• 대한기계학회논문집A
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• 제35권7호
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• pp.745-751
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• 2011

입자강화 알루미늄 복합재의 강도를 계산하기 위하여 압밀 후 냉각할 때 일어나는 전위 펀칭을 유한요소로 모델링 하였다. 다양한 입자의 체적비에서 입자의 크기가 강도에 미치는 영향을 고려하기 위하여 강화 입자 주위에 변형률 구배 소성과 테일러 전위 모델을 적용하였다. 변형률 구배는, 구형 단위 셀이 냉각하는 동안 입자와 기지재의 열팽창계수 차이에 의한 전위 펀칭이 일어날 때 형성되는 등가소성변형률로부터 구하였다. 펀칭된 영역에 걸쳐 평균적으로 변형률 구배를 고려함으로써 항복 응력이 증가하는 것을 관찰하였다. 유한요소 해석을 활용하여 다양한 입자 크기와 체적비에 대하여 SiC 강화 알루미늄 356-T6 복합재의 축대칭 단위 셀의 인장시 강도의 변화를 예측하였다. 예측된 강도는 실험 데이터와 잘 일치하며, 입자 크기 의존 효과를 분명히 보인다.

• Composites Research
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• 제32권3호
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• pp.141-147
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• 2019

In this study, micro-sized and nano-sized pure aluminum (Al) powders were compressed by unidirectional pressure at room temperature. Although neither type of Al bulk was heated, they had a high relative density and improved mechanical properties. The microstructural analysis showed a difference in the process of densification according to particle size, and the mechanical properties were measured by the Vickers hardness test and the nano indentation test. The Vickers hardness of micro Al and nano Al fabricated in this study was five to eight times that of ordinary Al. The grain refinement effect was considered to be one of the strengthening factors, and the Hall-Petch equation was introduced to analyze the improved hardness caused by grain size reduction. In addition, the effect of particle size and dispersion of aluminum oxide in the bulk were additionally considered. Based on these results, the present study facilitates the examination of the effect of particle size on the mechanical properties of compacted bulk fabricated by the powder metallurgy method and suggests the possible way to improve the mechanical properties of nano-crystalline powders.

• 한국주조공학회지
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• 제10권6호
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• pp.528-537
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• 1990

7XXX aluminum alloy powders produced by the self-manufactured rotating disc atomizer were investigated to determine the influence of the atomization parameters on the particle size distributions in air atmosphere. The particle size distributions are almost always bimodal with the dominant mode on the large particle size. Average powder size of 7XXX aluminum alloy is $74/{\mu}m~125/{\mu}m$ when melt is poured with the rate of 9g /sec at 730$^{\circ}C$ on a rotating disc of 30㎜ diameter at 6300rad/sec. The mass of finer particle increased when disc diameter, angular velocity, pouring temperature increased and pouring rate decreased. The powder shapes of bimodal change from acicular to tear-drop and from tear-drop to ligament with increasing powder size. Powder shape was determined by the atomization mechanism and oxidation in liquid state. Microstructure of powders appeared to be cell and cellular dendrite. The SDAS of Al-7.9wt%Zn-2.4wt%Mg-1.5wt%Cu-0.9wt%Ni Powders is $0.8{\mu}m~1.0{\mu}m$ for the powders of $size＋44{\mu}m~53{\mu}m$ and $1.6{\mu}m∼1.8{\mu}m$ for the powders of $size＋105{\mu}m~125{\mu}m$, repectively.

• 한국가스학회지
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• 제18권5호
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• pp.20-25
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• 2014

마이크로 크기의 알루미늄 분진의 폭발 특성에 대한 연구는 많이 조사되어 왔지만 나노 크기의 알루미늄 분진에 대한 연구는 매우 적다. 본 연구에서는 나노 및 마이크로 크기의 알루미늄 분진 (70 nm, 100 nm, $6{\mu}m$, $15{\mu}m$)이 분진폭발특성에 미치는 영향을 20 L 폭발시험 장치를 사용하여 실험적으로 조사하였다. 부유 상태의 알루미늄 분진의 입자 크기가 감소하면, 나노 크기에서의 알루미늄 분진의 폭발하한농도(LEC)는 마이크로 크기의 알루미늄분진보다 감소하였다. 나노 크기의 알루미늄 분진에서의 폭발특성은 마이크로 크기의 알루미늄 분진과 명확한 폭발성의 차이를 보이지 않았다. 투과 전자 현미경(TEM )에 의해 나노 크기의 알루미늄 입자의 관찰로부터 입자 간의 응집성의 증가가 나노 알루미늄 분진의 폭발성에 영향을 미칠 수 있을 것으로 추정되었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.202-208
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• 2001

Aluminum dross should be recycled in consideration of characteristics of the dross and its reutilization after processing. In this study, aluminum dross generated in the domestic secondary aluminum industry was processed to use it as raw material for producing aluminum hydroxide. Sample dross was classified according to its size. The dross smaller than 1mm was leached with sodium hydroxide solution to extract the remaining aluminum from the dross into the solution, and then aluminum hydroxide precipitate was recovered from the leach liquor. Purity of the obtained aluminum hydroxide was above 98 percent, and particle size of the sample was in range of 3-39${\mu}{\textrm}{m}$. From the result, it was suggested that this process could be applicable to recycling of aluminum dross.

• 한국주조공학회지
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• 제22권5호
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• pp.257-264
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• 2002

Effects of Ca content on the refinement of primary Si of Aluminum B390 alloy have been examined. Ca was found to have an effect on the refinement of primary Si particle. Primary Si particle size has been refined as Ca content of the melts decreased and cooling rate increased. A control of Ca content by the addition of $CuCl_2$ to the melt was the most efficient in the refinement of primary Si particles. The minimum size of primary Si particles in this study was $15.0\;{\mu}m$ when a residual content of Ca element in the alloy was 5ppm, Primary Si particle size was refined as primary Si crystallization temperature increased, which was attributed to the decrease of Ca content in the melts.

• 대한기계학회논문집A
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• 제28권6호
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• pp.739-746
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• 2004

The plastic deformation behavior of an aluminum alloy containing a particle and porosities was investigated at room temperature during equal channel angular pressing (ECAP). Finite element analysis by using ABAQUS shows that ECAP is a useful tool for eliminating residual porosity in the specimen, and more effective under friction condition. The simulation, however, shows considerably low density distributions for matrix near a particle at which many defects may occur during severe deformation. Finite element results of effective strains and deformed shapes for matrix with a particle were compared with theoretical calculations under simple shear stress. Also, based on the distribution of the maximum principal stress in the specimen, Weibull fracture probability was obtained for particle sizes and particle-coating layer materials. The probability was useful to predict the trend of more susceptible failure of a brittle coating layer than a particle without an interphase in metal matrix composites.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1157-1162
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• 2003

Behavior of aluminum alloy embedding a particle was investigated at room temperature under ECAP. Finite element analysis by using ABAQUS shows that ECAP is a useful tool for eliminating residual porosity in the specimen, and much more effective under friction condition. The simulation, however, shows considerably low density distributions for matrix near a particle at which rich defects may occur during severe deformation. Finite element results of effective strains and deformed shapes for matrix with a particle were compared with theoretical calculations under simple shear stress. Also, based on the distribution of the maximum principal stress in the specimen, Weibull fracture probability was obtained for particle sizes and particle-coating layer materials. The probability was useful to predict the trend of more susceptible failure of a brittle coating layer than a particle without an interphase in metal matrix composites.

• 지질공학
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• 제16권2호
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• pp.153-159
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• 2006

수질오염이 심각해지면서 수자원의 이용을 어렵게 하며 수자원의 관리를 위해 사용되는 시간적 기술적 경제적 부하도 증대시키고 있다. 그러므로 본 논문에서는 간단하고 신속하게 수질을 파악 할 수 있는 미규제 수질인자($E_{260}$과 입자수)를 도입하여 정수공정의 효율성을 평가하고자 하였다. 탁도저감을 목적으로 주입하는 알루미늄에 의해 용존성 알루미늄의 잔존량이 증가하는 경향이 있으므로 탁도 모니터링만으로는 안전한 수질을 기대하기가 어려움을 명확히 알 수 있었으며, 잔존알루미늄의 농도를 모니터링 하는 대신 간단 신속하게 분석할 수 있는 $E_{260}$인자를 이용할 수 있음을 밝혔다. 또한 탁도 뿐만 아니라 용존성 비소화합물의 모니터링에도 $E_{260}$은 효율적으로 사용되었다. 수처리공정의 효율을 개선하기 위해 수처리제의 교환을 고려할 때에도 탁도 자료만으로는 질적인 개선정도를 평가하기 어려웠으나, 수중의 입자를 계수함으로써 재선정도의 평가가 용이해져 적절한 수처리제의 선택을 가능하게 하므로 수질개선과 경제적 절약을 모두 달성하게 하였다. 따라서 효율적인 정수처리 뿐만 아니라 수자원의 관리 측면에서도 이들 인자는 매우 유용하게 사용될 수 있을 것으로 기대된다.

• 한국주조공학회지
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• 제14권1호
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• pp.62-74
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• 1994

The concentration and particle size distribution of non-metallic inclusions which suspended in the molten aluminum at $700^{\circ}C$ were measured by using LiMCA apparatus. The result revealed that the number of inclusions increased with increasing the applied current or decreasing the orifice diameter, while decreased with increasing the purity of aluminum. And also, it was found that the number of inclusions increased with increasing the amount of boron added to molten aluminum. This was found to be attributed to the formation of the inclusions of TiB and $V_3B_2$. It was investigated that the average concentration of inclusions in a constant volume of 20ml of molten aluminum was increased in the order of pure molten aluminum, molten aluminum containing 20ppm of boron and molten aluminum used repeatly in the experimental casting in this study.