• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.92-95
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• 2011

In manufacturing optical fibers, the process starts with the glass fiber drawing from the heated and softened silica preform in the furnace, and the freshly drawn glass fiber is still at high temperature when it leaves the glass fiber drawing furnace. It is necessary to cool down the glass fiber to the ambient temperature before it then enters the fiber coating applicator, since the hot glass fiber is known to cause several technical difficulties in achieving high quality fiber coating. As the fiber drawing speed keeps increasing, a current manufacturing of optical fibers requires a dedicated cooling unit with helium gas injection. A series of three-dimensional flow and heat transfer computations are carried out to investigate the effectiveness of fiber cooling in the fiber cooling unit. The glass fiber cooling unit is simplified into the long cylindrical enclosure at which the hot glass fiber passes through at high speed, and the helium is being supplied through several injection slots of rectangular shape along the cooling unit. This study presents and discusses the effects of helium injection rates on the glass fiber cooling rates.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.94-96
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• 2005

This paper is concerned with a fracture strength study of composite adhesive lap joints. The tensile and peel tests were carried out on specimen manufactured hybrid stacked composites such as the polyester and bamboo natural fiber layer. The main objective of the work was to test the failure strength of adhesive bonded joints using hybrid stacked composites with a polyester and bamboo natural fiber layer adjacent to the fiber orientation. From results, the load directional orientation, small amount and low thickness of bamboo natural fiber layer have a good effect on the tensile and peel strength of natural fiber reinforced composites. and these characters are have a great influence on fracture strength and failure shape of adhesive bonded joints using hybrid stacked composites in the difference of fiber orientation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.7
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• pp.833-839
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• 2013

In this study, an experiment was performed to monitor the two-dimensional shape of a cantilever composite structure using fiber Bragg grating (FBG) sensors. To monitor the shape of a composite structure, a deflection equation developed by NASA was applied and a composite beam attached to three FBG sensors was used. In the experiment, the shape of the composite beam was successfully estimated and an error was evaluated by comparing a real deflection. The error increased with real deflection; therefore, it was compensated by using the linear relationship between the error and the real deflection. After compensating the error, the measured deflection shows good agreement with the real deflection. Finally, the experiment shows that the FBG sensor and the deflection equation are suitable for monitoring the deflection curve of the beam structure with compensation of the error.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.98-105
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• 2016

In this study, projectiles with 2 kinds of nose shape: spherical and flat were impacted into normal concrete and fiber reinforced concrete panels. The fracture depth and form, crater diameter, tensile strain at rear face were evaluated. It was confirmed that smaller projectile nose areas resulted in deeper penetrations associated with concentrated impact forces and small front-face crater diameters in impact test. Conversely, larger projectile nose areas resulted in shallower penetrations and larger front-face fracture diameters. Similar front-face failure and strain distribution relationships based on the projectile nose shape were observed for normal and fiber-reinforced concrete although the rear-face tensile strain and scabbing were significantly reduced by the fiber reinforcement. In addition, a direct relationship was confirmed between the penetration depth based on the projectile nose shape and the tensile strain on the rear face. Thus the impact strain behavior is required to predict the scabbing behavior with penetration depth.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.810-813
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• 2003

Wide spread using of mobile and handy electronic apparatus is giving rise to a question on the harmfulness of health and causing troubles when electical and electronic equipments are in use. This paper reports on the experimental results obtained by using a pliable and structured specimen that has a long shape aperture, made of stainless steel fibers. Based on the TEM mode transfer structure that was designed and manufactured through HFSS, we measured electromagnetic shielding effectives, where the network analyzer was applied. We could draw a conclusion from this research that the metal fabric showed a good electromagnetic shielding effect, mainly by means of the good reflex loss at the fiber surface. Even though the material itself possesses a good absorption loss. the specimen revealed that structural factors. e.g.. the shape of the aperture. the size of the aperture, etc., can have a more influence on the shielding effect than the components of material have. A special notice is required for modeling and analyzing the electromagnetic characteristics of metal fabrics, because there exists a strong possibility that multiple reflection can happen on the surface of metal fibers. which can presume a model of fiber bundle and fabric structure.

• Journal of Welding and Joining
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• v.34 no.6
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• pp.62-68
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• 2016

Laser welding has superior characteristic such as low distortion, high welding speed, easy automation and real time control. But it is easy to occur weld defects such as porosity, crater, humping bead in the area of welding start and end. These weld defects can be suppressed by applying the wave shape control. In this study CW fiber laser was used for welding of $0.5mm^t$ pure titanium. Penetration properties were evaluated with the time of slope up and down. After then the bead shape was observed, and the maximum depth and the area of crater were measured. The bead shape of welding start area changed to be sharp with increase of slope up time and non-weld area of welding start increased. The crater and humping bead were suppressed with slope down time. The cooling rate of crater area was understood through measure of the hardness. Also, The distribution tendency of alloying elements was observed by EPMA and EDS. When wave shape control didn't applied to weld, the hardness of end weld increased due to rapid cooling rate and the hardness of rear part in the crater was higher than that of fore part. On the other hand, when the wave shape control was used for end weld, the increase of hardness in the end weld couldn't be found due to gradual cooling rate.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.789-795
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• 1999

In this study, carbon fiber reinforced cement composites(CFRCs) reinforced with short noncircular type carbon fibers were fabricated and properties(drying shrinkage, resistance to freezing and thawing, and fracture toughness) were compared with those of the CFRCs reinforced with circular type carbon fibers. It was found that these properties greatly depended on the shape and length of carbon fibers. The drying shrinkage of CFRCs reinforced with C-type carbon fiber was superior to other CFRCs. This effect was increased with a high aspect ratio of fiber. The resistance to freezing and thawing was increased with the fiber length and fiber volume percent, but there was on remarkable effect to fiber shape. Fracture toughness and resistance to crack propagation of CFRCs reinforced with C-CFs were improved compared with other CFRCs. It was believed that the more absorption of fracture energy into the larger interface caused an increase in fracture toughness and resistance to crack propagation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.3
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• pp.281-288
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• 2004

The hybrid composite material (Al/GFRP laminates) are applied to the fuselage and wing in a aircraft. Therefore, Al/GFRP laminates suffer from the cyclic bending moments. This study was to evaluate the effect of fiber stacking angle on the fatigue crack propagation and delamination behavior using the relationship between crack growth rate (da/dN) and stress intensity factor range (ΔK) in Al/GFRP laminates under cyclic bending moment. The variable delamination growth behavior in case of three different type of fiber orientations, i.e., [Al/O$_2$/Al], [Al/+45$_2$/Al] and [Al/90$_2$/Al] at the interface of Al layer and glass fiber layer was measured by ultrasonic C-scan images. As results of this study, It represent that the delamination shape should turns out to have more effective characteristics on the fiber stacking angle. The extension of the delamination zone in case of [Al/+45$_2$/Al] and [Al/90$_2$/Al] were not formed along the fatigue crack profile. The shape of delamination zone depend on fiber stacking angle and the variable type with the delamination contour decreased non-linearly toward the crack tip at the Al layer.

• Journal of the Korean Geosynthetics Society
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• v.2 no.1
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• pp.27-37
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• 2003

The factors affecting shear strength and friction characteristics of the fiber-mixed soil can be classified into engineering properties of soil; particle-size, distribution, and particle shape, physical and mechanical properties of fiber; shape, length, diameter, tensile strength, elastic modulus, friction coefficient, and mixed ratio and external factors; confined stress and compaction condition. In this study, a series of shear friction tests and pull-out tests were performed to evaluate the friction properties of fiber-mixed soil according to soil type, fiber type, fiber mixed ratio and compaction degree. The materials and test conditions used in this study are as follows. Soils: SM and ML; mixing fibers: three types of polypropylene fibers(net type 38mm and 60mm, and line type 60mm); reinforcement: geogrid; mixing ratio: 0.2% and 0.3%; degree of compaction : 85% and 95%.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.692-696
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• 2001

Thermo-mechanical behavior and mechanical properties of intelligent polymer matrix composite with SMA fiber are experimentally studied. It is found that increments of compressive thermal strain is observed as the pre-strain and TiNi volume fraction increase. The smartness of the SMA is given due to the shape memory effect of the TiNi fiber which generates compressive residual stress in the matrix material when heated after being prestrained. In the paper, alloy is based on the general purpose commercial code ANSYS. And for the purpose of easy and fast user's analysis, it is developed the Graphical User Interface by using Tcl/Tk language.