• Composites Research
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• v.29 no.6
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• pp.353-357
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• 2016

An appropriate way to fabricate a hybrid composite containing evenly dispersed carbon nano tubes(CNTs) is to stacking B-stage resin films that contain evenly dispersed CNTs and various reinforcing fiber layers alternatively. In the present study, B-stage resin films are manufactured via shear mixing and three-roll milling. CNT dispersion in resin via these two processes are evaluated by SEM on their fracture surfaces. For more efficient process, the dispersivities are evaluated according to the number of calendering passes. Samples are made for different number of passes during calendering, and their dispersions are evaluated via SEM fractographs as well as by measuring their electrical conductivities. Additionally, the optimal process conditions are obtained by measuring the electrical conductivity and evaluating their dispersivity of the samples prepared by gap mode and force mode.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.98-106
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• 1999

In this study cold rolling process for the irregular cross-sectional shape has been investigated. The product analyzed in present study is the steel cutter, which is frequently used to cut the desired shape on leather. Because steel cutter always has a irregular cross-section, after rolling process the workpiece is severely bended to every direction. The bending of the workpiece affects the processed performed after rolling such as heat treatment and grinding, then that of the workpiece becomes more severe. In this study, therefore, to prevent the bending of the workpiece to the left and right sides. rigid-plastic finite element method has been utilized and in order to find optimal roll geometry rapidly, one dimensional equal interval search technique has been also introduced. By using both rigid plastic finite element method and optimum technique, cold rolling process for the irregular cross-sectional shape has been successfully investigated.

• Transactions of Materials Processing
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• v.11 no.2
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• pp.147-154
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• 2002

The tension levelling Process is Performed to elongate the strip plastically In combination of tensile and bending strain so that all longitudinal fibers In the strip have an approximately equal amount ofn length and undesirable strip shapes are corrected to the flat shape. Thus paper is concerned with a simulation of the tension levelling process based on the analysis of tile unit model for the tension leveller. Analysis technique such as the sequential analysis of the unit model is suggested and verified with the assembly analysis of the unit model for the effective arts economic analysis of the full set of the tension leveller. Analysis of the full tension levelling Process using sequential unit models Is carried out for steel strips with the shape defect and provides the effect of the intermesh and optimum amount of the intermesh in tension levelling process.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1996.10a
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• pp.319-322
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• 1996

Automatic gauge control algorithm in rolling process is composed of several functions. Among them feedforward control method is used to compensate irregularity of input strip thickness before rolling process. Since it's very difficult to get an explicit relation between the degree of irregularity of input strip and manipulated variables, approximate linear equation like straight line is used in real system. Furthermore parameters included in such static equation should be changed by characteristics of input strip and modified by roll states. Despite this problem, rolling process use variables in feedfroward controller as a constant. Therefore this problem increases the possibilities of irregularity of thickness control. This paper presents an algorithm which can properly infer present states of process and intelligently manipulate the parameter of feedforward controller.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.405-408
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• 2009

Edge cracks in cold rolling always influence to the quality of productions, while the "V" shaped cracks were propagated by passing the roll gap. We set up the sizes and shapes of initial cracks in simulation according to the references from real productions. Different to in hot rolling, the cracks in cold rolling couldn't be reduced from propagation automatically after generated, even if these could be reduced by changing the process parameters. In this paper, we described the affections of process parameters on the propagation of edge cracks, such as reduction ratio and tension. We predicted that the dependence of the cracks propagations of changing of process conditions and expected to gain the smaller edge cracks. By raising the reduction ratio, the cracks were propagated increasingly in both transverse and rolling directions. And as tension raise, the cracks became propagated in both directions in which transverse direction was less effectively.

• Transactions of Materials Processing
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• v.6 no.2
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• pp.118-135
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• 1997

In order to analyze the deformation and residual curvature of steel sheets in the strip processing lines, a program for calculating curvature and work hardening of sheet was developed. Strip deformation caused by repeated bending under tension in the process lines was analyzed on the basis of the incremental-plasticity theory with the mixed hardenting model for the purpose of predicting the strip shape and the yield stress change. The developed calculation program was applied to predict curl and gutter of sheets within a 10% difference. The yield stress increment was also predicted with the similar accuracy. Application of the model to tension legvelling process showed that gutter could be controlled by intermesh and elongation. The yield stress increment in the electro-galvanizing line calculated by the developed program was found to be dependent on the yield strength, the applied tension and the diameter of the smallest roll.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.351-355
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• 2003

In this paper, a new barrier rib forming method of embossed barrier rib (EBR) formation process for the PDP rear panel was introduced. The process is mainly composed of green sheet fabrication, lamination of the green sheet on the rear glass panel having data electrodes, and roll embossing followed by firing. The EBR process has two advantages over the conventional barrier rib forming methods. One is the process requires less equipment investment than the conventional methods by about 20% of the current rear panel fabrication equipment investment owing to the simplified fabrication process. The other advantage is its reduced rear panel manufacturing cost by eliminating the time consuming and complicated processes and waste of materials in the conventional methods. In this study, general procedure of EBR fabrication process is described and the characteristics of prototype PDP using EBR panel are discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.5
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• pp.523-528
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• 2012

A bendable electronic module is developed for a mobile application by using a low-cost roll-to-roll manufacturing process. In the module, a thin silicon chip is embedded in a polymer-based encapsulating adhesive between flexible copper clad polyimide layers. A set of tests are conducted for the purpose of qualification: thermal shock, high temperature storage, and autoclave tests. During the autoclave test, delamination occurs at many places within the module layers. To investigate the failure mechanism, moisture diffusion analysis is conducted for the interior of the module under the autoclave test condition. For the analysis, the hygroscopic characteristics of the encapsulating materials are experimentally determined. Analysis results indicate the moisture saturation process in the interior of the module under the autoclave test condition.

• Transactions of Materials Processing
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• v.20 no.8
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• pp.611-618
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• 2011

Flow forming is an incremental forming process in which rollers are used to form cylindrical parts with repeated turning of both roller and starting material. Both sheet and tube can be used as the starting material. The process is highly useful for producing hollow shaped parts from a tube, with the benefit of the average strain in the final shape being significantly lower than that from a sheet material. In the present study, the flow forming process was studied and optimized for producing a hollow shaped part from seamless steel tube by both experiment and numerical analysis. Upon considering the difficulty of forming seamless steel sheet, the thickness reduction was distributed over several tool paths. In the end, an optimum process condition was attained, and the experiment verified the simulation results.

• Journal of the Korean Society of Radiology
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• v.17 no.3
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• pp.441-447
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• 2023

Lead(Pb), which is currently mainly used for shielding purposes in the medical radiation, has excellent radiation shielding functions, but is continuously exposed to radiation directly or indirectly due to the harmfulness of lead itself to the human body and the inconvenience caused by its heavy weight. Research on shielding materials that are human-friendly, lightweight, and convenient to use that can block risks and replace lead is continuously being conducted. In this study, based on the commonly used polyethylene terephthalate (PET) film and the fabric material used in actual radiation protective clothing, a multi-layer thin film was realized through sputtering and vacuum deposition of bismuth, tungsten, and tin, which are metal materials that can shield radiation. Thus, a shielding film was produced and its applicability as a radiation shielding material was evaluated. The radiation shielding film was manufactured by establishing the optimized conditions for each shielding material while controlling the applied voltage, roll driving speed, and gas supply amount to manufacture the shielding film. The adhesion between the parent material and the shielding metal thin film was confirmed by Cross-cut 100/100, and the stability of the thin film was confirmed through a hot water test for 1 hour to measure the change of the thin film over time. The shielding performance of the finally realized shielding film was measured by the Korea association for radiation application (KARA), and the test conditions (inverse wide beam, tube voltage 50 kV, half layer 1.828 mmAl) were set to obtain an attenuation ratio of 16.4 (initial value 0.300 mGy/s, measured value 0.018 mGy/s) and damping ratio 4.31 (initial value 0.300 mGy/s, measured value 0.069 mGy/s) were obtained. by securing process efficiency for future commercialization, light and shielding films and fabrics were used to lay the foundation for the application of films to radiation protective clothing or construction materials with shielding functions.