• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1818-1832
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• 1994

Transport process during solidification of an AI-CU alloy in a vertical annular mold of which inner wall is cooled is numerically simulated. A model which can take account of local density dependence on the solute concentration is established and incorperated in the analysis. Results show that thermally and solutally induced convections are developed in sequence, so that there is little interaction between them. Thermal convection effectively removes the initial superheat from the melt and vanishes as solidification proceeds from the cooling wall. On the other hand, solutal convection which is developed later over the meshy and the pure liquid regions leads to large-scale redistribution of the consituents. The degree of the initial superheating hardly affects overall solidification behavior except the early stage of the process, when the cooling rate is kept constant. Macrosegregation is reduced remarkably with increasing cooling rate, because not only the liquidus interface advances so quickly that time available for the solute transport is not enough, but also the interdendritic flow is strongly damped by rapid crystal growth within the mushy region.

• Journal of Energy Engineering
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• v.11 no.2
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• pp.99-105
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• 2002

A finite volume numerical approach is developed and used to simulate convection-dominated melting and solidification problems. The present approach is based on the enthalpy-porosity method that is traditionally used to track the motion of the liquid-solid front and to obtain the temperature and velocity profiles in the liquid-phase. The enthalpy-porosity model treats the solid-phase as the porosity in all computational cells that are located on the solid-liquid interfacial boundary. Concerning the computational cells that are fully located in the solid side of the interfacial boundary, the zero value of the porosity severely suppresses the velocity vector to practically a non-existent value that could be set equal to zero. A comparative analysis with the previous numerical approaches is performed to demonstrate the improved features of the presented model. Results of a melting and solidification experiments are also used to assess and evaluate the performance of the model.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.769-773
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• 2002

The die easting process was used to manufacture a motor housing for automobile. Specially automobile parts were required light and high strength. Therefore simulations have been carried out die casting process of motor housing. In this paper, we investigated about characteristics of the die casted motor housing with HPDC(High Pressure Die Casting) process. Also the MAGMAsoft was used as computer simulation code and used material was ADC12(Aluminum Die Casting Alloy). We present the results of filling behavior and solidification process of a motor housing cast. The analysis results obtained about filling behavior and solidification of cast showed good agreement with test results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.174-177
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• 2000

In this paper, The bulging behavior of the solidified shell in continuously cast slabs have been numerically analyzed using three-dimensional elasto-plastic and creep finite element method Three-dimensional model has been applied in order to investigate the effect of the narrow face shell on restraining the bulging deflection. Solidification analysis are carried out by two-dimensional finite difference method. In this way, strains occurring at the solidification front near the narrow face of the slab, as well as those occurring in the board face have been computed. The adequacy of the model has been checked against the experimental results. In addition, the effect of the slab width and casting speed on the bulging are discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.384-388
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• 1997

Recently,direct rolling process has been drawing increasing interests because production cost be greatly reduced by eliminating subsequent hot rolling processes. Such a process has been characterized to prosuce thin steel strip (thickness 1~5mm) directly from molten metal and to skip over the conventional hot rolling processes. However, since there are several process parameters, which affect the quality of product,and their relationship between the parametersare very complex,it is therefore very difficult to realize the process design and the quality control. To overcome these difficulties quantitative relationship between the parameters are investigated through a numerical analysis. Form these results, it is found that solidification final point is the most important paramter which is critical to quality of the strip. Also,the multiple regression model is obtianed to determine their relationship from the solidification final point and roll separating force which can be easily estimated

• Journal of Korea Foundry Society
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• v.3 no.2
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• pp.83-91
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• 1983

In this paper analytical and numerical methods fur analysis of solidification of castings are described, and the matrix method, one of numerical method, where the nodal point is designated on the element boundary was adapted. The cooling curve obtained by experimental values, when cast steel (0.29%C. 0.62%Si) was poured into $CO_2$ mold, is compared with that of computed values by exploiting computer (V77-600 Data Proceeding System, UNIVAC). The computed value is nearly approximation to the experimental. But the computed value shows a tendency that is a little higher than the experimental in solid-liquid coexisting temperature ranges and much lower than the experimental after solidification. It is considered to result from the lacks and difficulties of ultimately appropriate adaptation of various physical properties and also air cap between castings and mold.

• Journal of the Korean Society of Safety
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• v.27 no.4
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• pp.7-12
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• 2012

In this study, the solidification characteristics inside the AC7A casting material was analyzed using the numerical analysis method and was verified using the experimental method by the pre-heated temperature conditions of metal casting device. For the numerical analysis, "COMSOL Multiphysics", the commercial code based on the finite element analysis(FEA), was used in order to predict the thermal deformation of the AC7A casting material including temperature, displacement and stress distribution. Also, in order to verify the results calculated by the numerical analysis, the experiment for temperature measurement inside the AC7A casting material was performed using the K-type thermocouple under the same condition of numerical analysis method. In the numerical results, thermal deformation inside AC7A casting material was well-suited for manufacturing products when the pre-heated temperatures of the metal casting device was $250^{\circ}C$. When the results of the temperature distribution were experimentally measured and were compared with those of the numerical result, it appeared that there was some temperature difference because of the latent heat by phase change heat transfer. However, the result of cooling temperature and patterns were almost similar except for the latent heat interval. The solidification characteristics was closely related to the temperature difference between the surface and inside of the casting.

• The Journal of Engineering Geology
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• v.27 no.3
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• pp.245-253
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• 2017

Vietnam CFBC fly ash has high CaO content and can be used as a solidification agent for soft ground improvement. However, most fly ash is treated as landfill or waste. In order to utilize fly ash as a solidification agent for soil improvement, the characteristics of fly ash must be accurately determined. In this study, laboratory tests were conducted on fly ash from four CFBC power plants to evaluate the utility of Vietnam fly ash as a solidification agent. As a result of analyzing the physical properties, it was analyzed that all four samples were suitable as material for solidification agent and have suitable particle size for the improvement of soft ground. As a result of analysis of chemical characteristics, it was analyzed that the fly ash of one place could be used as a solidification agent because of the high content of free-CaO. The remaining three fly ash was not suitable for use as a solidification agent due to low Free-CaO content. However, it has a chemical composition similar to that of general fly ash in Korea, so it can be recycled in various ways.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.162-176
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• 2022

In Lead-based reactor (LBR) severe accident, the meltdown and migration inside the reactor core will lead to fuel fragment concentration, which may further cause re-criticality and even core disintegration. Accurately predicting the migration and solidification behavior of melt in LBR severe accidents is of prime importance for safety analysis of LBR. In this study, the Moving Particle Semi-implicit (MPS) method is validated and used to simulate the migration and solidification behavior. Two main surface tension models are validated and compared. Meanwhile, the MPS method is validated by the L-plate solidification test. Based on the improved MPS method, the migration and solidification behavior of melt in LBR severe accident was studied furthermore. In the Pb-Bi coolant, the melt flows upward due to density difference. The migration and solidification behavior are greatly affected by the surface tension and viscous resistance varying with enthalpy. The whole movement process can be divided into three stages depending on the change in velocity. The heat transfer of core melt is determined jointly by two heat transfer modes: flow heat transfer and solid conductivity. Generally, the research results indicate that the MPS method has unique advantage in studying the migration and solidification behavior in LBR severe accident.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.1
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• pp.1-7
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• 2019

In the modern industrial period, the introduction of mass production was most important progress in civilization. Die-casting process is one of main methods for mass production in the modern industry. The aluminum die-casting in the mold filling process is very complicated where flow momentum is the high velocity of the liquid metal. Actually, it is almost impossible in complex parts exactly to figure the mold filling performance out with the experimental knowledge. The aluminum die-castings are important processes in the automotive industry to produce the lightweight automobile bodies. Due to this condition, the simulation is going to be more critical role in the design procedure. Simulation can give the best solution of a casting system and also enhance the casting quality. The cost and time savings of the casting layout design are the most advantage of Computer Aided Engineering (CAE). Generally, the relations of casting conditions such as injection system, gate system, and cooling system should be considered when designing the casting layout. Due to the various relative matters of the above conditions, product defects such as defect extent and location are significantly difference. In this research by using the simulation software (AnyCasting), CAE simulation was conducted with three layout designs to find out the best alternative for the casting layout design of an automotive Oil Pan_BJ3E. In order to apply the simulation results into the production die-casting mold, they were analyzed and compared carefully. Internal porosities which are caused by air entrapments during the filling process were predicted and also the results of three models were compared with the modifications of the gate system and overflows. Internal porosities which are occurred during the solidification process are predicted with the solidification analysis. And also the results of the modified gate system are compared.