• Tribology and Lubricants
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• 제34권6호
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• pp.307-312
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• 2018

Unlike a typical static seals, spring-energized static seals exhibit improvement in leak-tightness by reinforcing the spring inside the aluminum lining. Thus, spring-energized static seals are widely used in various industrial fields, such as aerospace, semiconductors, and petrochemical industries. The primary objective of this study is to develop design guidelines for spring-energized static seals in a wide range of temperatures, including that of cryogenic environments, by analyzing the required performance and influence of design variables through simulations. There are various parameters that can be controlled to design a leak-tight seal. In this study, the finite element analysis (FEA) is performed by controlling the parameters related to the spring and the thickness of the aluminum lining, and the result of the leakage between the seal and the casing is confirmed. Considering the influence of each parameters, all of them are found to be important. However, it is observed that the spring-related variables are more important than the aluminum lining or other variables when complexity is considered. We can identify the threshold value of spring stiffness that changes leak-tight performance of the seal by performing FEA. Simulation results, under the conditions that are considered in this study, show that spring stiffness should be at least 3.6 N/m to maintain leak-tightness caused by the sufficient contact force between the aluminum lining and the upper and lower casings.

• Journal of Welding and Joining
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• 제15권5호
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• pp.134-143
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• 1997

The formation of thick alloyed layer with high Si content have been investigated on the surface of Al alloy (A5083) plate by PTA process with Si powder. Hardening characteristics and wear resistance of alloyed layer was examined in relation to the microstructure of alloyed layer. Thick hardened layer in mm-order thickness on the surface of A5083 plate can be formed by PTA process with wide range of process condition by using Si powder as alloying element because of eutectic reaction of Al-Si binary alloy. High temperature and rapid solidification rate of molten pool, which are features of PTA process, enable the formation of high Si content alloyed layer with uniform distribution of fine primary Si paticle. High plasma arc current was beneficial to make the alloyed layer with smooth surface appearance in wide range of powder feeding rate, because enough volume of molten pool was necessary make alloyed layer. Uniform dispersion of fine primary Si particle with about 30${\mu}{\textrm}{m}$ in particle size can be obtained in layer with Si content ranging from 30 to 50 mass %. Hardness of alloyed layer increased with increasing Si content, but increasing rate of hardness differed with macrostructure of alloyed layer. Wear resistance of alloyed layer depended on $V_{si}$(volume fraction of primary Si) and was remarkably improved to two times of base metal at 20-30% $V_{si}$ without cracking, but no more improvement was obtained at larger $V_{si}$.

• 천문학회지
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• 제55권1호
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• pp.11-22
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• 2022

We introduce the Transformable Reflective Telescope (TRT) kit that applies an aluminum profile as a base plate for precise, stable, and lightweight optical system. It has been utilized for optical surface measurements, developing alignment and baffle systems, observing celestial objects, and various educational purposes through Research & Education projects. We upgraded the TRT kit using the aluminum profile and truss and isogrid structures for a high-end optical test device that can be used for prototyping of precision telescopes or satellite optical systems. Thanks to the substantial aluminum profile and lightweight design, mechanical deformation by self-weight is reduced to maximum 67.5 ㎛, which is an acceptable misalignment error compared to its tolerance limits. From the analysis results of non-linear vibration simulations, we have verified that the kit survives in harsh vibration environments. The primary mirror and secondary mirror modules are precisely aligned within 50 ㎛ positioning error using the high accuracy surface finished aluminum profile and optomechanical parts. The cross laser module helps to align the secondary mirror to fine-tune the optical system. The TRT kit with the precision aluminum mirror guarantees high quality optical performance of 5.53 ㎛ Full Width at Half Maximum (FWHM) at the field center.

• Journal of Welding and Joining
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• 제11권2호
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• pp.74-85
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• 1993

Effect of Si metal powders addition with the plasma transferred arc(PTA) overlaying process on characteristics of the alloyed layer in aluminum alloy(A5083) has been investigated. The overlaying conditions were 175-250A in plasma arc current, 500mm/min in travel speed, the 5-20g/min in powder feeding rate. Main results obtained are summarized as follows. 1)Sufficient size of molten pool on surface of base metal was required for forming an alloyed layer; in a fixed travel, the formation of alloyed layer with clear and beautiful surface depend upon the plasma arc current and powder feeding rate; the greater plasma arc current and the smaller powder feeding rate were, the better bead was formed. Optimum alloyed conditions by which an excellent alloyed bead obtained was 225A in plasma arc current. PTA process made it possible to form an alloyed layer with up to 67wt% Si. 2)Microstructure in the alloyed layer was in accord with prediction from the Al-Si phase diagram 3)The hardness of the alloyed layer increased in proportion to Si content. 4)As volume fraction of primary Si increased, the specific wearness of the alloyed layer was significantly improved. However, no further improvement was found when the volume fraction was greater than about 30%. 5)Utilizing the PTA process, a crack free alloyed layer with maximum hardness of about Hv 310 could be obtained.

• 한국자동차공학회논문집
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• 제11권5호
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• pp.112-118
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• 2003

The friction coefficients of the rubber for clutch master cylinder were experimentally measured in this study. The cylindrical rubber samples for primary cup-seal and secondary cup-seal were tested against the aluminum or the steel plates of master cylinder housing under the various conditions of brake oil temperatures and normal loads. Dry sliding friction coefficients were also measured under various load conditions. The test revealed following results. First, the friction coefficient under fluid lubrication condition in general decreases, as the oil temperature or normal load increases. Second, the steel plate of low surface roughness yielded comparatively low friction coefficient on the range of 0.30∼0.67. On the other hand, the aluminum plate of high surface roughness yielded high friction coefficient on the range of 0.31∼1.15. Third, the friction coefficient of dry surface contact decreases as the normal load increases. This is contrary to the general principle of friction coefficient between metal plates.

• 자원리싸이클링
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• 제29권5호
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• pp.3-14
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• 2020

마그네슘은 구조용 금속 중 알루미늄과 철에 이어 세 번째로 풍부한 금속이다. 또 마그네슘은 범용 금속 중 가장 가벼운 금속으로, 밀도가 알루미늄보다 33 %, 철보다 77 % 낮다. 마그네슘 1차 지금을 생산하기 위해서는 다량의 에너지를 소비하지만, 마그네슘 스크랩을 리사이클링하면 1차 지금 생산과 비교하여 에너지 및 환경부하를 저감할 수 있다. 그러나 마그네슘 스크랩 중의 불순물 제거가 곤란하여 재생되는 양은 한정되어 있다. 본 논문에서는 마그네슘의 1차 지금 생산 및 리사이클링 공정에 대하여 고찰하였다.

• 한국주조공학회지
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• 제15권6호
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• pp.566-573
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• 1995

In this study, the microstructural characteristics such as primary silicon, eutectic silicon, $SiC_p$ dispersion behavior, compound amount and Si solubility in $Al/SiC_p$ composite fabricated by the squeeze casting under various conditions were investigated systematically. As applied pressure(MPa) increases, cooling rate and compound amount are increased. In gravity casting, the cooling rate of hypereutectic composite is slower than of hypoeutectic composite by exothermic reaction of primary Si crystallization. But the cooling rate of hypereutectic composite is faster than that of hypoeutectic composite fabricated by same applied pressure, because amount of primary Si crystallization in hypereutectic composite was decreased, on the contrary, primary ${\alpha}-Al$ in hypoeutetic composite was increased due to increase of Si solubility in matrix by applied pressure. The crystalized primary silicon in hypereutectic composite fabricated by squeeze casting become more fine than that in non-pressure casting This is because mush zone became narrow due to increase of Si content of eutectic composition by pressure and time for growth of primary silicon got shorter according to applied pressure. It is turned out that eutectic temperature and liquidus are decreased by the increasing of squeeze pressure in all the composite due to thermal unstability of matrix owing to increasing of Si solubility in matrix by the increasing of applied pressure, as indicated in thermal anaiysis(DSC) results.

• 분석과학
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• 제34권5호
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• pp.202-211
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• 2021

Volatile organic compounds (VOCs) in hazardous air pollutants (HAPs) have been regulated by the Air Pollution Control Act (1978) and their atmospheric concentrations have been monitored in 39 monitor sites in Korea. However, measurement standards of volatile organic compounds (VOCs) in HAPs at ambient levels have not been established in Korea. Primary reference gas mixtures (measurement standards) at ambient levels are required for accurately monitoring atmospheric VOCs in HAPs and managing their emissions. In this study, primary reference gas mixtures (PRMs) at 5 nmol/mol were developed in order to establish primary national standards of VOCs in HAPs at ambient levels. Primary reference gas mixtures (PRMs) were prepared in pressurized aluminum cylinders with special internal surface treatment using gravimetric method. Analytical methods using gas chromatography-flame ionization detector (GC-FID) coupled with a cryogenic preconcentrator were also developed to verify the consistency of gravimetrically prepared HAP VOCs PRMs. Three different columns installed in the GC-FID were evaluated and compared for the retention times and separation of eighteen target components in a chromatogram. Results show that the HAP VOCs PRMs at 5 nmol/mol were consistent within a relative expanded uncertainty (k=2) of less than 3 % except acrylonitrile (less than 6 %) and the 18 VOCs were stable for 1 year within their associated uncertainties.

• 한국주조공학회지
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• 제26권5호
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• pp.205-210
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• 2006

여러 전자기 재료 프로세싱 연구 중에서 연구 되어지지 않았던 Al-Si 합금의 조직제어를 직류 자기장과 교류 전류장을 사용하여 시도 하였다. 본 연구의 목적은 Al-Si 합금에서의 새로운 거시, 미시 조직제어를 하기 위해 사용된 전자기 진동의 영향을 조사하는 것이다. 전자기 진동이 초정 알루미늄의 형상 변화를 위해 낮은 진동수 (>60Hz)로 주어질 경우, 수지상의 형상이 구상화 형상으로 변해갔다. 전자기 진동이 공정 실리콘 형상 변화를 위해 주어졌을 경우, 높은 진동수 (>500Hz)에서 조대한 판상 조직이던 실리콘이 미세한 섬유상 조직으로 변화하고, 기계적 성질도 우수해졌다.

• 대한소아치과학회지
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• 제48권4호
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• pp.460-466
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• 2021

이 연구의 목적은 유치의 상아질면에서 염화알루미늄 지혈제와 황화철 지혈제의 적용이 레진강화형 글라스아이오노머(RMGIC)의 결합에 미치는 영향을 전단결합강도를 통하여 평가하는 것이다. 20개의 우식이 없는 유구치가 이용되었으며 상아질이 노출되도록 시편을 제작하여 지혈제의 종류에 따라 3개의 군으로 분류하였다. I군은 치면에 25% polyacrylic acid(PAA)를 10초간 사용한 군, II군은 21.3% 염화알루미늄 지혈제를 1분간 사용한 뒤 PAA를 10초간 적용한 군, III군은 20% 황화철 지혈제를 1분간 사용한 뒤 PAA를 10초간 적용한 군으로 설정하였다. 각 군당 10개의 시편에 RMGIC를 중합하여 전단결합강도를 측정하였다. 결합강도는 I군이 10.07 ± 1.83 MPa, 2군에서 7.62 ± 0.78 MPa, 3군에서 5.23 ± 0.78 MPa였다. 모든 군의 결합강도는 유의한 차이를 보였다. 이 연구를 통해 염화알루미늄 지혈제, 황화철 지혈제 모두 상아질에서 RMGIC의 전단결합강도를 감소시키며 황화철 지혈제가 염화알루미늄 지혈제보다 RMGIC의 전단 결합강도를 더 많이 감소시키는 것을 알 수 있었다.