• 한국세라믹학회지
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• 제36권12호
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• pp.1327-1334
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• 1999

Behaviors of abnormal expansion during calcination process of Ba2Ti9O20 ceramics and its related effects on the sintering characteristics were investigated as a function of precursors. When BaCO3 and TiO2 powders were used as starting materials. BaTi4O9 phase which has relatively large molar volume was formed drastically with abnormal ex-pansion during the calcination at 95$0^{\circ}C$ to 115$0^{\circ}C$ ON the contrary using BaTiO3 and TiO2 powders as starting materials led to retardation of the formation of BaTi4O9 phase and concurrently suppressed the abnormal expansion during cal-cination process. Especially the calcined powder of BaTiO3 and TiO2 had advantages in the densification and formation of Ba2Ti9O20 single phase in the sintering process.

• 한국세라믹학회지
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• 제22권6호
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• pp.9-14
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• 1985

When the barium titanate is Synthesized in Solid-solid reaction the abnormal expansion occurs at about 110$0^{\circ}C$. The mixture was made of corresponding to the theoretical composition of barium titanate. The mixture was fired at various temperature from 90$0^{\circ}C$ to 130$0^{\circ}C$, After that the specimen was tested closely with XDR dilatometer and SEM. The results indicate that 1, The activation energy of barium titanate formation was 42 Kcal/mole. 2, Thermal expansion up to to 90$0^{\circ}C$ was mainly caused by $CO_2$ whereas it was mainly caused by the formation of the secondary phase above 100$0^{\circ}C$. 3. Thermal expansion was not influenced by the forming pressure up to 1000kg/$cm^2$ but it was largely influenced bythe forming pressure above 200kg/$cm^2$.

• 한국세라믹학회지
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• 제23권4호
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• pp.41-46
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• 1986

When barium titanate was synthesized in solid-solid reaction the abnormal expansion occurred from 90$0^{\circ}C$ to 110$0^{\circ}C$. The equi molecular mixture of $BaCo_3$ and $TiO_2$ was sintered from 90$0^{\circ}C$ to 130$0^{\circ}C$ on the condition of air vacuum and $CO_2$ atomosphere. After that the specimens were tested closely with XDR Dilatometer and SEM The result indicated that: 1, Volume expansion to be synthesized barium titanate in solid-solid reaction was affected by atomosphere sintering. 2. The solid reaction ot fiorm barium titanate in vacuum atomosphere occurred faster than that in air atomosphere. In vacuum atomosphere the maxium volume expansion was about 30% at 90$0^{\circ}C$ for 2hrs, 3. The solid reaction to form barium titanate in 4CO_2$ atomosphere occurred slower than that in air atomosphere. In $CO_2$ atomosphere the maximum volume expansion was 13% at 100$0^{\circ}C$ for 2 hrs. 4. According to the result of x-ray the expanison was caused by the reaction to form $BaTiO_3$ and change $Ba_2TiO_4$ into 4BaTiO_3$.

• 한국분말재료학회지
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• 제11권5호
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• pp.383-390
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• 2004

In order to investigate behavior of abnormal expansion of the iron-copper compacts, we compared the dilatometric curves of the compacts which mixed the copper powder to the iron powder with those of compacts which mixed the copper powder to the iron-copper alloy powder. The dilatometric curves were obtained below the sintering conditions, which heated up to 115$0^{\circ}C$ by a heating rate of 1$0^{\circ}C$/min, held for 60min at 115$0^{\circ}C$ and cooled down at a rate of 2$0^{\circ}C$/min to room temperature. The dilatometric curves of the compacts showed the different expansion behavior at temperatures above the copper melting point in spite of same chemical composition. All of the compacts of former case showed large expansion, but all of the compacts in latter case showed large contraction. The microstructures of sintered compacts also showed the different progress in alloying of the copper into the iron powder. Namely we could observe the segregation at alloy part of copper into iron powder in case of the sintered compacts, which mixed the copper powder to the iron powder, but could not observe the segregation in compacts which mixed the copper powder to the iron-copper alloy powder. But the penetration of liquid copper into the interstices between solid particles was occurred at both cases. Therefore, the showing of the different dimensional changes in the compacts in spite of same chemical composition is due to more the alloying of copper into iron powder than the penetration of liquid copper into the interstices between solid particles.

• 한국세라믹학회지
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• 제26권6호
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• pp.783-788
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• 1989

The reason of abnormal expansion in BaTiO3 synthesized in the equimolecular mixture and synthesized in Ba-rich region were investigated at the point of crystal and microstructure. The shrinkage and the expansion of the mixtures in BaCO3-TiO2 system were determined by the mass of BaCO3 added to the equimolecular BaCO3 and TiO2, Ba2TiO4 which was much formed and BaTi2O3 were important crystal in the reaction of Ba-rich region. Sintering phenomena of unreacted BaCO3 activity and the secondary phase caused to generate microcracks in the specimens.

• 에너지공학
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• 제23권3호
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• pp.116-124
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• 2014

고온에서 운전되는 플랜트에서는 열변형에 의한 배관 사고를 예방하고 배관계통의 우선 검사관리 부위의 선정을 위해 배관 시스템하중 해석을 수행하는 경우가 많다. 본 연구에서는 국내 한 공정플랜트에서 설계변경에 따라 반응기와 반응기 사이에 추가 설치된 연결배관을 대상으로 배관 시스템응력해석을 수행하였다. 특히 배관에 일반적으로 설치되는 하중행거(hanger) 이외에 열팽창을 흡수하는 신축이음(expansion joint)이 함께 설치된 경우의 배관 특성을 연구하였다. 이를 위해 배관 응력을 형성하는 구조적 요인의 영향을 평가하기 위해 배관계에 포함된 행거와 신축이음이 비정상적으로 작동되는 경우도 가정하여 해석하였다. 추가적인 인입라인이 있는 경우도 해석을 수행하였다. 정상 운전 시 배관계의 시스템 응력 결과와 비정상적인 운전 경우의 해석결과를 비교하여 각각 배관요소의 역할을 연구하였다.

• 한국세라믹학회지
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• 제24권1호
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• pp.41-46
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• 1987

When barium titanate was synthesized in soild-solid reaction the abnormal expansion occurred from 900$^{\circ}C$ to 1100$^{\circ}C$. The equi-molecular mixture of BaCO3 and TiO2 was sintered from 800$^{\circ}C$ to 1300$^{\circ}C$ on the condition of air, vacuum and CO2 atmosphere. After that the specimens were tested closely with XRD, Dilatometer, SEM and EDS. The result indicated that; 1. The crystal phase which was concerned with expansion of BaTiO3 was Ba2TiO4 as the intermediate crystal phase. 2. The formation of Ba2TiO4 was affected by the firing atmosphere. 3. The expansion occurred when BaTiO3 changed to Ba2TiO4 and pore also expanded by the expansion of BaTiO3 body just as the model of expansion.

• 한국수소및신에너지학회논문집
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• 제19권3호
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• pp.182-188
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• 2008

In order to improve scavenging performance of free piston hydrogen fueled engine, this study estimate compatibility of uni-flow scavenging. The scavenging flow characteristics in the cylinder is investigated by flow visualization and PIV method. Consequently it has been found that the scavenging performance decreased with abnormal expansion of piston and delay of the exhaust valve opening timing. And the scavenging performance of exhaust valve located center in cylinder head is better than that of exhaust valve located side in cylinder head.

• 한국자동차공학회논문집
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• 제3권6호
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• pp.250-261
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• 1995

In this study, a rapid compression and expansion machine(RCEM) equipped with a swirl generator was designed and developed, in order to clarify normal and abnormal combustion(knocking phenomena). This RCEM is intended to simulate combustion process in actual automotive S.I.engines, having a high reproducibility in the compression stroke. Flame propagation and autoignition processes associated with normal and abnormal combustion were captured by the high speed schlieren photography. And swirl intensity. equivalence ratio and ignition position were varied to investigate the effect of turbulence, concentration in the unburnt gas region and flame propagation length. The knock intensity, knock mass fraction and knock mass fraction after autoignition were calculated by use of history of measured cylinder pressure.

• 한국구조물진단유지관리공학회 논문집
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• 제28권2호
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• pp.1-8
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• 2024

신축이음 장치는 교량 상부구조의 신축량을 수용할 목적으로 설치되며 공용중 충분한 유간을 확보하여야 한다. 안전점검 및 정밀안전진단 수행 시 유간부족 및 유간과다에 대한 손상을 명시하고 있으나, 유간에 따른 교량의 이상 거동을 판별하기 위한 기준이 미흡하다. 본 연구에서는 동일 신축이음부의 유간 데이터를 지속적으로 추적하여 데이터 기반의 유지관리 방안을 제시하였다. 689개소의 신축이음 장치에서 계절별 영향을 고려하여 총 2,756개의 유간 데이터를 수집하였다. 동일 위치에서 4개 이상의 데이터를 통해 신축거동을 분석할 수 있는 유간 변화 평가 방안을 마련하였으며, 신축거동에 영향을 미치는 인자를 분류하고 딥러닝과 설명 가능한 AI를 통해 각 인자의 영향도를 분석하였다. 유간 평가 그래프를 통해 교량 상부구조의 이상 거동을 협착 및 기능 고장으로 분류하였다. 이론적 거동을 보이고 있다하더라도 협착 가능성이 나타날 수 있는 사례 및 하절기 협착 가능성이 매우 높게 나타난 사례가 도출되었다. 협착 가능성은 낮으나 교량 상부구조에 기능상 문제점이 발생했을 가능성이 높은 사례와 시공오류에 따라 신축이음 장치가 재시공된 사례도 도출되었다. 딥러닝 및 설명 가능한 AI를 통한 영향인자 분석은 기존의 신축유간 계산식 및 교량 설계에 따른 결과로 설명 가능하여 신뢰 가능한 수준으로 판단되어 추후 모델의 개선을 통해 유지관리를 위한 가이드를 제시할 수 있을 것이라 판단된다.