• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.397-400
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• 2007

Recently, rheology forming technology has been interested in industrial and academic for light weight materials and to solve environmental issues. In this study, the rheology material production equipments were used to be made spiral shape by special design. And the experiment variables established stirring time 0 $\sim$ 1200 sec, stirring velocity 0 $\sim$ 100 rpm and several material temperature of semi - solid states. The rheology materials were made for established experiment conditions then measured mechanical properties. Sequence-production equipments were appended to fabrication system of rheology material for make rheology materials continually. Therefore, the development of sequence-production equipments were demanded for fine grains and for uniform globule shape rheology materials by a specially designed spiral stirrer machine.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.240-243
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• 2001

Recently, many automobile parts produced by semi-solid forming(SSF) process has been applied for improved weight reduction, better environmental protection and energy savings. SSF process was well developed for high volume production of light weight aluminum components. In this paper, knuckle has been manufactured with A357 by SSF and thor investigated for microstructures and mechanical properties followed by various heat-treatment conditions. It was found that the examined microstructure was equiaxed at the whole cross-section area and as a result, the mechanical properties were satisfied by 100MPa YS, 260MPa UTS and $14\%$ elongation.

• Transactions of Materials Processing
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• v.14 no.4 s.76
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• pp.338-350
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• 2005

Recently, in the field of automobile industry, to solve the problem of reducing the weight of automobile for the improvement of fuel efficiency and the protection of environment, the aluminum alloy parts have been substituted for the steel parts. However, the aluminum alloy does not have as good mechanical property as the steel part. To improve the mechanical property, the semi-solid die casting process is performed to make automobile parts. In the fabrication of semisolid material the control of the liquid segregation is very important to improve the material properties of aluminum alloy. In the present paper we examine the influence of the liquid segregation by the injection conditions in the semi-solid die casting has been investigated.

• Transactions of Materials Processing
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• v.8 no.4
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• pp.364-373
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• 1999

For material characterization of semi-solid materials, backward extrusion process, which has been used in forming of hollow-sectioned products, was analyzed by the upper bound analysis in the current study. The existing kinematically admissible velocity field was applied to steady state at which there was no change in the assumed regions of velocity field. For unsteady state, new velocity field, as a function of dead zone angle, was proposed. Through the whole analysis, fiction between die and workpiece was also considered. It has been studied how the process variables, such as friction factor and punch velocity, and material parameters, such as strength coefficient, strain rate sensitivity could affect on analysis results. Finally, by the comparison with the finite element analysis, the reliability and efficiency of the proposed velocity field were discussed.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.4
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• pp.593-600
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• 2012

Thixomolding of Mg-alloy is a semi-solid injection molding process utilizing thixotropic phenomenon. Using this process, higher strength, thinner wall section and tighter tolerance without porosity are obtained. It has been applied for production of near-net-shape magnesium component. To design optimal thixomolding process of Mg-alloy part, molding conditions such as slurry temperature, mold temperature and injection time should be determined properly. Selection of these parameters has been dependent upon engineers' experience and intuitiveness. In this paper, to improve mechanical properties of the thixomolded product, optimal selection of process variables such as injection velocity, barrel temperature and die temperature in the process has been studied through microstructural analysis and Taguchi method. Performance of the process is verified through experiments.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.848-851
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• 2002

In the field of automobile industry, lightweight problems are very important in terms of reducing fuel and protecting environment. To satisfy these demands, the attempt to substitute aluminum automobile components for cast steel part has been actively carried out. To fabricate the aluminum automobile suspension part that has the same mechanical properties with cast steel part, design conditions such as shape and dimension of part shall be established. Therefore in this study, shape and dimension conditions of suspension part were proposed. Aluminum automobile suspension part was fabricated by semi-solid die-casting process under the obtained design conditions. Moreover to evaluate the possibility of application to the automobile component, stress and fatigue analysis were performed by using ABAQUS S/W and compared with those of conventional automobile suspension part.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.61-64
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• 2003

In the field of automobile industry, suspension parts have been fabricated by the light metal part to substitute the steel part. For application light metal of suspension parts, mechanical property of high strength was performed. For anting semi-solid die casting of suspension part, die filling and solidification simulation have been carried out with Ostwald-de Waele rheological model. We designed the optimal die and secured injection condition as possible as laminar flow based on the result of computer simulation. Mechanical properties of knuckle part and heat treatment condition were investigated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.355-358
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• 2004

In this study, the deformation characteristics of grain-size controlled rheology materials surfaces were investigated as a part of the research on the surface crack prediction in semi-solid formed automobile components. The microstructure of rheology Al-Si alloys consists of primary and eutectic regions. In eutectic regions the crack initiation begins with initial fracture of the eutectic silicon particles and inside other intermetallic phases. Nano-deformation characteristics in the eutectic and primary region of semi-solid aluminum alloys (356 alloy and 319 alloy) were investigated through the nanoindentation/scratch experiments and the AFM observation.

• Transactions of Materials Processing
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• v.14 no.7 s.79
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• pp.642-648
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• 2005

Rotor in small-medium induction motor has been usually manufactured by aluminum diecasting. In order to improve the efficiency of induction motors, newly developed Cu-Ca alloys have been investigated. The electrical conductivity in the Cu alloys containing Ca less than $1.0wt\%$ was higher than $80\%$ IACS. Cu-Ca alloy is desirable for the thixoforming process because it has wide semi-solid range over $150^{\circ}C$. In this study, Cu-rotor with thixoforming process was developed to replace the conventional aluminum diecasting rotor. Analysis was performed for the microstructure of thixoforming rotor. Effect of incomplete filling on the efficiency of induction motor was discussed.

• Korean Journal of Microbiology
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• v.24 no.4
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• pp.385-388
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• 1986

In a study of the aerobic growth of Baker's yeast (Saccharomyces cerevisiae) on Maxon-Johnson medium (with glucose as substrate) solidified with kudzu root starch, it was observed that between 8 and 24 hour incubation. 10 and 12% solids stimulated greater cell production than did 6 and 8% solids. The concentration of solids also affected thd secretion of protein from the yeast cells with the highest content of extracellular protein at 10-24 hour incubation stimulated by 10% starch solids.