• Transactions of Materials Processing
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• v.27 no.3
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• pp.165-170
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• 2018

In order to increase the lifetimes of cold forging dies, insert rings are generally used. In this study, an insert ring and shrunk ring of the flange upsetting die were designed for the cold forging of an automotive wheel nut. The Stress distribution occurring in the die during forging was simulated using a commercial finite element analyzing program. The effects of the fitting interference and inclined angle of the insert ring on the compressive stress of the die inside were also investigated. The simulated data were compared with the real lifetimes of the forging dies. The maximum compressive stress acting on the edge of a forging die should have the most influence on die lifetime, an idea which could help develop the die design with the longest lifetime. The design of the most optimal forging die with the longest lifetime is made possible by analyzing the maximum inner pressure and principal stress between the shrunk ring and insert ring.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.5
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• pp.91-97
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• 2020

A split-die design for the cold forging of symmetric parts such as those having a hexagonal cross-section is presented in this paper. Parts with a hexagonal cross-section, such as bolt heads and nuts, should be forged with a die that has a hexagonal-shaped hole. A split type die is required to mitigate the buildup of stress concentrations located at the corners of the hexagonal hole. Generally, the insert of a hexagonal die is made by cutting each corner of a cylinder using a hexagonal hole and then combined with the die and shrink-fitted. However, split dies face problems when extruding material at the corners of the hexagonal split die. To address this problem, two types of split dies were evaluated: rounded hexagonal dies and angular hexagonal dies. The effects of the pre-stress ring on the dies were compared and analyzed and results show that using the angular split hexagonal die can extend the lifetime of forging dies.

• Transactions of Materials Processing
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• v.25 no.5
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• pp.313-318
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• 2016

The plasma vapor coatings on two kinds of die steels have been carried out in order to identify the most optimized conditions. When TiN or TiAlN coatings were carried out on the substrates, the coating layer thicknesses were not significantly changed, and the optimized coating thickness was identified as ~ 5 μm. When the optimized coating conditions and stress analysis were applied to the primary piston dies for fabrication of aluminum cylinders, an extended life time of the die was observed. The methodology for extending the life time of dies was discussed in terms of microstructures and stress analysis.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.12
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• pp.1264-1270
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• 2004

A fast switching thyristor with a superior trade-off property between the on-state voltage drop and the turn-off time could be fabricated by the proton irradiation method. After making symmetric thyristor dies with a voltage rating of 1,600 V from 350 $\mu$m thickness of 60 $\Omega$ㆍcm NTD-Si wafer and 200 $\mu$m width of n-base drift layer, the local carrier lifetime control by the proton irradiation was performed with help of the HI-13 tandem accelerator in China. The thyristor samples irradiated with 4.7 MeV proton beam showed a superior trade-off relationship of $V_{TM}$ = 1.55 V and $t_{q}$ = 15 $\mu$s attributed to a very narrow layer of short carrier lifetime(～1 $\mu$s) in the middle of its n-base drift region. To explain the small increase of $V_{TM}$ , we will introduce the effect of carrier compensation at the low carrier lifetime region by the diffusion current.ffusion current.t.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.271-275
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• 2004

A fast switching thyristor with a superior trade-off property between the on-state voltage drop and the turn-off time could be fabricated by the proton irradiation method. After fabricating symmetric thyristor dies with a voltage rating of 1,600V from $350{\mu}m$ thickness of $60{\Omega}cm$ NTD-Si wafer and $200{\mu}m$ width of N-base drift layer, the local carrier lifetime control by the proton irradiation was performed with help of the HI-13 tandem accelerator in China. The thyristor samples irradiated with 4.7MeV proton beam showed a superior trade-off relationship of $V_{TM}=1.55V\;and\;t_q=15{\mu}s$ attributed to a very narrow layer of short carrier lifetime(${\sim}1{\mu}s$) in the middle of its N-base drift region. To explain the small increase of $V_{TM}$, we will introduce the effect of carrier compensation by the diffusion current at the low carrier lifetime region.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.6
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• pp.96-102
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• 2000

The finishing process for dies and molds is an important process because it has influence on final quality of products. And it is difficult to automatize finishing process so that the process has depended on expert's skill until now. However, recently a study on development of die automatic finishing machine has been progressed, and actually this machine is applied to fabrication of die. But the research about tooling system is not enough and finishing tool must have high machining efficiency and adaptability of curved surface. So, this study investigated the application of conductive elastic tool which is composed of metal-resin bonded pellet and elastic backing material. The metal-resin bonded pellet is used to finish the surface by conventional mechanical grinding or electro-chemial grinding method. And elastic backing material is used to follow the curved surface. So conductive elastic tool has long lifetime, uniform removal rate and adaptability of curved surface.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.3
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• pp.297-312
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• 2012

For future multi-core processors, 3D integration is regarded as one of the most promising techniques since it improves performance and reduces power consumption by decreasing global wire length. However, 3D integration causes serious thermal problems since the closer proximity of heat generating dies makes existing thermal hotspots more severe. Conventional air cooling schemes are not enough for 3D multi-core processors due to the limit of the heat dissipation capability. Without more efficient cooling methods such as liquid cooling, the performance of 3D multi-core processors should be degraded by dynamic thermal management. In this paper, we examine the architectural impact of cooling methods on the 3D multi-core processor to find potential benefits of liquid cooling. We first investigate the thermal behavior and compare the performance of two different cooling schemes. We also evaluate the leakage power consumption and lifetime reliability depending on the temperature in the 3D multi-core processor.

• 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.

• The Korean Journal of Archival Studies
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• no.72
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• pp.165-203
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• 2022

Many people create records in digital space, and the amount of digital records left after individual dies has increased. The digital record left by the deceased is different from the record heritage that has physical substances. In many cases, the records of the deceased not just belong to the deceased, and many deceased did not explicitly disclose their online accounts and method of dispose of digital records during their lifetime, so this problem may lead to problems of inheritance to the bereaved family. In addition, digital records may be neglected or deleted after a person's death due to software problems, specific platform's terms of use, account deletion by bereaved family, etc. This leads to the problem that daily records, which are important clues to the social aspects at the time, are easily lost. Several studies have revealed that individuals are interested in preserving their digital records, but do not know how to do it, so they are benign neglect. For this reason, it is necessary to pay attention to personal digital records and personal digital legacy, and to prepare related policies and plans. Accordingly, this study analyzes problems related to the management of digital records after an individual's death, related to laws and systems, the status and policies of platforms and industries, the status of personal record management, etc. Various solutions were suggested, such as a need for enactment for digital personal record management act, platform's explicit policy for individual's post-mortem records, digital records management plan for archival institutions, individual's a preemptive management plan for his/her own records, and a method for writing a will related to digital account information.