• Journal of the Korean Society for Precision Engineering
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• v.25 no.5
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• pp.34-42
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• 2008

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.306-309
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• 2007

In this study, hydroforming characteristic of the double-layered tube was investigated in the hydroforming process. The double-layered tube can be made outer surface on the stainless steel by only one processing. The free bulging test was performed to analysis optimized pressure and axial feeding amount of the double layered tubes. And the experimental results between stainless/carbon and carbon/carbon double-layered tube were compared with the forming data. Moreover analysis model that can be hydroformability and predictable forming pressure of double-layered tube was presented.

• Journal of Korea Foundry Society
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• v.18 no.5
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• pp.481-487
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• 1998

Shell sand is widely used to make a complex shape castings due to its good collapsibility. When molten metal is poured into the mold, various gases are generated by the thermal decomposition of binder in the shell core. Casting defects such as blow hole and blister come from these gases. If it is possible to predict the evolution of gas quantitatively, it may provide effective solutions for minimizing the casting defects. To examine the gas evolution by shell core quantitatively, casting experiment and calculation were carried out. Gas pressure and gas volume evolved by shell core were measured in the experiment, and temperature distribution in the shell core was obtained by heat transfer analysis. From the result above, prediction on the gas volume evolved during pouring was tried. As forming pressure of the shell core increased and forming temperature decreased, the gas evolution increased. There was a close relationship between the calculated gas volume evolved and the measured one.

• Transactions of Materials Processing
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• v.11 no.1
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• pp.54-60
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• 2002

The purpose of the present paper is to investigate the effect of Process parameters such as internal pressure, amount of axial feeding, and frictional condition between the die and the material on the tube hydro-formability. For carbon steel tubes(STKM 12A, STBH 410 and SPS 290), simple bulging, circular bulging and Tee-fitting tests are performed to evaluate the hydro-formability of these materials which is determined by deformation characteristics such as thickness distribution, forming height and branch dome shape. The formabilities obtained from these tests are analysed and compared with the results of the numerical simulation.

• Transactions of Materials Processing
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• v.3 no.1
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• pp.51-62
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• 1994

Cup drawing test and U-bending test were performed to evaluate the friction characteristics of sheet materials for the different deformation modes involved in stamping process. The coefficient of friction calculated from the each test was compared to that obtained from the draw bead friction test. It was clarified that the cup drawing test could be simply used for evaluating the friction characteristic of sheet material in deep drawing process with high contacting pressure. However the U-bending test is suitable to evaluate the frictional characteristic of sheet material in bending process with low contacting pressure.

• Journal of the Korean Ceramic Society
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• v.22 no.6
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• pp.9-14
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• 1985

When the barium titanate is Synthesized in Solid-solid reaction the abnormal expansion occurs at about 110$0^{\circ}C$. The mixture was made of corresponding to the theoretical composition of barium titanate. The mixture was fired at various temperature from 90$0^{\circ}C$ to 130$0^{\circ}C$, After that the specimen was tested closely with XDR dilatometer and SEM. The results indicate that 1, The activation energy of barium titanate formation was 42 Kcal/mole. 2, Thermal expansion up to to 90$0^{\circ}C$ was mainly caused by $CO_2$ whereas it was mainly caused by the formation of the secondary phase above 100$0^{\circ}C$. 3. Thermal expansion was not influenced by the forming pressure up to 1000kg/$cm^2$ but it was largely influenced bythe forming pressure above 200kg/$cm^2$.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.537-543
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• 1991

In this study, the strain rate effects are considered in the formulation by introducing the constitutive equation of the strain rate sensitive materials and rigid-viscoplastic finite element program is developed for axisymmtric extrusion. The effect of strain rate sensitivity on the flow characteristics and forming pressure are investigated and the experiments are carried out for extrusion with pure lead specimens. The theoretically predicted forming pressure showed reasonably good agreement with the experimental values.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.70-73
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• 2003

Semi-solid processing is now becoming of great interest for the production of various parts by pressure die casting. Many advantages are associated with this forming process at the condition that the forming operation is performed under appropriate conditions in terms of alloy microstructure, injection velocity and pressure. In this study, to look into the relation along them, the experiment of semi-solid die casting has been peformed with various condition of injection, and investigated their microstrucure and solid fraction

• Journal of the Korean Society for Precision Engineering
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• v.22 no.1
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• pp.103-108
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• 2005

In this study, to develop a flash-less mold for forming of shoe-outsole, experiments and forming analysis were carried out. In order to reduce the extra-materials, offset method and mass distribution method are used in the preform design. The vertical mold structure pressing the preform was introduced to produce a flash-less shoe-sole. To measure the contact status of parting surface of mold, the pressure film has been used. The guide-gutter system and the continuous pressing mold have been developed for the discharge of extra-materials and re-pressing. By the investigation, flash of shoe-outsole was considerably reduced.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.239-244
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• 2001

Hot hydrostatic extruder was developed. The main objective of the development is forming fine wire and tube. On account of effectiveness and high performance, the extruder was designed to have double action. Therefore the main cylinder and mandrel can be driven independently. To cope with severe condition of high temperature and pressure, wire-wound container equipped with heater was used. Sealing technique also is important in this process, so seal ring was made of super-elastic metal. Another key for successful forming is choice of proper pressure medium. Fine wire and tube produced by the extruder can be used in semiconductor industry and medicine.