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Sohn, Dongwoo,Lee, Youngmin,Ahn, Mu-Young,Park, Yi-Hyun,Cho, Seungyon Elsevier 2018 Fusion engineering and design Vol.137 No.-
<P><B>Abstract</B></P> <P>In the design process of a solid-type ceramic breeding blanket, it is important to identify the characteristics of functional materials in the form of pebble beds. In this study, the mechanical and thermal behaviors of lithium ceramic pebbles are numerically simulated using an in-house code developed for the discrete element analysis. First, the packing configurations of pebble beds under cyclic loadings are found and discussed in terms of the packing factor, average stress, and average coordination number. In particular, we investigate the effects of pebble size distributions and friction coefficients on the pebble packing. Subsequently, based on the resulting packing configurations, we analyze the heat conduction through the lithium ceramic pebble beds considering the elastic contact between the spherical pebbles. We then qualitatively evaluate the effective thermal conductivities of pebble beds, which also depend upon the pebble size distributions and friction coefficients. The results of the discrete element simulations reveal that a large size difference and low friction coefficient of pebbles lead to close packing and high thermal conductivity of the pebble beds.</P>
불일치 계면을 수반하는 최적화 문제에서 다면체 유한요소를 이용한 효율적인 격자망 업데이트 기법
손동우(Dongwoo Sohn),윤길호(Gil Ho Yoon) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
In optimization process to determine optimal placement of components whose shapes are already given and independently modeled, continuous mesh reconstruction for the updated configurations is required. However, this mesh update involves the nonmatching interface problem and thus may make the optimization process inefficient. In this study, using polyhedral elements, we propose an efficient scheme for solving three-dimensional optimization problems that require remeshing. Because the polyhedral elements accommodate arbitrary numbers of nodes and faces, they can be utilized to connect the nonmatching meshes during the optimization process. The effectiveness of the proposed scheme is demonstrated through several numerical examples.
다각뿔 요소와 마칭큐브 알고리즘을 이용한 격자망 생성 기법
손동우(Dongwoo Sohn),한지훈(Jihoon Han),조영삼(Young-Sam Cho),임세영(Seyoung Im) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
Novel types of finite elements, termed poly-pyramid elements, are developed by moving least square approximation. The poly-pyramid elements are composed of one polygonal face and several triangular faces, and they have basic properties of finite elements such as the partition of unity, the linear completeness, and the Kronecker delta condition. Furthermore, those elements are applied for mesh generation in combination with marching cube algorithm. After preparing a structured mesh with hexahedral elements, the surface information of a given geometry is soaked into the structured mesh. Subsequently, only the hexahedral elements located around the surface are trimmed according to the marching cube algorithm. The trimmed elements are reconstructed by decomposing themselves into the several poly-pyramid elements. The effectiveness of the proposed meshing scheme is demonstrated throughout numerical examples.
독립적으로 모델링된 삼차원 부분구조물의 연결을 위한 임의 형상 유한요소
손동우(Dongwoo Sohn) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
Nonmatching interfaces between independently modeled substructures may commonly occur in three-dimensional analyses with conventional elements. However it is difficult to connect the nonmatching meshes because their interfaces are complicatedly composed of various types of polygons. In this study, we proposed a simple and efficient scheme for dealing with three-dimensional nonmatching interfaces by using arbitrarily shaped finite elements, i.e. polyhedral elements that have an arbitrary number of polygonal faces. Only the elements on the nonmatching interfaces are converted into the polyhedral elements to accommodate the polygon-shaped interfaces. That is, the polyhedral elements are used as the transition elements to construct compatible meshes. The strain smoothing technique in cellbased smoothed finite element method is applied to further improve the efficiency and accuracy of the finite element analysis. The effectiveness of the proposed scheme is demonstrated through numerical examples.