• Proceedings of KOSOMES biannual meeting
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• 2007.11a
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• pp.121-124
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• 2007

• Proceedings of the KWS Conference
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• 1994.10a
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• pp.134-137
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• 1994

In this study, The mean weld current is used to correct depth direction, and weight-value, specially devised to check right-left deviation by placing more weight on the left- and right-most part of weld current during weaving, to correct weaving direction. The methodology of “design of experiments” was introduced to find out dorminant weld parameters affecting these for values.

• International Journal of Ocean System Engineering
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• v.3 no.2
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• pp.95-101
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• 2013

This study is mainly interested in roundness of a circular moonpool structure in FPSO. Because this structure needs abrasion-resistance on inner wall, we should do buttering widely and deeply by using Inconel. But a general buttering can cause a severe distortion at structures. If someone can analyze the roundness by thermal distortion under Inconel over-lay, an erection policy can be established. In this study, shrinkage methodology by designed stress-strain curve was used and the result allowed deciding an appropriate block size.

• Korean Journal of Heritage: History & Science
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• v.35
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• pp.138-158
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• 2002

To compare and analyze technical system related to manufacturing of ironware during the period of the Three Kingdoms, an analysis was conducted on the minute system of metalwork, as study objects, of the remains of the Mt. Wolpyeong fortress wall in Daejeon in the period of capital during the era of the Three Kingdoms in the 5th century, the Sanwol-ri remains in the 6th century in Gunsan and the remains of ironware excavated from the great ancient tomb of Hwangnam of the Silla dynasty in the 5th century. The result of analysis shows that in the most of the casting products, the minute system of white cast iron were contained. While the iron part of decarbonization was in the system by casting as white cast iron in the central part, on the surface layer it was turned out that comparatively uniform 100% pearlite system of about 1~2mm degree was existing. The part of pearlite on the surface layer was caused by decarbonization, which appears in all the parts of blade front end and handle. Therefore, it was found that the iron part of decarbonization was manufactured by casting, and then was processed at the high temperature by decarbonization. For the products of forging, after processing the products on the basis of pure iron for materials, they manufactured the ironware that raises the strength by carbonizing that keeps carbon infiltrated on the necessary part, by the method of black smith welding that add pure iron to steel, or by varying the method of heat processing onto the part required of strength. Though limited, we could understand that the technical systems for manufacturing skill of ironware in the areas of Baekje and Silla were different each other. In the technical system for Hwangnam great ancient tomb in the Silla area, it is found that they had raised the strength on the necessary part by applying the steelmaking method of carbonizing in the last stage of production of products, in the meantime in Baekje area, it appears that they had produced steel in advance in the first stage of production of the products, and used the produced steel only to the necessary part.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1179-1185
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• 2011

Cold and hot-rolled carbon steel sheets are commonly used in railroad cars or commercial vehicles such as the automobile. The sheets used in these applications are mainly fabricated by spot welding, which is a type of electric resistance welding. However, the fatigue strength of a spot-welded joint is lower than that of the base metal because of high stress concentration at the nugget edge of the spot-welded part. In particular, the fatigue strength of the joint is influenced by not only geometrical and mechanical factors but also the welding conditions for the spot-welded joint. Therefore, there is a need for establishing a reasonable criterion for a long-life design for spot-welded structures. In this thesis, ${\Delta}P-N_f$ relation curves have been used to determine a long-life fatigue-design criterion for thin-sheet structures. However, as these curves vary under the influence of welding conditions, mechanical conditions, geometrical factors, etc. It is very difficult to systematically determine a fatigue-design criterion on the basis of these curves. Therefore, in order to eliminate such problems, the welding residual stresses generated during welding and the stress distributions around the weld generated by external forces were numerically and experimentally analyzed on the basis of the results, reassessed fatigue strength of gas welded joints.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.1
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• pp.109-115
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• 2019

In arc-welding applying to the present automobile part manufacturing process, a wrist-hollow type arc welding robot can shorten the welding cycle time, because feedability of a welding wire is not affected by a robot posture and thus facilitates high-quality arc welding, based on stable feeding with no entanglement. In this paper, we will propose the optimization of wrist design for a wrist-hollow type 6-Axis articulated robot. Specifically, we will perform the investigation on the optimized design of inner diameter of hollow arms (Axis 4 and Axis 6) and width of the upper arm by using the simulation of robot motion characteristics, using a Genetic Algorithm (i.e., GA). Our simulations are based on $SolidWorks^{(R)}$ for robot modeling, $MATLAB^{(R)}$ for GA optimization, and $RecurDyn^{(R)}$ for analyzing dynamic characteristics of a robot. Especially $RecurDyn^{(R)}$ is incorporated in the GA module of $MATLAB^{(R)}$ for the optimization process. The results of the simulations will be verified by using $RecurDyn^{(R)}$ to show that the driving torque of each axis of the writs-hollow 6-axis robot with the optimized wrist design should be smaller than the rated output torque of each joint servomotor. Our paper will be a guide for improving the wrist-hollow design by optimizing the wrist shape at a detail design stage when the driving torque of each joint for the wrist-hollow 6-axis robot (to being developed) is not matched with the servomotor specifications.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.397-400
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• 2004

The direct extrusion with porthole die can produce condenser tube which has the competitive power in costs and qualities compared with the existing conform extrusion. In general, porthole die extrusion has a great advantage in the forming that produces the hollow sections difficult to produce by conventional extrusion with a mandrel on the stem. Especially, condenser tube manufactured by porthole die belongs to sophisticated part and demands tighter dimension tolerance and higher surface finish than any other part. In order to confirm the general of porthole die extrusion, we perform the 3D FE analysis of hot porthole extrusion in non-steady state by using DEFORM 3D and investigate a pattern of elastic deformation for porthole die through the stress analysis using ANSYS 5.5 during extrusion process.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.6
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• pp.830-836
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• 1986

In this study, the effect of hydrogen absorbed in welding process on the fatigue behaviour of the weld bond was quantitatively made clear. The influence of cyclic loading rate on the fatigue characteristics of the manual arc weld bond was inspected under the condition of constant amount of hydrogen. Moreover, the fatigue cracking mechanism concerning the diffusible hydrogen in the welded part was discussed in connection with fractographs of the fracture surfaces.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.43-45
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• 2005

For application of advanced high strength hot-rolled steels (i.e. DP590, DP780) to automotive lightweight chassis parts, various technologies from design to forming test, optimization of welding condition and investigation of coating properties were tried. The target part of this study was automotive rear sub frame and we could make $16.8\%$ weight reduction by reducing the material thickness and optimizing the design. In addition, the formability and weldability of the newly developed AHSS, DP780, were evaluated.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.43-45
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• 2005

A precise bonding technique, transmission laser bonding using energy transfer, for polymer micro devices is presented. The irradiated IR laser beam passes through the transparent part and absorbed on the opaque part. The absorbed energy is converted to heat and bonding takes place. In order to optimize the bonding quality, the temperature profile on the interface must be obtained. Using optical measurements of the both plates, the absorbed energy can be calculated and heat transfer model was applied for obtaining the transient temperature profile. The transmission laser bonding has a potential in the local precise bonding in MEMS or Lab-on-a-chip.