• Journal of the Korean Ceramic Society
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• v.31 no.10
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• pp.1169-1175
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• 1994

Five Al2O3/SiC/metal composites with four different particle sizes of green SiC abrasive grains are grown by the directed oxidation of an commercially available Al-alloy. Oxidation was conducted in air at 100$0^{\circ}C$, 96 hours long. Slip casted SiC-fillers were placed on the alloy or SiC powder deposited up to the required layer thickness. Their microstructures are described and measurements of density, elastic constants, frexural strength, fracture toughness and work of fracture are reported. The results are compared with those of commercial dense sintered Al2O3. The properties of produced materials have a strong relationship to not only the properties of Al2O3, SiC, Al and Si but also to the phase share and phase distribution. The composite materials are dense (0.5% porosity), tough (KIC = 3.4~6.4 MPa{{{{ SQRT { m} }}), strong ({{{{ sigma }}B = 170~345 MPa) and reasonably shrinkage free producible. The reinforcements is attained mainly through the plastic deformation of ductile metal phase.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.830-833
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• 2006

In this work, we provided a novel test method to verify the sealing materials for flexible LCD cell. The ultraviolet type curing sealing material with low process temperature was suitable for LCD cell assembly. We also proposed the sealing materials which passed 13200 times bending test within 20 mm curvature.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.466-469
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• 2006

We have developed the world's thinnest flexible electrophoretic displays (EPDs). The thin-film displays are 95 ..m thick, which is nearly the same thickness as a standard sheet of paper. Weighing 0.44g including external connection cables, these displays are also probably the world's lightest. We have also developed 7.1-inch-diagonal(paperback-sized) high-resolution flexible EPDs. The displays are large enough to be used as practical e-paper. More than 7 million transistors work correctly on plastic, enabling us to see 3-megapixel images. These flexible displays include active-matrix TFT devices that are fabricated using Suftla transfer technology. Suftla technology demonstrates the potential to achieve thin, flexible displays that will be used as an e-paper in the near future.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.9-15
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• 2001

In the case of a crack propagation, a portion of the work of inelastic deformation near the crack tip is dissipated as heat. In order to understand the thermal effect on fracture toughness, tensile test was carried out using thermocouples to monitor the variation of temperature with SA516 Gr70. The experimental results show that the temperature of specimen was increased $3.6^{\circ}C$ at static load condition. And the thermal effect was investigated connected with the steady-state stress in the vicinity of a crack propagation in the elastic-plastic C-T specimen theoretically. And fracture toughness, the energy to make crack surfaces, presented correctively. The fracture toughness with considering heat at the blunting of the crack tip ws lower about 19.3% than that of ignoring heat. So, it is resonable to apply the fracture toughness with considering thermal energy and it would be good explanation for constraint effect depending on the configuration in the presence of excessive plasticity.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.5
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• pp.167-175
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• 1998

A mathematical formulation is presented to model anisotropy from the deformation textures developed in a forming process. In this work, a micro-mechanical-based polycrystalline analysis is implemented into a consistent finite element method for the anisotropic, viscoplastic deformation of polycrystalline metals. As suggested by Taylor, the deformation of each grain in an aggregate is assumed to be same as the macroscopic deformation of an aggregate or a macro-continuum point. Algorithms are developed to represent the plastic anisotropy, such as the anisotropic yield surface and R-value, from the predicted deformation texture. As applications, the evolution of texture in rolling, upsetting and drawing/extrusion processes are simulated and the corresponding changes of mechanical properties such as yield surface and R-value are predicted.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.4
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• pp.64-75
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• 1991

The design of structures of modern industry has developed to satisfy stringent service, realiability and safety. Up to now, geometric profile which means surface foughness and dimension accuracy is mainly treated in manufacturing process of work surface. But it is inevitable to evaluate changes of surface geometry as well as the nature of alterations in surface layers because surface of workpiece changes as a result of phase transformation, chemical changes, plastic deformation and stress changes. This paper is to present principal data for safety design by verifying the effect of grinding conditions and method in grinding layers and to explain the method of measuring surface integrity. In this paper, structural steel(SM20C) is used as a workpiece. Of integrity, surface roughness in view of surface texture is analyzed by frequency domain and residual stress, structures and defect of ground layers in view of surface metallurgy are investigated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.460-464
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• 1997

By the used of a similar numerical method as in the previous paper, the forming limit stain of coatedsheet metals is investigated in which the FEM is applied and J2G(J/sab 2/-Gotoh's corner theory) is utilized as the plasticity constitutive equation. Coated two-layer sheets and sheets bonded with dissimilar sheets on both surface planes are stetched in a plane-strain atate, with various work-hardening exponent n-values and thicknesses of each layer. Processes of shear-band formation in such composite sheets are clearly illustrated. It is concluded that, in the coated state, the higher limiting strain of one layer is reduced due to the lower limiting stain of the other layer and vice, and does not necessarily obey the rule of linear combination of the limiting stain of each layer weighted according thickness.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.932-936
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• 1997

In order to increase the productivity of electrical parts, manufacturing processes using progressive die have been widely used in the industry. If closed-die forging process may be included in the series of the forming process, however, there arise many problems in the die design, such as determination of blank size, feeding method and formability, etc. For the proper design of a process, a prediction of the process is requred to obtain many design parameters. In this work, three-dimensional rigid-plastic finite element analysis is carried out to simulate precision forging process. The forging process of STEM, a part of photo pick-up hologram device, is simulated with the two types of processes, open die forging and semi-closed die forging, respectively. Form the results of analyses, the forging processes can be predicted successfully, which enables to design appropriately the die and the process.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.1
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• pp.94-100
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• 2001

Distortion is a potential problem with all welded fabrication and should be caused dimensional changes and mismatch of joints during welding fabrication. Correction unacceptable weld distortion is extremely costly and in some case impossible. The aim of the present work is to verify the variation of the compressive force, tensile force and distortion during plastic deformation under Tungsten-inert-gas(TIG) welding, on type 304 stainless steel. Experimental results show that possibili-ty if measuring deformation during welding and good correlation was found between analytical and experimental result ad finite element methods have been used to model temperature analysis.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.1
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• pp.127-132
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• 2001

By the use of a similar numerical method as the forming limit strain by coating method of coated sheet metals is investigated, in which the FEM is applied and J2G(J2-Gotohs Corner Theory) is utilized as the plasticity constitutive equa-tion. Circular bonded sheet metals with dissimilar sheets on both surface planes are stretched in a plane -strain state, with various work-hardening exponent n-values and thicknesses of each layer. Processes of shear-band formation in such com-posite sheets are clearly illustrated. It is concluded that, it the bonded state, the higher limiting strain of one layer is reduced due to the lower limiting strain of the other layer and vice versa, and does not necessarily obey the rule of linear combination of the limiting strain of each layer weighed according thickness.