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풍력 발전 블레이드 복합재 GFRP의 인장 특성의 온도 의존성
허용학(Yong-Hak Huh),김종일(Jong Il Kim),김동진(Dong Jin Kim),이건창(Gun Chang Lee) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.4-2
본 연구에서는 풍력 발전 블레이드용 재료인 GFRP(Glass fiber-Reinforced Plastic) 복합재의 인장특성의 온도에 따른 의존성을 고찰하였다. 섬 유 방향이 0° 와 0/± 45°로 적층된 두 종류의 복합재로 제작된 인장 시험편으로부터 인장 강도와 탄성계수 그리고 포아송비에 대한 특성을 상온, -30℃, -50℃ 그리고 60℃에서 측정하였다. 인장 시험으로부터 섬유방향이 축방향으로 적층된 복합재의 인장강도와 탄성계수는 섬유 적층 방향의 의존성을 보였고 단축으로적층된 복합재의 강도 및 탄성 계수가 상대적으로 우수함을 보았다. 그리고 시험온도의 의존성도 확인할 수 있었으며, 포아송비는 온도의 영향이 크지 않음을 확인할 수 있었다. In this study, dependency of the tensile properties for wind turbine blade material, GFRP(Glass Fiber Reinforced plastic), on the testing temperature was examined. With the tensile specimen manufactured from the uniaxial (0°) and triaxial (0/± 45°) laminate composite plates, tensile strength, elastic modulus and Poisson’s ratio for these material were measured at the four different testing temperatures o f room temperature, -30°C, -50℃ and 60℃. It was found that tensile strengths and elastic moduli for the uniaxial laminates were greater than those for triaxial laminates over the testing temperature range. Tensile strength for two laminates was significantly dependent on the testing temperature, while dependency of the elastic modulus on the temperature was insignificant. Furthermore, it could be said that the Poisson’s ratio was not nearly the same with the change of the testing temperature.
허용학(Yong-Hak Huh),김동진(Dong Jin Kim),이해무(Hae Moo Lee),홍성구(Sung Gu Hong),박준협(Jun Hyub Park) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.10
Fatigue limit of the copper film coated by Sn was estimated using Goodman diagram and Gerber diagram. To obtain the high cycle fatigue life curve, S-N curve, of the film, the high cycle fatigue test was carried out by applying the constant amplitude load to the film specimen with three different stress ratio of 0.05, 0.3 and 0.5 and the frequency of 40 ㎐ at room temperature in air. The free-standing film specimen 15.26㎛ thick was fabricated by etching process. The fatigue limits and S-N curves at the respective stress ratios were determined from the experimental works. It was shown that the S-N curves were dependent on the stress ratio and the fatigue limit was increased with decreasing the stress ratio. The dependency of the fatigue behavior was presented in empirical relationship. Using these relationships, the fatigue limit was predicted.
이축성과 위상차의 영향을 고려한 이축 하중하에서 구멍 주위에서의 피로 균열 발생 방향 예측
허용학(Yong-Hak Huh),박휘립(Pilip Park),김동진(Dong-Jin Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
To predict the direction of the fatigue crack initiated from a hole under various types of biaxial fatigue loads with different phase difference and biaxiality, fatigue parameters were investigated. Axial and torsional biaxial fatigue loads were selected with the respective combination of five different phase differences of 0, 45, 90, 145 and 180 degrees and five biaxialities of 0, 1/ √3, 1, √ 3, ∞. Directions of the fatigue crack initiation around the hole were found to approach to the circumferential direction of the specimen with increment of the phase difference for fatigue tests with phase differences less than 90°. Whereas directions for tests with phase differences greater than 90° went away from the circumferential direction and those were symmetric to the directions for tests with phase difference less than 90°. With increase of biaxilities, the fatigue crack initiated more apart from the circumferential direction of the specimen. These crack initiation direction were predicted using maximum tangential stress range and maximum shear stress range obtained at far-field and around the hole. Comparing these two stress parameters, The crack initiation direction can be successfully explained by using the direction of the maximum tangential stress range obtained around the hole and at far-field.