• Journal of Industrial Technology
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• v.16
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• pp.257-265
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• 1996

When machining of a free-form surface with a ball endmill it is very important to select proper cutting conditions considering the geometrical shape of a workpiece to make the production more effective and reduce the machining time. Even though the same cutting conditions and materials are used, the cutting system of different geometry part machining shows the different static/dynamic characteristics. In this study, through various cutting experiments, we can construct the data base of stable cutting conditions for the machining of a Zine Alloy. We can get some relational plots between the optimal feedrates and classified shape features and parameters. On the basis of these results, we can develop the feedrate optimization program OptiCode. The developed program make it possible to reduce the cutting time and increase the machining accuracies.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.975-976
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• 2006

The present paper is a parameter study of zinc flake production using a Simoloyer CM01 horizontal high energy rotary ball mill. The manufactured flakes have a dimension in thickness (t) < $1{\mu}m$ and diameters (d) 5-100 ${\mu}m$, consequently a ratio d/t up to 200. The flake geometry is mainly controlled by the variation of process parameters such as rotary speed of the rotor, ratio of powder/ball charge, load ratio of the system, process temperature, operating model and the quantity of process control agent (PCA). The Zn flakes were characterized by SEM, tap densitometry, laser diffraction and water coverage measurement.

• Tribology and Lubricants
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• v.11 no.5
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• pp.20-25
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• 1995

Diamond films were prepared by a hot filament vapor deposition onto polycrystal silicon nitride substrates. Different kinds of silicon nitride containing CaO and $Fe_{2}O_{3}$ were manufactured to investigate the impurity effect of substrate on the morphology of diamond films and their wear behaviors. Nucleation rates and morphologies of diamond films deposited on various kinds of silicon nitride were compared. The highest nucleation rate was observed in a substrate containing 1% of CaO. Wear tests were performed with a silicon nitride ball on the disk geometry to investigate the tribological behavior of diamond film against silicon nitride. This study demonstrated that different morphologies of diamond film due to substrate impurities produced different wear behavior against silicon nitride.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.102-106
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• 1996

In the ball end-milling process of a 3-dimensional mold, it is important to select cutting conditions and tool path considering the geometrical shape of a workpiece to reduce machining time. In this study, experiments were performed to decide allowable feed rate not breaking stability of system for different geometrical shapes. It was found that downcut is more stable than upcutting in machining side wall and downward is preferable to upward in inclined part depending on the angle of the inclination and depth of cut.

• Journal of the Korean Society of Industry Convergence
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• v.4 no.4
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• pp.365-369
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• 2001

This paper presented a new model of virtualized CNC milling machine. The model verifies the over cut, the under cut and the surface roughness using NC file generated from CAM and cutting condition. The model uses Z-map model to verify workpiece. In this paper, the model used the velocities of x, y and z direction and obtained a center point of a hall end mill for modeling Z-map of workpiece. To investigate the performance of the model, simulation study was carried out. As the results, the model gave geometry accuracy of workpiece, the surface roughness and the chip loads in finish cutting that can predict tool chipping. The virtualized CNC machine can he used a flat end mill, a ball end mill and a rounded end mill.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.111-119
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• 1997

The operating characteristics of the check valve in the clutch piston of an automatic transmission have a great effect on the shifting performance. This paper addresses the modeling, dynamic analysis, and optimization of the check valve. It was found that the vortex causes a pressure drop, which is related to the rotating speed of the clutch piston, oil volume discharged from the check valve, and valve geometry. Maximizing the oil volume discharged, geometry of the check valve is optimized. The results can be used to design an improved check valve which provides a suitable oil pressure curves for achieving smoother shifting.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.205-211
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• 2000

Friction control is highly desirable for optimization of tribological systems. In this work, the effect of geometric structure of the solid surface on friction is investigated using a Scanning Electron Microscope equipped with a tribotester. Silicon and silicon oxide specimens were used and undulations on the surface were fabricated by mechanical and chemical methods. It is shown that the friction coefficient depends on the relative dimensions of the ball and the width of undualation. By optimizing the geometry of the undulation, friction reduction may be achieved.

• Korean Journal of Computational Design and Engineering
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• v.13 no.3
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• pp.200-208
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• 2008

Total Hip Replacement(THR) is a surgical procedure that replaces a diseased hip joint with a prosthesis. A plastic or metal cup forms the socket, and the head of the femur is replaced by a metal ball on a stem placed inside the femur. Due to the various types and shapes of human hip joint of every individual, a selected commercial implant sometimes may not be the best-fit to a patient, or it cannot be applied because of its discrepancy. Hence extracting geometry parameters of hip joint is one of the most crucial processes in designing custom-made implants. This paper describes the framework of a methodology to extract the geometric parameters of the hip joint. The parameters include anatomical axis, femoral head, head offset length, femoral neck, neck shaft angle, anteversion, acetabulum, and canal flare index. The proposed system automatically recommends the size and shape of a custom-made hip implant with respect to the patient's individual anatomy from 3D models of hip structures. The proposed procedure creating these custom-made implants with some typical examples is precisely presented and discussed in this paper.

• Honam Mathematical Journal
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• v.34 no.1
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• pp.103-111
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• 2012

Wetzel[5] proved if ${\Gamma}$ is a closed curve of length L in $E^n$, then ${\Gamma}$ lies in some ball of radius [L/4]. In this paper, we generalize Wetzel's result to the non-Euclidean plane with much stronger version. That is to develop a lower bound of length of a triangle inscribed in a circle in non-Euclidean plane in terms of a chord of the circle.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.12
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• pp.8-15
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• 2021

Cold forging is a method in which molding is performed at room temperature. It has a high material recovery rate and dimensional precision and produces excellent surface quality, and it is mainly used for the production of bolted or housing products. The lifespan of cold forging molds is generally determined by the wear of the mold, plastic deformation of the mold, and fatigue strength. Cold forging molds are frequently damaged due to fatigue destruction rather than wear and plastic deformation in a high-temperature environment as it is molded at room temperature without preheating the raw material and mold. Based on the results analyzed through FEM, an effective mold structure design method was proposed by analyzing the changes in tensile and compressive stresses on molds according to the number of molds and reinforcement rings and comparing the product geometry and mold stress using three existing mold models.