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Development of High Performance Asphalt Mastic using Fine Taconite Filler
문기훈,Augusto Cannone Falchetto,박주영,정진훈 대한토목학회 2014 KSCE Journal of Civil Engineering Vol.18 No.6
Low temperature cracking is a very serious distress for asphalt pavements built in Northern U.S. and Canada. As temperaturerapidly decreases, thermal stresses develop in the restrained asphalt surface layer and, when the temperature reaches a critical value,cracking occurs. A “simple” solution to overcome this problem is to use a very soft asphalt binder with high relaxation properties,which limits the accumulation of high stress and the formation of cracks. However, these types of binder may lead to significantpermanent deformation at high temperature (e.g., rutting) and, therefore, cannot be used for real pavement constructions. In thisresearch, the possibility of obtaining stiffer asphalt binders by adding fine taconite filler available in Minnesota was investigated. Twodifferent types of asphalt binders were selected and from each binder, three different types of asphalt mastics were prepared based onthe amount (i.e., level) of taconite particles used as filler: 5%, 10% and 25%. Bending Beam Rheometer (BBR) and Dynamic ShearRheometer (DSR) tests were performed to evaluate the low and high temperature properties of asphalt binder and correspondingmastics. From these experimental works, creep stiffness, m-value, thermal stress and shear complex modulus were calculated andthen graphically and statistically compared. It was observed that asphalt mastic containing 5% taconite filler presents similarproperties at low temperature and better performances at high temperature compared to the corresponding asphalt binder. On theother hand, asphalt mastics containing higher amount of taconite fines (10% and 25%) are much more brittle compared to the originalbinder at low temperature, even though higher rutting resistance was observed at high temperature.
문기훈,김규태 한국연소학회 2020 한국연소학회지 Vol.25 No.2
Strong acoustic interactions via a cross-talk section were investigated in two coupled model gas turbine combustors. In particular, we focused on the dynamical state of different acoustic interaction modes using several time series analysis methods, including phase portraits, Poincaré maps, correlation dimensions, and histograms. Our results demonstrate that a period-1 limit cycle occurs for a push-push mode. By contrast, when a push-pull mode is excited in the system, a period-3 attractor emerges in the cross-talk section.
문기훈,김규태 한국연소학회 2022 한국연소학회지 Vol.27 No.1
Driving mechanisms of self-excited azimuthal instabilities of can-annular lean-premixed combustors were experimentally investigated in combination with 3D FEM-based eigenvalue analysis and acoustic wave decomposition method. We show that the fluctuation energy required to excite a standing azimuthal mode in annular cross-talk section is supplied locally in individual combustors by meeting the Rayleigh criterion, while the behavior in four combustor sections is dictated by degenerate longitudinal-mode at the same frequency
니켈코팅 및 열처리가 알루미늄/철 하이브리드 구조의 계면 특성 및 기계적 특성에 미치는 영향
문기훈,이준엽,이은경 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5
전세계적인 환경규제에 따라 자동차 업계에서는 차량 경량화를 위해 고성능 알루미늄 합금에 대한 수요가 증가하고 있다. 또한 높은 기계적 특성이 요구되는 브레이크 디스크, 엔진 블록, 실린더 헤드와 같은 부품들의 경량화를 위해 철과 알루미늄이 결합된 Al/Fe hybrid structure에 대한 연구가 활발히 진행 중이다. 하지만 두 금속 간의 접합은 열적 특성의 차이에 의한 낮은 젖음성으로 접합이 잘 되지 않은 문제점이 있다. 따라서 본 연구는 이종 주조법으로 철과 알루미늄 합금을 접합시킨Al/Fe hybrid structure의 계면 접합을 향상시키기 위해 니켈 코팅과 열처리를 도입했으며, 이에 따른 효과를 미세구조적 분석 및 열역학적 계산을 통해 접합 향상 메커니즘을 확인했다. 니켈 코팅은 계면에서 산화물 생성 억제를 통해 물리적 접합을 향상시켰으며, 열처리는 원소 간의 상호 확산을 유도하여 계면에서 우수한 화학적 결합을 발생시켰다. 또한 알루미늄 합금의 고온 특성에 유익하다고 알려진 nickel-bearing phase의 형성을 촉진시켰다. Al matrix 내부에서 확산에 따른 원소 농도변화로 생성된 상들의 변화를 열역학적 상태도로 분석한 결과, 확산된 원소 중 니켈과 알루미늄 합금의 구리의 원소 비율에 의해 결정되는 것을 확인했다.