• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.5
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• pp.413-420
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• 2014

Although the transfer forming process has various advantages, it is also inefficient for the use of multiple press machines, especially for small part sizes. In this study, a new forming process was proposed to use multiple tandem dies in a single press machine. A rotary transfer forming device was developed to combine the advantages of the progressive and transfer forming process. In this study, a detailed forming process using this device was analyzed, and the device was designed to perform four series of tandem forming processes in a single press. In order to analyze the feasibility of this forming process, simple forming dies were made. As a result, the position accuracy was 4 arcsec, and the forming speed reached up to 20 strokes per minute. It is thought that this rotary transfer forming device can help to save initial setup costs through the more efficient use of space in a press machine.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.4
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• pp.126-133
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• 2015

To enhance the productivity and quality of the compound process of progressive dies and transfer dies, the semi-progressive method is applied in the material supply step to produce blanks, and then the transfer method is applied. Parts are transferred among processes by means of the finger and transfer bar in the transfer die, and the final seat cushion panel is produced. The main challenge in the current study is how to deform a seat cushion panel while meeting the design specifications without any defects. In order to obtain this technology, a sheet metal-forming simulation and die forming of the seat cushion panel were adopted; as a result, a compound die-forming technology for the automotive seat cushion panel, combining both semi-progressive die and transfer die for continuous production, was successfully developed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.556-559
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• 2008

In this study, the failure in circular cup deep drawing simulation at warm temperature is predicted using forming limit diagram (FLD). The FLD is used in sheet metal forming analysis to determine the criterion for fracture prediction. The simulation with heat transfer of circular cup deep drawing at warm temperature was conducted. To predict the failure, the simulation with heat transfer used FLD at temperature in the vicinity of maximum thinning. The result of the simulation with heat transfer shows that the drawn depth increases with increasing temperature and is in accord with the experimental results above $150^{\circ}C$. The FLD provides a good guide for the failure prediction of warm forming simulation with heat transfer.

• Transactions of Materials Processing
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• v.17 no.7
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• pp.501-506
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• 2008

In this study, a forming magnesium alloy circular cup was simulated accounting for heat transfer at elevated temperatures. In order to predict the failure of magnesium alloy sheet during simulation, the forming limit diagram, which is used in sheet metal forming analysis to determine the criterion for failure, was investigated. For the failure prediction in the simulation accounting for heat transfer, the forming limit diagram for a temperature the same as the temperature of the blank element was used. The result of the simulation showed that the drawn depth increases with the increase of the die-holder temperature, and is in accord with the experimental results above the die-holder temperature of $150^{\circ}C$. The forming limit diagram provided a good guide for the failure prediction of warm forming simulation accounting for heat transfer. In addition, the effect of the tool shoulder radius on the drawn depth at various tool temperatures is verified using the simulation conditions which agreed with the experimental results.

• Journal of Photoscience
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• v.12 no.3
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• pp.155-162
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• 2005

Results of studies of SET-promoted dipole-forming photochemical group transfer reactions of phthalimide and ${\alpha}-ketoamide$ derivatives are discussed. Azomethine ylide forming photochemical reactions, which are initiated by intramolecular SET from tethered silylmethyl-, carboxymethyl-, and ${\beta}-hydroxyethyl$ containing electron donors to excited states of phthalimides, related maleimides, and conjugated imides, are presented first. Following this, investigations of regioselective 1,4-dipole forming photochemical reactions of N-trialkylsilylmethyl- and N-trialkylstannyl-${\alpha}$-ketoamides are described.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.66-69
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• 2004

A new concept of multi-point dieless elasto-forming method has been developed to make various shape of curved surface without conventional dies. The developed dieless elasto-forming system consists of discrete punches controlled by servo motors and various kinds of elastomers(rubber and foam). To predict optimal position of punch elements, DTF(deformation transfer function) was introduced, and FEM analysis was carried out. The optimal arrangement of elastomer was selected considering characteristics of each elastomer, and a desired concave shape was formed. The experimental results were consistent with the numerical ones.

• Transactions of Materials Processing
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• v.28 no.1
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• pp.5-14
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• 2019

In order to reduce the weight of automobile parts, automobile parts using aluminum alloy are being developed. Aluminum alloy for automobile parts is mainly made of Al6xxx (Al-Mg-Si) type alloy, which is excellent in hot forming property, and it can increase mechanical properties by the use of heat treatment. In this study, hot forming was performed using Al6082. Before the hot forming, the forming analysis was performed using the DEFORM-3D finite element analysis program in this case. For the forming analysis, the heat transfer coefficient was derived from the experiment, and the forming analysis was performed by applying it. At the forging analysis, the temperature of Al6082 material was set to 813K and that of the mold was set to room temperature. After the forging analysis, the experiment was performed, and the forging analysis and the experimental results were compared.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.62-65
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• 2002

A dieless forming system which consists of hydraulic punch elements and elastomer/fluid pads, was developed for sheet metal forming. 2-D curved surface forming was carried out using open-loop, closed-loop, and repeated forming method. Closed-loop exhibited higher decision than open-loop forming. Repeated forming also showed reduced spring back and possibility of high precision.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.11
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• pp.1190-1198
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• 2012

A hot forming of large thick Al plate using a grid-type hybrid die is a process to make a shell plate for the production of a spherical LNG tank. This process is characterized by using a grid-typed die with an additional air cooling system for reducing the cooling time of the heated plate after hot forming. The process consists of the plate's feeding, heating, forming and cooling in detail and each of them is continuously performed along the rail. This paper was designed to propose the analytical and experimental methods for determining the convection and interfacial heat transfer coefficients required in hot forming analysis of Al plate. These values in the analysis are to reproduce numerically the cooling performance of grid-typed die and cooling device. Interfacial heat transfer was obtained from the heat transfer experiments for different pressures and inverse analysis method. To verify the efficiency of the coefficient values obtained from above methods, FE analysis and experiment of the hot spherical-forming process were conducted for a small-scaled model. The convection coefficient was also calculated from flow analysis of air released by cooling device within grid-typed die using ANSYS-CFX.

• Transactions of Materials Processing
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• v.22 no.2
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• pp.101-107
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• 2013

The heat transfer characteristics between die and sheet and die and coolant are important parameters in hot press forming process. The determination of the quenching time that guarantees full martensitic transformation requires proper understanding of these heat transfer characteristics. The contact area changes drastically during the quenching process due to volume changes of both die and sheet by temperature drop as well as phase transformation. Several types of modeling techniques are tested in order to select the most suitable. The effect of quenching time as well as die heat conductivity on martensitic transformation is investigated and predictions are compared to experimental results.