• Transactions of Materials Processing
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• v.15 no.1 s.82
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• pp.15-20
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• 2006

The rapid thermal response (RTR) molding is a novel process developed to raise the temperature of mold surface rapidly to the polymer melt temperature prior to the injection stage and then cool rapidly to the ejection temperature. The resulting filling process is achieved inside a hot mold cavity by prohibiting formation of frozen layer so as to enable thin wall injection molding without filling difficulty. The present work covers flow simulation of thin wall injection molding using the RTR molding process. In order to take into account the effects of thermal boundary conditions of the RTR mold, coupled analysis with transient heat transfer simulation is suggested and compared with conventional isothermal analysis. The proposed coupled simulation approach based on solid elements provides reliable thin wall flow estimation for both the conventional molding and the RTR molding processes.

• Transactions of Materials Processing
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• v.15 no.9 s.90
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• pp.692-696
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• 2006

Micro fabrication of polymeric materials becomes increasingly important. And it is considered as a low-cost alternative to the silicon or glass-based Micro Electro-Mechanical System(MEMS) technologies. In the present study, micro channels were fabricated via LiGA(Lithographie, Galvanoformung, Abformung) process used for Capillary Electrophoresis(CE) chip. Taguchi method was applied to investigate the effects of process conditions in injection molding(melt temperature, injection speed, mold temperature and packing pressure) on the transcription characteristics of the micro channel. It was found that the skin layer disturbs a formation of micro channel. Furthermore, mold temperature and injection speed were two important factors to affect the replication characteristics of micro channel.

• Transactions of Materials Processing
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• v.16 no.6
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• pp.443-446
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• 2007

The semi-solid process has been developed near net-shape components for kinds of methods. Thixo-forming with reheating prepared billet and rheo-forming with cooled melt until semi-solid state. Material is applied electromagnetic stirring system to slurry with aluminum 6061 alloy. An experiment has variation factors which are pressure, solid-fraction, stirring current and stirring time. The mechanical properties are compared to forge sample with to apply heat treatment T6. This study is researched function a virtual pressure and fine shape zone. Optimum pressure is found to prevent defect of porosity.

• Progress in Superconductivity and Cryogenics
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• v.19 no.2
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• pp.14-18
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• 2017

This study presents three dimensional (3-D) seeding technique which is a modification of interior seeding. 3-D seeding is beneficial for shortening the processing period and enhancing the magnetic properties of REBCO bulk superconductors fabricated by melt growth. Oxygen channels were provided by using divided powder compacts instead of by using a rubber insert. Microstructure observations revealed that the grains grown from the seeds impinged each other and formed low angle grain boundaries of (001)/(001). It has been shown that the 3-D seeding technique reduces the volume fraction of a-c growth sector and thereby maximizes the area of a-b growth sector which attribute to the high magnetic characteristics of single grain REBCO bulk superconductors.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.221-224
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• 2003

Polyvinyl chloride (PVC)/gypsum Polymer blend materials were prepared by melt blending of PVC with gypsum and additives. Effect of gypsum content on the properties of PVC/gypsum Polymer blend material was studied by investigating physico-mechanical properties, thermal properties and morphology development. It was found that the replacement of gypsum for methylene-butadiene-sarene (MBS) component in PVC/gypsum polymer blend material enhanced the tensile strength, but gradually decreased its impact strength. Besides, with the increase of gypsum content, the elongation at break of material gradually decreased. The Presence of the different gypsum contents made a shift of g1ass transition temperature and increased the thermal stability as well as the processing temperature range of polymer blends. The observation of morphology, the results of the physico-mechanical properties and thermal properties proved simultaneously that PVC/gypsum Polymer blend material with the gypsum content of 22.56 wt.% reached the optimum results among five kinds of PVC/gypsum Polymer blend materials investigated.

• Journal of Korea Foundry Society
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• v.16 no.6
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• pp.523-536
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• 1996

This paper relates to fabrication processing analysis of metal matrix composites by the injection of liquid metal into a fibrous preforms. One dimensional heat transfer analysis during squeeze infiltration process of aluminum base composites has been studied. An analysis method was investigated for the temperature distribution, infiltration velocity and melt infiltration characteristics with the commercial preform with short fiber array. When molten metal is infiltrated in a fibrous preform with random orientation, phase transformation will be occurred in a region such as molten metal, solidified region, preform region and infiltration composites region. a mathematical modelling for a solidification phenomena in fabrication process of metal matrix composites using a squeeze infiltration technique was investigated by the basic relations for liquid metal into a fibrous preform. The temperature distribution of theoretical results was compared with experimental data.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.259-264
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• 2005

The shrinkage of the product in injection molded part occurs due to the volume change with variation of temperature and pressure and is influenced by the processing conditions of injection molding. Mold designers greatly concerns the shrinkage of parts for a high dimensional accuracy. In this study, bar type HIPS specimen with 15x19 grid on the surface was tested. The amount of shrinkage of flow and transverse directions was examined with respect to the injection molding conditions such as melt temperature, injection speed, holding pressure, mold temperature and cooling time. As the packing pressure increased, the difference of shrinkage of both directions is decreased and the absolute shrinkage value also decreased.

• Fibers and Polymers
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• v.3 no.3
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• pp.103-108
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• 2002

The viscosity effect of matrix polymer on melt exfoliation behavior of an organoclay in poly($\varepsilon$-caprolactone) (PCL) was investigated. The viscosity of matrix polymer was controlled by changing the molecular weight of poly($\varepsilon$-eaprolactone), the processing temperature, and the rotor speed of a mini-molder. Applied shear stress facilitates the diffusion of polymer chains into the gallery of silicate layers by breaking silicate agglomerates down into smaller primary particles. When the viscosity of PCL is lower, silicate agglomerates are not perfectly broken into smaller primary particles. At higher viscosity, all of silicate agglomerates are broken down into primary particles, and finally into smaller nano-scale building blocks. It was also found that the degree of exfoliation of silicate layers is dependent upon not only the viscosity of matrix but thermodynamic variables.

• Macromolecular Research
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• v.11 no.4
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• pp.224-230
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• 2003

The blends of polypropylene (PP) with glass filled thermotropic liquid crystalline polymer (LCP-g) have been prepared by melt mixing techniques at different blend ratios. The thermal, dynamic mechanical, crystalline and morphological characteristics of these blends were investigated. Higher percent crystallinity was observed for 10% level of LCP-g in the blend in comparison to that of other blend ratios. The thermal stability increased with LCP-g concentration in the blend with PP. The variation of storage modulus, stiffness and loss modulus as a function of blend ratios suggested the phase inversion at the 50% level of LCP-g in the blend. The scanning electron microscopy (SEM) photographs showed the creation of voids and destruction of the fiber structures during the dynamic mechanical measurements. Processing behavior of the blends depended on the fiber forming characteristics of LCP-g, which again varied with the molding temperatures.

• Journal of the Semiconductor & Display Technology
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• v.11 no.4
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• pp.7-12
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• 2012

Extrusion is one of the most important operations in the polymer-processing industry. Development of models for extrusion and computer tools offer a route to developing reliable and optimized process designs. The models are based on the analysis of physical phenomena encountered during the process. Balance equations for mass, momentum and energy are fundamental to the problem. A predictive computer model has been developed for the single screw extruders with conventional screws of different geometry. The model takes into account melting zones of the extruder and describes an operation of the extruder system, making it possible to predict mass flow rate of the polymer, pressure and velocity profiles along the extruder screw channel. The simulation parameters are the material and rheological properties of the polymer; the screw pitch, and screw speed.