• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.05a
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• pp.32-38
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• 1999

Fatigue crack propagation behavior for block load in high strength aluminum alloys was investigated in this study. The materials used in this study are aluminum alloy 5052-H32. Initial crack was made by applying cyclic load to a through crack with chevron notch. Crack length was measured from calibration curve, which was plotted by known crack length and resistance of standard specimens. Load was obtained from linear regression formula. Unloading elastic compliance method was applied to check the crack closure and cracked area. The present study results can be usefully applied to predicting the change of crack propagation rate, the crack closure, and the delay of crack propagation.

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.452-455
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• 1999

ORV which vaporizes LNG to NG is consisted of tube and header whose substrate is aluminum alloy. The corrosion of the tube is very severe because of sea water being used as the heating source. In this research to protect ORV substrate material, the corrosion behavior of aluminum alloys was investigated for the sacrificial role of Al-Zn alloy for ORV tubes. The electrochemical behavior of aluminum alloys in sea water was investigated. The corrosion behavior of thermally-sprayed and cladded samples were compared through salt spray tests. Al-Zn alloy can act as a sacrificial anode and cladded Al-Zn alloy has a better corrosion resistance than that of thermally sprayed one. The galvanic effect of Al-Zn to substrate material was conformed from scratched sample tests.

• Bulletin of the Korean Chemical Society
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• v.21 no.9
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• pp.860-866
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• 2000

Hydrocarbostyril, which is a key intermediate in our new synthetic route to 6-nitroquipazine, can be prepared from 1-indanone oxime by Beckmann rearrangement. We have optimized the reaction by using a Lewis acid, aluminum chloride,in the yield of 91% instead of common acids such as polyphosphoric acid,and sulfuric acid used in conventional Beckmann rearrangement (20% in the literature, 10% in our experiment).The optimized condition is established by usingthree equivalents of aluminum chloride in CH2Cl2 at -40 $^{\circ}C$ - room tempera-turefor 40 min. We have applied this condition to other 1-indanone derivatives, such as 4-methyl-, 4-methoxy-, 4-nitro and 6-nitro-1-indanones. The mechanism ofthis BR has been proposed on the basis of the effect of tem-perature and substituenton product ratio, with the aid of PM3 calculation for a model system.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.250-253
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• 2004

A finite element model is developed for the process of squeeze casting of metal matrix composites. The fluid flow and the heat transfer are fundamental phenomena in squeeze casting. The equations for the clear fluid flow and the flow in porous media are used to simulate the transient metal flow. To describe heat transfer in the solidification of molten aluminum, the energy equation is written in terms of temperature and enthalpy. A direct iteration technique is used to solve the resulting nonlinear algebraic equations. The cooling curves and temperature distribution during infiltration and solidification were calculated for a simplified model with pure aluminum. The developed program can be used for squeeze casting process of complex geometry, boundary conditions and processing parameter optimization.

• Corrosion Science and Technology
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• v.4 no.1
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• pp.33-38
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• 2005

Some feasibility studies are conducted to produce an advanced ceramic coating, which reveals superior chemical and mechanical strength, on metal base structure used in chemical plant. This advanced coating on metallic frame can replace ceramic delivery pipe and reaction chamber used in chemical plant, which are operated in hi-temperature and corrosive/erosive environment. An dual spraying is adopted to reduce the residual stress in order to increase the coating thickness and the residual stress is estimated by in-situ manner. Then new methodology is tried to form special coating of yttrium aluminum garnet(YAG), which reveals hi-strength and low-creep rates at hi-temperature, superior anti-corrosion property, hi-stability against Alkali-Vapor corrosion, and so on, on iron base structure. To verify the formation of YAG during thermal spraying, XRD(X ray diffraction) technique was used.

• Journal of Korea Foundry Society
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• v.40 no.3
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• pp.85-96
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• 2020

The effect of an aluminum scrap addition ratio on the tensile and solidification cracking properties of the AC4A aluminum alloy in the as-cast state and heat-treated state were investigated in this study. Generally, the expected problem of using scrap in aluminum casting is an increase of hydrogen and Fe element inside the aluminum melt. Another issue is an oxide film which has a weak interface with the molten aluminum and acts as potent nucleation sites for internal porosity and crack initiation. Solidification cracking is one of the critical defects that must be resolved to produce high quality castings. A conventional evaluation method for solidification cracking is a relative and qualitative analysis method which does not provide quantitative data on the thermal stress in the solidification process. Therefore, a newly designed solidification cracking test apparatus was used in this study, and the device can provide quantitative data. As a result, after conducting experiments with different scrap addition ratios (0%, 20%, 35%, 50%), the tensile strengths and elongations in the as-cast state were 214, 187.7, 182.1 and 170.4MPa and 4.6%, 3.4%, 3.1% and 2.3%, respectively. In the case of the T6 heat-treated state, the tensile strengths and elongations were 314.9, 294.6, 293.1 and 271.1MPa and 5.4%, 4.6%, 3.8% and 3.1%, respectively. The strength of the solidification cracking was 3.1, 2.4, 2.2and 1.6MPa as the scrap addition ratio increases.

• Fire Science and Engineering
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• v.24 no.2
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• pp.89-96
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• 2010

In this research, exterior material combustion experiment was really tested to evaluate fire risks of aluminium complex panel which is used a lot for building exterior material. As a result, We saw fast fire spreading of aluminium complex panel. The reason is polyethylene in aluminum complex panel combust spreading fast fire flame vertically. In this test, the highest heat release rate of aluminum complex panel was 1,144 kW and surface temperature which is measured by thermocouple went up to more than $903.3^{\circ}C$, that temperature is quite a higher than $660^{\circ}C$ which is aluminum melting temperature. So, fire of aluminum complex panel can be evaluated to give us severe damage both by fast fire spreading vertically and by fire spreading through openings internally. These results from real experiment will be able to use to predict fire spreading of aluminum complex panel by comparing to modeling materialization of aluminum complex panel in the future.

• Journal of Navigation and Port Research
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• v.31 no.10
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• pp.825-831
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• 2007

The use of high-strength aluminum alloys for ship and offshore structure generally has many benefits compared to the structural steels. These materials are used widely in a variety of fields, especially in the hull and deck of high speed craft, box-girder of bridges, deck and side plates of offshore structure. The structural weight can be reduced using these aluminum structure, which can enable high speed The characteristics of stress-strain relationship of aluminum structure are fairly different from the steel one, because of the influence of Heat Affected Zone(HAZ) by the welding processing. The HAZ of aluminum is much wider than that of steel with its high heat conductivity. In this paper, the ultimate strength characteristics of aluminum stiffened panel subjected to axial loading, such as the relationship between extent of HAZ and the behavior of buckling/ultimate strength, are investigated through the Finite Element Analysis with varying its range.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.6
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• pp.401-405
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• 2017

Because silicon thin film solar cells have a high absorption coefficient in visible light, they can absorb 90% of the solar spectrum in a $1-{\mu}m$-thick layer. Silicon thin film solar cells also have high transparency and are lightweight. Therefore, they can be used for building integrated photovoltaic (BIPV) systems. However, the contact electrode needs to be replaced for fabricating silicon thin film solar cells in BIPV systems, because most of the silicon thin film solar cells use metal electrodes that have a high reflectivity and low transmittance. In this study, we replace the conventional aluminum top electrode with a transparent aluminum-doped zinc oxide (AZO) electrode, the band level of which matches well with that of the intrinsic layer of the silicon thin film solar cell and has high transmittance. We show that the AZO effectively replaces the top metal electrode and the bottom fluorine-doped tin oxide (FTO) substrate without a noticeable degradation of the photovoltaic characteristics.

• Journal of Institute of Convergence Technology
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• v.5 no.1
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• pp.7-12
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• 2015

Sheet metal formability can be defined as the ability of metal to deform without necking or fracture into desired shape. Every sheet metal can be deformed without failure only up to a certain limit, which is normally known as forming limit curve(FLC). In this paper, the dome stretching tests and tensile tests have been performed to obtain forming limit curve of aluminum alloy. During the experiment, failure strain is measured using digital image correlation(DIC) method. DIC method is a whole-field measurement technique that acquires surface displacements and strains from images information which characterized a random speckle as intensity grey levels. Recently years, this DIC method is being developed and used increasingly in various research. DIC results demonstrated the usefulness and ability to determine a strain.