• Journal of the Korean Society of Combustion
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• v.11 no.3
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• pp.1-7
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• 2006

A reaction mechanism of methane partial oxidation, which consists of thermal and plasma chemistry reaction pathways, has been investigated using with an arc-jet reactor. The reaction zone of the arc-jet reactor is spatially separated into thermal and non-thermal plasma zone. Methane conversion rates, selectivity of $H_2$ and $C_2$ chemicals in each zone are obtained, which reveals clearly different characteristics of reaction pathways depending on the temperature conditions. The conversion rates obtained in thermal plasma zone is higher than those in non-thermal plasma zone. The selectivity, however, obtained in non-thermal plasma zone is significantly higher than those in thermal plasma zone. Further parametric study on $O_2/C$ ratio, arc length and SED shows that the present process is mainly governed by thermal chemistry pathways.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.6
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• pp.681-689
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• 2009

Disk grinding was often applied to deburring process in order to enhance the final product quality. Inherent chamfering capability of the flexible disk grinding process in the early stage was analyzed with respect to various process parameters including workpiece length, wheel speed, depth of cut and feed. Initial chamfered edge defined as arc zone was characterized with local radius of curvature. Averaged radius and arc zone ratio was well evaluated using neural network system. Additional neural network analysis adding workpiece length showed enhance performance in predicting arc zone ratio and curvature radius with reduced error rate. A process condition design parameter was estimated using remaining input and output parameters with the prediction error rate lower than 2.0% depending on the relevant input parameter combination and neural network structure composition.

• Journal of Welding and Joining
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• v.26 no.2
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• pp.92-97
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• 2008

In welding of thin plate, some defects such as melt through and unmelted zone occur easily at welding start, however there is a limited study on those problems. Therefore the effects of start block and arc length on melt through and unmelted zone at start were investigated in this study. When start block height was lower than base metal, there was melt through at start. And when the height was even with base metal, no unmelted zone existed. Unmelted zone was increased as start block height increased from 0mm to 0.5mm. However unmelted zone was not much changed as the height increasing from 0.5mm to 1.0mm. When gap existed between start block and base metal, melt through occurred. However, unmelted zone was increased as the contact force of start block on base metal was increased from 0kgf to 7.5kgf. And when arc length was decreased from 3.8mm to 3.0mm, unmelted zone was decreased. It was concluded that the optimum condition to prevent melt through and to minimize unmelted zone would be with start block height 0.25mm, contact force 3.0kgf, and arc length 3.4mm. This optimum condition was applied to the mass production line and resulted in satisfied outcome.

• Journal of Ocean Engineering and Technology
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• v.13 no.4 s.35
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• pp.28-36
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• 1999

Wet underwater arc welding process is investigated by using experimentally developed flux coated underwater arc welding electrode and SS400 steel plate of 12mm thickness as base metal. Three kinds of different flux covered wet arc welding electrode of 4mm diameter(BK-01, BK-02, BK-03) are individually developed, and one of the improved underwater welding electrode (BK-03) may be put to practical use for underwater wet arc welding process. The results obtained from this experimental study are as follows : 1. Arc stability of developed underwater wet welding electrode is better than that of the domestic covered arc welding electrode. 2. Workability of welding electrode, remove ability of slag and bead appearances using improved underwater wet welding electrode are remarkably better than that of others. 3. Heat affected zone of test specimen welded in the underwater gets to become a lot smaller than that of test specimen welded in the air, and the maximum hardness of heat affect zone of developed underwater wet welding electrode is lower to that of domestic arc welding electrode.

• Journal of Welding and Joining
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• v.10 no.4
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• pp.222-229
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• 1992

A prediction of penetration and heat affected zone by using Finite Element Method in CO$_{2}$ Arc Welding has been discussed this paper. The temperature distribution of a base metal produced by the CO$_{2}$ arc welding processing is analyzed by using a three dimensional finite element model. The common finite element program ANSYS 4.4A was employed to obtain the numerical results. Temperature dependent material properties, effect of latent heat, and the convective boundary conditions are included in the model. Numerically predicted sizes of the penetration and the heat affected zone are compared with the experimentally observed values. As a result, there was a slight difference between numerical analysis values and experimentally observed values. For in the case of heat affected zone, it was not considered a precise forced convective coefficient value, and in the case of penetration, it was not, considered a arc force.

• Journal of Welding and Joining
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• v.34 no.5
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• pp.70-76
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• 2016

In this study, Microstructure and tensile properties in arc brazed joints of 1000MPa grade DP steel using Cu-Si insert metal were investigated. The fusion zone was composed of Cu phase which solidified a little Fe and Si. The former phase formed due to dilute the edge of base material by arc, although Fe was not solid solution in Cu at the room temperature. Cu3Si particles formed by crystallization at $1100^{\circ}C$ during faster cooling. After the tensile shear test, there are no differences between the brazed joint efficiencies. The maximum joint efficient was about 37% compared to strength of base metal. It is better than that of arc brazed joint of DP steel using Cu-Sn filler metal. Fracture position of all brazing conditions was in the fusion zone. Crack initiation occurred at three junction point which was a stress singularity point of upper sheet, lower sheet and the fusion zone. And then crack propagated across the fusion zone. The reason why the fracture occurred at fusion zone was that the hardness of fusion zone was lower than that of base material and heat affected zone. The correlation among maximum load and hardness of fusion zone and EST at fractured position was $R^2=0.9338$. Therefore, this means that hardness and EST can have great impact on maximum load.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.185-188
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• 2006

The sea water pipe of engine room in all kinds of ships is being surrounded with severe corrosive environment. Therefore it's leakage part due to corrosion is inevitably prevented by various welding method. In this case corrosion property of welded zone may be considerably different by each welding materials. In this study corrosion resistance of the welded zone of sea water pipe with some welding materials such as shielded metal arc welding materials, inert gas arc welding materials was investigated with electrochemical method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.293-300
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• 1999

A mathematical model for the analysis of roll gap phenomena in strip temper rolling process is described. The mechanical peculiarities of temper rolling process, such as high friction value and non-circular contact arc, low reduction and non-negligible entry and exit elastic zones as well as central restricted deformation (preliminary displacement or sticking) zone etc., are all taken into account. The deformation of work rolls is calculated with the influence function method and arbitrary contact arc shape is permitted. The strip deformation is modeled by slab method and the entry and exit elastic deformation zones are included. The restricted deformation zone near the neutral point is also considered. The concept and the calculation method of limiting preliminary displacement are used to determine the length of the central restricted deformation zone. The comparison of the model results with the measured mill data is also made.

• Journal of the Korean Society of Safety
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• v.5 no.3
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• pp.33-38
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• 1990

In this study, the transient temperature distribution of welded zone was analyzed by Finite Element Method for the optimal design of weldment. This study was carried out for the steel plate 8mm thick, 100mm wide, 100mm long that butt weld. The weld was made with a heat input of 2,250 joule/cm(arc current ： 180 amperes ； arc voltage ：25 volts ； and arc travel steed ： 0.28 cm/sec). In the analysis of temperature, cooling in the welded zone by the conduction between materal was almost completed at 600 sec when a unique temperature field was formed. after this, the material was gradually cooled by the heat transfer to the circumference. In the early phase the temperature in base metal zone is little changed. but after the rise in temperature the whole area is cooled gradually.

• Journal of Welding and Joining
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• v.31 no.1
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• pp.58-64
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• 2013

The following results were obtained, microstructures and tensile properties in arc brazed joints of DP(dual phase) steel using Cu-5.3wt%Sn insert metal was investigated as function of brazing current. 1) The Fusion Zone was composed of ${\alpha}Fe+{\gamma}Cu$ and Cu23Sn2. The reason for the formation of these solid solutions. Despite, Fe & Cu were impossible to solid solution at room temperature. It's melting & reaction to something of insert metal & Base Metal (DP Steel) by Arc. Brazing Process has faster cooling rate then Cast Process, Supersaturated solid solution at room temperature. 2) The increase Hardness of Fusion Zone was directly proportional to the rise of welding current. Because, ${\alpha}Fe+{\gamma}Cu$ phase (higher hardness than the Cu23Sn2.(104.1Hv < 271.9Hv)) Volume fraction was Growth, due to increasing the amount of base metal melting by High current. 3) The results of tensile shear test by Brazing, All specimens happen to fracture in Fusion Zone. On the other hand, when Brazing Current increasing tend to rise tensile load. but it was very small, about 26-30% of the base metal. 4) The result of fracture analysis, The crack initiate at Triple Point for meet to Upper B.M/Under B.M/Fusion Zone. This Crack propagated to Fusion zone. So ruptured by tensile strength. The Reason to in the fusion zone fracture, Fusion zone by Brazing of hardness (strength) was very lower then the base metal (DP steel). In addition the Fusion Zone's thickness in triple point was thin than the base metal's thickness in triple point.