• Composites Research
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• v.15 no.1
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• pp.32-40
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• 2002

This study developed fabrication process of $SiC_p/Al$ metal matrix composites as electronic packaging materials by squeeze casting method. The $SiC_p$ preform were fabricated in newly designed preform mold using about 0.8 % of inorganic binder(SiO$_2$) and 5 vol.% of $Al_2O_3$fiber. To infiltrate the molten metal into the preform, fabrication condition such as the temperature and the pressure were selected. Applying the fabrication conditions, heat transfer analysis were preformed using finite element method and thus analyzed the temperature distribution and cooling characteristic during the squeeze casting. For the fabricated composites, impact toughness and thermal expansion coefficient were measured. The metal matrix composites developed in this study have 0.2~0.3 J impact toughness, $8~10 ppm/^{\circ}C$ thermal expansion coefficient and $2.9~3.0g/cm^3$density which is appropriate properties for electronic packaging application.

• Journal of the KSME
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• v.32 no.1
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• pp.46-56
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• 1992

이 글에서는 현재까지 개발된 금속복합재료의 제조공법 중에서 비교적 보편화되어 있는 분말야 금법, 가압용침법, 복합주조법 등에 대하여 소개하였고, 제조된 재료가 가지는 일반적인 기계적 성질에 대하여 설명하였다. 그리고 금속복합재료의 대표적인 응용분야와 현재 국내에서도 큰 관심을 끌고 있는 자동차엔진의 부품소재로서 금속복합재료의 응용기술에 대해 소개하였다. 국 내에서 금속복합재료의 관련 연구는 주로 학교와 연구소를 중심으로 발전되어 왔으나 근년에 자동차 산업의 비약적인 발전과 항공산업 분야에서 잠재적인 수요가 예측되면서 일부 기업체에서 응용 연구를 시작하였다. 그러나 금속복합재료의 기초 소재가 되는 경합금과 보강재의 제도기 술은 선진국에 비해 크게 뒤져 있다. 현재까지 국내에서의 연구동향은 주로 금속복합재료의 제조공정개발과 물성 평가에 치중하여 왔다. 기계공업이 발전하면서 점점 더 고기능성 소재가 요구되어지는 현황을 감안할 때 금속복합재료의 실질적 응용분야의 개척과 함께 기초 소재의 개발 연구는 시급한 과제이다.

• Composites Research
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• v.16 no.6
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• pp.48-55
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• 2003

This research makes comparisons of empirical fatigue-lives between AC8A A1 alloy and the metal matrix composites(A1/A12O3, A1/A12O3/A12O3p), and also includes comparisons of fatigue-lives between empirical fatigue-lives and estimated fatigue-lives from regular-periodic load testing, AE method to predict fatigue-crack initiation before visible in sight and SEM(scanning electron microscope) photographs of each material. According to the test results of the notched specimen. the fatigue life of the hybrid metal matrix composites and the metal matrix composites, which are more brittle than the base matrix was shorter than that of the base matrix under both types of loads. In addition, the fatigue-life estimated from the damage summation method and that from experiments at random loads were fairly identical.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.5
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• pp.435-444
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• 2011

This paper deals with the structural assessment of metallic and non-metallic stiffened/monocoque plated marine structures under a lateral pressure load to identify appropriate combination of material and section configuration, especially at the preliminary marine structural design stage. A generic rectangular plated structure is exemplified from the metallic superstructure of a marine vessel and its structural topology is varied for the structural assessment. In total 13 different structural topologies are proposed and assessed using appropriate elastic solutions in conjunction with a set of stress and deflection limits obtained from practice. The geometry dimensions and weights of the structural topologies are calculated, and subsequently, the costs of the materials used in the structural topologies are reviewed to discuss the cost-effectiveness of the materials. Finally, conclusions are made with the aim of suggesting suitable structural topology for the marine structural member considered in this paper.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.2
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• pp.112-120
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• 1998

A nondestructive evaluation technique was developed for the quantitative determination of the reinforcement volume fractions in particulate reinforced metal matrix composites. The proposed technique employed a composite micromechanics which accounts for the microstructure of the composite medium together with the measurement of anisotropic electrical conductivity. When the measured conductivity was coupled with the theoretically predicted conductivity, the unknown reinforcement volume fraction was calculated. An analytical model based on the Mori-Tanaka method was described which relates the NDE signatures to the composite microstructure. The volume fractions were calculated using eddy current measurements made on a wide range of silicon carbide particulate ($SiC_p$) reinforced aluminum (Al) matrix composites. The calculated $SiC_p$ volume fractions were in good agreement with the measured volume fractions in the range of 0-30%. The technique was also found to be effective in estimating the total volume percentage of reinforcement and intermetallic compound formed during the processing stage.

• Journal of Conservation Science
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• v.31 no.4
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• pp.477-488
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• 2015

At this, in this study, some tests were conducted to come up with a method to minimize intervention, to reduce the secondary damage to original materials, and to produce remarkable reinforcing effects. The followings show objective standards. The proportion of original material to steel reinforcement bar (the ratio of steel reinforcement bar) needs to be calculated in light of weathering intensity. Second, in the case of partial damage, prosthetic treatment is applied to add new stone materials to original materials. In that case, the ratio of steel reinforcement bar should be calculated based on material that is highly resistant to weathering. With the results of this study, it is possible to suggest conditions that can structurally stabilize stone cultural heritage, according to the weathering area. As a result, the ratio of steel reinforcement bars can be 0.13 to 0.23 in the case of $800kgf/cm^2$ or less, 0.24 to 0.28 in $800kgf/cm^2$ or higher, and 0.29 to 0.5 in $1200kgf/cm^2$ or higher. In particular, there is the need to take the coefficient of rupture of stone material and the properties of the steel reinforcement bar into account in cases of calculating the ratio of steel reinforcement bars according to weathering intensity.

• Korean Journal of Materials Research
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• v.9 no.3
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• pp.315-321
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• 1999

Metal matrix composites have been extensively studied because of their excellent characteristics for structural application. $Al_2O_3$ and SiC have been used as a common reinforcement owing to their good mechanical properties. However the manufacturing cost of these ceramic reinforcement is expensive, so the use of the composites has been restricted to special purposes. In this study, we tested the application possibility as a reinforcement of $Al_2O_3$-TiC powder synthesized by SHS(Self-propagating High-temperature Synthesis) process to Al alloy matrix composite. Also, $Al_2O_3$ short fibers were added with the synthesized powders in order to apply to the Al matrix hybrid composites. Squeeze infiltration casting process was used to make the composite with 25vol% of reinforcement. Microstructure and crystal structure were examined by SEM, OM and XRD, also the mechanical properties were studied by the compressive test and wear test.

• Composites Research
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• v.25 no.3
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• pp.65-69
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• 2012

The main objective of this study is to investigate the effect of metal z-pinning on the failure behavior of cocured composite single-lap joints. Three different pin diameters (0.3, 0.5, and 0.7 mm) and three pin areal densities (0.5, 2.0, and 4.0%) were examined. The specimens were fabricated by T700-12K-31E#2510 unidirectional prepreg from Toray. Stainless steel pins were used for z-pinning. Test results showed that except one case with extremely low pin density of 0.5%, all other z-pinned joints exhibited lower initial crack stresses than those of the unpinned joint. However the ultimate strength of the z-pinned joint increased up to 45% at most. Furthermore, even after the complete failure of the joint, the z-pins sustained the carried load to a certain degree experiencing large deformation and provided the stable fracture behavior for the composite joint.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.585-589
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• 2001

Many experimental results have revealed that the development of cavitaition during tensile deformation is limited by the Presence of liquid phases. However, the presence of liquid phases does not always lead to high-strain-rate superplasticity, because too much liquid causes intergranular decohesion at grain boundaries/interfaces in metal-matrix composites. Thus, it is important to examine the nature of interfaces of superplastic composites in order to understand the origin of superplastic flow related to liquid grain boundaries during high-strain-rate superplastic deformation. This study shows that a large elongation is obtained at the temperature, that is close to the onset temperature for partial melting in the superplastic composites, but the elongation significantly decreases at slightly higher temperatures, which are close to the end temperature fur partial melting. This indicates that there is an optimum amount of the liquid phase for obtaining high-strain-rate superplasticity in these materials.

• Geotechnical Engineering
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• v.14 no.4
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• pp.61-76
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• 1998

Various kinds of reinforced soil methods have been developed by many researchers or companies for their economic merits mainly. These methods have generally used sandy soils which have high permeability as embanking or backfill material. That is because, if poor embanking materials, especially like a clayey soil which has very low permeability, are used in a reinforced soil embanking, and if excessive pore water pressure is produced by external factors, the friction resistance between reinforcing members and Boils decrease, as a result possible damage or collapse of the body of a reinforced embankment. In fact, clayey Boils can also be used as a embanking materials with reinforcement which has high permeable capacity, and are expected to be able to dissipate the excess pore water pressure effectively. In this study reinforcing effects have been examined through a serries of direct shear tests in which clayey soils are reinforced with nonwoven geotextiles of which permeability is very high and tensile strength is relatively weaker than geogrids which are usually used in reinforced soil wall. Even though such nonwoven geotextile are used as reinforcement of high saturated clayey soils. the test results show the possibility that nonwoven geoteztiles could be used as a reinforcement for reinforced soil walls effectively.