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김종환(Jong-Hwan Kim),김재훈(Jae-Hoon Kim) 한국항공우주학회 2004 韓國航空宇宙學會誌 Vol.32 No.8
본 연구에서는 비행체 구조재료인 A12024-T3에 대하여 공력가열환경을 모사할 수 있는 복사가열기를 제작하였으며, 1℃/sec~30℃/sec 가열률 범위에서 열기계적 인장특성을 평가 하였다. 가열환경에 따른 재료강도 평가를 위하여 급속가열 인장시험 결과와 일정 온도로 30분 노출후의 인장시험결과를 항복응력 측면에서 비교 고찰하였다. 급속가열 인장시험 결과로부터 시간-온도계수를 응용한 가열률-항복온도 계수를 도출하였으며, 항복응력을 가열률과 항복온도로 표현되는 실험적 master 수식을 제안하였다. 본 연구 결과를 통하여 획득 된 급속가열 인장시험결과들은 초음속 비행체 설계시 선정재료의 안전여유를 판단하는 기 초자료로 활용될 수 있다. The thermomechanical tensile characteristics were evaluated for A12024-T3 under heating rates from 1 ℃/sec to 30℃/sec by using an infrared heating equipment to simulate aerodynamic heating. The rapid heating test results were compared with tensile test results after 1/2 hour exposure in terms of yield stress to investigate the influence of heating condition. A heating rate-yield temperature parameter was suggested for rapid heating based on time-temperature parameters, and master yield stress curve was obtained by using these parameter. These test results can be used for margin of safety of supersonic vehicle structures subjected to aerodynamic heating.
도영대(Youngdae Doh),유지창(Jichang Yoo),김창기(Changkee Kim),이도형(Dohyung Lee),함희철(Heecheol Ham) 한국추진공학회 2009 한국추진공학회 학술대회논문집 Vol.2009 No.5
급속 가열 상황에 있는 추진기관에 있어 가장 중요한 문제는 열해석으로 추진기관의 거동을 파악하는 것이다. 열은 추진제의 물성저하를 야기 시켜 자연발화 시킨다. 급속가열을 받는 추진지관에서 가장 바람직한 반응을 얻기 위해서는 추진기관의 케이스가 추진제에서 점화가 일어나기 전에 구조적으로 완전히 파손되어야 한다는 것이다. 본 논문에서 열해석을 위해 유한요소법을 이용하여 급속가열 상황에 놓인 고체 추진기관의 반응을 조사하였다. The most important thing is to analyze the Fast Cook Off problem of the solid motor case exposed to direct flame is a heat transfer analysis. Heat causes degradation and ignition of the propellant. To archive an acceptable reaction level in Fast Cook Off, the rocket motor case generally must fail structurally prior to propellant ignition. We investigate the responses of the solid motor case exposed to Fast Cook Off by using finite element method for the thermal analysis.
손동휘(Dong-Hwi Sohn),서영수(Young-Soo Seo),박근(Keun Park) 한국소성가공학회 2009 금형가공 심포지엄 Vol.2009 No.11
Rapid mold heating has been recent issue to enable the injection molding of thin-walled parts or micro/nano structures. High-frequency induction is an efficient way to heat mold surface by electromagnetic induction in a non-contact manner, and has been recently applied to the injection molding due to its capability of rapid heating and cooling of mold surface. The present study covers a three-dimensional finite element analysis to investigate heating efficiency and structural safety of the induction heating process of an injection mold. To simulate the induction heating process, an integrated simulation method is proposed by effectively connecting an electromagnetic field analysis, a transient heat transfer analysis and a thermal stress analysis. The estimated temperature changes are compared with experimental measurements for various types of induction coil, from which heating efficiency according to the coil shape is discussed. The resulting thermal stress distributions of the mold plate for various types of induction coils are also evaluated and discussed in terms of the structural safety.
이도형(Dohyung Lee),김창기(Changkee Kim),연정모(Jeongmo Yeon),정정용(Jungyoung Jung),유지창(Jichang Yoo) 한국추진공학회 2009 한국추진공학회 학술대회논문집 Vol.2009 No.11
본 연구에서는 추진기관 급속가열시험을 실시하여 그 특성을 분석 평가 하였다. 연소관은 카본 에폭시 복합재를 사용하였고 추진제는 둔감 특성을 향상 시켜주기 위해 HTPE 추진제를 사용하였다. 반응 형태를 정량적으로 판단하기 위해 음압 및 열유속 센서를 사용하였다. 급속가열 시험한 HTPE 모타들의 반응형태는 Type V 인 연소반응을 나타내었다. Fast cook-off test with rocket motors was performed and characteristics of the results were analyzed. The material of the motor case was carbon epoxy composite. The motor was loaded with HTPE propellants to improve the insensitive munitions characteristics. In the tests, sound pressure and heat flux sensors were used to determine the category of response according to the standard. The reaction response of all of the HTPE motors tested by fast cook-off was judged as Type V burning.
급속가열 및 압축의 효과가 7인치 도광판의 복굴절 분포에 미치는 영향에 관한 실험적 연구
민인기(I. K. MIn),홍석관(S. K. Hong),강정진(J. J. Kang),김민구(M. G. Kim),정의철(E. C. Jung),윤경환(K. H. Yoon) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
As the growth of injection molding technology, injected-molded optical products require higher dimension accuracy and optical stability than ever. In the present study, four kinds of molding mechanisms, i.e., conventional injection molding(CIM), injection/compression molding(ICM), rapid heat and cooling the mold(RHCM) and rapid injection/compression molding(RICM) were chosen to investigate the optical anisotropy of 7 inch LGP by examining the in-plane and gap-wise distribution of birefringence and extinction angle. As a result, the compression process could decrease flow-induced birefringence for the whole region and rapid heating could decrease the birefringence level than conventional molding mechanism. Finally, for the combination of compression and rapid heating, the reversal flow was detected from the distribution of extinction angle near the gate.
황의철 ( Hwang Eui-chul ),김규용 ( Kim Guy-yong ),이상규 ( Lee Sang-kyu ),손민재 ( Son Min-jae ),백재욱 ( Baek Jae-wook ),남정수 ( Nam Jeong-soo ) 한국건축시공학회 2018 한국건축시공학회 학술발표대회 논문집 Vol.18 No.2
In this study, surface spalling and explosive spalling of ring-type ultra-high strength concrete under rapid heating and slow heating were investigated. In rapid heating, the internal temperature difference of the concrete is large, so that continuous surface spalling occurs. However, in slow heating, the difference in the internal temperature of the concrete is small, resulting in explosive spalling at a time. Since the heating condition has a great influence on the internal temperature of the concrete, it is necessary to consider the spalling of the concrete under various heating conditions.
김종환,이기범,이경용,Kim, Jong-Hwan,Lee, Kee-Bhum,Lee, Kuong-Yong 한국군사과학기술학회 2005 한국군사과학기술학회지 Vol.8 No.2
The thermomechanical characteristics were evaluated for 17-4PH stainless steel widely used in supersonic airframe subjected to both aerodynamic loading and heating. The thermomechanical tests were conducted under both elevated temperature and rapid heating condition from $1^{\circ}C/sec\;to\;28^{\circ}C/sec$. The thermomechanical behaviors under rapid heating were compared with those of elevated temperature after 1/2 hour exposure in terms of yield stress to investigate the influence of heating rates. A heating rate-yield temperature parameter was suggested for rapid heating based on time-temperature parameters, and master yield stress curve was obtained by using these parameters. The experimental results and methodology from this study can be used as basic engineering data when designing supersonic vehicle structures subjected to aerodynamic loading and severe heating environment.