• Transactions of the Korean Society of Mechanical Engineers
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• v.1 no.4
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• pp.196-202
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• 1977

The solidification process in a cylinder with finite thickness in studied by explicit finite difference method. The temperature distribution, the solidification front profile and the dischrged latent heat for the process are obtained. It is found that the solidification front profile is almost linear except in the vicinity of the initation of phase change. This result motivates us to use linear relations between the position of solidification and time for approximate calculations.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.1
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• pp.102-113
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• 2000

In this study, a three-dimensional gravity casting problem has been examined to investigate a coupled phenomenon of the filling and solidification process. This work simultaneously considers the two key phenomena of metal casting : the fluid flow during mold filling, and solidification process. The VOF method is used to analyze the free surface flow during filling and the equivalent specific heat method is employed to model the latent heat release during solidification. The time-implicit filling algorithm is applied to save the computational time for analyzing the mold filling process. The three-dimensional benchmark problem used in the MCWASP VII has been solved using both the implicit and explicit algorithm, and the present results are compared with the benchmark experimental results and the other numerical results.

• Journal of Korea Foundry Society
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• v.7 no.1
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• pp.28-37
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• 1987

The progression of the solidification wave front in V-section and finned casting was studied by use of the pour-out test, employed with high. Purity aluminum. The results obtained were as follows; a) The shape of solidification wave front at the inside and outside corners did not change according to solidification time, but it changes according to the corner angles at a given molding and melting condition. b) The cooling fin effect could be repserented as functions of solidification time and fin sise, and this result could be applied to enhance the accuracy of the section modulus method in the design of T and V section.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.1
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• pp.12-24
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• 1999

A computer program has been developed for analyzing the two-dimensional, unsteady conservation equations for transport phenomena in the molten region of twin-roll continuous casting in order to predict the turbulent velocity, temperature fields, and solidification process of the molten steel. The energy equation of the cooling roll is solved simultaneously with the conservation equations of molten steel in order to consider heat transfer through the cooling roll. The results show the velocity, temperature and solidification pattern in the molten region with roll temperature as a function of time. The results for velocity and temperature fields with solidification are compared with those without solidification, giving different thermofluid characteristics in the molten region. We also investigated the effects of revolutional speed of roll, superheat and nozzle geometry on the turbulent flow, temperature and solidification in the molten steel and temperature fields in the cooling roll.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.597-601
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• 1997

The technology of Semi-Solid Forging(SSF) has been actively developed to fabricate near-net shape products using light and hardly formable materials. Generally, the SSF process is composed of slug heating,forming,compression holding and ejecting step. After forming step in SSF, the slug is comperssed during a certain holding time in order to be completely filled in the die cavity and be accelerated in solidification rate. This paper presents the analysis of temperature,solid fraction and shrinkage at compression holding step for a cylindrical slug,then predicts the solidification time to obtain the final shaped part. Enthalpy-based finite element analysis is performed to solve the heat transfer problem considering phase change in solidification.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.10
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• pp.3361-3370
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• 1996

Micro-Macro approach is conducted for the mixture solidification to handle the closely linked phenomena of microscopic solute redistribution and macroscopic solidification behavior. For this purpose, present work combines the efficiency of mixture theory for macro part and the capability of microscopic analysis of two-phase model for micro part. The micro part of present study is verified by comparison with experiment of Al-4.9 mass% Cu alloy. The effect of back diffusion on the macroscopic variables such as temperature and liquid concentration, is appreciable. The effect, however, is considerable on the mixture concentration and eutectic fraction which are indices of macro and micro segregation, respectively. According to the diffusion time, the behavior near the cooling wall where relatively rapid solidification permits short solutal diffusion time, approaches Scheil equation limit and inner part approaches lever rule limit.

• 한국기계연구소 소보
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• s.17
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• pp.111-123
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• 1987

Two dimensional computer simulation of solidification behavior using FDM as simulation tool was applied to AI-bronze casting. By the comparison of computer simulation with the experimental results, it was showed that the final shrinkage position and solidification time are good accordance with results of computer simulation. It is expected that this software will be widely applied to casting design or rise ring for directional solidification.

• Journal of Korea Foundry Society
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• v.17 no.6
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• pp.608-614
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• 1997

The effect of mold preheating temperature on the microstructure such as grain size, eutectic silicon morphology was investigated for the Al-7wt%Si-0.3wt%Mg alloy. Microstructural variations have been characterized as a function of Sr addition and cooling rate during solidification. Microstructures were correlated with cooling rate, local solidification time and eutectic nucleation temperature, etc. In this study, Sr addition caused increase of local solidification time, undercooling and reduction of eutectic plateau temperature. In logarithmic scale, local solidification time was in inverse proportion to cooling rate. Eutectic nucleation temperature was in inverse proportion to cooling rate of logarithmic scale. Increasing the cooling rate refined dendrite arm spacing and eutectic silicon. Dendrite arm spacing was logarithmically in inverse proportion to cooling rate. Without modifier addition, eutectic silicon was modified at cooling rate of $7^{\circ}C/s$ or higher.

• Journal of the Korean Applied Science and Technology
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• v.22 no.4
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• pp.379-384
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• 2005

In general, water treatment sludge (WTS) had high concentration of heavy metal, thus it made the reuse or recycling of WTS difficult. The optimal solidification conditions for maximum suppression of heavy metal elution from WTS were decided in this study. Under the optimal solidification conditions (i.e., temperature, $320^{\circ}C;$ ratio of WTS and MgO, 9:1; solidification time, 1hr), all of heavy metal including aluminum were not detected. Therefore there are no problems for reuse or recycling of WTS which was solidified under the optimal solidification conditions found in the study.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.3
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• pp.260-270
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• 1998

The viscous plane stagnation-flow solidification problem is theoretically investigated. An analytic solution at the beginning of solidification is obtained by expanding the temperature and thickness of solidified layer in powers of time. An exact expression for the steady-state thickness of solidified layer is also obtained. The .fluid flow toward the cold substrate inhibits the solidification process. As Stefan number becomes larger, or Prandtl number becomes smaller, the solidification is more strongly inhibited by the fluid flow. The transient heat flux at the liquid side of solid-liquid interface is increased, as Stefan number or Prandtl number is increased.