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태양광 복사 가속화 시험을 통한 에폭시 폴리머의 색 변화 특성 연구
이상봉(Sang-Bong Lee),이동건(Dong-Geon Lee),김명준(Myung-Jun Kim),이수용(Soo-Yong Lee),박정선(Jung-Sun Park),강태엽(Tae-Yeop Kang),백상화(Sang-Hwa Baek) 한국항공우주학회 2016 韓國航空宇宙學會誌 Vol.44 No.11
태양광 복사에 의한 기계적 부품의 강성 및 강도 저하, 변색 등의 영향이 다양한 항공우주산업분야에서 관찰되고 있다. 이러한 현상에 대한 연구를 위해 자연 상태의 태양광에 대한 노출 시험을 수행할 수 있지만 균일한 시험환경 구현이 어렵고 과다한 시간과 비용이 요구된다는 문제점이 있다. 이를 극복하고자 본 논문에서는 자연 상태의 태양광 복사강도(1,120W/㎡)를 가속화 할 수 있는 시험 장치를 개발하고, 섬유강화 복합재료에 사용되는 epoxy polymer에 대한 가속화 시험을 통하여 태양광 복사에 따른 색 변화 특성을 연구하였다. 시험 시편은 인장 시험 규격인 ASTM-D638에 따라 제작하였으며, 시험 기간에 따른 색변화 특성에 관한 가속계수와 역제곱 모형을 산출하였다. 본 연구를 통해 복사강도가 증가할수록 동일한 변화량에 도달하기까지 소요되는 시간을 단축할 수 있다는 것을 확인하였다. There are a number of effects by solar radiation in many aerospace industrial fields, such as degradation of mechanical properties, sealing effect of sealants or decolorization. Because it takes long time to investigate these effects by using the light of natural state, new methods are developed for accelerating this phenomenon. In this paper, we developed an apparatus to simulate accelerated solar radiation phenomenon selecting irradiation intensity 1,120W/㎡ as the designed environment. Epoxy polymer as the composite material was chosen and processed by ASTM-D638, a reference for tensile test of polymer and plastic. Total color shift was selected as the test category to evaluate acceleration of the test. We obtained acceleration factors and numerical model from test data and concluded it can shorten test periods by accelerated irradiation intensity of 1,120W/㎡.
박지훈,백상화,최현준,Park, Ji-Hoon,Baek, Sang-Hwa,Choi, Hyen-Jun 해양환경안전학회 2020 해양환경안전학회지 Vol.26 No.5
본 논문에서는 상용코드인 ANSYS CFX를 통한 해양레저 스포츠 및 야외 활동 시 사용 가능한 휴대용 수평축 수차의 유입유속(U) 및 주속비(TSR, Tip Speed Ratio) 변화에 따른 성능해석을 수행하였으며, 해석결과 및 유동장 분석을 통해 설계에 대한 검토 및 장치의 성능을 확인하였다. 또한, 추가적으로 블레이드의 피치각도(α<sub>pitch</sub>) 변화에 따른 성능해석을 통해 수차의 성능개선에 필요한 데이터를 획득하고자 하였다. 본 논문의 연구 결과 수치해석 케이스 중 주속비 4인 경우, 모든 유입속도 및 블레이드 피치 각도에서 가장 높은 성능을 보였으며, 설계 유속 이하의 일부 조건에서도 설계 출력인 30 W 이상의 출력을 보였다. 그리고 수치해석 케이스 중 가장 높은 출력과 출력계수는 유입유속 1.5 m/s, 블레이드 피치 각도 3°, 주속비 4에서 보였으며, 출력 약 85 W, 출력계수 약 0.30이었다. A performance analysis was conducted according to changes in inflow velocity and the tip speed ratio of a portable horizontal-axis hydro turbine that can be used for marine leisure sports and outdoor activities by using the commercial computational fluid dynamics software ANSYS CFX. By using the analysis result and flow field analysis, the design was reviewed and the performance of the device was confirmed. In addition, data necessary to improve the performance of the hydro turbine were acquired by performing an additional performance analysis according to the variable blade pitch angle. The results among the numerical analysis cases show that the highest performance at all inflow velocities and blade pitch angles if achieved at a tip speed ratio of 4. The output power was found to be 30 W even under some conditions below the design flow rate. Among the numerical analysis cases, the highest output power (~ 85 W) and power coefficient (~ 0.30) were observed at an inlet flow rate of 1.5 m/s, a blade pitch angle of 3°, and a tip speed ratio of 4.
대형 환경시험조 내의 복합무기체계 재료에 대한 열유동 수치해석
김성대(Sung-Dae Kim),유성열(Seong-Ryoul Ryoo),백상화(Sang-Hwa Baek),이정용(Jeong-Yong Lee),박소진(So-Jin Park),김철주(Chul-Ju Kim),고한서(Han Seo Ko) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
A numerical analysis for temperature distribution of four different materials such as iron, silicon, aluminum and PVC has been performed in this study to predict thermal behaviors of combined weapon systems in a large environmental tester. Thus, experimental conditions have been proposed using a calculating software (SolidWorks 2007 COSMOS FloWorks) to prepare for field tests and analyze heat flow inside the environmental tester and temperature distributions of materials. The boundary conditions of the analysis are composed of inlet and outlet conditions of the environmental tester with different pressures and the limit of low temperature of -30℃. The soaking time of the system in the environmental tester has been calculated by this commercial program in this study to carry out the experiment.
대형 환경시험조 내의 복합무기체계 유동 분석을 위한 수치해석 연구
김성대(Sung-Dae Kim),유성열(Seong-Ryoul Ryoo),백상화(Sang-Hwa Baek),이정용(Jeong-Yong Lee),박소진(So-Jin Park),김철주(Chul-Ju Kim),고한서(Han Seo Ko) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Thermal behaviors of combined weapon systems have been analyzed in this study by developed computational programs. Also, temperature distributions of the materials of the system have been measured at the experimental conditions. Field tests in the large environmental tester have been prepared by the calculated thermal flow characteristics and the measured temperature distributions of the materials for the weapon systems. The boundary conditions of the analysis are composed of inlet and outlet conditions of the environmental tester with various pressures and the limit of low temperature of -25℃. The developed program has predicted the soaking time of the system in the environmental tester so that the experiment can be performed for the predicted soaking time.
대형 환경시험조 내의 2.5톤 트럭에서 열전달계수 변화에 따른 열분포의 수치해석적 연구
김성대(Sung-Dae Kim),유성열(Seong-Ryoul Ryoo),최지훈(Jee-Hoon Choi),백상화(Sang-Hwa Baek),이정용(Jeong-Yong Lee),박소진(So-Jin Park),김철주(Chul-Ju Kim),고한서(Han Seo Ko) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
An experimental and numerical analysis has been performed in this study to predict thermal behaviors of a 2.5 ton truck in a large environmental tester. Also, temperature distributions of the materials of the truck have been measured for the experimental conditions. The measured temperature distributions of the materials and the calculated thermal flow characteristics for the 2.5 ton truck have been analyzed to for field tests in the environmental tester. The boundary conditions of the analysis are composed of inlet and outlet conditions of the environmental tester with various pressures and the limit of low temperature of -32℃. The soaking time of the system in the environmental tester has been calculated by developed programs in this study to carry out the experiment in the obtained conditions.