개에서 분리된 細菌의 抗生劑 感受性 및 Methicillin-resistant staphylococci에서의 mecA, femA, femB 遺傳子의 발현

Thesis (master`s)--서울대학교 대학원 :수의학과 수의내과학전공,2001.Maste

소비자의 가치의식과 의류제품평가

학위논문(석사)--서울대학교 대학원 :의류학과,1995.Maste

Characterization of Fracture Toughness in Composite Laminates by Generalized Locus Method

다양한 실험을 통해 섬유강화 복합적층판의 파괴특성을 파악하고 파괴인성 평가방법으로 일반궤적법을 적용하였다. 흑연/에폭시 중앙균열시편, 흑연/에폭시 쌍외괄보 시편 및 유리/에폭시 3점굽힘 시편에 대한 실험을 통하여 일반궤적법은 선형파괴뿐 아니라 비선형파괴에도 적용할 수 있는 일반적인 방법임을 확인할 수 있었다. 또한 쌍외팔보 실험에서 흑연/에폭시 시편에 단?뗌?가 첨가되면 충간파괴인성이 약 15% 향상됨을 알 수 있었다.Various experiments have been performed to characterize fracture behavior of fiber reinforced composite laminates, and the generalized locus method was applied to evaluate fracture toughness. The generalized locus method was found to be a general method for analyzing both linear and nonlinear fracture preblems through the tests of center cracked graphite/epoxy specimen, double cantilever beam graphite/epoxy specimen and glass/epoxy 3-point bending specimen. Additionally, interlaminar fracture toughness of graphite/epoxy specimen reinforced by random short fibers was found to be greater than that of unreinforced specimen by 15%.Various experiments have been performed to characterize fracture behavior of fiber reinforced composite laminates, and the generalized locus method was applied to evaluate fracture toughness. The generalized locus method was found to be a general method for analyzing both linear and nonlinear fracture preblems through the tests of center cracked graphite/epoxy specimen, double cantilever beam graphite/epoxy specimen and glass/epoxy 3-point bending specimen. Additionally, interlaminar fracture toughness of graphite/epoxy specimen reinforced by random short fibers was found to be greater than that of unreinforced specimen by 15%

Fracture of Graphite/Epoxy Composites under Mixed Mode Deformation

중앙에 균열이 있는 복합재료(Graphite/Epoxy) 유한평판에서 균열길이와 균열각도의 변화에 따른 파괴 현상을 실험하였다. 응력강도계수와 변형에너지 방출율을 유한평판에 대한 혼합모우드 수정계수를 이용하여 구하였다. 또한 전자현미경을 이용하여 파괴단면이 균열각도의 변화에따라 어떤 형상을 나타내는지 알아보고 그 이유에 대하여 고찰하였다.중앙에 균열이 있는 복합재료(Graphite/Epoxy) 유한평판에서 균열길이와 균열각도의 변화에 따른 파괴 현상을 실험하였다. 응력강도계수와 변형에너지 방출율을 유한평판에 대한 혼합모우드 수정계수를 이용하여 구하였다. 또한 전자현미경을 이용하여 파괴단면이 균열각도의 변화에따라 어떤 형상을 나타내는지 알아보고 그 이유에 대하여 고찰하였다

Analysis of Characteristics of Automotive Leaf Spring

상용 유한요소 해석 프로그램인 MARC를 이용하여 트럭이나 소형버스의 현가 장치로 많이 쓰이는 겹판스프링을 모델링하고 판사이의마찰에 의해 생기는 하중-변위 히스테리시스 곡선을 재현하여 겹판스프링의 특성을 해석하였다. 또한 실제 겹판스프링에 스트레인시스 곡선을 재현하여 겹판스프링의 특성을 해석하였다. 또한 실제 겹판스프링에 스트레인 게이지를 부착하여 각부분에서의 변형률값을 구하고 유한 요소 해석 결과와 비교하였다. 유한요소 해석에서의 하중에 따른 변위값은 거의 유사한 결과를 나타냈지만 변형률에서는 많은 차이를 보였다. 그러나 유한요소 해석에서의 하중-변위 곡선과 시험에서의 하중-변위곡선은 마찰력 차이는 있었지만 정스프링 정수값은 거의 같음을 확인할 수 있었다.Characteristics of leaf spring was analyzed by using commercial finite element analysis program MARC and the load-displacement hysteresis curve was successfully simulated which is occurred by interleaf friction. Compression test was performed to practical leaf springs for trucks from which load-displacement and load-strain results were obtained. It is found that load-displacement hysteresis curve and static spring rate were in good agreement with FEM results. However, meaured strain values and friction force were different from those of FEM results.Characteristics of leaf spring was analyzed by using commercial finite element analysis program MARC and the load-displacement hysteresis curve was successfully simulated which is occurred by interleaf friction. Compression test was performed to practical leaf springs for trucks from which load-displacement and load-strain results were obtained. It is found that load-displacement hysteresis curve and static spring rate were in good agreement with FEM results. However, meaured strain values and friction force were different from those of FEM results

Analysis of Delamination in Carbon/Epoxy Composite Material Using Mixed Mode Bending Specimen

탄소/에폭시 복합재료의 혼합 모우드 층간분리 연구를 위하여 혼합 모우드 굽힘시험이 수행되었다. 레버를 이용하여 시편에 하중을 가함으로써 모우드 Ⅰ과 Ⅱ 굽힘 하중이 동시에 작용하도록 하였다. 하중레버의 하중부과점 위치와 시편에 작용하는 굽힘하중점 위치를 변화시킴으로써 다양한 혼합 모우드 비를 얻을 수 있었다. 총변형에너지방출율을 모우드 분리하기 위하여 단순보 이론과 컴플라이언스법 그리고 수정된 단순보 이론을 병행적용하였고 그 결과 유한요소 해석 결과와 잘 일치하였다.A mixed mode bending test was performed to investigate the mixed mode delamination for carbon/epoxy composite material. By loading the specimen with a lever, a single applied load could produce mode I and mode II bending loads on the specimen simultaneously. Various mixed mode ratios could be produced by changing the applied load position on the loading lever and the bending load position on the specimen. This test was analyzed using beam theory, compliance method and modified beam theory to decompose total strain energy release rate into the mode I and mode II components. The results agreed well with those of finite element analysisA mixed mode bending test was performed to investigate the mixed mode delamination for carbon/epoxy composite material. By loading the specimen with a lever, a single applied load could produce mode I and mode II bending loads on the specimen simultaneously. Various mixed mode ratios could be produced by changing the applied load position on the loading lever and the bending load position on the specimen. This test was analyzed using beam theory, compliance method and modified beam theory to decompose total strain energy release rate into the mode I and mode II components. The results agreed well with those of finite element analysi

Analysis of Mode Ⅱ and Mixed Mode Delamination in Carbon/Epoxy Composite Material

탄소/에폭시 복합재료의 층간분리 연구를 위하여 순수 모우드 Ⅱ ELS 시험과 혼합 모우드 Ⅰ/Ⅱ mixed mode bending 시험이 수행되었다. 순수 모우드 Ⅱ 임계변형에너지방출율은 1105 J/m²로 측정되었다. 혼합 모우드 비는 loading lever의 하중 부과점 위치와 시편에 작용하는 굽힘 하중점 위치를 변화시킴으로써 다양하게 구할 수 있었다. 이론과 시험을 병행한 결과 이들은 잘 일치하여 일반적으로 사용될 수 있는 시험 방법으로 정립될 수 있음을 확인하였다.ELS test and mixed mode bending test were performed to investigate the mode Ⅱ and mixed mode delamination respectively for carbon/epoxy composite material. Mode Ⅱ critical strain energy release rate was 1105 J/m². Various mixed mode ratios could be produced by changing the applied load position on the loading lever and the bending load position on the specimen. Mixed mode delamination was analyzed using beam theory and the result agreed well with test result which confirmed the validity of this analysis.ELS test and mixed mode bending test were performed to investigate the mode Ⅱ and mixed mode delamination respectively for carbon/epoxy composite material. Mode Ⅱ critical strain energy release rate was 1105 J/m². Various mixed mode ratios could be produced by changing the applied load position on the loading lever and the bending load position on the specimen. Mixed mode delamination was analyzed using beam theory and the result agreed well with test result which confirmed the validity of this analysis