• Design & Manufacturing
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• v.6 no.2
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• pp.24-30
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• 2012

In this study, the hot forging technology for precision forming of spline teeth of the inner race in the auto-transmission was developed in order to minimize its finishing allowance. Several blocker and finisher shapes for the precision hot forging process of the inner race were proposed and the forging processes were analyzed using the three-dimensional finite element method. The optimum hot forging process was obtained considering some parameters such as metal flow patterns, forging defects and forming load. Blocker and finisher dies for the hot forging process were designed by selecting the most suitable shapes obtained from the finite element analysis. Experimental works were also performed in order to verify the optimum design of hot forging process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.383-386
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• 2002

This paper reports on the fluid flow simulation results of an active microvalve. The mechanical and fluidic analysis are done by finite element method. The designed structure is normally closed microvalve using buckling effect, which is consist of three separate structures; a valve seat die, an actuator die and a small piezoelectric actuator. It is confirmed that the complete laminar flow and the lowest flow leakage are strongly depend on the valve seat geometry. In addition, turbulent flow was occurs in valve outlet according to increase seat dimension, height and inlet pressure. From this, we was deducts the optimum geometry of the valve seat and diaphragm deflection that have an great influence fluid flow in microvalve. Thus, it is expected that our simulation results would be apply for constructing integrated chemical analyzing system or drug delivery system.

• Journal of Korea Foundry Society
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• v.35 no.4
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• pp.80-87
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• 2015

The Al die casting process has been widely used in the manufacturing of automotive parts when the process requires near-net shape casting and a high productive rate. However, porosity arises in the casting process, and this hampers the wider use of this method for the creation of high-durability automotive components. The porosity can be controlled by the shot condition, but, it is critical to set the shot condition in the sleeve, and it remains difficult to optimize the shot condition to avoid air entrapment efficiently. In this study, the 4.5 mm, 2.0 mm plate die castings were fabricated under various shot conditions, such as plunger velocities of 0.7 m/s ~ 3.0 m/s and fast shot set points of the cavity of -25%, 0%, 25%, and 50%. The mold filling behavior of Al melts in the cavity was analyzed by a numerical method. Also, according to the shot conditions, the results of numerical analyses were compared to those of die-casting experiments. The porosity levels of the plate castings were analyzed by X-ray CT images and by density and microstructural analyses. The effects of the porosity on the mechanical properties were analyzed by tensile tests and hardness tests. The simulation results are in good general agreements with the die-casting experimental results. When plunger velocity and fast shot set point are 1.0 m/s and cavity 25% position, castings had optimum condition for good mechanical properties and a low level of porosity.

• Transactions of Materials Processing
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• v.7 no.5
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• pp.439-444
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• 1998

Recently many automotive parts have been made with stainless steels by deep drawing processes, But there are various problems occurred in deep drawing works of stainless steels compared with low carbon steels. For the severe deep drawing of complex cylindrical housing optimum process planning is required to eliminate intermediate annealing improve shape accuracy and maintain surface integrity without drawing defects such as tears wrinkles and scratches or galling. Therefore in this study a sample process planning of the severe of the severe deep drawing process is applied to a complex cylindrical housing needed for a 6 multi-stepped deep drawing of type STS 305 . A series of experiments are performed to investigate optimum process variables such as drawing rate radius and clearance. Through experiments the variations of the thickness strain distribution and hardness distribution in each drawing step are observed. Also the effects of other factors on formability such as drawing oil, blank holding force and die geometry are examined and discussed.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.196-202
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• 1998

Recently, developments in the frontier industry have brought a rapid increase in the use of brittle materials such as silicon wafer, ferrite, sintered carbide, MgO single crystal and die steel. Because of high hardness and brittleness the cracking and chipping are apt to generate in the grinding of brittle materials, but have replaced gradually the high precision grinding. In this study, the optimum system of in-process electrolytic dressing controlled by computer was developed for improving the defects, and could maintain the optimum dressing condition at all times. The control of in-process dressing was simplified using this system, was able to maintain a stable dressing current and was unrelated to the change of dressing condition according to the variation of gap and oxide layer. Therefore, the optimum in-process electrolytic dressing system was constructed and the analysis of grinding mechanism with this system was studied.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.2
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• pp.59-65
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• 2006

The purposes of using cutting fluid during cutting have been cooling, lubricating, chip washing and anti-corroding. However, the present manufacturing industry restricts the use of cutting fluid because cutting fluid contains poisonous substances which are harmful to the human body. Therefore environmentally conscious machining and technology have more important position in machining process because cutting fluids have significant influence on the environment in milling process. In this study, environmentally conscious machining can be obtained by the way of selecting the optimum machinig conditon using the design of experiment. Cutting using oil-mist showed better cutting characteristics than dry, air and fluid cutting with respect to by cutting force, tool wear and surface roughness. Also, the optimum machining condition for cutting using oil-mist could be selected through Taguchi method.

• Transactions of Materials Processing
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• v.9 no.6
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• pp.598-603
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• 2000

In order to improve trial-and-error based conventional practices for optimizing forming processes, a direct design method to guide iterative design practices, called the ideal forming theory, has been previously developed. In the theory, material elements are required to deform following the minimum Plastic work Path. The theory can be used to determine the ideal initial blank shape needed to best achieve a specified final shape while resulting in optimum strain distributions. In this work, the direct design method based on the ideal forming theory was applied to design initial design shape for VCR deck chassis. Based on the solution of the ideal forming theory, FEM analysis was utilized to evaluate an optimum blank shape to be formed without tearing. Simulation results are in good agreement with experimental data. It was shown that the proposed sequential design procedure based on direct design method and FEM can be successfully applied to optimize the die design Procedure of sheet metal forming processes.

• Transactions of Materials Processing
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• v.21 no.3
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• pp.207-214
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• 2012

High temperature deformation behavior of a $Ni_{30}Fe_{53}Co_{17}$ alloy, with its extraordinary low coefficient of thermal expansion less than $10{\times}10^{-6}K^{-1}$ at temperatures ranging from room temperature to 673K, was investigated by conducting a series of compression tests. From an empirical processing map, the appropriate working temperature-strain rate combination for optimum forming was deduced to be in the ~1373K, $10^{-2}s^{-1}$ region. This region has a relatively high power dissipation efficiency, greater than 0.36. Furthermore, open die forging of a 100mm diameter billets was performed to confirm the variation of thermo-physical properties in relation to microstructure. The coefficient of thermal expansion was found to increase considerably with increasing the open die forging temperature and decreasing the cooling rate, which in turn provides a drastic increase in the average grain size.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.1
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• pp.101-106
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• 2012

The press bulging process is very useful and productive method to produce round-type mechanical components which have not been able to be manufactured because of limitation of the conventional press technology. The application of the press bulging process has expanded very quickly in the hydraulic and electronic industry and more recently it has been used to produce other mechanical parts such as the automobile and shipping parts. This expanding application also has brought some unsolved problems and leads many researchers to put their effort into the die design of the press bulging process. In this study, to obtain the optimum die shape for the press bulging process, various process parameters have been considered such as corner radius, bulging height, pressing length, and forming load, etc. The main interest of this paper is to verify the press bulging process which has more than 4.0 in height-length ratio. From this aspect, Finite Element analysis shows great ability to simulate the precise deformation process and gives us manufacturing database. Consideration of strain, stress, and strain-rate for the various cases has been also taken to keep the forming load within a particular range.

• Journal of Korea Foundry Society
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• v.19 no.5
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• pp.410-418
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• 1999

To overcome the undesirable deformation, peeling off and geometrical restrictions which were mainly caused by differences in thermal expansion coefficients during the cladding of aluminum strip and stainless strip, new processing method based on vacuum die casting is designed and implemented in fabricating Fe-17wt%Cr steel (stainless steel). To increase cast-bonding ability, the surface of Fe-17wt%Cr steel is electrochemical etched to have optimum pit size (above 0.2 mm) and pit density (above 30%). The implementation of vacuum die casting by using surface treated stainless steel (Fe-17wt%Cr Steel) produces good trial products having acceptable cast-bonding ability. The enabling conditions for cast-bonding are pouring temperature $690^{\circ}C$, filling speed 30 m/sec and casting pressure $800\;kg/cm^2$. The microscopic observation of cast-bonded Al/Fe-17wt%Cr steel does not show any evidence of intermetallic compounds. The bonding strength of trial products is $150-400\;kg/cm^2$ and this is stronger than conventionally cladded metal having $30-70\;kg/cm^2$.