• International Journal of Naval Architecture and Ocean Engineering
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• 제6권4호
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• pp.922-934
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• 2014

In casting steels for offshore construction, manufacturing integral casted structures to prevent fatigue cracks in the stress raisers is superior to using welded structures. Here, mold design and casting analysis were conducted for integral casting steel. The laminar flow of molten metal was analyzed and distributions of hot spots and porosities were studied. A prototype was subsequently produced, and air vents were designed to improve the surface defects caused by the release of gas. A radiographic test revealed no internal defects inside the casted steel. Evaluating the chemical and mechanical properties of specimens sampled from the product revealed that target values were quantitatively satisfied. To assess weldability in consideration of repair welding, the product was machined with grooves and welded, after which the mechanical properties of hardness as well as tensile, impact, and bending strengths were evaluated. No substantive differences were found in the mechanical properties before and after welding.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.174-179
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• 2005

In the super slow speed die casting process, the casting defects due to melt flow should be controlled in order to obtain sound casting products. The casting defects that are caused by molten metal were cold shut formation, entrapment of air, gas, and inclusion. But the control of casting defects has been based on the experience of the foundry engineers. The calculation of simulation can produce very useful and important results. The calculation data of die casting process condition from the computer simulation by the Z-CAST is made to insure that the liquid metal is injected at the right velocity range and that the filling time is small enough to prevent premature solidification. The parameters of runner shape that affected on the optimized conditions that was calculated with simple equation were investigated. These die casting process control techniques of automobile valve body mid-plate have achieved good agreement with the experimental data of tensile strength, hardness test, and material structure photographies satisfactory results.

• 한국주조공학회지
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• 제27권4호
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• pp.153-158
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• 2007

Molten metal flow in vacuum die casting was characterized by a numerical analysis. The VOF method was used to simulate the filling behaviors of molten metal during filling process. The various vacuum degrees of no vacuum(760 mmHg), 650, 500, 250 and 60mmHg were artificially applied in cavity. And the filling behaviors of molten metal with the applied vacuum conditions were simulated and compared with those of experiment. The results showed that molten metal was partially filled into cavity when vacuum was applied and the filling length of molten metal in cavity was increased with increasing applied reduced pressure in cavity. Also, the simulated filling behaviors of molten metal were apparently similar to those of experiment, indicating the numerical analysis developed in this study was highly effective. Through the result of fluid flow simulation, both relation equations of filling length and filling velocity with the variation of pressure conditions in cavity were calculated respectively and the internal gas contents of casting was significantly reduced by the modification of vacuum gate system.

• 대한치과기공학회지
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• 제5권1호
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• pp.13-17
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• 1983

The experimental investication wax performed to study fitness of casting crowns with various investment widely used in Korea. 36 wax patterns were invested and casted according to the regular casting method. The result were as follow : 1. Casting with cristobalite investments of Shofu were seen apart, 0.04mm the tightest space in the linguo and bucco-cervical margin. And the largest deviation, 0.1mm was shown in the central groove 0.1mm was shown in the central groove area of occlusal surface(Jensen Metal) 2. Casting with cristobalite investments of kerr were seen apart, 0.04mm the tightest space in the linguo and bucco-cervical margin And the largest deviation, 0.09 was shown in the central groove area of occlusal surface(Jensen Metal) 3. Casting with Quartz investments of G-C were seen apart, 0.04mm the tightest space in the linguo-cervical margin, And the largest deviation, 0.1mm was shown in the central groove area of occlusal surface(Jensen Metal) 4. Casting with cristobalite investments of shofu were seen apart, 0.01mm the tightest space in the linguo-cervical margin, And the largest deviation, 0.03mm was shown in the central groove of occusal surface(Bo-sung A type gold alloy) 5. Casting with cristobalite investments of kerr showed the best fintness in linguo-cervical margin. And the largest deviation, 0.02mm was shown in the central groove area of occlusal surface(Bosung A type gold alloy) 6. Casting with Quartz investments of G-C were Seen apart, 0.02mm the tightest space in the linguo-cervical margin, And the largest deviation, 0.04mm was shown in the central groove area of occlusal surface(Bo-sung A type gold alloy) 7. Casting with cristobalite investments of shofu were seen apart, 0.01mm the tightest space in the linguo-cervical margin. And the largest deviation, 0.08mm was shown in the buccal cusp area of occlusal surface(Bo-sung B type gold alloy) 8. Casting with cristobalite investments of kerr shown the best fitness in linguo-cervical margin. And the largest deviation, 0.04mm was shown in the central groove atea of occlusal surface(Bosung B type gold alloy) 9. Casting with Quartz investments of G-C were seen apart, 0.03mm the tightest space in the linguo-cervical margin. And the largest deviation, 0.04mm was shown in the central groove area of occlusal surface(Bo-sung B type gold alloy) 10. Casting with cristobalite investments of kerr shown the best fitness and Bo-sung A type gold alloy showed the best fitness.

• 한국정밀공학회지
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• 제14권1호
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• pp.126-141
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• 1997

The purpose of this research is to develope a FEM program for analyzing solidification processes of axisymmetric casting, considering phase changes and the contact between the metal and mold. Tempera- ture recovery method is employed fro considering the phase changes releasing the latent heat and the coin- cident node method is used for calculating the amount of heat transfer between the metal and mold. Tan- gent modulus algorithm is adopted for calculating flow stress and a gap element is employed for modeling the interface between the mold and metal in finding deformed shapes. In order to verify the developed program, axisymmetric aluminum and steel casting processes are simulated. Temperature distribution, phase front position, and shrinkage and porosity creation are compared with measurements, FIDAP results, and good agreements are examined.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권3호
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• pp.144-151
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• 2003

IPMC(Ionic Polymer-Metal Composite) is promising candidate material for bio-related actuators mainly due to its biocompatibility and wet and soft properties. The widely used commercialized Nafion film has a few kinds of fixed thicknesses but more various film thicknesses are required for extensive applications. Especially for the enhanced force as an actuator, the thick film is essential. Various Nafion films with thickness of 0.4-1.2mm have been prepared by casting of liquid Nafion. Also, IPMC actuators using casted Nafion films have been fabricated and the basic mechanical properties such as stiffness, displacement and force were measured and analyzed. These results can be used for the optimized design of actuators for different applications.

• 한국환경보건학회지
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• 제18권1호
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• pp.1-5
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• 1992

A study was performed to measure the heavy metal concentrations of suspended particles in iron castings during February, 1990. The heavy metal concentrations were analyzed using patricles atomic absorption spectrophotometer. The results were as fellows 1. The concentrations of suspended paticles by casting process were at furnace 4.19mg/m$^{3}$ at pouring 2.93mg/m$^{3}$ at nonferrous furnace 3.90mg/m$^{3}$, at molding 1.17mg/m$^{3}$, jung ja 2.23mg/m$^{3}$, desanding 5.42mg/m$^{3}$, sand treatment 4.82mg/m$^{3}$, finishing 1,20mg/m$^{3}$. 2. Among the total of 8 iron casting workplaces, the concentrations Fe of furnace was 0.36mg/m$^{3}$, Cu of nonferrous furnace 0.02mg/m$^{3}$, Pb of pouring 0.02mg/m$^{3}$, Cr of desanding 0.01mg/m$^{3}$ and Mn of furnace 0.03mg/m$^{3}$.

• 한국주조공학회지
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• 제18권3호
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• pp.262-270
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• 1998

Gravity tilt pour casting can effectively guarantee the reduction of various casting defects by controlling the rotation speed and the tilting angle of the mold during tilt pouring. The relationship between casting process parameters and the soundness of castings has been investigated in order to determine the optimum process variables in the gravity tilt pour casting process. In order to evaluate the effect of rotation speed on mold filling patterns, a video camera was employed to visualize the in-situ fluid flow behavior of the molten metal, and the relevant fluid velocity was also estimated. X-ray and mechanical tests were also performed to evaluate the effect of fluid velocity on casting quality. With the rotation speed lower than 0.5 r.p.m., which is nearly corresponding to the critical velocity of stability in the fluid flow, sound castings were obtained without having any casting defects. It can be concluded that the gravity tilt pour casting process is an effective process for manufacturing sound casting products with enhanced physical and mechanical properties.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.612-615
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• 1996

In the continuous casting process, molten metal contacts the mold wall and the molten metal surface is subject to the mold oscillation. The mold oscillation results in the oscillation marks on the surface of solidified steel, which has undesirable effects on the quality of slabs. In order to reduce the oscillation marks by achieving soft contact of molten metal with the mold surface, alternating magnetic field is applied to the surface of molten metal. However, if the magnetic field strength becomes too strong, the melt flow induced by the magnetic field. causes the instability of the molten metal surface, which has also the bad influence on the slab quality. Therefore, it is very important to choose the optimal position of the inductor coil and the optimal level of electric power to minimize the surface defects. In the present work, as a first step toward the optimization problem of the process, numerical studies are performed to investigate the effects of coil position and the electric power level on the meniscus shape and the flow field. As numerical tools, the boundary integral equation method(BIEM) is used for the magnetic field analysis and the finite difference method (FDM) with orthogonal grid generation is used for the flow analysis.

• 대한치과기공학회지
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• 제37권2호
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• pp.69-76
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• 2015

Purpose: In this study, the marginal fitness of ceramic Co-Cr metal crown made by precision casting, milling, and selective laser melting method were compared. Methods: The ceramic Co-Cr metal crown manufactured by precision casting used the lost wax(LC specimen) method. The abutment were scanned and then made by milling(CM specimen), selective laser melting(CS specimen) method. The specimen were cut bucco-lingual and mesio-distal, and absolute marginal discrepancy and marginal gap were measured using a digital microscope. The surface roughness of the crown was also observed. Results: On the bucco-lingual axial, absolute marginal discrepancy was the LC specimen $31.72({\pm}4.58){\mu}m$, the CM specimen $78.29({\pm}3.28){\mu}m$ and the CS specimen $143.13({\pm}3.83){\mu}m$, respectively. On the bucco-lingual axial, marginal gap was the LC specimen $22.70({\pm}1.46){\mu}m$, the CM specimen $22.70({\pm}1.49){\mu}m$ and CS specimen $99.60({\pm}1.57){\mu}m$, respectively. Conclusion: For ceramic Co-Cr metal crowns, LC specimen was superior for absolute marginal discrepancy and marginal gap. The surface of metal crowns by selective laser melting were the roughest.