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김택기,조형규,김문상,임성호,전찬원 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.11
본 연구는 P-3C 해상초계기 외부에 Radome 을 추가로 장착할 때 야기되는 공력성능 변화에 대한 예측을 수치해석을 이용하여 수행한 뒤 항공기 감항인증에 필요한 자료를 제공하는데 목적이 있다. 항공기 형상에 관한 상세 정보를 획득하기 어려워 프라모델을 통해 외형 정보를 획득하였다. 3D-Scan 을 사용하여 완성된 형상을 프로펠러를 탈착한 상태에서 상공 7,620m 의 순항조건에서 해석을 진행하였으며, Radome 의 유무에 따른 공력성능 자료를 비교하였다. This study has a goal to prepare aerodynamic performance data for airworthiness certification of radome built-in P-3C Orion aircraft using numerical analysis tool. A plamodel is scanned using 3D scanner to obtain aircraft configuration, which is very hard to acquire from the aircraft industry. P-3C is simulated at the flight condition of 7,620m altitude cruising condition. Aerodynamic performance data are analyzed to understand the effect of radome on the aerodynamic performance.
Fe-25Cr-14Co-2Si-1.5 Ti 합금의 자기적 특성에 미치는 열처리 효과
김택기,김윤배,송세안 대한금속재료학회(대한금속학회) 1986 대한금속·재료학회지 Vol.24 No.4
To study the effect s of heat treatment on the magnetic properties of ductile Fe-Cr-Co permanent magnets, a composition of Fe-25Cr-l4Co-2Si-1.5Ti alloy was prepared by induction melting, and the optimum heat treatment procedure and the microstructures of the alloy were investigated. After step aging treatments, it was concluded that aging at high temperature effects largely on the squareness of the demagnetization currve and aging at low temperature effects largely on the coercive force. The sample which was thermomagnetically treated for 10 minutes at 675℃ showed clearly the evidence of spinodal decomposition of the FeCo-rich phases from the Cr-rich matrix.
Alnico 5 의 열처리에 따른 2 상분리조직과 자기특성
김택기,김윤배,송세안,임동묵 대한금속재료학회(대한금속학회) 1986 대한금속·재료학회지 Vol.24 No.5
In order to study a relation between microstructures and magnetic properties in Alnico 5, Fe-24Co-14Ni-8Al-3Cu alloy was prepared by induction melting, and then optimum heat treatment procedures and microstructures of this alloy were investigated systematically. In Alnico 5, the cooling rate(c) in a magnetic field from 900℃ to 600℃ and the optimum aging time(t) at 600℃ have a relation of log(t)=0.417 log(c) + 0.884. However, the final magnetic properties are highly dependent on the cooling rate. Spinodally decomposed structures of this alloy show that the faster the cooling rate, the smaller the size of the FeCo-rich precipitates and the larger the aspect ratio. Length of the long axis of the FeCo-rich precipitates at a given cooling rate is not uniform due to the interconnection of sub sequent precipitates by magnetic field effect, and this tendency seems to be stronger when the cooling rate is slower. But the length of the short axis of the precipitates is almost same at a given cooling rate. The length of the short axis (ℓ) and cooling rate (c) in magnetic field have a relation of log (ℓ)=2.385-0.317 log(c) Optimum solution treatment temperature of the low temperature solution treatment method is 860℃. It is concluded that the low temperature solution treatment method is more desirable than the high temperature solution treatment method in improving the hard magnetic properties
Fe-25 Cr-14 Co-2 Si-1.5 Ti 합금의 자기적 경화과정
김택기,김윤배,서원근 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.6
The magnetic hardening process according to the heat treatment of a Fe-Cr-Co hard magnetic alloy was investigated. It could be described that the magnetic hardening process of this alloy was divided into three parts. In the heat treatment of the first stage, the thermomagnetic treatment, FeCo-rich (α₁) phases were precipitated. The aspect ratio of precipitates was determined in this stage. The heat treatment of the second stage caused precipitates to grow, improving the magnetic properties of the alloy. The alloy became brittle due to the rapid increase of the hardness by the second stage. In the heat treatment of the third stage, the concentration of the matrix (α₂) and the precipitates (α₁) changed gradually with little change in the shape and volume fraction of the precipitates. The coercive fores of the alloy increased largely in this last stage.
자장열처리가 비정질 Fe80-xCoxSi6B14 합금의 자기적 성질에 미치는 영향
김택기,조용수,김기환 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.6
Amorphous Fe_(80-x)Co_xSi_6B_(14)(10≤X≤70) alloys were annealed below their Curie temperatures in AC magnetic field in order to improve soft magnetic properties. Magnetization measurements were made as a function of applied AC magnetic field and annealing temperature and time. Magnetic measurement results clearly demonstrated that some beneficial effects can be provided by applying AC field during annealing, in improvement of the soft magnetic properties : a significant decrease both in coercive and in AC Power loss, and a tendency toward a square shape of hysteresis loop were observed in the our present study. The optimum experimental condition to obtain best magnetic properties for the amorphous Fe_(80-x)Co_xSi_6B_(14) alloys was determined to be AC field annealing treatment at 380℃ for 30 min with H_a≥30 Oe.