• 보존과학연구
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• s.26
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• pp.57-75
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• 2005

The burial custom in the Youngsan river area was to build a jar-coffin and lay the body in state, however the methods in building and moulding the massive jar, as well as in which kiln it was made has not been examined precisely. Thus, this research not only investigates previous results related to the manufacturing methods of massive jar-coffins, but also examines samples that were excavated and collected. The clay used to produce jar-coffin consists a large portion of unglazed qualities, which was split-moulded from the bottom up to the mouth area. The interior was finished by applying water, whereas the exterior was decorated by regularly pasting or stamping in parallel with a lattice design. It can be presumed that the finished jar-coffin was not moved, but the ceiling and walls were built around it as a kiln, for the jar-coffin to be oxidized or to reduce the flame condition in a temperature approximately $700~1,200^{\circ}C$The results from the research, however, show limitations to exploit the exact manufacturing method, therefore there is a need for in-depth examinations: mineralogical investigation on a large amount of jar-coffin samples through a polarized light microscope; substance analysis using various equipments; speculation on the temperature in the place of production and the flame inside.

• Laser Solutions
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• v.13 no.3
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• pp.19-26
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• 2010

In this study, fundamental experiment was conducted with various strength of UHSS (Ultra High Strength Steel) by $CO_2$ laser. And then, butt and lap joint laser welding with boron alloyed steel and Al-Si coated boron alloy steel have been done by changing laser beam feature, existence of gap and existence of coating layer to know welding characteristics of those materials. As a result, in case of fundamental experiment with various strength steel, hardening was found in the weld metal of all tested materials and softening was found at the heat affected zone of SGAFC 1180. In case of laser butt welding of UHSS, mechanical properties was improved by using small laser beam diameter and Al-Si coating layer caused fracture of weld metal. In case of laser lap welding of UHSS, Al-Si coating layer resulted in formation of intermetallic compound at the fusion boundary where fracture occurred. Al-Si coating layer caused lowering mechanical properties of weld metal.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.4691-4696
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• 2010

The This research paper deals with research on the 3D strip layout design of HEV UV terminal by utilizing the Cimatron Die Design, an automation module. To ensure smooth stamping of the product, strip layout was corrected for 33.5 degrees of slope, and blank layout of the double-width, 1-line, 1-pull out inner carrier was then optimized as a single arrangement. To mass-produce two different terminals from one common die, 3D strip layout design and die design were completed in 29 different processes.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.3
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• pp.199-205
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• 2016

A thin sheet of metal with corrugated structures has been utilized in various devices: heat exchangers, separators in fuel cells, and many others. However, it is not easy to fabricate thin corrugated structures using a single-step stamping process due to their geometrical complexity. To solve this problem, firstly, a plate type heat exchanger was redesigned to attain the optimal value of aspect ratio and the optimal shape of corrugated structures for the actual loading conditions. A forming analysis of the corrugated plate was then carried out to determine the process parameters. From this work, the optimal value of aspect ratio was found to be 4.6. In addition, the process parameters of heat exchanger forming were optimized using the optimal value of aspect ratio, and the analytical results were evaluated through experiments. The results obtained indicated good agreements between them.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.7
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• pp.43-50
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• 2012

Database for the information of the shape accuracy is constructed with the finite element stamping analysis of the center pillar member. Analyses are carried out in order to investigate the effect of tool compensation on the product quality previously performed by an expert in the press shop. The compensation procedure is provided with three sequences for improving shape accuracy of the member by reducing the amount of springback. The analysis result shows that shape inaccuracy in the product is caused by sagging and twisting phenomena from displacement of the section part due to excessive amount of springback. From the database with springback analyses, design modification guidelines are proposed for improving the shape accuracy. The guideline is directly applied to a member with the similar shape and the sound product is obtained successfully reducing the amount of springback.

• Journal of the Korean Society for Heat Treatment
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• v.29 no.4
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• pp.181-189
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• 2016

The variation in microstructure and mechanical properties during heat treatment was examined in a series of 0.27% C-1.0% Si-1.5% Mn steels with chromium contents in the range of 0 to 1.0 wt%. It was found that chromium decreased the martensite packet size through the austenite grain refinement and increased tensile strength in the as-quenched steel, about 70 MPa per 1.0 wt%. The 0.27% C-1.0% Si-1.5% Mn-1.0% Cr steel showed tensile strength of 1700 MPa in the as-quenched steel. The 0.27% C-1.0% Si-1.5% Mn-1.0% Cr steel revealed a full martensitic structure after air cooling from $900^{\circ}C$ to room temperature, showing air hardening characteristics. Tempering at $150^{\circ}C$ slightly decreased the tensile strength and increased elongation, which is in a good agreement with impact toughness result.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.2
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• pp.21-26
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• 2000

Flow forming is a chipless metal forming method for axi-symmetric parts, which is more economical. efficient and versatile method of producing parts than the other sheet metal forming process such as stamping or deep drawing. In this study, flow forming process with 1-Roller is applied to produce auto-transmission parts of automobiles which have been produced by Press drawing process so far. It can be known that flow forming process is applicable to the flexible manufacturing system due to the low cost for the establishment and it can be combined with press forming process to promote productivity and to improve the accuracy of products.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.136-140
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• 2000

It is desirable to predict springback quantitatively and accurately for the tool and process design in sheet stamping operations, however, it is blown very difficult. The result of springback analysis by the finite element method is sensitively influenced by numerical factors such as blank element size, number of integration point, punch velocity, contact algorithm etc. In the present work, a parametric study by Taguchi method is performed in order to evaluate the influence of numerical factors on springback Quantitatively and to obtain the combination of numerical factors which yields the best approximation to experimental data. Since springback is determined by the residual stress after forming process, it is important to evaluate stress distribution accurately. The oscillation in the time history curve of stress obtained by explicit FEM says that the stress solution at termination time is in very unstable state. Therefore, a variability study is also carried out in this study in order to assess the stability of implicit springback analysis starting from the stress solution by explicit forming simulation. The 2D draw bending process, one of the NUMISHEET '93 benchmark problems, is adopted as an application model.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.124-127
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• 2000

The finite element analyses of the wrinkling initiation and growth in the sheet metal forming process provide the detailed information about the wrinkling behavior of sheet metal. The direct analyses of the wrinkling initiation and growth, however, bring about a little difficulty in complex industrial problems because it needs large memory size and long computation time. For the description of wrinkling growth, the mesh elements should be sufficiently small and the size of finite element matrix becomes large. In the static implicit finite element method therefore, the direct analysis of wrinkling growth in a complex sheet metal forming process is rather difficult. From the industrial viewpoint of tooling design, the readily available information of possibility and location of wrinkling is sometimes more preferable to the detailed time-consuming information. In the present study, therefore, the wrinkling factor that shows locations and relative possibility of wrinkling initiation is proposed as a convenient tool of relative wrinkling estimation based on the energy criterion. The location and relative possibility of wrinkling initiation are predicted by calculating the wrinkling factor in various sheet metal forming processes such as cylindrical cup deep drawing, spherical cup deep drawing, and elliptical cup deep drawing. The wrinkling factor is also implemented in the analysis of the door inner stamping process to predict wrinkling.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.186-191
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• 2001

Spinning process is a chipless metal forming method for axi-symmetric parts, which is more economical, efficient and versatile method for producing parts than the other sheet metal forming process such as stamping or deep drawing. In this study, a fundamental experiment was conducted to improve productivity with process parameters such as tool path, angle of roller holder($\alpha$), feed rate($\gamma$) and corner radius of forming roller(Rr). These factors were selected as variables in the experiment because they were most likely expected to hale an effect on spring back. The empirical results were analyzed to know how much spring back was affected by these factors. And also thickness and diameter distribution of a multistage cup obtained by spinning process were observed and compared with those of a commercial product produced by conventional deep drawing.