• Structural Engineering and Mechanics
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• 제84권4호
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• pp.453-464
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• 2022

Thin plates are the most common spatially stressed members in engineering structures that bear out-of-plane loads. Therefore, it is of great significance to study the deformation performance characteristics of thin plates for structural design. By constructing 12 basic displacement and deformation basis vectors of the four-node square thin plate element, a deformation decomposition method based on the complete orthogonal mechanical basis matrix is proposed in this paper. Based on the deformation decomposition method, the deformation properties of the thin plate can be quantitatively analyzed, and the areas dominated by each basic deformation can be visualized. In addition, the method can not only obtain more deformation information of the structure, but also identify macroscopic basic deformations, such as bending, shear and warping deformations. Finally, the deformation properties of the bidirectional thin plates with different sizes of central holes are analyzed, and the changing rules are obtained.

• 대한조선학회논문집
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• 제33권3호
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• pp.94-102
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• 1996

유한변형문제에서 변형구배텐서를 탄소성 성분으로 분해하기 위한 가산분해와 곱분해방법에 대해서 설명하고, 이 두 방법에서 파생되는 역학량들의 의미와 그 차이점을 보였다. 변형구배에 대한 기존의 곱분해와 가산분해로 얻어지는 변형속도구배는 가산적으로 표현되지 않으며, 소성변형속도구배는 탄성변형의 영향을 받고 있다. 본 연구에서는 공축소성 가정을 도입하고, 수정된 곱분해를 통하여 소성변형속도구배가 탄성변형에 영향을 받지 않는 가산적인 변형속도 구배를 얻었다.

• 한국재료학회지
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• 제29권6호
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• pp.343-348
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• 2019

Structural and mechanical effects of the dynamical precipitation in two copper-base alloys have been investigated over a wide range of deformation temperatures. Basing upon the information gained during the experiment, also some general conclusion may be formulated. A one concerns the nature of dynamic precipitation(DP). Under this term it is commonly understood decomposition of a supersaturated solid solution during plastic straining. The process may, however, proceed in two different ways. It may be a homogeneous one from the point of view of distribution and morphological aspect of particles or it may lead to substantial difference in shape, size and particles distribution. The effect is controlled by the mode of deformation. Hence it seems to be reasonable to distinguish DP during homogeneous deformation from that which takes place in heterogeneously deformed alloy. In the first case the process can be analyzed solely in terms of particle-dislocation-particle interrelation. Much more complex problem we are facing in heterogeneously deforming alloy. Deformation bands and specific arrangement of dislocations in form of pile-ups at grain boundaries generate additional driving force and additional nucleation sites for precipitation. Along with heterogeneous precipitation, there is a homogeneous precipitation in areas between bands of coarse slip which also deform but at much smaller rate. This form of decomposition is responsible for a specially high hardening rate during high temperature straining and for thermally stable product of the decomposition of alloy.

• 한국컴퓨터그래픽스학회논문지
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• 제28권4호
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• pp.13-22
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• 2022

본 논문에서는 최소 입자 단위의 역동적인 회전 움직임을 나타낼 수 있는 MPM(Material Point Method) 기반 단일 프레임워크를 소개한다. 우리가 표현하고자 하는 입자는 다양한 형상(Shape)을 가질 수 있음과 동시에, 선형(Linear momentum), 회전(Angular momentum) 운동을 함께 묘사할 수 있다. 그 결과 기존 구형 입자의 선형 움직임만을 나타내던 입자 기반 시뮬레이션과는 달리, 시각적으로 단일 입자의 역동적인 모습을 표현할 수 있다. 제안하는 프레임워크는 회전 운동을 큰 변형(Large Deformation)으로부터 분해 및 추출 할 수 있다는 점에서 MPM을 활용하였다. 본 기법은 MPM 적분 과정 중 계산되는 변형 구배 텐서(Deformation Gradient Tensor)를 극 분해(Polar Decomposition)하는 과정을 통해 회전 텐서(Rotation Tensor)를 추출하고, 각 입자의 선형 운동과 함께 이를 적용하여 결과적으로 입자 자체의 회전, 선형 운동을 동시에 표현 하는 것이 가능하다. 본 연구에서는 제안하는 기법의 검증을 위해 바람에 흩날리며 회전하는 입자의 모습 및 움직이는 물체와 정지한 입자간의 상호작용 시뮬레이션을 기존 MPM을 이용한 시뮬레이션과의 비교를 통해 진행하였다.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제22권1호
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• pp.13-23
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• 2015

We introduce a decomposition on a symplectic subspace determined by symplectic structure and study its properties. As a consequence, we give an elementary proof of the deformation of the Grassmannians of symplectic subspaces to the complex Grassmannians.

• 전자공학회논문지CI
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• 제42권3호
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• pp.63-72
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• 2005

본 논문에서는 가상성형 시스템에 적합한 Radial Basis Function(RBF) 기반의 변형 기법과 변형된 얼굴 구성 요소를 얼굴 영상에 혼합하는 기법을 제시한다. 가상성형을 위한 변형 기법은 유동적인 얼굴 구성 요소들을 변형함에 있어 부드러움과 정확성을 가져야 하고 변형 부위 이외의 다른 얼굴 구성 요소에는 왜곡을 주지 않는 지역성도 가져야 한다. 이를 위해 제안된 가상성형 시스템은 자유형태 변형 모델을 기반으로 RBF에 의해 격자들의 변형 정도를 계산한다. 성형의 정확성을 위해 변형 오차는 기준곡선 정점들의 목표 위치와 실제 변형된 위치 사이의 오차제곱합을 이용하여 Singular Value Decomposition(SVD)에 의해 반복적으로 RBF 매핑 함수의 계수들을 계산하여 보정한다. 변형된 얼굴 구성 요소는 Euclidean Distance Transform(EDT)에 의해 계산된 혼합 비율을 사용하여 원본 얼굴 영상과 합성된다. 제안된 변형 기법과 합성 기법은 가상성형 결과의 정확도와 왜곡 측면에서 우수한 성능을 보인다는 것을 실험적으로 확인하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.252-268
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• 2009

In the present study, a grid deformation technique has been incorporated into the unsteady compressible and incompressible viscous flow solvers on unstructured hybrid meshes. An algebraic method based on the basis decomposition of normal edge vector was used for the deformation of viscous elements, and a ball-vertex spring analogy was adopted for inviscid elements among several spring analogy methods due to its robustness. The present method was validated by comparing the results obtained from the grid deformation and the rigid motion of entire grids. Fish swimming motion of an NACA0012 airfoil and flapping wing motion of a generic fighter were simulated to demonstrate the robustness of the present grid deformation technique.

• 한국전산유체공학회지
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• 제14권3호
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• pp.33-48
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• 2009

In the present study, a fast grid deformation technique has been incorporated into the unsteady compressible and incompressible viscous flow solvers on unstructured hybrid meshes. An algebraic method based on the basis decomposition of normal edge vector was used for the deformation of viscous elements, and a ball-vertex spring analogy was adopted for inviscid elements among several spring analogy methods due to its robustness. The present method was validated by comparing the results obtained from the grid deformation and the rigid motion of entire grids. Fish swimming motion of an NACA0012 airfoil and flapping wing motion of a generic fighter were also simulated to demonstrate the robustness of the present grid deformation technique.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.143-145
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• 2007

The correlation between crystallization and deformation behavior in the supercooled liquid region (SLR) of a $Cu_{54}Ni_{6}Zr_{22}Ti_{18}$ bulk metallic glass (BMG) alloy is investigated by compression tests, differential scanning calorimetry (DSC), electron energy loss spectrometry (EELS) and high resolution transmission electron microscopy (HRTEM). In the SLR, This BMG alloy was strongly depended on the deformation temperature and the alloy exhibits important change in deformation behavior after a given time which is directly connected to the development of crystallization. Compressive stress impeded decomposition and consequently retarded forming of nano-crystal, which led to enlarge the homogeneous deformation region of the BMG alloy in SLR during compression test.

• 대한기계학회논문집A
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• 제20권9호
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• pp.2800-2811
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• 1996

The deformation of a structure shall be called homologous, if a given geometrical relation holds, for a given number of structural points, before, during, and after the deformation. Some researchers have utilized the idea on structural design with finite element method. The approaches use the decomposition of the FEM equation or equality of eqality equations to obtain homologous deformation. However, weight reduction and response constraints such as stress, displacement or natural frequency cannot be considered by those theories. An optimization method solving the above problems is suggested to gain homologous deformation. Homology constraints can be considered under multiple loadindg conditions as well as a single loading condition. Homology index is defined for the multiple loading conditions Examples are solved to present the performances of the method.