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Dissertations / Theses on the topic 'Micro-extrusion'
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Chi, Xiaopeng. "Micro-extrusion of fine ceramic latticework." Thesis, Queen Mary, University of London, 2008. http://qmro.qmul.ac.uk/xmlui/handle/123456789/447.
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Microextrusion freeforming of ceramic lattices from high solids ceramic pastes is a method for forming complex multi-scale hierarchical porous structures. It has the advantages of low shrinkage stress, high sintered density and environmental compatibility. A user friendly graphical user interface (GUI) was created so that the micro-extrusion freeforming worktable could be made very easy to manipulate even for a beginner. A solvent-based approach to paste preparation for extrusion freeforming was established, involving selection of solvent, polymer and dispersant. The parameters in the process such as solid fraction in the paste, paste viscosity, extrusion rate, X, Y table velocity, filament diameter and the volatilization of the solvent were studied. A substrate material which provided sufficient adhesion to resist shrinkage efficiently and also allowed the extruded lattice to be easily detachable was selected. The extrusion pressure in the alumina paste was monitored and was found to be useful in predicting and optimizing the extrusion behaviour. Hydroxyapatite (HA)/ tricalcium phosphateTCP and alumina lattices were directly fabricated using 80-500 μm diameter filaments. This thesis reports the implementation of design and fabrication of these scaffolds for tissue engineering, band gap materials and micro-fluidic devices. Multi-scale hierarchical void structures were fabricated and tested in vivo for regenerative medical applications. A co-extrusion nozzle assemble was design to produce tubular alumina lattice.
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Jayasuriya, M. Janaka K. ""Micro stream" a CAD package for streamlined extrusion dies utilizing a microcomputer." Ohio : Ohio University, 1985. http://www.ohiolink.edu/etd/view.cgi?ohiou1184009445.
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Hutchins, Cathleen Ruth. "Consolidation of copper and aluminum micro and nanoparticles via equal channel angular extrusion." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1560.
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Laing, Jeffrey M. "Finite Element Modeling and Validation of a Novel Process for Extruding Thin Wall Hollow Copper Profiles." Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1327333357.
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Vaitkus, Victor L. "A Process for the Direct Hot Extrusion of Hollow Copper Profiles." Ohio University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1212718629.
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Costa, Débora Delai. "Eficácia de diferentes técnicas de retratamento endodôntico de canais radiculares curvos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/179924.
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Introdução: Os objetivos deste estudo foram comparar a extrusão apical de debris durante a desobturação com WaveOne Gold, ProTaper retratamento, D-RaCe ou limas manuais; descrever as falhas e/ou fraturas ocorridas nos instrumentos de NiTi; e comparar o WaveOne Gold com os sistemas ProTaper e RaCe em relação à quantidade de material obturador remanescente, transporte apical (TA) e tempo de trabalho após a desobturação e após o repreparo de canais radiculares curvos. Materiais e Métodos: Quarenta canais mésiovestibulares de molares superiores foram preparados, obturados e divididos em 4 grupos (n=10): WOG) WaveOne Gold Primary e Medium; PTG) ProTaper Retreatmento e ProTaper Next; RCG) D-RaCe e RaCe; e LM) Limas manuais. A extrusão de debris foi determinada subtraindo-se o peso final do peso inicial dos Eppendorfs. Os instrumentos de NiTi (n=18) foram analisados em MEV antes e após a desobturação. A quantidade de material obturador remanescente e o TA foram avaliados em micro-TC. O tempo de trabalho foi anotado e comparado. Os dados foram estatisticamente analisados (α=.05). Resultados: WOG extruiu menos debris do que LM e RCG (P<.05), e foi similar ao PTG (P>.05). Não houve diferença entre LM, PTG e RCG (P>.05). A análise em MEV mostrou, dos 18 instrumentos avaliados, 3 fraturas e 10 deformações. Nas duas etapas avaliadas, WOG apresentou similar (P>.05) e menor (P<.05) quantidade de material obturador remanescente do que PTG e RCG, respectivamente. A quantidade de material no WOG e RCG foi menor após o repreparo (P<.05). Na desobturação, WOG teve maior TA em 4mm do que em 2mm (P<.05). Em 2mm, o TA do WOG foi menor do que RCG (P<.05), e em 4mm foi igual ao PTG e RCG (P>.05). Na desobturação, o tempo de trabalho no grupo LM foi maior que nos demais (P<.05). No repreparo, WOG foi mais rápido do que PTG e RCG (P<.05). Conclusões: Todos os instrumentos causaram extrusão de debris, sendo que o WOG apresentou os menores valores. Nenhum sistema removeu completamente o material obturador de raízes mésiovestibulares de molares superiores. Considerando os baixos valores de TA obtidos, os instrumentos avaliados foram considerados seguros para desobturação e repreparo de canais curvos. A desobturação com LM foi mais lenta do que com os instrumentos de NiTi. O sistema reciprocante foi mais rápido do que os rotatórios no reprepro.Introduction: The aims of this study were to assess the amount of apically extruded debris during filling removal with WaveOne Gold, ProTaper Retreatment, D-RaCe or hand files; to describe failures of NiTi instruments; and to compare WaveOne Gold with ProTaper and RaCe systems regarding remaining filling material, apical transportation (AT) and working time after filling removal and after shaping of curved root canals. Methods: Forty mesiobuccal canals of maxillary molars were prepared, filled, and assigned into 4 groups (n=10): WOG) WaveOne Gold Primary and Medium; PTG) ProTaper Retreatment and ProTaper Next; RCG) D-RaCe and RaCe; HF) Hand files. The amount of extruded debris was determined by subtracting the final from the initial Eppendorfs weight. The NiTi instruments (n=18) used for filling removal were analyzed pre and post-operatively by SEM. Micro-CT analysis assessed the residual filling material and AT. Working time was recorded and compared. Data were statistically analyzed (α=.05). Results: WOG produced less debris compared with HF and RCG (P<.05), and similar to PTG (P>.05). HF, PTG and RCG showed no difference (P>.05). SEM analyses after filling removal showed, from the 18 instruments evaluated, 3 fractures and 10 deformations. In both evaluated steps, WOG had similar (P>.05) and less (P<.05) amount of filling material as PTG and RCG, respectively. The remaining material in WOG and RCG was lower after shaping (P<.05). In filling removal, WOG had higher AT at 4mm than at 2mm (P<.05). At 2mm, AT of WOG was lower than RCG (P<.05), and at 4mm, was equal to PTG and RCG (P>.05). In filling removal, working time in HF group was significantly higher than others (P<.05). In shaping step WOG was faster than PTG and RCG (P<.05). Conclusions: All instruments tested caused debris extrusion, with WOG presenting the lowest values. Neither system could completely remove the filling material of mesiobuccal canals of maxillary molars. Considering the low AT values obtained, the instruments evaluated were safe for filling removal and shaping of curved canals. Filling removal with HF was slower than with the NiTi files. The reciprocating system was faster than the rotary in shaping the root canals.
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Raynaud, Jonathan. "Elaboration de pièces 3D multimatériaux par fabrication additive." Thesis, Limoges, 2019. http://www.theses.fr/2019LIMO0101.
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Actuellement, les pièces HTCC et LTCC (High and Low Temperature Co-fired Ceramics) sont élaborées selon deux procédés : le coulage en bande pour le substrat diélectrique en céramique et la sérigraphie pour la réalisation des pistes et vias métalliques. Un procédé de fabrication additive hybride, capable de construire une pièce 3D en céramique / métal, pourrait trouver un intérêt majeur dans la fabrication de composants utilisés en micro-électroniques. En effet, un des principaux avantages de la fabrication additive est de pouvoir réaliser des géométries qui ne peuvent actuellement pas être obtenues en micro-électronique, ce qui permettrait d’obtenir un gain de performances comparé aux circuits actuels. L’objectif de ce travail est de proposer un nouveau procédé d’obtention de pièces monolithiques multimatériaux utilisant le couplage de deux technologies de fabrication additive .Une stratégie combinant la stéréolithographie et la micro-extrusion est proposée pour la fabrication de pièces multimatériaux HTCC et LTCC. Les pièces modèles sont des circuits électroniques dans les trois dimensions de l’espace comprenant un substrat diélectrique ainsi que des pistes horizontales et des vias. Des structures innovantes ont également été construites (blindage continus et vias obliques). La caractérisations de ces composants conduit à des valeurs similaires à celles des HTCC et LTCC réalisés par des procédés conventionnelsCurrently, HTCC and LTCC (High and Low Temperature Co-fired Ceramics) parts are produced by two processes: tape casting for the dielectric ceramic part and screen printing for the realization of metal tracks and vias. The main objective of this work is to propose a new process for obtaining monolithic multi-material parts using the coupling of two additive manufacturing technologies. In this respect, a hybrid additive manufacturing process capable of building a 3D ceramic / metal part could be of major interest in the manufacture of such electronic components. Stereolithography and robocasting seem to be complementary processes to achieve this goal. The advantage of using additive manufacturing instead of conventional methods is to be able to achieve forms that can not currently be obtained in microelectronics, which would allow a performance gain compared to current circuits. A strategy combining stereolithography and robocasting is proposed for the simple manufacture of HTCC and LTCC multi-material parts. The model parts are electronic circuits in the three dimensions of the space including a dielectric substrate as well as horizontal tracks and vias. To improve the performance of current circuits new geometries are being studied, such as armored or inclined vias. They will then be characterized in microwave to verify the application of selected materials in these frequency ranges
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Clark, Peter G. "Multi-scale modelling describing thermal behaviour of polymeric materials. Scalable lattice-Boltzmann models based upon the theory of Grmela towards refined thermal performance prediction of polymeric materials at micro and nano scales." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5768.
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Micrometer injection moulding is a type of moulding in which moulds have geometrical
design features on a micrometer scale that must be transferred to the
geometry of the produced part. The difficulties encountered due to very high shear
and rapid heat transfer of these systems has motivated this investigation into the
fundamental mathematics behind polymer heat transfer and associated processes.
The aim is to derive models for polymer dynamics, especially heat dynamics, that
are considerably less approximate than the ones used at present, and to translate
this into simulation and optimisation algorithms and strategies, Thereby allowing
for greater control of the various polymer processing methods at micrometer scales.
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Clark, Peter Graham. "Multi-scale modelling describing thermal behaviour of polymeric materials : scalable lattice-Boltzmann models based upon the theory of Grmela towards refined thermal performance prediction of polymeric materials at micro and nano scales." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5768.
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Micrometer injection moulding is a type of moulding in which moulds have geometrical design features on a micrometer scale that must be transferred to the geometry of the produced part. The difficulties encountered due to very high shear and rapid heat transfer of these systems has motivated this investigation into the fundamental mathematics behind polymer heat transfer and associated processes. The aim is to derive models for polymer dynamics, especially heat dynamics, that are considerably less approximate than the ones used at present, and to translate this into simulation and optimisation algorithms and strategies, Thereby allowing for greater control of the various polymer processing methods at micrometer scales.
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Petruš̆̌̌̌ić, Stojanka. "Macro and micro forms of thermosensitive hydrogels intended for controlled drug release applications." Thesis, Lille 1, 2011. http://www.theses.fr/2011LIL10175/document.
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L’objectif de cette thèse est de mettre au point des formes adéquates d’hydrogels thermosensibles destinées à une application textile transdermique de libération contrôlée de médicament. Les travaux concernent les hydrogels thermosensibles à base de poly(N-isopropylacrylamide) (PNIPAAm). Ce polymère a été combiné sous une forme linéaire et/ou réticulée avec l’alginate, pour former des hydrogels ayant une structure de réseaux de polymères interpénétrés. On améliore ainsi les propriétés du PNIPAAm pur. Des hydrogels de PNIPAAm et d’alginate de calcium (CA) ont d’abord été synthétisés sous forme de films. La présence de CA contribue à l’amélioration des propriétés mécaniques, sans modifier la température de transition de phase du PNIPAAm. Nous avons ensuite appliqué la technique d’extrusion électrostatique pour préparer des microsphères d’hydrogel. Les paramètres du procédé ont été variés afin de comprendre et d’optimiser les conditions de fabrication de microsphères ayant un diamètre inférieur à 20 µm et une forme sphérique régulière. Nous avons utilisé la polymérisation en suspension inverse pour synthétiser des microsphères qui sont de forme plutôt régulière et sphérique, avec un diamètre variant de 20 à 80 µm. Leur structure était poreuse, en forme de nid d’abeille. La libération de l’hydrochlorure de procaïne des microsphères d’hydrogel a été étudiée avec une cellule de diffusion de Franz. L’incorporation de CA dans le réseau de PNIPAAm engendre une libération de type légèrement négatif, tandis que le PNIPAAm pur présente un type positif. La libération de procaïne dépend non seulement du phénomène de diffusion mais aussi du comportement de l’hydrogel au gonflementThe objective of this thesis is to develop adequate forms of thermosensitive hydrogels intended for a textile-based controlled transdermal drug release application. This work deals with thermosensitive hydrogels based on poly(N-isopropylacrylamide) (PNIPAAm). This polymer was combined in both linear and crosslinked form with alginate to form hydrogels with interpenetrating polymer network structure. Thus, the properties of conventional pure PNIPAAm hydrogel have been improved. Hydrogels of crosslinked PNIPAAm and calcium alginate (CA) were initially synthesized in the form of films. The presence of CA contributes to the improvement of mechanical properties without affecting the volume phase transition temperature (VPTT) of PNIPAAm. The technique of electrostatic extrusion was applied for the preparation of hydrogel microbeads. Operating parameters were varied to understand and optimize the conditions of the production of microbeads below 20 µm in diameter and of regular spherical shape. Inverse suspension polymerization was afterwards used for the preparation of microbeads of regular spherical shape and diameter in the range from 20 to 80 µm. They had porous, honeycomb-like structure. A Franz diffusion cell was employed to investigate the release of procaine hydrochloride from selected hydrogel microbeads. The incorporation of CA in PNIPAAm network resulted in slightly temperature-negative drug release pattern in comparison with temperature-positive drug release from the pure PNIPAAm hydrogel microbeads. The mechanism of the drug release at temperatures above and below the VPTT of microbeads depended on hydrogel swelling behavior and not solely on diffusion
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Lanzarini, Julien. "Elaboration et caractérisation thermo-physique de micro-composants fonctionnels à base de poudres magnétocaloriques." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2053.
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Les travaux de cette thèse proposent le développement d’un procédé de fabrication de composants micro-structurés à base d’unmatériau magnétocalorique. A plus long terme, ces composants de type lame mince seront intégrés à des dispositifs deréfrigération magnétique. Leur réalisation par les procédés conventionnels tels que l’usinage n’est pas envisageable dansl’optique d’une industrialisation. La solution envisagée est basée sur la mise en forme de composants par réplication d’uncomposite magnétocalorique. Ce micro-composite est défini par le mélange des poudres magnétocaloriques hydrogénées detype La(Fe,Si)13 dans une matrice thermoplastique (PP, LDPE). Cette technique permet de bénéficier des avantages desprocédés de mise en forme des polymères comme l’extrusion ou le moulage par injection. Le développement d’un tel procédéest divisé en deux parties. La première partie concerne l’élaboration et la caractérisation du micro-compositemagnétocalorique. Les tests réalisés en mélangeur ont permis de proposer plusieurs formulations micro-compositesmagnétocaloriques selon différents taux de charge. Cette première partie du développement étudie les différents aspects dumatériau micro-composite comme la rhéologie et les propriétés magnétocaloriques des mélanges. La caractérisationrhéologique basée sur les tests au rhéomètre capillaire est réalisé afin d’évaluer la capacité de mise en forme des mélangesassociée au procédé d’extrusion-conformage. Les propriétés propres aux matériaux magnétocaloriques telles que la variationde température adiabatique (ΔT) et la température de Curie (Tc) sont investiguées. Le contrôle de la Tc par mesure DSC a misen évidence des problématiques de déshydrogénation des poudres liées à la température d’élaboration. L’impact du taux decharge en poudre est étudié par la mesure des ΔT permettant d’estimer les performances finales du micro-composite. Ladeuxième partie traite du développement du procédé de mise en forme par extrusion-conformage. Une ligne d’outillages dédiéeà l’extrusion-conformage des lames micro-structurées a été réalisée et validée à l’échelle du laboratoire. La stabilité de latempérature de Curie a été vérifiée tout au long du processus d’élaboration des composants micro-structurés. Les paramètresd’extrusion tels que la température d’extrusion ont pu être définis afin d’éviter la déshydrogénation des poudresmagnétocaloriques. Les composants extrudés sont caractérisés en termes d’homogénéité du taux de charge en poudre et detolérances géométriques aboutissant à laThis thesis proposes the development of a method of manufacturing micro-structured components made of a magnetocaloricmaterial. In the long term, these blade-type components will be integrated in magnetic refrigeration devices. On an industrialscale, their production by the conventional process, machining, is not possible. The solution proposed is based on shaping thecomponent by a replication process via a magnetocaloric composite material. This micro-composite is defined by the mixtureof hydrogenated magnetocaloric powders of La(Fe,Si)13 in a thermoplastic matrix (PP, LDPE). This technique allowsutilization of the polymer shaping process, extrusion. The development of this process is divided into two parts. The first partconcerns the development and characterization of the magnetocaloric micro-composite. Results from tests performed with themixer allow the proposal of several micro-composite formulations under different loading rates. These formulations are thenstudied for various aspects of micro-composite material. The rheological characterization based on capillary rheometer tests istaken to evaluate the shaping ability of the mixtures associated with the extrusion process. Specific properties ofmagnetocaloric materials such as the adiabatic temperature variation (ΔT) and the Curie temperature (Tc) are also investigated.The control of the Tc by DSC measurement highlighted problematic dehydrogenation of the powders as a result of theelaboration temperature. The impact of loading rate is studied by measuring the ΔT in order to estimate the final performanceof the micro-composite. The second part deals with the development of the shaping process by extrusion. A tooling linededicated to extrusion of the micro-structured blades is carried out and validated at the laboratory scale. The stability of Tc ischecked throughout the elaboration process of the micro-structured components. The extrusion parameters are defined to avoidthe dehydrogenation of magnetocaloric powders. The extruded components are characterized in terms of homogeneity of thepowder loading rate and geometric tolerances resulting in the validation of the developed process. The industrial transfer isnow possible to a large scale production
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Lu, Bo. "Rheology and dynamics at the interface of multi micro-/nanolayered polymers." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI133.
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Les travaux de cette thèse concernent des études fondamentales liées à la rhéologie et dynamique des chaines aux interfaces/interphases dans des structures polymères multi- micro et nano-couches obtenues par le procédé de coextrusion. Des couples de matériaux modèles présentant une compatibilisation physique et/ou chimique aux interfaces ont été étudiés. L’objectif ultime consiste en la compréhension des phénomènes multi-physiques et multi-échelles mis en jeu lors de l’élaboration du confinement de ces matériaux. Dans un premier temps, l'influence de «l'interphase diffuse» sur le comportement rhéologique aux échelles micro- et nanométriques a été étudiée. Malgré le caractère compatible du système PVDF/PMMA, ce travail met en évidence que les chaines macromolécules des deux polymères présentent une certaine hétérogénéité locale dans la dynamique spatiale, allant de l’échelle des segments jusqu’à la conformation globale des chaînes. L’étude par spectroscopie diélectrique, montre que cette hétérogénéité est dépendante de la composition de l'interphase. Cette dernière est gouvernée à son tour par la diffusion mutuelle des chaines aux interfaces. Les résultats obtenus ont été analysés et modélisés en se basant sur les concepts de la dynamique moléculaire. La deuxième partie de cette étude porte en l’étude de l’effet d’une interphase diffuse (et ou réactive) sur les propriétés microstructurales, rhéologique et en particulier sur la dynamique moléculaire dans les multi- micro et nano-couches confinés. Les systèmes élaborés ont été analysés à différentes échelles par différents moyens spectroscopiques. L’effet du confinement sur la structure cristalline est mis en exergue. Ces systèmes ont été étudiés sous sollicitations en cisaillement et en élongation en viscoélasticité linéaire (VEL) et non-linéaire (VENL). Des modélisations ont été alors possible et elles étaient établies en se basant sur les mécanismes physiques et physico-chimiques mis en jeu. En concomitance avec cette seconde partie, nous avons démontré que la formation du copolymère greffé au niveau de cette interphase réactive présente une influence sur la dynamique moléculaire aux échelles micro- et nanométriques. Par conséquent, un nouveau processus de relaxation interfaciale diélectrique est démontré. Sa signature est dépendante du temps ouvert à la réaction ainsi que du nombre de couches. Le dernier volet de la thèse a porté sur l'effet du l’ultra-confinement sur les propriétés microstructurales, la dynamique et les propriétés diélectriques à l’état fondu et solide. En outre, des moyens type 2D-WAXS/SAXS, spectroscopie diélectrique multifréquences ont été déployés pour mener à bien ces travaux. Enfin, les résultats de cette thèse présentent une première approche pour le contrôle des propriétés d’interphases dans les structures multinanocouches. Les applications visées sont principalement la plastronique, l’énergie ou l’emballage alimentaire à propriétés Ultra-barrièreInterphase developed at the polymer–polymer interface crucially determines the overall macroscopic properties of multilayered polymers from coextrusion. A better understanding of the interfacial properties involving rheology and dynamics is essential for establishing the processing-structure-property relationship. Therefore, this thesis is focused on a fundamental study of the role of interphase in rheology and dynamics of multicomponent polymers, towards tailoring the interface/interphase in multilayered structures from coexrusion process. The work proceeded from the diffuse interphase in compatible multilayered systems to the reactive interphase in reactive counterparts. Starting with a preliminary study on a model compatible system of PVDF/PMMA blends, we firstly revealed their blending phenomena and physics, involving dynamic heterogeneity in segmental and terminal scales, and locally structural heterogeneity due to the nanoscale interphase. Particularly, the local heterogeneity significantly altered the thermorheological and dynamic behaviours. Based on the findings with blends, we were able to further clarify the effects of interdiffusion and diffuse interphase formation on the structure, rheology and dynamics in compatible multilayered PVDF/PMMA systems fabricated by forced-assembly multilayer coextrusion. The remarkable changes in the rheological and dynamic behaviors of these compatible multilayers were explained in terms of the physical picture for interdiffusion mechanism and physics of diffuse interphase occurring in coextrusion process. Secondly, we incorporated in situ interfacial chemical reaction to multilayered systems based on PVDF-g-MAH/PA6 in comparison to PVDF/PA6 pair, thereby allowing us to probe the generated reactive interphase with graft copolymers from bilayer to multi nanolayers. Influence of interfacial reaction and formed interphase on the resulting macroscopic rheological behaviors and microscopic dynamics were preliminarily elaborated using a stacked model bilayer of PVDF-g-MAH/PA6, by taking into account the factors involving interfacial morphology development, copolymer architecture and reaction extent/time, etc. Based on this preliminary investigation, we further probed the role of interfacial reaction and reactive intephase formation in the coextruded multilayered structures alternating of PVDF-g-MAH/PA6 with the layer thickness varying from micro- to nanoscale. Therein, we investigated systematically the layer architecture/structure, morphology, dielectric properties, charge transport dynamics, and especially the uniaxial extensional rheology of the reactive multilayered polymers in the presence of reactive interphase. Findings obtained in this thesis are aimed at a better understanding of the interfacial properties including rheology, dynamics and dielectric properties, towards controlling the interface/interphase and confinement in multilayered polymers from coextrusion and for their advanced applications
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Chomat, Dimitri. "Élaboration et mise en forme de composites micro-fibrillaires par fibrillation in-situ : optimisation de la microstructure et des propriétés mécaniques résultantes." Thesis, Lille 1, 2013. http://www.theses.fr/2013LIL10127.
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L'élaboration de composites micro-fibrillaires a été réalisée par fibrillation in-situ à partir de couples de polymères immiscibles. Dans un premier temps, un mélange polypropylène / polyamide 6 (PP/PA6) a été utilisé comme référence pour la mise au point du procédé d'extrusion - étirage en continu. En faisant varier les paramètres rhéologiques, il est apparu que la fibrillation est soumise aux conditions d'un rapport de viscosité inférieur à 4 et d'un rapport d'élasticité inférieur à 1 durant le mélangeage. Des expériences portant sur la température de mise en forme des composites micro-fibrillaires par injection ont montré que la préservation de la morphologie nécessite une température inférieure à la température de fusion de la phase dispersée. Dans un deuxième temps, ces travaux ont porté sur l'incorporation de nanocharges d'argile dans un but de compatibilisation du mélange PP/PA6. Différentes voies d'ajout de la montmorillonite modifiée ont été testées. Parmi celles-ci, il a été vu que la pré-dispersion de la nanocharge dans la matrice PP aboutit à une migration des feuillets d'argile du PP vers l'interface PP/PA6 lors du procedé de fibrillation in-situ. Un affinement des fibrilles a été constaté à cette occasion, entraînant une amélioration de la résistance au choc. Enfin, une dernière partie a été consacrée au développement d'un composite micro-fibrillaire bio-sourcé acide polylactique / polyamide 11 sur la base des résultats précédemment acquis. Bien qu'une morphologie partiellement fibrillaire ait été formée lors de l'étirage, la mise en forme du composite par injection a entraîné la destruction des fibrilles par échauffement et relaxationElaboration of microfibrillar composites based on immiscible polymer blends was performed by means of in-situ fibrillation. First, a polypropylene / polyamide 6 blend (PP/PA6) was used as a reference in order to develop an extrusion - drawing process. Upon variation of rheological parameters, it appeared that fibrillation requests a viscosity ratio less than 4 and an elastic ratio less than 1. Experiences about influence of processing temperature demonstrated that the injection step must be proceed at a temperature lower than the melting temperature of the dispersed phase in order to preserve the morphology. In a second part, this study dealt with the incorporation of organically modified montmorillonite with the aim of compatibilizing PP/PA6 blends. Several ways of nanoclay addition have been tested. Among them, nanoclay pre-dispersion in the PP matrix lead to the migration of clay platelets from PP to PP/PA6 interface during the in-situ fibrillation process. Hence, fibrils refinement was observed, inducing an improvement of impact resistance. Finally, one last part was dedicated to the development of a poly(lactic acid) / polyamide 11 bio-based micro-fibrillar composite. Whereas a partially fibrillar morphology was formed upon drawing, injection of the composite involved fibrils destruction due to overheating and subsequent relaxation
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Lin, Chun-Kai, and 林群凱. "Micro-pipe Extrusion on Metal Plates." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/32858246703524000377.
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碩士國立高雄應用科技大學
模具工程系碩士班
102
New high-tech products tend to be size-miniaturized and weight-minimized. There are also difficulties in gripping the micro billets during the micro-pipe forming processes. Sticking occurs because of decreasing body force as well increasing surface force in the micro drawing processing. Additionally the insufficient number of grains in the pipe wall leads to fracturing in the micro drawing process. This work investigates pipe extrusion on the sheet metal to avoid the difficulties in the micro drawing process. Therefore, the modification and adjustment on the stamping die become easier and more robust. The choice of sheet material and thickness gauge is more versatile. Consequently pipe extrusion from sheet metal exhibits advantages in low volume and high variety in production economy. The parameters affecting micro-pipe extrusion on commercial aluminum sheets were investigated. DEFORM-2D software was used to analyze the optimal forming conditions. Three thickness gauges 1, 1.5 and 2 mm as well as three relief holes 0.1, 0.2 and 0.5 mm were used. Two lubrication conditions, fully lubricated and one-side lubricated, were used. Tool-trial was conducted to verify the results of the forming simulation. The result of simulation indicates that the forming load can be effectively reduced with the aid of the relief hole, though the extrusion efficiency is reduced as well. Forming with fully lubricated condition provides higher extrusion from the relief hole, while the one with one-side lubrication provides higher extrusion from the pipe-hole. The difference is caused by the formation of dead metal near the pipe-hole in forming with fully lubricated condition. Under the condition of one-side lubrication, relief hole of 0.1 mm provides best extruding efficiency with the aluminum sheet of 2 mm thick. Relief holes of 0.2 and 0.5 mm provide best extruding efficiency with the aluminum sheet of 1 mm thick. The trial of the forming tool also verifies the result of the simulation.
15
Kao, Chia-Hsien, and 高嘉賢. "Study on ultrasonic vibration-assisted micro extrusion." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/95907367555996495355.
Full textAbstract:
碩士國立勤益科技大學
機械工程系
101
With the trend of smaller elements, the mechanisms in micro metal forming due to minimized sizes are different to that in conventional macroscopic forming. Further, ultrasonic vibration-assisted forming could reduce the forming stress and exceed the forming limit of conventional forming process; hence adopting the characteristics of ultrasonic vibration-assisted forming to overcome the problems caused by micro forming is a feasible method. This study comprises three topics including the development of the apparatus for ultrasonic vibration-assisted micro forming, the effects of ultrasonic vibration on micro upsetting and the ultrasonic vibration-assisted micro extrusion. With the goal of minimizing the apparatus and upgrading the control precision, the apparatus for ultrasonic vibration-assisted micro forming was firstly designed and manufactured, and the apparatus was then used in the experiments of ultrasonic vibration-assisted micro upsetting and micro extrusion. By the similarity principle, the specimen was minimized with a ratio (λ) and used in the experiments of conventional micro upsetting (CMU) and axial ultrasonic vibration-assisted micro upsetting (AUMU) to investigate the size effect to the forming characteristic and the impact of ultrasonic vibration. At last, this study proposed the transverse ultrasonic vibration method to overcome the difficulties of ultrasonic vibration-assisted extrusion. The die for micro gear extrusion was designed as bisected die, and longitudinal vibration was applied to the bisected die to produce the transverse vibration during the micro gear extrusion experiment. As the apparatus for ultrasonic vibration-assisted forming was built, the laser displacement meter was used to measure the actual displacement and the linear errors were then calibrated. In this manner, the actual displacement precision in this experimental flatbed was successfully improved form 30μm to within 3μm, and the load precision was 0.5N. In the results form micro upsetting, the plastic stresses decreased with smaller specimens, and the smaller size, the larger stress reduction. As the grain size increased the plastic stress also decreased but the effect was relatively less significant. When ultrasonic vibration was applied to forming process, the plastic stresses were all decreased. By smaller specimen sizes, the stress reduction was more significant than that in conventional upsetting. In the results of micro extrusion, ultrasonic vibration effectively decreased the forming force during the micro gear forming, and the reduction increased with the increase energy of ultrasonic vibration. The surface roughness was decreased by ultrasonic vibration, and the decreasing trend in roughness increased with the higher ultrasonic energy.
16
Wang, Teng-Chiao, and 王騰鉸. "ECAE Processed Copper for Backward Extrusion of Micro Cups." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/08887592413589058797.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系碩士班
96
This paper describes a micro backward extrusion process of cups using the fine-grained copper produced by equal channel angular extrusion (ECAE). Copper was first annealed, deformed by multi-pass ECAE at room temperature and heat treated to obtain a microstructure with a grain size of about 2 microns. Microstructure was carefully examined and some mechanical properties including hardness and stress-strain relationship were also investigated. The results show that the hardness of copper was increased after the ECAE. Moreover, the ECAE processed copper has larger total strain than those from the annealed copper in the simple upsetting test. The fine-grained copper obtained by the ECAE was used in a micro backward extrusion process to produce the cups with the inner diameter of 3 mm and the wall thickness of 0.1 mm. A commercial package was also employed to simulate the process and the predicted shapes of cups were close to those from experiments. It was concluded that the ECAE processed copper provides better formability and edge quality in the micro backward extrusion of cups.
17
Wu, Lin-Chi, and 吳麟麒. "Effect of Punch Shapes on Micro Backward Extrusion of Brass." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/20384628108432118735.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系碩士班
101
Punch shape plays an important role on affecting the forming load and material flow in the micro backward extrusion process. An impropriate design of the punch shape may cause inhomogeneous material flow and thus result in stress concentrations or an extreme forming load. These situations may lead to damage the punch and reduce its life. Therefore, the understanding of the effect of punch shapes on the forming load is widely interested. This study considered four types of punch shapes which were flat, conical, spherical and standardized shapes in order to investigate the effect of the punch shapes on the micro backward extrusion of brass. Brass (JIS C2600) materials were first annealed at 500, 600, and 700 ˚C and resulted in different microstructures with grain sizes of 50, 70 and 111m, respectively. The annealed brass materials were carefully machined as cylindrical billets with the same dimension of 1.1 mm in diameter and length. The billets were later used in the experiments of the micro backward extrusion to form cups with 1.1 mm diameter and 0.2 mm thickness. The study considered the processes with and without preforming stages. A finite element package DEFORM-2D was used to predict the effective stresses, effective strains, velocity fields and forming loads in order to investigate the effect of the four types of punch shapes on the backward extrusion processes. The predicted results were then applied to the design of the punches for experiments. The experimental results were compared with the predicted ones and the influences of punch shape, grain size and punch speed on material flow and forming load were investigated. The results show that the forming loads in an increasing order are spherical, standardized, conical and flat punches in the cases without a preforming stage. In the cases with a preforming stage, the preform from the conical punch can reduce the forming loads of flat and standardized punches. The preform form the spherical punch leads to an increase in forming load and a less quality of the inner surface. Moreover, the preform form the spherical punch results in uncompleted die filling. The results also show that the hardness of the extruded cups and the forming load reduces as grain size increases. The forming load increase with the punch speed.
18
Lin, Wei-Chou, and 林韋州. "The influence of ultrasonic-vibration on micro extrusion of copper." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/67558168349580921861.
Full textAbstract:
碩士國立勤益科技大學
機械工程系
102
With the miniaturization of components, the mechanism of metal forming between microscopic and macroscopic was significantly different because of size effect. Besides, owe to reducing the forming stress, ultrasonic-vibration assisted forming approach was a feasibility method to overcome the problem of micro forming process. Traditional and ultrasonic vibration micro-extrusion experiments were conducted using previous developed experimental ultrasonic-vibration assisted forming equipment. During the extrusion process, radial ultrasonic vibration was applied to explore the extrusion ratio effect for the extrusion force and ultrasonic vibration. Experimental results show that ultrasonic vibrations effectively reduced the extrusion forces, and the effect of reducing extrusion force by ultrasonic vibration is obvious with the extrusion ratio of the mold. Moreover, experimental measurements of the surface roughness find that the surface roughness of the extruded specimens was reduced by ultrasonic vibration. On the other hand, owe to the mechanism of ultrasonic vibration occurring at high speed, it is difficult to be measured in the experiments. Therefore, this study used finite element analysis out of considering the temperature and material softening effects, and the tradition micro-extrusion (MCE) and radial ultrasonic vibration micro-extrusion (MRUE) analyses were conducted. Furthermore, this study tried to overcome the difficult of measurement during the process. Finally, a precise finite element model was constructed according to comparing with simulation and experimental results. Simultaneously, the tradition and ultrasonic-vibration micro-extrusion analysis were conducted using different extrusion ratio and friction to observe those effect on the forming force. Simulation results show that the extrusion force was reduced with the extrusion ratio, and the friction effect of ultrasonic vibration disappeared, only existing stress superposition effect, under no friction condition. However, when friction existed, the friction and stress superposition effect of ultrasonic vibration occurred at the same time. In addition, friction force was reduced by ultrasonic-vibration effect with the coefficient of friction and the extrusion ratio.
19
HUANG, YU-LUNG, and 黃昱龍. "A Study on Characteristics of Micro Backward Extrusion ofCopper Powder." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/9hyjhc.
Full textAbstract:
碩士國立高雄應用科技大學
模具系碩士在職專班
103
The developments in electronics products, mobile phones and note books lead to a constant increase in the needs of micro metal parts. However, the fabrication of metal parts at micro scale is affected by size effects. The characteristics of the metal flow are different from traditional metal forming processes. One of the factors influencing the metal flow is grain size. Moreover, the miniaturized products increase the degree of difficulty in die fabrication that results in an increase in the lead time. It is therefore widely interested in developing a new technique in order to control metal flows, reduce the number of the forming stages, and thus increase the quality and shorten the lead time. This study used copper powder in micro powder extrusion processes to produce green compacts of the cup with 2 mm diameter. The green compacts were sintered to form the products. This study investigated the effect of the forming load on the hardness and porosity of the product. The study applied 5 forming loads, 4 kN, 5 kN, 6 kN, 8 kN and 10 kN on the punch to produce the green compacts of the cups having different wall thicknesses of 0.1 mm, 0.2 mm and 0.3 mm. The green compacts were sealed into quartz tubes in a vacuum condition and sintered at 600 °C in order to increase the strength. The sintered products were examined by an optical microscope and a scanning electron microscope to understand the variations in the microstructure. The dimensions, hardness and porosity of the products were also measured. The results showed that an increase in forming load led to an increase in the hardness and a decrease in the porosity of the products. The case using 10 kN load had the lowest porosity of 9.2 % and the highest hardness of 86.9 Hv. The hardness is lower than 110 Hv which was measured in an annealed copper wire. The distribution of hardness showed that the rim of the cup had higher hardness but the distribution was not uniform. The observations from the scanning electron microscope also showed the hardness distribution was associated with the variation of the porosity.
20
Ruei-Chen-Lin and 林睿宸. "Preform Design for the Extrusion of Micro Multiple Stepped Rod." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/ec3z7w.
Full textAbstract:
碩士國立高雄應用科技大學
模具系碩士在職專班
103
Micro screw is one of micro fasteners which are widely used in electronics products and mechanical equipment. Micro screws can be produced by metal forming processes including forward extrusion and thread rolling. The billets for the thread rolling, which are fabricated by the forward extrusion, commonly require the shape with multi-stepped rods. The preform design for the forward extrusion still exist challenges. Therefore, the development of the preform design for the extrusion of the multi-stepped rod can help the fastener industries. This study proposed a preform design for the forward extrusion process to manufacture the billets with multi-stepped rod which will be used in a thread rolling to fabricate AISI 1008 low carbon steel micro screws. The study considered the ratio of area reduction and volume distribution to design the preforming stages for the forward extrusion of the micro multi-stepped rod. The processes were simulated by DEFORM 2D to predict the die filling and strain distribution which were used to evaluate the preforms. Finally, the proposed preforms were used to design and fabricate dies for experiments and the dimension and hardness of the extruded rods were examined. Simulation and experimental results show the forming load increased with the punch stroke. The dimensions of the extruded multi-stepped rod were very close to the design values. The greatest hardness appeared in the region with the smallest diameter in which the largest strain occurred in the simulation. Moreover, the ratio of area reduction is one of keys to preform design. The proposed preform design can be used to successfully produce the micro multi-stepped rod.
21
HIEP, NGUYEN DINH, and 阮廷俠. "A Study on Warm Micro Backward Extrusion of SUS304 Stainless Steel." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/05093895740297984447.
Full textAbstract:
碩士國立高雄應用科技大學
精密模具與機械產研碩士外國專班
99
In trend of miniaturization, micro features are used widely in micro products. The micro parts include connector pins, miniature screws, micro spring, chip lead frames and micro cups. However, the micro sizes of these parts cause difficulties in transferring the conventional metal forming techniques to fabricate the components at micro scale. Therefore, the developments of new methods for micro metal forming have been widely interested. In this study, micro backward extrusion process of SUS304 stainless steel was performed at elevated temperature. To obtain stress-strain curves for the simulation of the processes, the experiments of micro simple upsetting were applied. The predicted results were then analyzed in order to design the die for the micro extrusion processes. Two kinds of punches with 1.6 and 1.8 mm diameter were used to backwards extrude the billets inside the die with 2 mm inner diameter. All processes were lubricated with water-based graphite and conducted under isothermal conditions at 400 ºC. The results show that the developed extrusion system can be used to produce the stainless steel components with micro cup-shaped geometries. The predicted loads are close to those measured in the experiments although the strokes of the processes are not consistent with experimental ones due to elastic deformations. Moreover, the variations in the rim height and wall thickness of the cups produced by 1.8 mm diameter punch are greater than those by 1.6 mm diameter punch. The results imply that material flows are more inhomogeneous in the cases with thinner wall than the ones with thicker wall in the micro backward extrusion processes.
22
Lin, Shih-Hong, and 林仕弘. "Effect of Particle Shape on Micro Backward Extrusion of Copper Powder." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/ekunu7.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系
103
Powder extrusion is one of near-net-shape forming processes. It has the characteristics of high material usage rate, high accuracy, less secondary machining, less forming stage, saving energy, long die life and automation. The powder extrusion is a potential process for industrial applications. This study investigated the effect of the particle shape on the micro cylinder extrusion and micro backward extrusion of copper powder. Dendritic and spherical particles of copper powders were used in the conditions without lubricant and binding material. After the produced specimens were sintered at 600 °C for 1 hour and cooled in the furnace, their porosities, hardness distributions and microstructures were examined. The cylindrical billets were also used in simple upsetting tests for obtaining the stress strain curves in order to understand material flow behaviors. The results showed that the porosity increased with the forming load and the specimens from spherical particles had lower porosities and higher relative densities. The shape of particle did affect the distribution of hardness in the extruded cup. In the case of the dendritic particle, the hardness was higher in the rim of the cup. However, in the case of spherical particles, the hardness was higher in different regions which were the round and bottom of the cup. The specimens from spherical particles had greater average values of hardness than those from dendritic particles. Moreover, the microstructures observed on the scanning electron microscope showed that the pore distribution and structure compactness had similar trends to the variation of hardness distribution.
23
Hsia, Hsin-Sheng, and 蕭新聖. "Effects of Temperature and Grain Size on Micro Backward Extrusion of Copper." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/70482674086933144153.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系
99
Temperature and grain size are important factors which significantly affect flow behaviour in metal forming processes. The influence is even more pronounced at micro scale, because so-called size effects cause inhomogeneity within the material and inaccuracy in the shape of the produced item. To investigate the influence of temperature on flow behaviour in micro metal forming, this study developed a metal forming system which is capable of conducting micro backward extrusion processes at elevated temperatures. The study also used equal channel angular extrusion (ECAE) and annealing techniques to adjust the microstructure of copper at different grain sizes of 4.9, 39.5 and 63.4 m. The treated copper was then carefully machined to form billets for the use in micro backward extrusion processes for producing cups with an outer diameter of 2 mm at three temperatures of 25, 200 and 400 ºC. The punches with different diameters were used in the processes to fabricate the micro cups with various wall thicknesses of 0.05, 0.1 and 0.2 mm. In this manner, it was possible to investigate the effect of grain size and temperature on the deformation, wall thickness and rim height variations of the extruded cups. The results clearly show that both grain refinement and an appropriate increase in forming temperature could improve material flow behaviour and thus lead to smoother rims and less variation in wall thickness of the extruded cups. Moreover, an increase in forming temperature may reduce load but it could cause recrystallization and grain growth which is detrimental to the die filling. The study also shows that the rim height difference of the fine-grained copper has a high sensitivity to temperature, particularly in the cases with a relatively small clearance between the punch and die.
24
Lee, Ming-Kai, and 李名凱. "The Design and Analysis of a Progressive Die for Micro-pipes Extrusion." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/85311879801300048996.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系
103
The miniaturization of products has driven the need for various break-through in production technology, either forming or machining, micro wire production process of micro-axle clamping faces problems, which is attributed to the decreasing body force and increasing surface force in the micro forming or cutting processes. To overcome these shortcomings, the present study sheet in a progressive dies shift to the way micro tube extrusion forming,there are also various advantages in forming with progressive stamping dies, which include preventing the mis-feed of grippers, easy for tool modification, abundant choice of sheet materials and sizes. Therefore, a micro tube forming system via progressive stamping die can meet the “low-volume and high-variety” production economy. In this study, A 1050-H14 aluminum micro tube extrusion forming of analysis and test, using DEFORM-2D and 3D finite element analysis software to simulate the optimum molding conditions, blanks thickness 1 mm and 2 mm select two blanks Select 6 mm diameter and 10 mm are two, and the blank appearance includes a side laced with bridges with designs to suit the production progressive stamping and mold to mold test results validate the simulation. Simulation results are displayed in the sheet extrusion forming were thinner the larger the diameter and thickness of the punch out of those better efficiency due to the long range bound sheet material less likely to flow out toward the outer edge, and therefore easier to axis extruded tube at the center of this case corresponds to the neutral zone is further away from the extrusion and, therefore, has more plate material is extruded. When the mold test can be found in the billet thickness 1 mm 10 mm diameter extrusion efficiency is the best.
25
Tran, Mai-Van, and 陳梅文. "Application of Micro Backward Extrusion to Manufacturing the Housing of Pin Receptacle." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/29641883252640692949.
Full textAbstract:
碩士國立高雄應用科技大學
精密模具與機械產研碩士外國專班
97
A pin receptacle is the conducting element used in a printed circuit board (PCB) to provide the electrical contact between the component lead and the PCB. In recent years, the pin receptacle has been manufactured by using a high speed turning technology which is relatively time consuming and wastes material. Therefore, there is a need in developing a new method for fabricating the pin receptacle. This study proposed a micro extrusion process for manufacturing the micro housing of pin receptacle which is made by annealing copper (JIS C1100) and especially used in the PCB. The aim of the research is to investigate the possibility of using the proposed method and understand the material flow during the filling process. A commercial software DEFORM 3D was applied to simulate the micro extrusion processes which consist of a preforming and the final stage. The predicted results including the loads and the material flow were used to evaluate the designed die profiles and the processes. To prepare the dies for the experiments, a micro electrical discharging machining technique was applied. Experiments were then carried out at room temperature and the products were carefully examined. The results show that the predicted loads are in good agreement with experimental ones. However, the die cavity of the flange was not completely filled in the final stage of the processes. Moreover, the eccentric between punch and bottom die might be one of the reasons for the variation in the wall thickness of the housing of pin receptacle. A further study on preforms and an improved die design could solve these problems.
26
Chih-Hsien, Yen, and 顏志憲. "Effects of Grain Size on Extrusion of Micro U-shaped Grooves of Copper." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/24977592271678976959.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系
98
With advances in technology, electronics production technology has greatly upgrade and the size of electronic components are gradually miniaturized. But in order to enhance their computing speed and reduce it’s volume, the density within the unit volume increase caused heat effects upgrade. This study produced a U-shaped extrusion similar heat sink to overcome today's electronic product miniaturization of thermal effects, and use this process probe into filling with different grain sizes for the micro extrusion. The effects of grain size on extrusion of micro U-shaped grooves of copper were investigated by simulation and experimental approaches. Commercially produced copper rods were treated by equal channel angular extrusion (ECAE), annealing at 580 ºC and 800 ºC and resulted in three kinds of mean grain sizes, 5.7m, 39.5m and 61.9m, respectively. The billets with 2 mm diameter and 1.5 mm height for experiments were machined from the processed coppers by the highest possible accuracy to minimize geometry effects. The billets were then extruded in forward or backward direction into the die having the grooves with 0.4 mm height and 0.07mm, 0.13 mm or 0.18 mm width. The results show that the predicted loads are in good agreements with the experimental ones. Moreover, from the section images of the extruded products, complete die filling can be achieved by all three kinds of the billets. The billets with fine grains, which obtained by the ECAE, lead to a higher load but a better surface finishing.
27
CHIANG, KUANG-CHIEN, and 蔣廣騫. "A Study on Characteristics of Combined Micro Forward and Backward Extrusion of Copper Powder." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/99ng52.
Full textAbstract:
碩士國立高雄應用科技大學
模具系碩士在職專班
103
Electronics industry, medical equipment and automotive parts related products constantly shorten the life cycle of the products. The situation leads to the need in the simplification of manufacturing processes which are capable to produce the metal products with complex geometries. Thus, the lead time can be shorten in order to meet rapidly change in market demands. The study used copper powder with dendritic shape and an average size of 45 μm in micro forward and backward extrusion processes with a single stage to produce copper parts having an forward-extruded rod and a backward-extruded cup. The study investigated the effect of forming load on the porosity and hardness of the produced parts. In the processes, only pure copper powder was used, and no binder and lubricant were applied. The process neither used a preforming stage in order to reduce the processing time and costs. The forming loads, 4 kN, 5 kN, 6 kN, 10 kN and 12 kN, were considered to produce green compacts. The green compacts were then sintered at 600 ºC for 1 hour and cooled in the furnace. The dimensions, rod length, cup height and wall thickness of the sintered parts were measured. The microstructures were also examined by an optical microscope and a scanning electron microscope in order to understand the variation in material flows and porosity. Moreover, the hardness of the parts was also measured and compared with the copper wire. The results showed that an increase in forming load caused an increase in hardness and density, and a decrease in porosity. The average relative density of the parts was in a range between 81% and 93% and the average porosity was from 11.3% to 18.23%. The regions near the rim had lower hardness with an average value of 60 Hv, and the regions in the rod however had higher hardness with an average value of 90 Hv. Moreover, the images of microstructure also showed that an increase in forming load does reduce the porosity in the parts. Keywords: micro forward and backward extrusion, micro extrusion, copper powder
28
Lin, Jian-Chen, and 林劍塵. "Effects of Temperature and Grain Size on Combined Micro Forward and Backward Extrusion of Copper." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/85017259206779560822.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系
98
Micro-extrusion process plays an important role in manufacturing micro-metal parts which are widely used in micro-products. The process with complicated forming behaviors is affected by many factors including grain size, temperature, friction and lubrication conditions. However, most studies of micro extrusion focused on the cold forming and considered only one of the factors. There is a need in investigation on the effects of grain refinement and temperature increase on the behaviors of materials flow in order to further understand the micro-extrusion process. This study develops a micro extrusion system with temperature control in order to study the effects of temperature and grain size on the combined micro forward and backward extrusion of copper. The equal channel angular extrusion and annealing techniques were employed and studied to produce three kinds of coppers with mean grain sizes, 4μm, 35.8μm and 61.8μm. The treated coppers were used to prepare the billets with 2 mm diameter and 2.5 mm height for conducting micro extrusion processes. The 1.6 mm and 1.8 mm diameter punches were used to compress billets into the die with 2 mm diameter in the portion of backward extrusion and 1 mm diameter in the portion of forward extrusion at room temperature, 200 ºC and 400 ºC, respectively. The material of the billet was thus forced to flow backwards and forwards. The parts with a backwards-extruded cup and a forwards-extruded pin were fabricated. The conclusions of the study describes as follows: (a) The ECAE processed copper with refined grains has the highest strength and the most regular shape of the compressed specimens obtained by simple upsetting processes; (b) The experiments of the micro forward and backward extrusion show the grain refinement significantly reduces the differences in both the rim height and the wall thickness of the cup. This trend also occurs as the forming temperature increases; (c) Both temperature increase and grain refinement improve the flow behaviors of copper. This effect can greatly reduce the irregularity of the product shape which results from the micro extrusion at room temperature using the billets with relatively larger grains, and thus improves the quality of the products.
29
Lin, Jui Pin, and 林瑞斌. "Effects of Punch Geometry on Filling of Shoulder fillets in Micro Backward Extrusion of Pins." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/63814069458086441066.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系碩士班
96
This study uses finite element analysis (FEA) and experimental approaches to investigate the effects of punch geometry on the filling of shoulder fillets in the micro backward extrusion of pins. The process consists of billet shearing, performing and finish stages. In this study, brass (JIS C2700) wires were used to prepared the billets. Simple upsetting tests and ring compression tests were employed to obtain stress-strain curves and friction factors, respectively. The obtained data was then used in an FEA software, DEFORM, to simulate the micro backward extrusion of the pin with the minimum diameter of 0.82 mm. The variation of punch diameter and the effects of punch geometry on the filling of shoulder fillets were investigated. Based on the predicted results, some punches with different diameters and a set of dies were designed and fabricated and the experiments were conducted in order to examine the folding and crack in the extruded pins and their dimensions. The experimental works thus help reduce the time for die set up in mass production and decrease the cost. A set of punch profiles has been proposed and successfully used in the micro backward extrusion to manufacture the pins with complete filling of shoulder fillets.
30
LIU, LI-XIU, and 劉立修. "The Micro-Extrusion of Magnesium Alloy with Servo Motion Curve of Punch at Elevated Temperature." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/wc3a87.
Full textAbstract:
碩士國立虎尾科技大學
機械與電腦輔助工程系碩士班
106
Magnesium (Mg) alloys are used extensively for the manufacture of lightweight structural and functional automotive and electronics parts, due to the low density and high specific strength of such alloys. Development of new forming processes using servo motion curve of the punch is attracting attention in the metal forming industry. The ductility of the Mg alloy was found to be improved by controlling the servo motion curve of the punch. It also can be enhanced the formability of workpiece and the life of die. In this study, the influence of the servo motion curve of punch on the workability of Mg alloys of micro extrusion is examined. Microstructure and mechanical properties including hardness and stress-strain curve are examined. A magnesium alloy is used in a micro forward extrusion with servo motion curve of punch at the elevated temperature. A finite element analysis of micro extrusion with servo motion curve of punch at the elevated temperature are also applied in this study. Finally, the formability, shaped size, stress distribution and surface roughness of magnesium alloy micro extrusion are improved with servo motion curve of punch at the elevated temperature.
31
Lai, Jiang-Cheng, and 賴建成. "Effects of Grain Size and Lubrication Conditions on Micro Forward and Backward Extrusion of Brass." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/36058495694312237817.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系碩士班
101
In this study, the brass C2700 tubes with 1.1 mm outer diameter and 0.5 mm inner diameter were treated by annealing with 400, 500 and 600℃to obtain the grain sizes in 20, 34, and 80 m, respectively. The treated tubes were the machined and ground as 0.6 mm length specimens for the experiments of micro forward and backward hollow extrusion. The surface roughness of the specimens and the punch were Ra 0.283 m and Ra 0.176 m, respectively. Two lubrication condition, a dry condition and a molybdenum disulfide lubricated condition, were carried out in the experiments. By measuring the extruded dimensions, the upper cup height and the rod length, and compared with calibration curves established by DEFORM-3D finite element simulations, it is possible to estimate the friction factors in the processes. The results show that grain size has stronger effects in the processes with the lubricated conditions than those without lubrication. The friction factor increases with the grain size. The forming load decreases with the grain size.
32
Tsung, Lu Chia, and 呂佳聰. "Study on Hot Extrusion Characteristic of Aluminum Matrix Composites with micro- and nano-size SiC particles." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/49227766184098876967.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
91
The purpose of this paper is to discuss the mechanical properties of A6061 Aluminum and Aluminum Matrix Composites (AMC) under hot extrusion. By adding three different sizes of nano- and micro- SiC particles (102μm, 14μm and 50nm), and each reinforcement is properly measured by volume fraction. After powder sintering, the ingots are extruded under different extrusion temperatures of 420℃ and 470℃. The ingots with different sizes and quantities of SiC are extruded under different temperatures. The products are treated by T6 heat treatment, then mechanical property tests of hardness and tensile strength are proceeded. Coordinated with the observation of cross-section under SEM after tensile test, the influences of adding different SiC particles on tensile strength of the products are analyzed. The experimental results reveal that the most important factor affecting the hardness of product in aging treatment. On the other hand, the size of the reinforcements and volume fraction gave less effect. On the tensile strength aspect, adding nano-particles can apparently raise the mechanical strength of extruded product. Comparing with the Aluminum Matrix Composites (AMC) of adding micro SiC particles, the AMC of adding 1vol.﹪50nm SiCp has the same tensile strength with that adding 10 vol.﹪14μm SiCp, and it has better ductility and yield strength than the AMC of adding micro SiCp.
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Chen, Lee-Lon, and 陳儷仁. "A New Design Method of Fish Tail Die to Improve Flow Uniformity in Micro Injection/Extrusion Processes." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/80282451343331145576.
Full textAbstract:
碩士國立雲林科技大學
機械工程系碩士班
90
This paper presents a new design methodology to improve flow uniformity for Extrusion sheeting dies or Micro injection molding gates. Micro injection molding involves the injection of polymer into a micro mold. Since most of the cavities are very tiny, very small gates are usually needed. To ensure polymers to fill the cavity completely, reaction injection molding becomes one of the possible solutions because their low viscosity. But tiny gates could also result in jetting phenomena, air pocket and sometimes even degrading qualities of molded parts, especially for micro-optical components. How to design a simple gate geometry to provide uniform velocity distribution becomes one of the major topics in micro injection molding process. Thus a new and simple method was developed to optimize the gate design of micro injection molds. Tauguchi’s method of experiment design was involved in the flow simulation. Some dimensions of the gate geometry were regarded as factors for evaluation. The optimal factor levels of gate dimensions that could statistically result in maximum flow uniformity can be achieved. Flow visualization technique was used to verify the “Fluent” flow simulation results. The simulation results agree with the experiments captured by high-speed camera. For semi-circular fish tailed gate, the bets gate geometry obtained from Taguchi’s method can result in flow uniformity of 1.0, which means 100% uniform. The simulation presented here, has increased our understanding on the complex phenomena occurred inside a micro injection mold. It will help us to reach our final goal to help the molders to be able to design a micro injection mold-gates with high uniformity and quality before the parts are actually molded.
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Lin, X., Adrian L. Kelly, D. Y. Ren, Michael Woodhead, Philip D. Coates, and K. S. Wang. "Geometrical dependence of viscosity of polymethylmethacrylate melt in capillary flow." 2013. http://hdl.handle.net/10454/9681.
Full textAbstract:
NoThe shear viscosity of polymethylmethacrylate (PMMA) melt is particularly investigated by using a twin-bore capillary rheometer at four temperatures of 210, 225, 240, and 255 degrees C with different capillary dies. Experimental results show that the geometrical dependence of shear viscosity is significantly dependent on melt pressure as well as melt temperature. The measured shear viscosity increases with the decrease of die diameter at lower temperatures (210 and 225 degrees C) but decreases with the decrease of die diameter at higher temperatures (240 and 255 degrees C). Based on the deviation of shear viscosity curves and Mooney method, negative slip velocity is obtained at low temperatures and positive slip velocity is obtained at high temperatures, respectively. Geometrical dependence and pressure sensitivity of shear viscosity as well as temperature effect are emphasized for this viscosity deviation. Moreover, shear viscosity curve at 210 degrees C deviates from the power law model above a critical pressure and then becomes less thinning. Mechanisms of the negative slip velocity at low temperatures are explored through Doolittle viscosity model and Barus equation, in which the pressure drop is used to obtain the pressure coefficient by curve fitting. Dependence of pressure coefficient on melt temperature suggests that the pressure sensitivity of shear viscosity is significantly affected by temperature. Geometrical dependence of shear viscosity can be somewhat weakened by increasing melt temperature. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3384-3394, 2013