• Proceedings of the KWS Conference
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• 2002.05a
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• pp.266-268
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• 2002

• Journal of Welding and Joining
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• v.33 no.2
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• pp.69-77
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• 2015

High strength steels have been continually being developed to improve in fuel economy in automotive and ensure safety of passengers. New bonding and welding methods have been required for improving weldability on high strength steels. In this study, resistance spot welding and Weld-bond with nugget diameters of 4.0mm, 5.0mm, 6.0mm and 7.0mm were produced and tested, respectively. In order to confirm the effect of nugget diameters on tensile shear characteristic of the Weld-bond, tensile shear characteristics of Weld-bond were compared with those of resistance spot welding and adhesive bonding. Peak load of Weld-bond were increased as the nugget diameter increases. After appearing maximum peak load continuous fracture followed with second peak owing to load being carried by resistance spot weldment. Fracture modes of the adhesive layer in Weld-bond fractures were represented by mixed fracture mode, which are cohesive failure on adhesive part and button failure at resistance spot welds. The results showed that the tensile shear properties can be improved by applying Weld-bond on TRIP steel, and more apparent with nugget diameter higher than 5${\surd}$t.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5419-5424
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• 2014

A weld scallop is a small quadrant or half circle type hole installed in the weld line cross area for easy welding operation. Many types of T-bars with a scallop can be welded in a block assembly stage in shipbuilding. The difficulties arise from the fact that scallops are to be filled by build-up welding after welding of the cross line is complete. In this study, a non-scallop block joint welding method was developed using special type CBM (ceramic backing material). The wedge shaped CBM was devised to insert a CBM into just the V groove of weld line cross area without weld scallop. A saw-toothed shape was adopted for easy cutting of the unnecessary part in the CBM fitting process. The applicability of the developed method was verified through welding experiments based on the yard welding conditions.

• Journal of Welding and Joining
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• v.32 no.2
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• pp.29-36
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• 2014

Recently, in order to enhance the function and usefulness of products, cladding of dissimilar materials that maximizes the performance of the material is being widely used in all areas of industry as an important process. Clad steel plate, produced by cladding stainless steel plate, an anticorrosive material, on carbon steel plate, is being used to produce pressure vessels. Stainless steel plate has good corrosion resistance, and carbon steel plate has good rigidity and strength; clad steel can satisfy all of these qualities at once. This study aims to find the ${\delta}$-ferrite behavior, mechanical properties, structure change, integrity and reliability of clad steel weld on hot rolled steel plates. For this purpose, multi-layer welding, repair welding and post weld heat treatment were implemented according to welding procedure specifications (WPS). In order to observe the mechanical properties and toughness of clad steel weld zone, post weld heat treatment was carried out according to ASME Sec. VIII Div.1 UW-40 procedure for post weld heat treatment. With heat treatment at $625^{\circ}C$, the hold time was used as the process variable, increased by intervals that were doubled each time, from 80 to 1,280 min. The structure of weld part was typical cast structure; localized primary austenite areas appeared near central vermicular ferrite and fusion line. The heat affected zone showed rough austenite structure created by the weld heat input. Due to annealing effects of heat treatment, the mechanical properties (tensile strength, hardness, impact value) of the heat affected area tended to decrease. From the results of this study, it is possible to conclude the integrity of clad steel welds is not affected much in field welding, repair welding, multi-layer welding, post weld heat treatment, etc.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.729-737
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• 2008

As increasing demand on marine structures and skyscrapers, a deep shaft pile foundation is more to be used for the place having weak ground strength. Because heavy horizontal force is generally applied on upper part of pile foundation used in civil or architectural construction, steel pile is largely used with its high resistance to shear force and bending moment, and its capability to carry heavy loads. The steel pile has advantage in good constructibility, high applicability on site and easy handing, but has disadvantage in cost, more expensive than other material pile. This study is about the Composite pile that makes economical construction possible by reducing material cost of pile; using steel and PHC pile simultaneously while preserving the advantage of steel pile that large resistance to horizontal force and bending moment. A Non Welding connection method is applied to this composite pile and this method could reduce the cost and period of construction and could increase the quality of construction by solving the problem of current welding method and by improving the workability of pile connection. In this study, characteristics of driveability of non welding composite pile is analyzed prior to main project while the purpose of main project is proving the applicability of Non Welding Composite Pile by conducting various kind of loading test to analyze the characteristics behaviour of Non Welding Composit Pile and by verifying stability of non welding connection pile.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.1
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• pp.28-36
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• 2020

In shipbuilding industry, there is conducting most of works by welding at the shipyard, and the volume of welding is increasing with international trends of green ships. Welding joint is guaranteed quality through non-destructive testing (NDT). The manual welding inspection report is produced by identifying the drawings designed, which results in losses the many workforce and occurs human errors. To solve these problems, this paper covers a system that reports on inspection information is automatically generation by input data based on shipbuilding-specific CAD. The developed system analyzes the shape data from drawings of modeling. Also, the system determines welding joints through expansion of the part boundary and generates tag numbers. In addition, it provides the function to automatically extract the information needed for inspection such as weld length, thickness and etc. We conducted test to verify the usefulness of the developed system and confirmed that the welding inspection information extracted through system matches the information shown in drawings of modeling.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.2
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• pp.120-126
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• 2015

Recently, the ever-increasing use of fossil fuels for rapid industrial development and population significantly caused an environment pollution and global warming such as climate change. So research and development of sustainable and eco-friendly energy have been performed. Especially the interest in nuclear fusion fuel was significantly increased from the developed countries. The system of fusion energy production was tritium separation, storage and delivery, and purification. Republic of Korea is in charge of Storage and Delivery System (SDS) in the International Thermonuclear Experimental Reactor (ITER). Welding part of the SDS bottles for storing the tritium is known to be susceptible to hydrogen embrittlement. In this study, conducted a study for the relaxation of the stability and hydrogen embrittlement of the weld area. The hydrogen heat treatment was processed through the Pressure-Composition-Temperature (PCT) device according to the time variation. Also mechanical properties such as impact test and hardness test according to using the alkaline cleaning liquid for hydrogen embrittlement relief and the fracture was observed by scanning electron microscopy (SEM) after the mechanical properties evaluation.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.1
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• pp.96-102
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• 2012

The current establishment of car engineering plastic piping polyethylene (PE) tube used as bonding state or part of the health or safety of fusion is very important. A part of these fusion methods to determine the soundness of the short-term trials and long-term tests can be largely classified. Typical tests included short-term strength, tensile strength, impact strength, compressive strength, resiliency and compression. Polyethylene (PE) pipes installed in the domestic terms of overall penetration rate of 45% has been used. However, polyethylene (PE) pipes have reliability problems, and these occurs mostly in part by defective welding. Therefore, the test is necessary for safety. Non-destructive methods (ultrasonic testing) are difficult to be used. Therefore, Polyethylene (PE) pipe are used. Fusion of thses materilas is necessary in these field however, its technical, and basic research has not been studied well. In this research, short-term strength of welding parts, its tensile strength, hardness, fatigue, and microstructure have been analyzed to find the optimum process conditions to improve mechanical properties.

• Journal of Welding and Joining
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• v.34 no.3
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• pp.61-68
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• 2016

Characteristics of dissimilar metal welds between alloy steel ASTM A387 Gr. 91 and carbon steel ASTM A516 Gr.70 made with Flux cored arc welding(FCAW) have been evaluated in terms of microstructure, mechanical strength, chemical analysis by EDS as well as corrosion test. Three heat inputs of 15.0, 22.5, 30.0kJ/cm were employed to make joints of dissimilar metals with E91T1-B9C wire. Post-weld heat treatment was carried out at $750^{\circ}C$ for 2.5 h. Based on microstructural examination, tempered martensite and lower bainite were formed in first layer of weld metal. The amount of tempered martensite was decreased and the amount of lower bainite was increased with increasing heat input and layer. Heat affected zone of alloy steel showed the highest hardness due to the formation of tempered Martensite and lower Bainite. Tensile strengths of dissimilar welds decreased with increasing heat inputs. Dissimilar welds seemed to have a good hot cracking resistance due to the low HCS index below 4. The salt spray test of dissimilar metals showed that the corrosion rate increased with increasing heat inputs due to the increase of the amount of lower Bainite.

• Journal of Welding and Joining
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• v.35 no.3
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• pp.68-74
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• 2017

Characteristics of dissimilar metal welds between alloy steel ASTM A387 Gr. 91 and carbon steel ASTM A516 Gr.70 made with Flux cored arc welding(FCAW) have been evaluated in terms of microstructure, mechanical strength, chemical analysis by EDS as well as corrosion test. Three heat inputs of 15.0, 22.5, 30.0kJ/cm were employed to make joints of dissimilar metals with E71T-1C wire. Post-weld heat treatment was carried out at $750^{\circ}C$ for 2.5 h. Based on microstructural examination, Intragranular polygonal ferrite and grainboundary ferrite were formed only in first layer of weld metal. Another layers consisted of acicular ferrite and $Widmannst{\ddot{a}}tten$ ferrite. The amount of acicular ferrite was increased with decreasing heat input and layer. Heat affected zone of alloy steel showed the highest hardness due to the formation of tempered martensite and lower bainite. Lower and upper bainite were formed in heat affected zone of carbon steel. Tensile strengths of dissimilar metal welds decreased with increasing heat inputs. Dissimilar metal welds showed a good hot cracking resistance due to the low HCS index below 4. The salt spray test of dissimilar metals welds showed that the weight loss rate by corrosion below 170 hours was decreased with increasing heat inputs due to the increase of the amount of acicular ferrite.