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한정우(Jeong Woo Han),우은택(Eun Taek Woo),한승호(Seung Ho Han) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.7
혼합모드 피로하중을 받는 균열을 갖은 CTS 시편에 대하여 균열경로 예측이론과 Tanaka 의 등가 응력확대계수식을 적용하여 피로균열진전거동을 평가하였다. 새롭게 생성되는 균열선단의 응력확대계수 산정은 ANSYS 를 이용한 유한요소법을 통해 이루어졌고, 균열경로와 균열증분은 마이크로소프트 엑셀에 프로그래밍한 균열경로예측식과 Paris 식으로 계산되었다. 균열증분으로 새롭게 생성된 균열선단의 기하학적인 정보는 엑셀의 기능을 이용해 ANSYS 의 KSCON 명령어가 인식할 수 있게 변화시켜 균열모델링을 용이하게 하였다. 반복적인 균열해석을 위해 유한요소법과 엑셀을 결합한 FECTUM(Finite Element Crack Tip Updating Method)을 개발하였다. 개발된 FECTUM 을 편측 3 점 굽힘을 통해 혼합모드의 구현이 가능한 SENB 시편(Single Edge Notched Bend Specimen)에 적용해본 결과, 균열경로는 물론 파단될 때까지의 피로하중 반복수의 차이가 3% 미만으로 잘 일치하는 모습을 보여, 개발된 기법의 타당성을 검증하였다. To estimate the fatigue crack propagation behavior of compact tension shear (CTS) specimen under mixedmode loads, crack path prediction theories and Tanaka’s equation were applied. The stress intensity factor at a newly created crack tip was calculated using a finite element method via ANSYS, and the crack path and crack increment were then obtained from the crack path prediction theories, Tanaka’s equation, and the Paris’ equation, which were preprogrammed in Microsoft Excel. A new method called the finite element crack tip updating method (FECTUM) was developed. In this method, the finite element method and Microsoft Excel are used to calculate the stress intensity factors and the crack path, respectively, at the crack tip per each crack increment. The developed FECTUM was applied to simulate the fatigue crack propagation of a single-edge notched bending (SENB) specimen under eccentric threepoint bending loads. The results showed that the number of cycles to failure of the specimen obtained experimentally and numerically were in good agreement within an error range of less than 3%.
안대균(Ahn Dae Gyun),우은택(Woo Eun Taek),조윤현(Cho Yun Hyun),한승호(Han Seung Ho) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
For the sustainable development of wind energy, the energy industries have invested in the development of highly efficient wind generator such as an axial flux permanent magnet(AFPM) generator. The AFPM generator, however, has a history of overheating on the stator surface, so that power production decreases significantly. A proper cooling system, therefore, is needed. Although in the case of low capacity generator, a convective-type cooling system has been developed, the size of the air blower must be increased when the generator’s capacity exceeds 2.5MW. In this study, a newly developed conductive-type cooling system was proposed for the 2.5MW AFPM generator installed on an offshore wind turbine. Through electromagnetic-thermal analysis, the characteristics of the heat transfer in the generator were investigated. For the application of the proposed cooling system, the temperatures on the surfaces of stator and permanent magnet were 86 and 68℃, respectively, which could not affect the decrease of the power production efficiency.(KETEP 20134030200320)