
163

Preparação, irradiação e caracterização de blendas PEAD reciclado/EPDM / Preparation, irradiation and characterization of recycled HDPE/EPDM blends

GABRIEL, LEANDRO 22 December 2016 (has links)
Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2016-12-22T16:34:05Z No. of bitstreams: 0 / Made available in DSpace on 2016-12-22T16:34:05Z (GMT). No. of bitstreams: 0 / A reciclagem de refugos é um processo estratégico que viabiliza a expansão do mercado de plásticos, podendo gerar novos produtos. A obtenção de blendas poliméricas é uma alternativa nesse processo, já que é conhecida a perda de propriedades mecânicas dos termoplásticos nas etapas de reprocessamento. Neste trabalho, o polietileno de alta densidade (PEAD) reciclado teve adições de borracha do monômero etileno-propileno-dieno (EPDM) puro em baixos teores (1 %, 5 % e 10 %), cujo objetivo foi formar blendas miscíveis e um produto final mais resistente ao impacto. O PEAD foi submetido a quatro ciclos de moagem, extrusão e injeção (reprocessamento) e misturado ao EPDM puro por extrusão sem o uso de qualquer aditivo. Os grânulos da blenda formada foram usados para confeccionar os corpos-de-prova por injeção para seu uso nas distintas metodologias analíticas. O processo de irradiação gama foi aplicado nas doses de 50 kGy e 100 kGy e os parâmetros físico-químicos e mecânicos dessas amostras foram comparados aos das não irradiadas. Tanto as blendas irradiadas como as não irradiadas mostraramse visualmente e microscopicamente homogêneas, indicando a compatibilidade da mistura, que também é verificada por seu comportamento térmico. Os parâmetros mecânicos provenientes dos ensaios de tração e flexão, foram semelhantes nas amostras do termoplástico virgem e do reciclado; o processo de irradiação nas blendas gerou sua reticulação, sendo esta verificada não só pelo aumento dos valores desses parâmetros como também pelo aumento da fração gel. A resistência ao impacto aumentou cerca de duas vezes e meia nas amostras com maior teor de EPDM e cerca de 6 a 7 vezes nestas mesmas amostras irradiadas a 50 kGy e 100 kGy respectivamente. O novo material obtido tem fortes indicativos para a sua utilização na pequena e média indústria de plástico, uma vez que já com 1 % de EPDM apresentam melhores características mecânicas em relação ao termoplástico reciclado quatro vezes e essas características foram incrementadas após o processo de irradiação gama. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
164

Chancen und Grenzen der Substitution von metallischen Konstruktionswerkstoffen in der Fördertechnik: Opportunities and limits of the substitution of metallic construction materials in conveying technology

Eichhorn, Sven, Kluge, Patrick, Penno, Eric, Eckardt, Ronny, Müller, Christoph, Feig, Katrin, Alt, Christoph, Schubert, Christine January 2017 (has links)
Auf der Grundlage technischer, wirtschaftlicher und ökologischer Kriterien werden drei Prototypen unterschiedlicher Anwendungen in Holz- und Metallbauweise untersucht und deren Unterschiede bewertet. / Based on technical, economic and ecological criteria, three prototypes of different applications in wood and metal construction are examined and their differences are evaluated.
165

Bedeutung der Kunststofftribologie in der Fördertechnik

Sumpf, Jens 04 September 2018 (has links)
In der Fördertechnik werden zunehmend Transportketten und Gleitelemente aus thermoplastischen Kunststoffen eingesetzt. Wesentliche Vorteile sind der schmierungsfreie und damit saubere und wartungsarme Betrieb, die geringe Eigenmasse sowie die mit hoher Gestaltungsfreiheit und Effizienz verbundene Fertigungstechnologie im Spritzgießverfahren. Die Bauelemente der Fördersysteme werden in der Praxis sehr unterschiedlich beansprucht. Da jedoch die mechanischen und tribologischen Eigenschaften der Kunststoffe signifikant von den Belastungs- und Umgebungsbedingungen, insbesondere der Temperatur, abhängig sind, ist die Entwicklung und Charakterisierung geeigneter Werkstoffsysteme sehr komplex. Im Vortrag werden diese Herausforderungen thematisiert und Möglichkeiten zur praxisnahen Untersuchung und Bereitstellung von Kennwerten vorgestellt. / In conveyor systems, transport chains and sliding elements made of thermoplastic materials are increasingly used. Major advantages are lubrication-free and so clean and low-maintenance operation, low weight as well as design-flexible and efficient injection molding manufacturing. In practice, components of conveyor systems are stressed in very different ways. However, mechanical and tribological properties of plastics are significantly dependent on load and environmental conditions, in particular temperature. Therefore, the development and characterization of suitable material systems are very complex. In the talk, these challenges are addressed and opportunities for practical investigation and provision of characteristic properties are presented.
166

Auslegung von Stetigförderern mit Kunststoffgleitketten

Sumpf, Jens, Bartsch, Ralf, Bergmann, André 12 February 2019 (has links)
Transportketten aus thermoplastischen Kunststoffen gehören zu den am häufigsten eingesetzten Zugmitteln in der Stetigfördertechnik. Wesentliche Vorteile, insbesondere gegenüber Stahlketten, sind eine geringe Masse, eine hocheffiziente Fertigung sowie sehr gute Reibungs- und Verschleißeigenschaften, die den schmierungsfreien Betrieb der Förderer ermöglichen. Die Dimensionierung der Förderanlagen erfolgt primär über eine zulässige Kettenzugkraft. Das setzt voraus, dass sowohl die im System vorherrschende als auch die für die Kette ertragbare Zugkraft bekannt ist. Der Beitrag behandelt zum einen die Herausforderungen bei der Ermittlung dieser Werte, z. B. lastabhängige Reibkoeffizienten und fehlende Dauerfestigkeitswerte. Zum anderen wird auf die reibungsbedingte Erwärmung der Gleitelemente eingegangen. Diese beeinflusst signifikant die mechanischen Eigenschaften und führt teilweise zum Aufschmelzen der Kunststoffelemente, wird jedoch nach den üblichen Dimensionierungsmethoden nicht berücksichtigt. / Transport chains made of thermoplastic materials are among the most frequently used traction mechanisms in conveying technology. Fundamental advantages, in particular compared to steel chains, are a low mass, a highly efficient production and excellent friction and wear properties that allow lubrication-free operation of conveyors. The dimensioning of conveyor systems is primarily carried out via a permissible chain tractive force. This presupposes that the system's prevailing forces and the chain's maximum allowable tractive force are known. The paper deals on the one hand with the challenges of identifying these values, such as load-depending coefficients of friction and missing fatigue strength values. On the other hand, the frictioninduced heating of the sliding elements is discussed. This heating significantly affects the mechanical properties and partially leads to melting of the plastic elements, but is not taken into account by the common dimensioning methods.
167

Entwicklung von Qualitätshalbzeugen aus Spezialholzwerkstoffen für Anwendungen im Maschinenbau und in der Fördertechnik: Entwicklung von Qualitätshalbzeugen aus Spezialholzwerkstoffen fürAnwendungen im Maschinenbau und in der Fördertechnik

Eichhorn, Sven, Weber, Andreas, Feig, Katrin, Müller, Christoph, Krug, Detlef January 2015 (has links)
Es wurde ein plattenförmiges Qualitätshalbzeug aus Spezialholzwerkstoffen für den konstruktiven Einsatz im Maschinebau, mit dem Schwerpunkt Fördertechnik entwickelt. Mit diesem Halbzeug sind ökologisch vorteilhafte Konstruktionen möglich. Entwicklungsschwerpunkte waren: einstellbare, hohe absolute und spezifische mechanische Eigenschaften mit kleinen Streuungen. Die Entwicklung wurde durch verschiedene Werkstoffprüfungen von Labor- und Industriewerkstoffen begleitet und deren Ergebnisse mittels speziell erarbeitetet Bewertungskriterien evaluiert. Weiterhin wurde das Werkstoffverhalten von diversen Holzwerkstoffen unter dynamischer Belastung klassifiziert. / A panel-shaped high quality semi-finished product made of special wood-based materials for structural applications in mechanical engineering, with a focus on materials handling technology, was developed. With said semi-finished product ecologically advantageous constructions are possible. Development priorities were: adjustable, high absolute and specific mechanical properties with little variation. The development was accompanied by various materials tests of laboratory and industrially manufactured materials, and their results were evaluated by specially developed evaluation criteria. Furthermore, the material behaviour of various woodbased materials under dynamic loading was classified.
168

[en] CONVENIENCE STORES ORDERS PICKING: A CASE STUDY / [pt] PICKING DE PEDIDOS DE LOJAS DE CONVENIÊNCIA: UM ESTUDO DE CASO

ANDRE REBIBOUT VIANA DE AZEVEDO 14 December 2020 (has links)
[pt] Devido ao ambiente competitivo entre as empresas, as exigências por redução de custo e maior entrega de valor ao cliente são crescentes. Desta forma, o gerenciamento efetivo da cadeia de suprimentos é cada vez mais necessário. Um componente essencial desta cadeia é o estoque, que possui dentre outras funcionalidades o papel de concretizar o atendimento da demanda do cliente final. Para tal, faz-se presente ao longo da cadeia de suprimento do cliente, edificações destinadas ao posicionamento e manuseio de estoques denominadas armazéns ou centros de distribuição. Estas instalações possuem atividade dinâmica, destacando-se a operação de picking, que corresponde por 50 porcento a 75 porcento dos custos de operação do armazém. O picking é o processo de coletar de seus locais de armazenagem os itens necessários para o atendimento dos pedidos dos clientes. Esta operação tem sido bastante impactada pelas recentes tendências do varejo devido à demanda cada vez mais complexa, maior variedade de itens e menor frequência de reposição. Um exemplo deste modelo, pouco explorado pela literatura, é o suprimento de lojas de conveniência. A partir desta carência de estudos, este trabalho pretende desenvolver um guia de avaliação de armazéns voltados ao suprimento de lojas de conveniência. Para tal, foi elaborada uma revisão de escopo da operação de picking e um estudo de caso contemplando três armazéns de duas empresas brasileiras com o intuito de demonstrar suas principais similaridades e diferenças. / [en] Due to the competitive environment among companies, the demands for cost reduction and greater added value for the customer are increasing. Therefore, effective supply chain management is extremely necessary. An essential component of this chain is the inventory, which has, among other features, the role of fulfilling the demand to the final customer. In order to support this, buildings are designed for positioning and handling inventories; they re called warehouses or distribution centers and are present throughout the customer supply chain. These facilities have dynamic activity, especially the picking operation, which corresponds for 50 percent to 75 percent of the warehouse s operating costs. Picking is the process of collecting the items needed to fulfill customer orders from their storage locations. This operation has been greatly impacted by recent retail trends due to increasingly complex demand, a greater variety of items and less frequency of replacement. An example of this model, little explored in the literature, is the supply of convenience stores. Based on this lack of studies, this work intends to develop a guide for evaluating warehouses aimed at supplying convenience stores. To this end, a scope review of the picking operation and a case study covering three warehouses of two Brazilian companies were prepared in order to demonstrate their main similarities and differences.
169

Textilverstärkte Zugmittel für die Antriebs- und Fördertechnik mit formschlüssiger Krafteinleitung / Textile-reinforced power transmission belt for the drive and conveying engineering with form-closed force application

Hübler, Jörg 01 July 2013 (has links) (PDF)
Die Arbeit befasst sich mit einem neuen textilverstärkten Zugmittel mit formschlüssiger Krafteinleitung. Im Grundlagenteil werden Aufbau, Eigenschaften und Dimensionierungsgrundlagen von Rollenketten und Zahnriemenantrieben erörtert, sowie textile und elastomere Werkstoffe betrachtet. Aus den Betrachtungen zum Stand der Technik, der Maschenware mit hochfesten Filamentgarnen und deren polymeren Beschichtungen wird der Entwicklungsansatz abgeleitet. Mit Hilfe eines Spezialkettenwirkverfahrens werden die textilen Zugträger als Recht/Links-Maschenware hergestellt. Das besondere daran ist die teilungsgenaue Einbindung der Bolzen in die Maschenstruktur bei der Fertigung. Eine anschließende elastomere Beschichtung verbessert die mechanischen Eigenschaften erheblich und fixiert die Bolzen axial. Dabei werden reaktive Polyurethane im Gießverfahren und thermoplastische Elastomere im Spritzgießverfahren eingesetzt. Drei ausgewählte textile Bindungen mit verschiedenen Beschichtungen wurden statisch und dynamisch, anhand von Proben und endlos verbundenen Zugmitteln, ausführlich untersucht. Die daraus abgeleiteten Bauteil-Wöhlerlinien und Leistungsdiagramme bilden die Grundlage zur Auslegung der textilverstärkten Zugmittel für Anwendungen im Maschinenbau. / The dissertation deals with a new textile reinforced with form-closed force application. The basis of structure, properties and sizing basics of roller chain drives and belt drives are discussed and considered textile and elastomeric materials. From consideration of the prior art, the knitted fabric with high tenacity filament of polymeric coatings and their development approach is derived. Using a special knitting process, the textile chain tension members are produced as a right / left-knit fabric. The special thing about it is the exact distribution of involvement of the pins in the mesh structure during manufacturing. Subsequent elastomeric coating significantly improves the mechanical properties and fixes the bolt axially. These reactive polyurethanes by casting and thermoplastic elastomers are used in injection molding. Three selected textile bonds with different coatings were statically and dynamically examine in detail the basis of samples and associated endless traction means. The derived component S/N curves and performance charts are the basis for the design of textile-reinforced tension means for applications in mechanical engineering.
170

Die Diskrete Elemente Methode als Simulationsmethode in der Vibrationsfördertechnik

Dallinger, Niels 05 October 2017 (has links) (PDF)
Vibrationsförderer sind Stetigförderer, welche Fördergüter durch periodische Schwingbewegungen in gerichtete Bewegungen versetzen. Vibrationsförderer sind in der Handhabungstechnik, der Zuführung von Mikrobauteilen und feinen Pulvern, sowie in der Schüttgut verarbeitenden Schwerindustrie weit verbreitet. In dieser Arbeit erfolgt nach der Betrachtung des Stands der Technik von Vibrationsförderern und den Interpretationsmöglichkeiten der Förderorganbewegung, die Vorstellung und Diskussion weiterer analytischer Berechnungsansätze. Anschließend werden Störprozesse, die während des Guttransportes auf Vibrationsförderern immer wieder beobachtet werden, erstmals klassifiziert und mathematisch beschrieben. Um die DEM-Simulation von Vibrationswendelförderern und linearen Vibrationsförderern unter Verwendung des Gleit-, Wurf- und Haft-Gleitförderprinzips in der Software LIGGGHTS zu ermöglichen, wurde eine Softwareerweiterung entwickelt. Diese Erweiterung umfasst zwei Module, welche die Bewegungen von importierten CAD-Geometrien auf Basis von als Fourierreihen definierten harmonischen Schwingungen höherer Ordnung ermöglichen. Das Befehlsmodul viblin ermöglicht die Definition von translatorischen Schwingungen. Das Modul vibrot ermöglicht die Definition von Rotationsschwingungen um eine raumfeste Achse. Beide Bewegungsmodule ermöglichen die Definition von komplexen Schwingungszuständen der CAD-Geometrien. Untersuchungen der Mikroprozesse innerhalb einer Arbeitsperiode zeigen, für die Förderarten Wurf und Gleiten, alle notwendigen Abschnitte der Kraft- und Geschwindigkeitsverläufe am Fördergut. Die durchgeführten Validierungen stellen die Verwendung der DEM als Simulationswerkzeug in der Vibrationsfördertechnik sicher. Auf der Basis der abschließend durchgeführten Parameterstudien können in Zukunft Kalibrierungsmethoden bezüglich des Verhaltens von Partikeln auf vibrierenden Unterlagen entwickelt werden. / Vibratory conveyors are continuous conveyors which move the materials to be conveyed by periodic vibrations of the conveyor chute. Vibrating conveyors are used in handling technology, the supply of micro components and fine powders, as well as in bulk material processing heavy industry. Within this work the state of the art of vibratory conveyors and alternative interpretations of the conveyor movement are introduced. Afterwards further analytical approaches are discussed. Subsequently, interfering processes, which occur during the transport of the materials on vibratory conveyors are classified and mathematically described. To simulate vibrating spiral conveyors and linear vibration conveyors using the sliding, throwing or sticking-glide conveyor principle in the software LIGGGHTS, a software extension was developed. This extension includes two software modules, to define the movements of imported CAD geometries on the basis of as Fourier series defined harmonic oscillations. The viblin command module allows the definition of translatory vibrations. The module vibrot allows the definition of rotational vibrations around a fixed axis. Both motion modules allow the definition of complex vibrational states of the CAD geometries. Investigations of the micro processes within a working period showed all necessary sections of the force and speed progression on the conveyed particles for the conveyor principles of micro throw and slide. The validations constitute the basic function of the DEM as a simulation tool in the vibratory conveyor technology. The final parameter studies can be used to develop calibration methods to describe the motion of particles on vibrating plates

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