• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.27 no.3
• /
• pp.183-189
• /
• 2014

In this paper, a polyhedral element is presented to solve three-dimensional problems by developing shape functions based on Wachspress coordinates and moving least square approximation. A subdivision of polyhedrons into tetrahedral domains is performed for the construction of shape functions of polyhedral elements, and numerical integration of the weak form is carried out consistently over the tetrahedral domains. The weight functions for moving least square approximation are defined by solving Laplace equation with boundary values based on Wachspress coordinates on polyhedral element faces. Polyhedral elements presented in this paper have similar properties to conventional finite element regarding the continuity, the completeness, the node-element connectivity and the inter-element compatibility. Numerical examples show the effectiveness of the present method for solving three-dimensional problems using polyhedral elements.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.22 no.4
• /
• pp.335-341
• /
• 2009

In this paper, review of developed MLS-based finite elements and a proposal for their applications are described. The shape functions and their derivatives of MLS-based finite elements are constructed using Moving-Least Square approximation. In MLS-based finite element, using the adequate influence domain of weight function used in MLS approximation, kronecker delta condition could be satisfied at the element boundary. Moreover, because of the characteristics of MLS approximation, we could easily add extra nodes at an arbitrary position in MLS-based finite elements. For these reasons, until now, several variable-node elements(2D variable element for linear case and quadratic case and 3D variable-node elements) and finite crack elements are developed using MLS-based finite elements concept. MLS-based finite elements could be extended to 2D variable-node triangle element, 2D finite crack triangle element, variable-node shell element, finite crack shell element, and 3D polyhedron element. In this paper, we showed the feasibility of 3D polyhedron element at the case of femur meshing.

• Computational Structural Engineering
• /
• v.35 no.1
• /
• pp.17-24
• /
• 2022

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.27 no.4
• /
• pp.239-245
• /
• 2014

Finite element modeling of composite structures may be cumbersome due to complex distributions of reinforcements. In this paper, an efficient scheme is proposed that can generate periodic meshes for the composite structures. Regular meshes with hexahedral finite elements are first prepared, and the elements are then trimmed to fit external surfaces of reinforcements in the composite structures. The trimmed hexahedral finite elements located at interfaces between the matrix and the reinforcements correspond to polyhedral finite elements, which allow an arbitrary number of nodes and faces in the elements. Because the trimming process is consistently conducted by means of consistent algorithms, the elements of the reinforcements are automatically compatible with those of the matrices. With the additional consideration of periodicity of reinforcements in a representative volume element(RVE), the proposed scheme provides periodic meshes in an efficient manner, which are compatible for each pair of periodic boundaries of the RVE. Therefore, periodic boundary conditions for the RVE are enforced straightforwardly. Numerical examples demonstrate the effectiveness of the proposed scheme for finite element modeling of complex composite structures.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.11a
• /
• pp.833-840
• /
• 1996

중립면은 셸 (솔리드 모델) 유한 요소 생성, 로보트 이동 경로 계산, 특징 형상 판별 등에서 사용될 수 있다. 그러나 기존 중립면 계산 알고리즘들은 연립 방정식을 수렴성이 보장되지 않는 수치 해법으로 풀어야 했기 때문에 발전이 미비했다. 본 논문은 복셀-이등분 면의 교자성을 이용한 중립면 계산 알고리즘을 제시한다. 교차성은 보로노이 영역을 사용, 단순한 기하학적 요소간의 거리 비교로 판별한다. 이런 기하학적인 접근 방법은 기본적으로 수렴성 문제가 배제된다.

• Tunnel and Underground Space
• /
• v.30 no.1
• /
• pp.15-28
• /
• 2020

In this study, a procedure was introduced to estimate strength and deformation modulus of the 3-D discrete fracture network(DFN) systems using the distinct element method(DEM). Fracture entities were treated as non-persistent square planes in the DFN systems. Systematically generated fictitious fractures having similar mechanical characteristics of intact rock were combined with non-persistent real fractures to create polyhedral blocks in the analysis domain. Strength and deformation modulus for 10 m cube domain of various deterministic and stochastic 3-D DFN systems were estimated using the DEM to explore the applicability of suggested method and to examine the effect of fracture geometry on strength and deformability of DFN systems. The suggested procedures were found to effective in estimating anisotropic strength and deformability of the 3-D DFN systems.

• Journal of the Korean Society for Precision Engineering
• /
• v.13 no.11
• /
• pp.106-113
• /
• 1996

Using stainless steel as the cold forged parts especially the outer parts of automobile is gradually increasing because it can bear up against the erosion and the wear. During cold forging of the stainless steel the working pressure acting on die surface are very high therefore the wear on die surface can be greatly increased. In cold forging processes, die failure must be considered before die design. One of the main reasons of die failure in industrial application of metal forming technologies is wear. The die wear affects the tolerances of forged parts, metal flow and costs of processes etc. The only way to to control these failures is to develop methods which allow prediction of the die wear and which are suited to be used in the desing stage in order to optimize the process. In this paper, the rigid-plastic finite element method was combined with the wear prediction routine and then the forward extrusion process using stainless steel was analysed simultaneously. To minimize the die wear the FPS algorithm was applied and the optimal conditions of die configuration are suggested.