• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1992.03a
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• pp.103-114
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• 1992

Cogging is generally the initial and primary step in the manufacture of practically all large open-die forgings, and consists of forging and ingot by reducing the cross-section and simultaneously enlarging the body. A three-dimensional thermo-viscoplastic finite element model is used to study the distribution of internal stresses and strains of workpiece and temperature of workpiece and die during cogging process. Simulations are carried out on an circular ingot, using v-die and flat die, to study the effects of die configuration, die width, penetration depth, temperature gradient, die overlapping and pass design.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.2
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• pp.35-40
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• 2014

Wire drawing is aplastic deformation process that produces a wire with a desired diameter by pulling the end of the wire through a die. During the cold wire drawing process, the temperature between the wire and the die bearing is increased. This temperature increase causesenergy consumption increase, bad wire quality, and decreased die life. To reduce friction and avoid high temperature between the wire and the die in the cold wire drawing process, a dry lubricant with soap particles is used. It is not possible to reused the lubricant onceiron oxide is attached to the soap particlesat high pressure die. In this study, recycling technologies for wasted soap particles with processes of crushing, separation, and screening are developed. From the evaluation, the recycling efficiency was found to be 86.97%.

• Design & Manufacturing
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• v.2 no.1
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• pp.21-26
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• 2008

In this research, jar die of cosmetic products which is difficult to produce variously was developed and can be obtain the productivity improvement by flexibility with two system which can control the die temperature. Flow analysis of jar was performed to find out the curvature radius of parts. In order to reduce thickness of jar, cycle time, deformation, uniform curvature of internal jar was maintained by rapid cooling. In external of dies, cooling channel, injection molding condition, die temperature control system were researched to make dies low temperature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.75-78
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• 2000

There are several effective factors to influence die life in the warm forging process. For instance process design die design and die materials etc This study presented heat treatment method which could improve toughness and wear resistance simultaneously in high temperature to apply high speed tool steels like SKH51 to die material for warm forging process. To verify the feasibility of application of heat treatment method mentioned above wear test was performed under the condition of constant time in 40$0^{\circ}C$ Wear coefficient was examined to search a relation between wear amount and time for each material and heat treatment method in 30, 60, and 130 minutes. To quantify the toughness-behavior between room and high temperature impact test was performed and heat fatigue test also fulfilled to compare with the resistance of heat check in room, 200, 400, and $600^{\circ}C$ temperature. On the basis of experimental results mentioned above high speed tool steel was applied to verify appropriateness of newly proposed heat treatment method for die of rotor pole used in automobile alternator. As a result die life of high speed tool steel applied newly proposed heat treatment is longer than that of STD61.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.2
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• pp.202-210
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• 2011

The fabrication method of aspheric lens is changed from machining to press molding so as to improve the productivity. In the case of the press molding method, the temperature control of the molding die is most important, because the temperature of each molding die determines the quality of lens. But any practical method for direct measuring of the lens temperature and the die internal temperature is yet unknown. Besides, in the case of the press molding system in which the heating and pressing and cooing of a die is done at separate work stations, the lens productivity of the system for small lens is yet too low. The paper shows an improved structure of convective sequential system, the lens productivity of which is three times as many as the conventional convective system. To know the die internal temperature, numerical results are given using ANSYS. A new convective sequential system is developed and tested. Finally, the Taguchi method is applied in order to optimize the setting conditions of individual work station of the system.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.12
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• pp.67-74
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• 2010

The fabrication method of aspheric lens is changed from machining to press molding so as to improve the productivity. In the case of the press molding method, the temperature control of the molding die is most impotent, because the temperature of each molding die determines the quality of lens. But any practical method for direct measuring of the lens temperature and the die internal temperature is yet unknown. Besides, in the case of the press molding system in which the heating and pressing and cooing of a die is done at one work station, the cycle time for the system is yet too long. The paper shows an improved structure of radiant sequential system in which the heating and pressing and cooing of dies is done at individual work station so as to cut down the cycle time. To know the die internal temperature, numerical results are given using ANSYS. An experimental radiant sequential system is developed and tested. Finally, the Taguchi method is applied in order to optimize the setting conditions of individual work station.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.219-222
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• 2005

The temperature difference between die and workpiece has frequently caused various surface defects. The non-homogeneous temperature distribution of forged part should be analyzed to prevent the generation of various defects related with the temperature. The surface temperatures were mainly affected by the coefficient of thermal contact conductance. The precise coefficient is necessary to predict accurately the temperature changes of die and workpiece. The experiment is preformed to measure the temperature distribution of die and workpiece in closed die upsetting. And then, the coefficient is classified into function of pressure and confirmed by the comparison between experiments and FE analyses using the other model. The FE analysis to predict the temperature distribution is performed by commercial software $DEFORM-3D^{TM}$. However, it might be impossible to measure directly the temperature distribution of forged part. Therefore, the comparisons between measured temperature and predicted values are performed with the hardness of Al6061-forged part.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.370-373
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• 2008

Small size gas turbine disk requires good mechanical strength and creep properties at high temperature. In this study, Waspaloy was used as a superalloy to satisfy these specifications. The control of microstructure was needed to satisfy material properties at high temperature. In order to do this, we studied forging conditions and material analysis. Therefore die and preform design conducted so that hot forged gas turbine disk could have a good microstructure. The die and preform shapes are designed with consideration of the predefined hydraulic press capacity and the microstructure of forging product. Also we carried out the hot compression test for Waspaloy in various test conditions. From these results, we obtained the forging conditions as material temperature, die velocity etc. To verify these forging conditions, we conducted FE simulations by means of the DEFORM 2D-HT. In this study, the hot closed die and preform designs were completed to offer high temperature material properties of a small size gas turbine.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.1
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• pp.1-7
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• 2020

The backside metallization process is typically used to attach a chip to a lead frame for semiconductor packaging because it has excellent bond-line and good electrical and thermal conduction. In particular, the backside metal with the Ag/Sn/Ag sandwich structure has a low-temperature bonding process and high remelting temperature because the interfacial structure composed of intermetallic compounds with higher melting temperatures than pure metal layers after die attach process. Here, we introduce a die attach process with the Ag/Sn/Ag sandwich structure to apply commercial semiconductor packages. After the die attachment, we investigated the evolution of the interfacial structures and evaluated the shear strength of the Ag/Sn/Ag sandwich structure and compared to those of a commercial backside metal (Au-12Ge).

• Journal of Korea Foundry Society
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• v.9 no.1
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• pp.39-48
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• 1989

A basic three dimensional thermal model has been developed to simulate the solidification sequence for gravity die casting process. The finite difference method was used to analyze the solidification process during all the casting cycles. The prediction of die temperature in the quasi-steady state was analyzed by the boundary element method. The influence of die cooling on the heat flow in the cast/mold system was also investigated. Predictions of the computer simulation on temperature profiles and location of shrinkage defects were in good agreement with those observed in experimental die castings. Models of computer simulation which is developed by this work can be useful for the design and process control of die casting.