• Journal of the Korean Society of Safety
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• v.14 no.4
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• pp.78-84
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• 1999

A compact air-preheating type heat exchanger was developed and tested for the ultra-high temperature heat recovery applications. For the direct use of exhaust gases up to $1200^{\circ}C$, the heat exchanger adopted a ceramic core with high strength and low thermal expansion coefficient less than $1{\times}10^{-6}^{\circ}C^{-1}$. The ceramic core was fabricated by special extrusion and bonding techniques. To minimize thermal stresses in the core, spring-loaded sealing mechanism was designed and successfully installed. 1-pass air flow scheme was adopted for the compactness and cost-savings. The pressure test for the ceramic core showed no failure under 35 kPa and less than 3% leak under 7 kPa. Flue gas simulation system was developed to investigate the performance of the heat exchanger. The test results showed normal operations of the heat exchanger up to $1200^{\circ}C$ of exhaust gases and relatively high heat recovery efficiencies of 31～39% depending upon exhaust gas temperatures..

• Journal of the Korean Society for Precision Engineering
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• v.9 no.1
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• pp.118-125
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• 1992

Joining of thermoplastics is an area of growing importance in the automotive, aerospace, electronics medical and other domestic appliance industries. While adhesive Bonding or mechanical fastening could be used to join thermoplastics, welding is very effective because of its speed and low cost. This study investgated the ultrasonic joining of thermoplastics. Four kinds of thermoplastics such as Acrylonitrile Butadiene Styrene, Polystyrene, Polyethylene and Polypropylene were used, ultilizing all possible joining combinations. In each combination of thermoplastics, the weldability of the joint was evaluated as a function of weld time, amplitude of vibration and pressure. It was generally found that joining of amorphous thermoplastics with semicrystalline thermopastics resulted in poor joints due to its different crystalline structure. Joining of the amorphous thermoplastics together and joining of the semicrystalline thermoplastics together produced the best joints owing to its same crystalline structure.

• Journal of Powder Materials
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• v.5 no.4
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• pp.303-311
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• 1998

Hard materials such as hardmetal, coated hardmetal, cermet, ceramics and diamond or c-BN sintered compact are a kind of grain-dispersed alloy with high volume of hard particles. These are used for cutting tools, wear-resistant tools, rock bits, high pressure apparatus, etc. The annual production in Japan is about 1.7 billion dollars (200 billion yen). This is greatly owed to the development in science and technology which has been accomplished by applying new concepts such as fine or uniform grain microstructure, orientation of crystal grains, functionally graded material, artificial lattice and coherent bonding in recent years. In this review, the development in recent years in Japan is briefly summarized.

• Electrical & Electronic Materials
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• v.8 no.4
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• pp.434-442
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• 1995

To improve dielectric and mechanical properties of insulating composite by plasma surface treatment, new plasma surface treatment process is designed with concentric and hemi-circle electrodes system. the plasma, which is generated between anode and cathode, is induced to the upper side of the electrode system and treats the surface of the insulators. The optimal surface treatment condition is that pressure : 0.5[torr], flux density : 100[gauss], discharge current : 500[mA] and treatment time : 3 minutes. The composite filled with glass cloth surface-treated by plasma shows the improvement in electric and mechanical properties, comparing non- and coupling agent treated samples.

• Journal of the Korean Ceramic Society
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• v.34 no.5
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• pp.491-499
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• 1997

High flexible lightweight composites containing tobermorite as a main mineral is produced using various amorphous silicates, lime, cement and fibers. Here, Mechanical properties of the composites were studied by observing microstructures of hydrates and fibers. Amorphous silicates having better hydraulicity retarded the crystallization of tobermorite due to better formation of C-S-H gel in water bath curing, but, difficult conversion from C-S-H gel to tobermorite in hydrothermal reaction. In the low molar ratio of CaO/SiO2 (0.67), faster crystalization was observed dued to more impurities such as Al2O3 alkali, resulting in improving mechanical properties due to small crystal size and many contact points. It was identified that a lot of calcium silicate hydates formed at surface of pulps increase bonding strength and the crack-resistance of matrix in the composites, but decrease hardness and compressive strength. The choice of amorpous silicates having better hydraulicity, low CaO/SiO2 adding each fibers bellow about 5% in the raw mixs and lower molding pressure should be needed at improve mechanical properties of composites.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.1
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• pp.90-94
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• 2004

Generally, a hydraulic cylinder block which is one of a vehicle parts that plays Important role in excavator power transmission, has copper alloy separation phenomenon by sliding motion between metals in high pressure condition. In this paper, to solve this problem, the interfacial reaction layer of Fe-Cu With SCM440 and copper alloy is studied through the melting method. As the result of this study, it is found that the interfacial reaction layer of $1{\mu}m$ created in the interface of Fe-Cu which has very strong physical bonding. It has been also confirmed that the melting method can improve life of the hydraulic cylinder block.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1821-1824
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• 2008

A novel in-mold packaging process has been developed to manufacture devices with closed channels. In this unified process, fabrication of open channels and forming the rigid cover on top of them are sequentially integrated in the same mold. The entire process is comprised of two phases. In the first phase, the open channels are fabricated under an exquisitely controlled temperature and pressure using the conventional micro injection molding technology. In the second phase, the closed channels are fabricated by conducting the injection molding process using the molded structure with the open channels as a mold insert. As a result, the in-mold technology can eliminate the bonding processes such as heating, ultrasonic or chemical processes for cohesion between the channel and the cover, which have been required in conventional methods.

• Journal of Korea Foundry Society
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• v.14 no.5
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• pp.429-437
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• 1994

Influence of interfacial structure between matrix and particle in A356/coated SiC composite fabricated by squeeze casting method was studied. Experimental variables are types of coated metallic film on SiC particles such as Cu, Ni-P, and applied pressure for squeeze casting. It was found that coating treatment on SiC particles improves the wetting of liquid A356 alloy on SiC particles. SiC particle distribution is very homogeneous in A356 matrix alloy which is fabricated by squeeze casting. Analysing the surface morphology of fractured A356/coated SiC, it was concluded that metallic thin film by coating treatment on SiC particle improves the interfacial bonding between particle and matrix, and so does on mechanical properties such as tensile strength. However, there was on significant difference in hardness between those composite made of as-received SiC particle and coated SiC particle.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.1
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• pp.28-34
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• 2013

For the senses of beauty and texture, internal components of small passenger cars are manufactured by texturing plastic with drawplate but those of deluxe passenger cars are manufactured by bonding pre-embossed skin to the surface of drawplate. As the pre-embossed skin is bonded at high temperature and pressure, the pattern of skin is distorted. The corner part is hardened and its dimension tolerance is changed by resulting in the increase with its defective rate. This study provides the method to design and manufacture the door trim track by vacuuming the non-patterned skin to upper-side drawplate which forms the pattern of descending skin. It is pressed to the plastic product with hot-press method and the damage of bossed-pattern is prevented. Valuation in this study has been done by analyzing, designing and experimenting method.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.2
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• pp.58-65
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• 2003

The conventional forming process such as squeeze casting or die casting for fabricating metal matrix composites products have a disadvantage such as non homogenous distribution of reinforcement, weak bonding between matrix and reinforcement and cost increase in parts fabrication. Thixoforming process has been accepted as a new method for fabricating the net shaped metal matrix composites with lightweight and wear resistance. In this paper, the effect of volume fraction and reinforcement sizes on mechanical properties in cylinder liner part of metal matrix composites has been investigated with processes parameters such as pressure and velocity. Moreover, the methods to obtain the thixoforged composites cylinder liner with high quality has been proposed. To evaluate the composites cylinder linear fabricated at the conditions proposed in this study, mechanical properties of fabricated composites cylinder linear were compared with those of commercial composites cylinder linear.