• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.8
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• pp.987-996
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• 1999

An algorithm for modeling the filling of metal into a mold and solidification has been developed. This algorithm uses the implicit VOF method for a filling and a general implicit source-based method for solidification. The model for simultaneous filling and solidification is applied to the two-dimensional filling and solidification of a square cavity. The effects of the wall temperature and gate position on the solidification are examined. The mixed natural convection flow and residual flow resulting from the completion of a filling are included in this study to investigate the coupled effects of the filling and natural convection on solidification. Two different filling configurations (assisting flow and opposite flow due to the gate position) are analysed to study the effects of residual flow on solidification. The results clearly show the necessity to carry out a coupled filling and solidification analysis including the effect of natural convection.

• Journal of Korea Foundry Society
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• v.34 no.4
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• pp.136-142
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• 2014

Numerical solution of thermal stress by CAE analysis could be an effective method in product development stage of castings to predict and treat the problem of solidification cracking of castings. Quantitative stress-strain data are necessary, in this case. Tension type apparatus of a solidification crack test which can measure stress-strain relationship quantitatively was developed and the test procedure was established by this research. Solidification crack strength obtained from the following test procedure could be utilized to evaluate it in terms of effect factors on thermo-plastic characteristic of solidifying alloy such as grain size of solid, grain morphology, distribution of solid grain, etc. Proposed test procedure is as follow: Prediction of temperature at the failure site of solidification cracked specimen by computer simulation of solidification, Calculation of solid fraction of the failure site from thermodynamic solution of solidification under Scheil condition.

• Journal of Korea Foundry Society
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• v.30 no.3
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• pp.100-110
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• 2010

The solidification sequence and formation of intermetallic phase of Fe-rich Al-Si-Cu alloy were investigated by using real-time imaging of synchrotron X-ray radiation. Effects of cooling rate during uni-directional solidification on the resultant solidification behavior was also studied in a specially constructed vacuum chamber in the SPring-8 facility. The series of radiographic images were complementarily analyzed with conventional analysis of OM and SEM/EDX for phase identification. Detailed solidification sequence and formation mechanisms of various phases were discussed based on real-time image analysis. The growth rates of $\alpha$-AlFeMnSi and ${\beta}-Al_5FeSi$ were measured in order to understand the growth behavior of each phase. It is suggested that real-time imaging technique can be a powerful tool for the precise understanding of solidification behavior of various industrial materials.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.10
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• pp.102-108
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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 compressed 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.

• Journal of Welding and Joining
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• v.19 no.6
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• pp.614-621
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• 2001

A study was carried out to determine the solidification cracking susceptibility of Ni-base superalloy as a function of Fe content in base metal. Three kinds of Ni-base superalloys with three different levels of Fe content were used. The solidification cracking susceptibility was evaluated by the Trans-Varestraint test at four different strain levels. Quantitative analysis of crack revealed that the solidification crack length and the temperature range in which hot cracking occurred in fusion zone (Brittle Temperature Range, BTR) decreased with a decrease in Fe content. Further, the thermo-calc data indicated that the solidification temperature range also decreased with decreasing Fe content. From these results, it was deduced that the improvement of the solidification cracking susceptibility with decreasing Fe content was attributed to the decrease of the solidification temperature range.

• Journal of Power System Engineering
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• v.19 no.3
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• pp.69-74
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• 2015

Check valves used in vessels include shock-release function on piping system, aside from basic back flow prevention. However, proper and enough protection of system is not obtainable due to use of high-pressure and bulk fluids, resulting from enlargement of vessels. In this study, casting analysis of check valves protecting systems in flow path from water hammering or back flow is conducted, using Z-CAST program. Also, molten metal filling, flow analysis, solidification analysis and shrinkage cavity analysis are conducted. The main results are as following. Regarding filling of each risering, molten metal showed stable supply condition without being isolated. It was identified that the final solidification exists on risering, but shrinkage cavity possibly might happens at the point of isolation solidification.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.1009-1018
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• 1994

An attempt is made to develop a kind of hybrid numerical method for computations of the thermal stresses during a solidification process. In this algorithm, the phase-change heat transfer analysis is perrformed by a finite volume method(FVM) and the thermal stress analysis in a solidifying body by a finite element method(FEM). The temperatures at the grid points calculated in the heat transfer analysis are transferred to those of gauss points in elements by a bi-cubic surface patch technique for the thermal stress analysis. A hyperbolic-sine constitutive law is used to prescribe the inelastic strain rate of material. Results for the unidirectional solidification process of a pure aluminum are compared with those of others and shows good agreement.

• Korean Journal of Materials Research
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• v.18 no.11
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• pp.577-582
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• 2008

Directional solidification experiments were carried out at $1-300\;{\mu}m/sec$ solidification rates in the single crystal superalloy, CMSX 10. The solid/liquid interface morphology changed from planar to dendritic, and the dendrite spacing became finer as the solidification rate increased. The pool size of the ${\gamma}/{\gamma}'$ eutectic, formed between dendrites, reduced as the solidification rate increased. The phase formation temperatures, such as the solidus, liquidus and eutectic, were estimated by differential scanning calorimetry (DSC) analysis. The morphology of the ${\gamma}/{\gamma}'$ phase, known to be eutectic, showed ${\gamma}'$ cells with a $\gamma$ intercellular network, and this ${\gamma}/{\gamma}'$ was composed of coarse and fine ${\gamma}/{\gamma}'$ regions. In this study, it is suggested that the ${\gamma}/{\gamma}'$ phase was a coupled peritectic.The solidification procedure of the ${\gamma}/{\gamma}'$ between dendrites is also discussed.

• 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.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.3
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• pp.110-122
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• 1996

Finite element analysis tool was developed to analyze the casting process. Generally, casting process consists of mold filling and solidification. Both filling and solidication process were simulated simultaneously to investigate the effects of process variables and to predict the defect. At filling process, thermal coupling was especially considered to investigate thermal history of material during the filling stage. And thermal condition at the final stage of filling is used as the initial conditions in a solidification process for the exact simullation of the actual casting processes. At mold filling process, Lagragian-type finite element method with automatic remeshing scheme was used to find the material flow. A perturbation method with artificial viscosity is adopted to avoid numerical instability in low viscous fluid. At solidification process, enthalpy-based finite element method was used to solove the heat transfer problem with phase change. And elastic stress analysis has been performed to predict the thermal residual stress. Through the FE analysis, solidification time, position of solidus line, liquidus line and thermal residual stress are found. Through the study, the importance of combined analysis has been emphasized. Finite element tools developed in this study will be used process design of casting process and may be basic structure for total CAE system of castings which will be constructed afterward.