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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.
무소음화학팽창제를 활용한 콘크리트 구조물 균열 생성시 천공홀 간격에 따른 최소요구팽창압 비교연구
손동우 ( Sohn Dongwoo ),이재하 ( Lee Jaeha ),김경진 ( Kim Kyeongjin ),조황기 ( Cho Hwangki ),김윤호 ( Kim Yunho ),박상민 ( Park Sangmin ) 한국구조물진단유지관리공학회 2017 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.21 No.2
Soundless Chemical Demolition Agent (SCDA) has been spotlighted for demolition of concrete structure or rock near or in urban areas and historical places since it does not produce dust or rock fragmentations compared to explosive and gas pressure blasting methods. However, there is no guideline or design code for the demolition of existing structures using SCDA. In this study, numerical analysis using ABAQUS is conducted in order to find a minimum required pressure for the initiation of crack in concrete body with SCDA and obtained results in this study could be a basic data for design of hole spacing for the demolition of the structures using SCDAs.
다절점 유한요소를 이용한 비균질 재료의 다중스케일 균열 진전
손동우(Dongwoo Sohn),임재혁(Jae Hyuk Lim),임세영(Seyoung Im) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
An efficient algorithm for multi-scale crack propagation, with the aid of variable-node finite elements, is described in this paper. We split the domain into global(coarse) mesh zone far from the crack tip and local(fine) mesh zone containing crack tip. A homogenization scheme is employed for representing the majority of the global zone in which the periodicity of RVE (Represent Volume Element) is valid. To capture the highly localized features around defects, we simply refine the local region involving cracks, and its neighboring elements are replaced with variable-node elements, which connect the zones of different mesh resolution in a seamless way, meeting the nodal connectivity across the interface of the two mesh zones. To demonstrate the simplicity and effectiveness of the scheme proposed, we will show numerical examples in relation to multiscale crack propagation.