• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.12
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• pp.1157-1163
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• 2012

Natural frequency of a nano-resonator via nano transfer printing is studied. Through a nano transfer printing, the hybrid metal/polymer membrane may evolve a wrinkle. Natural frequency of a wrinkled hybrid membrane decreases significantly, as the amplitude to wavelength ratio becomes larger. To address the design limit of a hybrid nano resonator, we perform parametric study using finite element analysis. Specifically, we study the effects of the Young's modulus ratio of the metal/polymer membrane, thickness ratio and wrinkle amplitude to wavelength ratio, respectively. The results from the parametric studies can serve as guideline to design hybrid nano resonators.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.546-551
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• 1997

In sheet metal forming, since the surface area of workpiece is apparently larger than the volume of it, the surface condition of the sheet metal is much varied. The formability of sheet metal is decided by the forming limit and the macroscopic suface defect as like fracture and wrinkle, and microscopic asponent, The factors affected in forming limit are stain herdening exponent, strain-rate scnsitivity exponent, anisotropic coefficient. The increasing of surface roughness is decresed the forming limit curve. It is known that the greater plastic deformation the more surface roughness by Kienzle, Osadaka. The purpose of this study is to investigate the influences of surface roughness in a uniaxial tension and the traperzoidal-shaped box drawing.

• Proceedings of the SCSK Conference
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• 2003.09a
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• pp.611-616
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• 2003

Korean ginseng(Panax Ginseng C.A. Meyer) known as a oriental miracle drug is an important medicinal plant. Ginseng has been used for geriatric, tonic, stomachic, and aphrodisiac treatments for thousands years. Also, it is an antibiotic and has therapeutic properties against stress and cancer. Ginseng is widely distributed all over the world. Among them, Korean mountain ginseng has the most valuable effect on pharmaceuticals. The roots of mountain ginseng contained several kinds of ginsenosides that have many active functions for the human body. However, the study of mountain ginseng has a limit because the mountain ginseng is very expensive and rare. So, we artificially cultured mountain ginseng adventitious roots using the bioreactor culture system. We induced callus from original mountain ginseng, directly dug up in mountain and aged about one hundred ten years. Separated adventitious roots were precultured in 500ml conical flasks and then, transferred in 20L bioreactors. The adventitious roots of mountain ginseng were harvested after culturing for 40days, dried and then, extracted with several solvents. In this study, we investigated the whitening effect, anti-wrinkle effect and the safety of tissue cultured adventitious roots extract of mountain ginseng in order to identify the merit as a cosmetic ingredient. Particularly, extract of mountain ginseng adventitious roots showed whitening and anti-wrinkle effects. The inhibitory effect of this extract on the melanogenesis was examined using B-16 melanoma cell. When B-16 melanoma cells were cultured with adventitious root extract, there was a dramatically decrease in melanin contents of 8-16 melanoma cell. And we identified this extract inhibited Dopa auto-oxidation significantly. Also, when transformed mouse fibroblast L929 cells were treated with this extract, there was a significant increase in collagen synthesis. The results show significant inhibited melanization and wrinkle without inhibiting cell viability.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.11
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• pp.108-115
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• 2009

In metal forming technologies, the stamping process is one of the significant manufacturing processes to produce sheet metal components. It is important to design stamping process which can produce sound products without defect such as fracture and wrinkle. The objective of this study is to propose the feasible formability diagram which denotes the safe region without fracture and wrinkle for effective design of stamping process. To determine the feasible formability diagram, FE-analyses were firstly performed for the combinations of process parameters and then the characteristic values for fracture and wrinkle were estimated from the results of FE-analyses based on forming limit diagram. The characteristic values were extended through training of the artificial neural network. The feasible formability diagram was finally determined for various combinations of process parameters. The stamping process of turret suspension to support suspension module was taken as an example to verify the effectiveness of feasible formability diagram. The results of FE-analyses for process conditions within fracture and wrinkle as well as safe regions were in good agreement with experimental ones.

• Journal of Industrial Technology
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• v.19
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• pp.67-74
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• 1999

The mechanical properties including forming limit and deep-drawability of commercially-used sheet metals were experimentally estimated in this study. Uniaxial tensile test to obtain basic mechanical properties was carried out, followed by limiting dome height (LDH) test and forming limit diagram (FLD) test to quantitatively evaluate the sheet-formability. Deep drawing and reverse drawing tests were also performed to find out the critical values of the blank holding force and the gap between the die and the blank holder which enabled the deep drawing and reverse drawing of a successful cop without any wrinkle or fracture. The thickness of the cup wall along the rolling-, transeverse- and $45^{\circ}$-directions was measured and compared with one another. And the punch force-stroke curve and the critical punch force expected from the theory coincided with the experimental result very well for mild steel while not for aluminium alloy.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.42 no.4
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• pp.1-6
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• 2005

Recently embedded passive technology which fabricate passive elements such as resistors and capacitors at the inner layer of PCB(Printed Circuit Board) is used to make high performance IT products. However, embedded capacitor has limit in full range circuit applications because of the low capacitance density. In this paper, a new embedded capacitor which has wrinkled electrodes and dielectric layer was proposed to overcome the limits. FEM(Finite Elements Method) technique was used to evaluate capacitance density of the wrinkled type embedded capacitor. Capacitance density of the wrinkled type embedded capacitor is larger than that of conventional planar type embedded capacitor by about 25.6%$\sim$39.6%. In case of thin film type embedded capacitor, proposed wrinkled structure has more enhanced effect on the capacitance density.

• Transactions of Materials Processing
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• v.16 no.8
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• pp.621-628
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• 2007

Nowadays, Exhaust Gas Recirculation(EGR) Cooler is one of the most favorite systems for reducing the generation amount of $NO_x$ and other particle materials from vehicles burning diesel as fuel. Efficiency of the system is mainly dependent on its heat transfer efficiency and this ability is affected by net heat transferring area of the system. For that reason, several types of heat transfer tube such as dimple, wrinkle and spiral types that have large net area are used. However, it is difficult to manufacture the rectangular tube with dimpled type structure because it experiences too much strain around the rectangular tube surface during the forming process. For that reason, in this study, numerical simulation for forming process of non-symmetric dimple shape on a thin sheet metal was carried out. Furthermore, theoretical forming limit curves(forming limit diagram, forming limit stress diagram) were proposed as criteria of formability evaluation. From the results of finite element simulation in view of stress and strain distribution, it is found that the designed process has robustness and feasibility to safely manufacture the dimpled rectangular tube.

• Transactions of Materials Processing
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• v.8 no.3
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• pp.269-275
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• 1999

A variable blank holding force method is proposed to improve deep drawing characteristics of sheet materials. In this method, the blank holding force (BHF) is controlled throughout a drawing process so that the punch load does not exceed a critical value, which is slightly less than the conventional process with the conforming process with the variable BHF is more flexible than the conventional process with the constant BHF and it could be used for improving the product's quality and drawability. In this paper we suggest a method controlling the BHF as a function of punch travel during the forming process. The optimization BHF curves are determined theoretically and experimentally. It is concluded that for the case of optimum BHF control methods the drawn cup height and the drawing formability achieved by this method are increased than those for constant BHF method. Also, as comparing the wall thickness distribution of the cup drawn by the constant BHF and the optimum BHF control, the BHF control reduce the wall thickness variation of the drawn cup at the cup wall and make the cup thickness distribution more uniformly than the constant BHF.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.616-620
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• 2001

The wrinkling in the flange and wall of a part is a predominent failure mode in stamping of sheet metal parts. In many cases this wrinkling may be eliminated by appropriate control of the blank holding force(BHF), but BHF affects the draw depth. Although the wrinkles of flange have been made in the incipient stage of drawing, if the height of wrinkles is maintained under a prescribed limit by decrease or extinction of wrinkles in the course of drawing, small BHP can be allowed so that the depth of drawing could be increased. Authors research the variation of the wrinkles in flange in the course of square cup drawing by using aluminium A1015 and aluminium alloy A5052.

• Transactions of Materials Processing
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• v.32 no.5
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• pp.276-286
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• 2023

The field of sheet metal forming using press technology has become essential in modern mass production systems. Draw bead is often used to enhance formability. However, optimal draw bead design often requires excessive time and cost due to iterative experimentation and sometimes results in some defects. Given these challenges, there is a need to enhance formability by introducing segmented blank holders without draw beads. In this paper, the feasibility of a localized holding strategy using segmented blank holders is evaluated without the use of draw beads. The possibility for improving the formability was evaluated by utilizing a combination of the forming limit diagram and the wrinkle pattern-based defect indicators. Artificial neural networks were used for predicting defect indicators corresponding to arbitrary input holding forces and the NSGA-II optimization algorithm is used to find optimum blank holder forces yielding better defect indicators than the original process with drawbeads. Using optimum holding forces obtained from the proposed procedure, the stamping process with the segmented blank holders can yield better formability than the conventional process with drawbeads.