• Proceedings of the KSME Conference
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• 2008.11a
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• pp.442-447
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• 2008

This paper presents a new approach to simulate fluid-solid interaction problems involving non-matching interfaces. The coupling between fluid and solid domains with dissimilar finite element meshes consisting of 4-node quadrilateral elements is achieved by using the interface element method (IEM). Conditions of compatibility between fluid and solid meshes are satisfied exactly by introducing the interface elements defined on interfacing regions. Importantly, a consistent transfer of loads through matching interface element meshes guarantees the present method to be an efficient approach of the solution strategy to fluid-solid interaction problems. An arbitrary Lagrangian-Eulerian (ALE) description is adopted for the fluid domain, while for the solid domain an updated Lagrangian formulation is considered to accommodate finite deformations of an elastic structure. The stabilized equal order velocity-pressure elements for incompressible flows are used in the motion of fluids. Fully coupled equations are solved simultaneously in a single computational domain. Numerical results are presented for fluid-solid interaction problems involving nonmatching interfaces to demonstrate the effectiveness of the methodology.

• Structural Engineering and Mechanics
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• v.50 no.6
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• pp.817-834
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• 2014

An experimental program was designed in the current work to examine the structural behavior of ferrocement beams reinforced with composite materials under three point loadings up to failure. The experimental program comprised casting and testing of twelve ferrocement beams having the dimensions of 120 mm width, 200 mm depth and 1600 mm length. The twelve beams were different in the type of reinforcements; steel bars, traditional wire meshes (welded and expanded wire meshes) and composite materials (fiberglass wire meshes and polypropylene wire meshes). The flexural performances of the all tested beams in terms of strength, ductility, cracking behavior and energy absorption were investigated. Also all the tested beams were simulated using ANSYS program. The results of the experimental tests concluded that the beam with fiber glass meshes gives the lowest first crack load and ultimate load. The ferrocement beam reinforced with four layers of welded wire meshes has better structural behavior than those beams reinforced with other types of wire meshes. Also the beams reinforced with metal wire meshes give smaller cracks width in comparing with those reinforced with non-metal wire meshes. Also the Finite Element (FE) simulations gave good results comparing with the experimental results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.591-598
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• 2002

The interface element method for non-matching FEM meshes is extended using stabilized nodal integration. Two non-matching meshes are shown to be joined together compatibly, with the aid of the moving least square approximation. Using stabilized nodal integration, the interface element method is able to satisfy the patch test, which guarantees the convergence of the method.

• 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 B
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• v.25 no.11
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• pp.1581-1593
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• 2001

An efficient variable-reordering method for finite element meshes is used and the effect of variable-reordering is investigated. For the element renumbering of unstructured meshes, Cuthill-McKee ordering is adopted. The newsy reordered global matrix has a much narrower bandwidth than the original one, making the ILU preconditioner perform bolter. The effect of variable reordering on the convergence behaviour of saddle point type matrix it studied, which results from P2/P1 element discretization of the Navier-Stokes equations. We also propose and test 'level(0) preconditioner'and 'level(2) ILU preconditioner', which are another versions of the existing 'level(1) ILU preconditioner', for the global matrix generated by P2/P1 finite element method of incompressible Navier-Stokes equations. We show that 'level(2) ILU preconditioner'performs much better than the others only with a little extra computations.

• Journal of Biomedical Engineering Research
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• v.28 no.1
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• pp.8-16
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• 2007

Finite element analysis (FEA) is an effective means for the analysis of bioelectromagnetism. It has been successfully applied to various problems over conventional methods such as boundary element analysis and finite difference analysis. However, its utilization has been limited due to the overwhelming computational load despite of its analytical power. We have previously developed a novel mesh generation scheme that produces FE meshes that are content-adaptive to given MR images. MRI content-adaptive FE meshes (cMeshes) represent the electrically conducting domain more effectively with far less number of nodes and elements, thus lessen the computational load. In general, the cMesh generation is affected by the quality of feature maps derived from MRI. In this study, we have tested various feature maps created based on the improved differential geometry measures for more effective cMesh head models. As performance indices, correlation coefficient (CC), root mean squared error (RMSE), relative error (RE), and the quality of cMesh triangle elements are used. The results show that there is a significant variation according to the characteristics of specific feature maps on cMesh generation, and offer additional choices of feature maps to yield more effective and efficient generation of cMeshes. We believe that cMeshes with specific and improved feature map generation schemes should be useful in the FEA of bioelectromagnetic problems.

• Structural Engineering and Mechanics
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• v.14 no.6
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• pp.625-647
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• 2002

Parallel execution of computational mechanics codes requires efficient mesh-partitioning techniques. These mesh-partitioning techniques divide the mesh into specified number of submeshes of approximately the same size and at the same time, minimise the interface nodes of the submeshes. This paper describes a new mesh partitioning technique, employing Genetic Algorithms. The proposed algorithm operates on the deduced graph (dual or nodal graph) of the given finite element mesh rather than directly on the mesh itself. The algorithm works by first constructing a coarse graph approximation using an automatic graph coarsening method. The coarse graph is partitioned and the results are interpolated onto the original graph to initialise an optimisation of the graph partition problem. In practice, hierarchy of (usually more than two) graphs are used to obtain the final graph partition. The proposed partitioning algorithm is applied to graphs derived from unstructured finite element meshes describing practical engineering problems and also several example graphs related to finite element meshes given in the literature. The test results indicate that the proposed GA based graph partitioning algorithm generates high quality partitions and are superior to spectral and multilevel graph partitioning algorithms.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.164-170
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• 2003

The finite element analysis of tires has been conventionally performed by either neglecting tread pattern or modeling only circumferential grooves. Besides, the tire analysis has been mainly limited to static or steady state rolling analysis. In this paper, a transient dynamic analysis of a patterned tire rolling over a cleat with an explicit finite element program is presented. The patterned tire with detailed tread blocks is modeled by a systematic mesh generation procedure, in which tire body and tread pattern meshes are separately generated in the beginning and then both meshes are combined by the tie constraint method. The cleat impact analysis is conducted by using both the patterned tire and the smooth tire models to predict the cleat enveloping characteristics. It is seen that the analysis results of the patterned tire model are in a good agreement with the experimental results.

• Structural Engineering and Mechanics
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• v.30 no.1
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• pp.119-129
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• 2008

A small strain and elastoplastic formulation of Polygonal Element Method (PEM) is developed for efficient analysis of elastoplastic solids. In this work, the polygonal elements are constructed based on traditional triangular finite meshes. The construction method of polygonal mesh can directly utilize the sophisticated triangularization algorithm and reduce the difficulty in generating polygonal elements. The Wachspress rational finite element basis function is used to construct the approximations of polygonal elements. The incremental variational form and a von Mises type model are used for non-linear elastoplastic analysis. Several small strain elastoplastic numerical examples are presented to verify the advantages and the accuracy of the numerical formulation.

• Journal of Magnetics
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• v.11 no.4
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• pp.151-155
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• 2006

The electromagnetic engine valve actuator is a key technology to achieve variable valve timing in internal combustion engine and the steel core and clapper of the electromagnetic engine valve actuator are laminated to reduce the eddy current loss. To design and characterize the performance of the electromagnetic engine valve actuator, FE (finite element) analysis is the most effective way, but FE (finite element) 3-D modeling of real lamination needs very fine meshes resulting in countless meshes for modeling and numerous computations. In this paper, the equivalent FE 2-D model of electromagnetic engine valve actuator is introduced and FE analysis is performed using the equivalent FE 2-D model.