• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.313-317
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• 2009

Electromagnetic forming(EMF) is a high-velocity forming process which uses electromagnetic Lorentz force. Advantages of this forming technique are improved formability, reduction in wrinkling, non-contact forming and applications of various forming process. But the application of electromagnetic forming technique is still limited in industry. Thus for continuous research and development of technique based on experiments, develop the forming equipment and carry out the forming experiments for validation of forming equipment.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.35-43
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• 2001

As the demands for lightweight construction and precision grow, there is an increasing interest on hydroforming technology. This paper deals with designing automobile subframe for applying welded blanks hydroforming. In applying welded blanks hydroforming to automobile subframe, it is a serious problem that blanks wrinkle in deformed shape. To suppress wrinklings in blanks, the sections of the die where blanks wrinkled is modified. In addition to this, it is intended that the sum of thickness variation about wrinkling regions be minimized. For this purpose, parameters for influencing formability are selected and evaluated using orthogonal array. Among these parameters, parameters having a major effect on formability are selected again. Using CCD(central composite design) with the selected parameters, response surface is build up and optimal design is performed.

• Transactions of Materials Processing
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• v.7 no.5
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• pp.496-504
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• 1998

The eccentric extrusion and bending process for the forming of the curved rectangular hollow tube is newly developed. Generally the bending process of hollow tube is the secondary process followed by the extrusion process of the hollow tube from the round billet. So many defects such as wrinkling and the difference of wall thickness can be happened during the secondary bending process. In order to avoid the defects the new process named as "the eccentric extrusion and bending process" is suggested and applied to the U-bending of rectangular hollow tube. In this paper the kinematically admissible velocity field between the dies surface and the internal plug boundary surface s developed for the curving velocity. By the using of this curving velocity field the curvature of extruded products can be calculated with the parameters such as eccentricity dies length friction constant aspect ratio.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.277-280
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• 2003

It was investigated that the "ㄱ" type angle product could be bended with a curvature during extrusion by extru-bending process. The bending process for the "ㄱ" type angle product can be developed by the hot metal extru-bending machine with the two punches moving in the different velocity. Because of non-symmetry of product, it is important to design the ruled surface contour of dies cavity for the welding and bending with two billets. So it is designed that the multi-hole container has two non-symmetric holes and non-symmetric contour of dies entrance. The results of the experiment show that "ㄱ" type angle product can be bended by the extrusion process and that the curvature of the product can be controlled by the velocity of punch and that the defects such as the distortion of section and the thickness change of the product and the folding and wrinkling of the product did not happen after the bending processing by the extrusion bending machine.

• Transactions of Materials Processing
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• v.19 no.1
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• pp.38-43
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• 2010

Electromagnetic forming (EMF) method is one of high-velocity forming processes, which uses electromagnetic Lorentz force. Advantages of this forming technique are summarized as improvement of formability, reduction in wrinkling, non-contact forming and applications of various forming process. In this study, the EMF apparatus is developed. It is designed to be stored in 10 capacitors connected in parallel, each with a capacitance of $50{\mu}F$ and maximum working voltage of 5kV. The system has capacitance of $500{\mu}F$ and maximum stored energy of 6.25kJ. And EMF experiments are carried out to verify the feasibility of the EMF apparatus, which has enough forming force from the results of EMF experiment. In addition, peak current carrying a forming coil is predicted from theoretical background, and verified the predicted value compared with experimental value using the current measurement equipment. Consequently, EMF apparatus developed in this study can be applied to various EMF researches for commercialization.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.604-609
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• 2001

In the sheet metal forming process, the drawbead is used to control the flow of material during the forming process. The drawbead provides proper restraining force to the material and prevents defects such as wrinkling or breakage. For these reasons, many studies for designing the effective drawbead have been conducted. For the analysis, the numerical method called the static-explicit finite element method was used. The finite element analysis code for this method has been developed and applied to the drawbead process problems. In result, convergence problem and computation time due to large non-linearity in the existing numerical analysis methods were no longer a critical problem. Futhermore, this approach could treat the contact friction problem easily by applying very small time intervals. It is expected that various results from the numerical analysis will give very useful information for the design of tools in sheet metal forming process.

• Food Science and Biotechnology
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• v.17 no.5
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• pp.1102-1105
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• 2008

The structural change and leakage of cellular substances of Saccharomyces cerevisiae attributed by high hydrostatic pressure (HHP) treatment were observed with scanning electron microscopy (SEM). S. cerevisiae (ATCC16664) was inoculated in apple juice for 10 min at $23^{\circ}C$ and the apple juice treated at 138, 207, 276, 345, and 414 MPa pressure for 30 sec at $23^{\circ}C$. Increased of roughness, elongation, wrinkling, and pores on yeast cell surfaces, the yeast cell walls were severely damaged by HHP treatment from 276 to 414 MPa. Inactivation of S. cerevisiae by HHP is dependent on structural changes on the cell walls observed with SEM.

• Archives of Plastic Surgery
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• v.42 no.2
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• pp.111-125
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• 2015

Patients with thick skin mainly exhibit the aging processes of sagging, whereas patients with thin skin develop wrinkles or volume loss. Asian skin is usually thicker than that of Westerners; and thus, the sagging of skin due to aging, rather than wrinkling, is the chief problem to be addressed in Asians. Asian skin is also relatively large in area and thick, implying that the weight of tissue to be lifted is considerably heavier. These factors account for the difficulties in performing a facelift in Asians. Facelifts can be divided into forehead lift, midface lift, and lower face lift. These can be performed individually or with 2-3 procedures combined.

• Journal of the Korean Society for Precision Engineering
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• v.4 no.4
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• pp.72-83
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• 1987

In axisymmetric tube reducing process for thin sheet metal tubes, the reduction ration of diameter is an important factor in the process design. For very thin sheet metal tubes, tube reducing cannot be successfully employed due to wrinkling of the edge portion of a tube as well as due to buckling of its rest portion. In the present study, thin sheet metal tubes are subjected to internal pressure during the tube reducing process in order to increase the forming limits. Analysis is made for the sound flow deformation in nonsteady tube reducing considering the normal anisotropy. Experiments are carried out for brass tubes. The present study is shown to give an effective guide line in designing the tube reducing process for very thin-walled sheet metal tubes. Hpwever, it is suggested that an analysis for instability should be made to design the process more effectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.359-362
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• 2003

The bending phenomenon has been known to be occurred by the different of velocity at the die exit. The difference of velocity at the die exit section can be obtained by the different velocity of billets through the multi-hole container and by the cohesion of billet inside the porthole die chamber. The bending phenomenon can be controlled by the different hole diameter. The experiments using aluminium material for the curved tube product had been done. The results of the experiment show that the curved tube product can be formed by the extru-bending process without the defects such as the distortion of section and the thickness change of the wall of tube and the folding and wrinkling. It is known that the welding and extruding of each billet has done simultaneously although the curved tube is extruded with four billets.