• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1221-1226
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• 2012

The hot-stamping technique is a forming method used for manufacturing high-strength parts, in which a part is cooled rapidly after press forming above the austenite transformation temperature. Boron steel, which contains a very small amount of boron, is one of the materials used for hot stamping. The purpose of this study is to investigate the mechanical properties of boron steel according to the heat-treatment conditions and the formability by using an Erichsen cupping test. Die quenching from various temperatures was conducted for different elapsed heat-treatment times. Laser-welded boron steel after quenching at 1173 K-0 s has a tensile strength of 1203 MPa. This is 79% of the tensile strength of the base metal (1522 MPa). The formability of boron steel was not significantly different from that at the mold temperature. However, it decreased with increasing forming speed. These properties provide practical information for the use of boron steels for hot stamping.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.4
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• pp.483-490
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• 2013

In aluminum sheet metal forming, the conventional forming methods of T4 or T6 heat-treated sheets result in low formability and dimensional accuracy. This study suggests a new forming method for aluminum sheets called as hot forming quenching (HFQ) that solves the problems faced in the conventional method. HFQ combines the heat treatment and forming processes through the forming die during the quenching of a solid solution. To evaluate the application of HFQ to the sheet forming of aluminum, an Erichsen and V-bending test are performed in this study to measure the dimensional accuracy and formability, which are then compared with those of the conventional forming method. Furthermore, the strength and hardness of the products formed by HFQ are measured to confirm the degradation in mechanical properties compared with the conventional forming method, which shows the validity of the application of HFQ to aluminum sheet metal forming.

• Proceedings of the KWS Conference
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• 1998.05a
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• pp.150-154
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• 1998

The purpose of this paper is to investigate optimum welding conditions of STS 304 thin sheet by GTA welding and control 6 $\delta$--fenite which is harmful in mechanical processing, corrosion problem and can be formed brittle a phase in using long term at high temperature. One series of automatic welds was made using argon plus 10, 20, 30 % nitrogen to ensure a fully austenite deposit. Results obtained were summarized as follows: 1) 6 $\sigma$ferrite content in the weld metals is influenced largely by the nitrogen content. 2) Additions of nitrogen to the shielding gas can significantly reduce the amount of retained delta ferrite and result in an increase in hot cracking. 3) Bead width was increased when Ar + $N_2$ shielding gas was used and travel speed was increased. 4) Ar+$N_2$ shielding gas made weld metal ductile and reduce 6 -$\delta$-ferrite.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.6
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• pp.97-102
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• 2023

This study is to provide improvement of tester for IoT system, which has recently become diversified and large-scale and It is about a method to improve the packet processing performance of the tester and securing flexibility in traffic protocol creation and operation. The purpose of this study is to design a OSS DPDK-based high-speed IoT network performance test system, which pre-verifies and measures the performance of data traffic transmission in an increasingly sophisticated high-capacity IoT network system. The basic structure of the high-speed IoT performance tester was designed using a DPDK-based traffic generator, the expected effect was suggested to traffic modeling and packet generation capability when the system was applied through experiments

• Journal of KIISE:Computing Practices and Letters
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• v.8 no.6
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• pp.647-656
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• 2002

Synchronization is the process of making replicated data on multiple devices be consistent, i.e., identical with each other. In Dec. 2000, major handheld computer manufacturers including Nokia, Ericsson, IBM published the SyncML protocol specification. In this paper, we describe the CNU SyncML server for PIMS(Personal Information Management System) service that we developed based on the SyncML specification. The server architecture and capabilities of the frames are presented along with the procedure of message processing by each frame. We put the CNU SyncML server to the conformance tests and interoperability tests to confirm its functionality. The session managing mechanism of the CNU SyncML server showed better performance than our previous implementations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.4
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• pp.413-420
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• 2012

An aluminum foil-laminated sheet is a laminated steel sheet on which aluminum foil is adhesively bonded. It is usually used on the outer panel of home appliances to provide an aluminum feeling and appearance on the surface of the product. The delamination of aluminum foil is one of the main problems during the stretch forming process. The purpose of this study is was to determine the delamination limit of an aluminum foil-laminated sheet in the stretch forming process. The delamination was dependent on the bonding strength between aluminum foil and steel sheet. The fracture behavior of the interface between the aluminum foil and the steel sheet was described by a cohesive zone model. A finite element was conducted with the cohesive zone model to analyze the relationship between the delamination limit and the bonding strength of the interface. The interface bonding strength was evaluated by lap shear and T-peel test. The delamination limit of the aluminum foil-laminated sheet was determined by using the bonding strength of the steel sheet. The delamination limit was also verified by the Erichsen test.