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NURBS 곡면기반의 기하학적 모델링과 셀 유한요소해석의 연동
최진복,노희열,조맹효,Choi, Jin-Bok,Roh, Hee-Yuel,Cho, Maeng-Hyo 대한기계학회 2007 大韓機械學會論文集A Vol.31 No.1
The linkage framework of geometric modeling based on NURBS(Non-Uniform Rational B-Spline) surface and shell finite analysis is developed in the present study. For this purpose, geometrically exact shell finite element is implemented. NURBS technology is employed to obtain the exact geometric quantities for the analysis. Especially, because NURBS is the most powerful and wide-spread method to represent general surfaces in the field of computer graphics and CAD(Computer Aided Design) industry, the direct computation of surface geometric quantities from the NURBS surface equation without approximation shows great potential for the integration between geometrically exact shell finite element and geometric modeling in the CAD systems. Some numerical examples are given to verify the performance and accuracy of the developed linkage framework. In additions, trimmed surfaces with some cutouts are considered for more practical applications.
최진복 한국전산구조공학회 2018 한국전산구조공학회논문집 Vol.31 No.5
압력용기의 내압은 압력용기 설계의 중요한 인자이며 이를 바탕으로 관련 설계기준 및 구조해석결과에 따라 압력용기의 두께 및 직경과 같은 기하학적 형상이 결정된다. 그러나 압력용기 내부에서 폭굉이 일어날 경우 이 폭굉압력을 적절히 고려 하여 압력용기를 설계할 수 있는 설계기준은 미흡한 실정이다. 일반적으로 폭굉이 발생할 경우, 초기 폭굉압력이 용기 벽면에 도달하여 반사하는 반사압력은 초기압력의 2배 이상이라고 알려진다. 그러나 폭굉압력은 구조물의 고유주기보다도 짧은 시간 안에 최대치에 도달한 후 급격하게 감소하는 경향을 보이며, 이 경우 실제 용기벽면이 받게 되는 압력은 반사압력에 비해 매우 작을 수 있다. 따라서 본 연구에서는 이러한 폭굉의 특성을 고려하여 압력용기가 견뎌야 하는 적절한 등가의 폭굉압 력을 산정하는 방법을 제안함으로써 폭굉을 고려한 효율적인 압력용기 설계기준을 제시하고자 하였다. The internal pressure is a critical parameter for designing a pressure vessel. The static pressure that a pressure vessel must withstand is usually determined according to the various codes and standards with simple formula or numerical simulations considering the geometric parameters such as diameter and thickness of a vessel. However, there is no specific codes or technical standards we can use practically for designing of pressure vessels which have to endure the detonation pressure. Detonation pressure is a kind of dynamic pressure which causes an impulsive pressure on the vessel wall in a extremely short time duration. In addition, it is known that the magnitude of reflected pressure at the vessel wall due to the explosion can be over twice the incident pressure. Therefore, if we only consider the reflected pressure, the design of the pressure vessel can be too conservative from the economical point of view. In this study, we suggest a practical method to evaluate the magnitude of maximum allowable pressure that the pressure vessel can withstand against the detonation inside a vessel. As an example to validate the proposed method, we consider the pressure vessel containing hydrogen gas.
최진복(Jinbok Choi) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
Although there has been a great advance in computing resources and power, the modal analysis is still very time consuming. A lot of reduction methods have been suggested to resolve this problem. Among of them, model order reduction(MOR) method has been recognized as one of the powerful methods because of its advantages such as simplicity of implementation and theoretical robustness. Especially, in this study, the MOR method applies to the thermo-mechanical problem which results in the quadratic eigenvalue problem(QEP). The QEP is not easy to solve directly so it is generally converted into the generalized eigenvalue problem(GEP). The doubled degrees of freedom during this procedure eventually increase the computation time and the coupling between mechanical and thermal part makes it difficult to apply the conventional reduction methods. But the MOR method can be successfully applied to this tightly coupled multi-physics problem and reduce the computing time dramatically.
NURBS 기반 캐드시스템의 곡면 모델링과 쉘 유한요소해석의 연동
최진복(Jin Bok Choi),노희열(Hee Yuel Rho),조맹효(Maenghyo Cho) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The linkage framework of surface geometric modeling and analysis based on the NURBS technology is developed in this study. The NURBS surfaces are generated by interpolating given set of data points or by extracting the necessary information to construct the NURBS surface from the IGES file which is generated by the commercial CAD systems in the present study. Some numerical examples that show the tendency of displacement convergence according to the paramterization method of the NURBS surface are given. And quadric shape surfaces which is generated exactly based on NURBS representation is considered. It is the one of the advantages of the NURBS equation to express quadric shape curves or surfaces exactly in the mathematical point of view. A trimmed surfaces which are often encountered during modeling process in the CAD systems are handled briefly in the present study.
NURBS 기반 캐드시스템의 곡면 모델링과 쉘 유한요소해석의 연동
최진복(Jin Bok Choi),노희열(Hee Yuel Rho),조맹효(Maenghyo Cho) 한국자동차공학회 2005 한국자동차공학회 Symposium Vol.- No.-
The linkage framework of surface geometric modeling and analysis based on the NURBS technology is developed in this study. The NURBS surfaces are generated by interpolating given set of data points or by extracting the necessary information to construct the NURBS surface from the IGES file which is generated by the commercial CAD systems in the present study. Some numerical examples that show the tendency of displacement convergence according to the paramterization method of the NURBS surface are given. And quadric shape surfaces which is generated exactly based on NURBS representation is considered. It is the one of the advantages of the NURBS equation to express quadric shape curves or surfaces exactly in the mathematical point of view. A trimmed surfaces which are often encountered during modeling process in the CAD systems are handled briefly in the present study.
최진복(Jinbok Choi),정광섭(Kwangsub Jung),조맹효(Maenghyo Cho) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
The classical continuum theory-based thin film model is independent of their size and the surface effect can be ignored. But the surface to bulk ratio becomes very large in nano-size structures such as nano film, nano wire and nano beam. In this case, surface effect plays an important role and its contribution of the surface effect must be considered. Molecular dynamics simulation has been a conventional way to analyze these ultra-thin structures but structures in the range between submicro and micro are difficult to analyze by classical molecular dynamics due to the restriction of computing resources and time. Therefore, in present study, the continuum-based method is considered to predict the overall physical and mechanical properties of the structures in nano-scale, especially, for the thin-film. The proposed continuum based-thin plate finite element is efficient and reliable for the prediction of nano-scale film behavior.