• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.6
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• pp.141-147
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• 1997

For the effective finite element analysis of the structures including material interfaces or contact surfaces, interface elements are proposed. Most of early works in this problem require not only iterative computation but also complex formulation because of the kinematic nonlinearities caused from the discontinuous behavior and the stress concentration phenomena. The proposed elements, however, are consistently formulated using relative displacements and tractions between top and bottom regular finite elements. The effectiveness of these elements are shown by solving various numerical sample problems including an leaf spring and comparing with results of general finite element analysis. As a result, more stable solutions are conveniently obtaines using interface elements than regular finite elements.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.3
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• pp.344-352
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• 2002

In the analysis of the 3 dimensional plate structures by the finite element method, the triangular elements are generally used for the global stiffness matrix of the analyzed system. But the triangular elements of the plates have some problems in the process of formulation and in the precision of analysis. The formulation of the finite element method to analyze 3 dimensional plate structures using quadrilateral elements is presented in this paper. The degree of freedom off nodal point is 6, that is, the displacements in the direction off-y-z is and the rotations about x-y-z axis and then the degree of freedom off element is 24. For the comparison of the analysis using triangular elements and quadrilateral elements, the rectangular plates subjected to the uniform load and a concentrated load on the centroid of the plate, for which the theoretical solutions have been obtained, are analyzed. The calculated deflections of the rectangular plates using the finite element method by the triangular elements and the quadrilateral elements are also compared with the deflections of the plates calculated by theoretical solutions. The defections of the rectangular plates calculated by the finite element method using the quadrilateral elements are closer to the theoretical solutions than the defections calculated by the finite element method using the triangular elements. The deflection of the centroid of plate, calculated by the finite element method, converges to that of theoretical solution as the number of elements is increased. This convergence is much more rapid for the case of using the quakrilateral elements than fir the case of using triangular elements.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.15 no.1
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• pp.57-65
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• 2011

In this paper, a good quality mesh generation for the finite element method is investigated for artificial hip joint simulations. In general, bad meshes with a large aspect ratio or mixed elements can give rise to excessively long computational running times and extremely high errors. Typically, hexahedral elements outperform tetrahedral elements during three-dimensional contact analysis using the finite element method. Therefore, it is essential to mesh biologic structures with hexahedral elements. Four meshing schemes for the finite element analysis of an artificial hip joint are presented and compared: (1) tetrahedral elements, (2) wedge and hexahedral elements, (3) open cubic box hexahedral elements, and (4) proposed hexahedral elements. The proposed meshing scheme is to partition a part before seeding so that we have a high quality three-dimensional mesh which consists of only hexahedral elements. The von Mises stress distributions were obtained and analyzed. We also performed mesh refinement convergence tests for all four cases.

• The Transactions of the Korea Information Processing Society
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• v.3 no.7
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• pp.1906-1916
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• 1996

For the medical analysis of the three-dimensional structure such as the mandible, it is necessary to reconstruct the structure into the finite number of analyzable elements. The information of the three-dimensional structure can be obtained from the cross-sections of the magnetic resonance image (MRI). A region corresponding to the structure is extracted from the inner part of the cross- section. By the triangulation of the sampled cross-section image, two-dimensional finite elements are generated. Three-dimensional finite elements are constructed by matching the two dimensional finite elements each other in space. In this paper a construction method of the optimal three-dimensional finite elements has been suggested, which uses the adjacent information abstracted from the triangulated two-dimensional finite elements. The elements are classified into the identical property sets by using the adjacent information of the traingulated two-dimensional elements. After applying the multistep matching algorithm to the classified two-dimensional finite elements, the optimal three-dimensional finite elements can be construccted. By analyzing the constructed finite elements, it is possible to get much more useful medical information about the three-dimensional struture of mandible.

• Structural Engineering and Mechanics
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• v.76 no.3
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• pp.379-393
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• 2020

In this paper, we propose an automatic procedure to improve the accuracy of finite element solutions using enriched 2D solid finite elements (4-node quadrilateral and 3-node triangular elements). The enriched elements can improve solution accuracy without mesh refinement by adding cover functions to the displacement interpolation of the standard elements. The enrichment scheme is more effective when used adaptively for areas with insufficient accuracy rather than the entire model. For given meshes, an error for each node is estimated, and then proper degrees of cover functions are applied to the selected nodes. A new error estimation method and cover function selection scheme are devised for the proposed adaptive enrichment scheme. Herein, we demonstrate the proposed enrichment scheme through several 2D problems.

• Geomechanics and Engineering
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• v.33 no.4
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• pp.369-380
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• 2023

The aim of this paper is to investigate stress analysis of semi-infinite soils consisting of two layers with twin rectangular tunnels under static loads. The region close to the ground surface and tunnel modelled within finite elements. In order to use a more realistic model, the far region is modelled within infinite elements. The material model of the layered soil is considered as elastic and isotropic. In the finite element solution of the problem, two dimensional (2D) plane solid elements are used with sixteen-nodes rectangular finite and eight-nodes infinite shapes. Finite and infinite elements are ordered to be suitable for the tunnel and the soils. The governing equations of the problem are obtained by using the virtual work principle. In the numerical process, the five-point Gauss rule is used for the calculation of the integrations. In order to validate using methods, comparison studies are performed. In the numerical results, the stress distributions of the two layered soils containing twin rectangular tunnels presented. In the presented results, effects of the location of the tunnels on the stress distributions along soil depth are obtained and discussed in detail. The obtained results show that the locations of the tunnels are very effective on the stress distribution on the soils.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.172-176
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• 2008

In this paper, three dimensional linear conforming variable-finite elements are presented with the aid of a smoothed integration (a class of stabilized conforming nodal integration), for mnltiscale mechanics problems. These elements meet the desirable properties of an interpolation such as the Kronecker delta condition, the partition of unity condition and the positiveness of interpolation function. The necessary condition of linear exactness is fully relaxed by employing the smoothed integration, which renders us to meet the linear exactness in a straightforward manner. This novel element description extend the category of the conventional finite elements space to ration type function space and give the flexibility on the number of nodes of element which are fixed in the conventional finite elements. Several examples are provided to show the convergence and the accuracy of the proposed elements, and to demonstrate their potential with emphasis on the multiscale mechanics problems such as global/local analysis, nonmatching contact problems, and modeling of composite material with defects.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1988.10a
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• pp.49-54
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• 1988

A procedure which may be useful in dealing with problems of half plane is considered. Boundary elements are combined with finite elements to facilitate their merits. Boundary elements for semi-infinite region are composed using the Melan's solution for half plane. Finite elements are used to model irregurarity or the nonhomogeneity of materials, which is usual in underground structures. In order to verify the procedure, a shallow tunnel under internal pressure is analysed using the finite element method, the boundary element method, and the combined method. It is shown that the developed Procedure is accurate enough compared with other method.

• Computational Structural Engineering
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• v.2 no.1
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• pp.55-64
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• 1989

A procedure which may be useful in dealing with problems of half plane is considered. Boundary elements are combined with nonlinear finite elements to facilitate their merits. Boundary elements for semi-infinite region are composed using the Melan's solution for half plane. Nonlinear finite elements are used to model irregularity or nonhomogeneity of elasto-plastic materials, which is usual in underground structures. In order to verify the procedure, a shallow tunnel under internal pressure is analysed using the nonlinear finite element method and combined method. It is shown that the developed procedure is accurate enough compared with other method.

• Journal of KSNVE
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• v.7 no.3
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• pp.467-475
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• 1997

A rotor-bearing system has been investigated, including internal damping and axial torque using finite dynamic elements. A procedure is presented for dynamic modeling of rotor-bearing system which consist of finite dynamic shaft elements, rigid disk, and bearing and seal. A finite dynamic element model including the effects of rotatory inertia, gyroscopic moments, axial force, and axial torque is developed using the frequency dependent shape function. The natural whirl speeds, stability, and unbalance response of rotor system are calculated on several cases and compared with the conventional finite elements.