• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3159-3174
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• 1994

A simple octree encoding algorithm based on a tetrahedron root has been developed to be used for fully automatic generation of three dimensional finite element meshes. This algorithm starts octree decomposition from a tetrahedron root node instead of a hexahedron root node so that the terminal mode has the same topology as the final tetrahedral mesh. As a result, the terminal octant can be used as a tetrahedral finite element without transforming its topology. In this part(I) of the thesis, an efficient algorithm for the tetrahedron-based octree is proposed. For this development, the following problems have been solved, : (1) an efficient data structure for storing the octree and finite elements, (2) an encoding scheme of a tetrahedral octree, (3) a neighbor finding technique for the tetrahedron-based octree.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2397-2405
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• 2000

The remeshing is a method to replace a distorted mesh by a new mesh without interrupting the finite element calculation. The remeshing procedure in this paper refers to the rezoning, for which a sm oothing process is developed to alleviate the distortions of mesh. In the paper, an automatic finite element rezoning system with tetrahedral elements for large deformation analysis has been developed. Our smoothing process is composed of two steps, a surface smoothing and a volume smoothing. In the surface smoothing, checking the dihedral angle and projection on surface patch reduced the change of shape and nodes penetrating die. The constrained Laplacian smoothing has been employed for the volume smoothing process. The state variables are mapped from old mesh to new mesh by using volume coordinates within a tetrahedral element. All these procedures have been linked to the NIKE3D program As illustrated in the examples the overall strategy ensures a robust and efficient rezoning scheme for finite element simulation of metal-forming processes.

• The Journal of Engineering Geology
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• v.20 no.1
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• pp.13-23
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• 2010

Toppling failure of a slope is defined as failure behavior accompanying the rotation of rock block which is different from other failure such as sliding along with discontinuities and so on. It generally occurs in the region that discontinuities were developed with inverse dip direction to a slope and it could play a critical role in judging stability of slope. In this study, the stability evaluation was performed about toppling failure on a jointed road cut-slope. To check the deformation behavior, numerical analysis is widely used. However common analysis programs are based on continuum model. Recently, many methods that discontinuity properties can be considered in continuum analysis are suggested. In this study, numerical analysis based on FEM(Finite Element Method) was performed using interface element applied in heterogeneous boundary to simulate effects of discontinuities.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.213-214
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• 2006

• Tunnel and Underground Space
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• v.11 no.3
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• pp.270-278
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• 2001

Two numerical methods such as DEM and FDM were adopted to analysis of rock slope stability, of which dimensions are about 150 m(length), 58 m(height), 70°dip, in Halla limestone mine. For this rock slope stability analysis, strength reduction method was used to calculate the safety factor of slope through numerical method. To keep the rock slope safely, it is proposed to reduce the height of the rock slope from 58 m to 45 m and to reduce the angle of the slope from 70°to 55°, too.

• Economic and Environmental Geology
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• v.50 no.2
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• pp.129-143
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• 2017

The shallow sediments in the southwestern Ulleung Basin consist of mass flow deposits such as slide/slump and debris flow deposits (DFD), caused by slope failure. These sediments are proven to be important in studying geological disaster and stability of the seafloor. In this paper, we analysised the flow accumulation and slope failure susceptibility of the Ulleung Basin on the basis of multi-beam data, collected in this area. We also studied the distribution pattern and the seismic characteristics of the DFD in the uppermost layer of the Ulleung Basin on the basis of seismic data. The slope susceptibility was calculated as the frequency ratio of each factors including slope, aspect, curvature and stream power index (SPI), which causes the slope failure. These results indicate that the slope failure is frequently to occur in the southern and western continental slope of the Ulleung Basin. The sediment flow (mass flow) caused by the slope failure converges to the north and northwest of the Ulleung Basin. According to the seismic characteristics, the uppermost layer in study area can be divided into four sedimentary unit. These sedimentary units develop from the south and southwest to the north and northwest in association with slope susceptibility and flow accumulation.

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.241-247
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• 2001

절리가 발달한 암반사면의 경우, 토사사면의 안전율 평가를 위해 널리 이용되는 한계평형법을 이용한 해석법은 파괴 활동면을 가장할 수 없기 때문에 사용이 곤란하다. 한편, 비등방 탄소성 모델(편재절리모델)을 사용하여 2조의 절리군을 가진 암반사면의 안전율을 계산할 수 있는 방법이 개발되었지만, 이 방법은 개별절리를 효과적으로 고려하지 못한다. 본 연구에서는 개별절리를 고려한 불연속체 해석에 의한 암반사면의 안정성 해석시 사면의 안전율을 평가하는 기법을 개발하였다. 이를 위해, 절리 전단강도 감소기법을 적용하였으며, UEDC의 내장 언어인 FISH를 사용하여 프로그램을 개발하였다. 또한 실제 절리 암반사면을 대상으로 절리를 측정하고, 개발된 기법에 의한 사면의 안전율을 구하였으며, 동일한 사면에 대해 등가연속체로 가정한 편재절리모델 해석을 수행하여 결과를 비교하였다.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.351-356
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• 2000

Various transition elements are generally used for the effective analysis of a complicated mechanical structure. In this paper, a solid-to-beam transition finite element which connects a continuum element and a $c^1-continuity$ beam element each other is proposed. The shape functions of the transition finite elements, which a 8-noded hexahedral solid element fur 3D analysis and a 4-noded quadrilateral plane element fur 2D analysis are connected to a Euler's beam element, are explicitely formulated. In order to show the effectiveness and convergence characteristics of the proposed transition elements. numerical tests are performed for various examples and their results are compared with those obtained by other methods. As the result of this study. following conclusions are obtained: (1)The proposed transition finite elements show the monotonic convergence characteristics because of having used the compatible displacement folds. (2)As being used the transition element in the finite element analysis, the finite element modelings are more convenient and the analysis results are more accurate because of the formulation characteristies of the Euler's beam element.

• Journal of the Korean Geosynthetics Society
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• v.8 no.1
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• pp.11-18
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• 2009

This paper presents a comparative study of reinforced soil slope by using LEM and SSR-FEM. Current analysis methods for reinforced soil wall are based on LEM. SSR-FEM assumes a reduction of soil strength by a factor to reach a critical state prior to failure based on continuum mechanics. In this study the comparisons are concerned with the factor of safety and the potential failure surface in reinforced soil wall. We investigated the stability of the reinforced soil wall with a slope of $60^{\circ}$ by LEM and SSR-FEM. The comparisons indicated good performance of the SSR-FEM on stability analysis of reinforce soil wall.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.607-610
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• 2005

A remeshing algorithm using tetrahedral elements has been developed, which is adapted to the mesh density map constructed by a posteriori error estimation. In the finite element analyses of metal forging processes, numerical error increases as deformation proceeds due to severe distortion of elements. In order to reduce the numerical error, the desired mesh sizes in each region of the workpiece are calculated by a posteriori error estimation and the density map is constructed. Piecewise density functions are then constructed with the radial basis function in order to interpolate the discrete data of the density map. The sample mesh is constructed based on the point insertion technique which is adapted to the density function and the mesh size is controlled by moving and deleting nodes to obtain optimal distribution according to the mesh density function and the quality optimization function as well. After finishing the redistribution process of nodes, a tetrahedral mesh is constructed with the redistributed nodes, which is adapted to the density map and resulting in good mesh quality. A goodness and adaptability of the constructed mesh is verified with a testing measure. The proposed remeshing technique is applied to the finite element analyses of forging processes.