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김경홍(Kyoung-Hong Kim),이춘세(Chun-Se Lee),안형준(Hyeong-Joon Ahn) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.11
This paper presents a finite element (FE) analysis of the torsional rigidity of a two-stage cycloid drive. The cycloid disk makes contact with a number of pin-rollers simultaneously and eccentric shafts transmit not only torque of the spur gear stage to the cycloid disk, but also that of the cycloid disk to the output disk. Contacts between the disk and pin-rollers are simplified as linear spring elements, and the bearing of eccentric shaft is modeled as a rigid ring that has frictional contact to the disk and an elastic support. FE analysis for an ideal solid cycloid drive was performed and verified by a theoretical calculation. Accurate contact forces were then estimated by iterating between FE analysis for contact forces and Hertz theory calculations for nonlinear contact stiffness. In addition, torsional rigidity of the cycloid drive is analyzed to show that the bearing and nonlinear Hertz contact theory should be considered in analysis and design of a cycloid drive, which was verified with experiments. Finally, the effects of contact stiffness, bearing stiffness and cycloid disk structural stiffness according to the cycloid disk rotation on the torsional rigidity were investigated.
축방향 유속에 노출된 5x5 지지격자 스트랩의 진동특성
김경홍(Kyoung Hong Kim),박남규(Nam Gyu Park),김경주(Kyoung Ju Kim),서정민(Jung Min Suh) 한국소음진동공학회 2012 한국소음진동공학회 학술대회논문집 Vol.2012 No.4
It is important to identify dynamic characteristics of nuclear fuel components. Since the fuel always exposed to turbulent flow, the dynamic contact between grids and rods is one of the fuel failure modes. The dynamic behavior of grids in nuclear fuels is quite complex, since two pairs of spring support are placed in the limited space. The strap in a cell has single spring and double dimples and this paper focuses on investigation of the grid strap(Test Fuel Strap, TFS) vibration in one cell. To identify the grid strap vibration, modal analysis of the strap is performed using Finite Element Method (FEM). Modal testing on a 5x5 grid structure without rods is performed. The modal testing results are compared to analytic results. In addition, random test considering rod effect is performed about a 5x5 grid with rods under real contact condition in the air. Finally, the strap vibration of a 5x5 fuel bundle in INvestigation of Flow INduced vIbraTion(INFINIT) facility is measured in real fluid velocity condition without heating. It is shown that modal frequencies from the test are almost equal to those peak frequencies in the INFINIT test.
김경홍(Kim, Kyoung-Hong),박남규(Park, Nam-Gyu),김경주(Kim, Kyoung-Ju),서정민(Suh, Jung-Min) 한국소음진동공학회 2012 한국소음진동공학회 논문집 Vol.22 No.7
Since the fuel is always exposed to turbulent flow, the grid strap shows flow induced vibration characteristics that impact on the nuclear fuel soundness. The dynamic behavior of grids in nuclear fuels is quite complex, since two pairs of spring and dimple support are contacted with rods by friction in the limited space. This paper focuses on investigation of the grid strap(test fuel strap, TFS) vibration in one cell. TFS consists of a single spring and double dimples. To identify the grid strap vibration, modal analysis of the strap is performed using finite element method(FEM). Modal testing on a $5{\times}5$ grid structure without rods is performed. The modal testing results are compared to analytic results. In addition, random test considering rod effect is performed about a $5{\times}5$ grid with rods under real contact condition in the air. Finally, the strap vibration of a $5{\times}5$ fuel bundle in investigation of flow induced vibration(INFINIT) facility is measured in real fluid velocity condition without heating. It is shown that modal frequencies from the test are almost equal to those peak frequencies in the INFINIT test.
김경록(Kyoung-rock Kim),팜반트룽(Pham van Trung),윤근위(Guen-wui Yoon),이명기(Myeong-gi Lee),김경홍(Kyoung-hong Kim),안형준(Hyeong-joon Ahn),이원(Won Yi) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5
본 논문은 유연보를 이용한 준영강성 제진기의 제어 모델에 관한 것이다. 유연보 이용 준영강성 제진기는 유연보에 가해지는 압축력에 의해 유발되는 음강성이 수직방향 스프링의 양강성과의 합이 0부근이 되는 준영강성 원리를 이용한다. 먼저 준영강성제진기의 핵심요소인 유연보의 무차원 엄밀해를 유도하고 테일러 전개로 간략하한 후 유한요소해석을 통해 검증하였다. 간략화한 유연보 모델로 유연보 이용 준영강성 제진기의 동역학 모델을 구성하고 비선형 진동특성을 확인하였다. 구성한 제진기 시스템 모델을 통해 설계 변수에 따른 제진기의 동특성 민감도를 분석하고, 압축력 이용 능동 제진을 위한 제어 모델을 유도하였다. 제진기의 동특성이나 능동 제어에 유연보 형상이 큰 영향이 있음을 확인하였다. This paper presents a control model of a quasi zero stiffness isolator using flexures. The isolator has the QZS characteristic acquired by combination of a negative stiffness of the flexure with compressive force and a positive stiffness of a vertical spring. First, non-dimensional exact model of the flexure or a key element of the QZS isolator is derived and the exact model of the flexure is simplified into an approximate model using Taylor series expansion, which is verrified with FE analysis. Based on the approximate model of flexure, a nonlinear dynamic model of the QZS isolator is constructed and its non-linear vibration characteristics are verified with simulations. Sensitivity analysis of dynamic characteristic of the QZS isolator according to design parameters is performed and an engineering model of the isolator for active control using compression force is derived. The shape of flexure has significant effect on the dynamics characteristic and control of the isolator.