• Electrical & Electronic Materials
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• v.9 no.8
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• pp.783-788
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• 1996

In this paper, the high-$T_c$ , superconductor (HTS) microstrip patch antenna which is directly coupled to a microstrip transmission line is designed and the numerical solution which evaluate near electromagnetic field of HTS antenna is presented. This solution uses the interpolation function with the vector edge triangular element. The advantage of this element is the elimination of spurious solutions attributed to the lack of enforcement of the divergence condition. The results of this method have a good agreement with $TM_10$ mode in HTS microstrip patch antenna and show that the computation of resonant length considering the fringing capacitance effect at radiating edge are proper.

• Structural Engineering and Mechanics
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• v.39 no.6
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• pp.767-793
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• 2011

An efficient edge-based smoothed finite element method (ES-FEM) has been recently developed for solving solid mechanics problems. The ES-FEM uses triangular elements that can be generated easily for complicated domains. In this paper, the complexity study of the ES-FEM based on triangular elements is conducted in detail, which confirms the ES-FEM produces higher computational efficiency compared to the FEM. Therefore, the ES-FEM offers an excellent platform for adaptive analysis, and this paper presents an efficient adaptive procedure based on the ES-FEM. A smoothing domain based energy (SDE) error estimate is first devised making use of the features of the ES-FEM. The present error estimate differs from the conventional approaches and evaluates error based on smoothing domains used in the ES-FEM. A local refinement technique based on the Delaunay algorithm is then implemented to achieve high efficiency in the mesh refinement. In this refinement technique, each node is assigned a scaling factor to control the local nodal density, and refinement of the neighborhood of a node is accomplished simply by adjusting its scaling factor. Intensive numerical studies, including an actual engineering problem of an automobile part, show that the proposed adaptive procedure is effective and efficient in producing solutions of desired accuracy.

• Coupled systems mechanics
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• v.1 no.1
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• pp.59-78
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• 2012

The available analytical methods of analysis for laterally loaded piles in level ground cannot be directly applied to such piles in sloping ground. With the commercially available software, the simulation of the appropriate field condition is a challenging task, and the results are subjective. Therefore, it becomes essential to understand the process of development of a user-framed numerical formulation, which may be used easily as per the specific site conditions without depending on other indirect methods of analysis as well as on the software. In the present study, a detailed three-dimensional finite element formulation is presented for the analysis of laterally loaded piles in sloping ground developing the 18 node triangular prism elements. An application of the numerical formulation has been illustrated for the pile located at the crest of the slope and for the pile located at some edge distance from the crest. The specific examples show that at any given depth, the displacement and bending moment increase with an increase in slope of the ground, whereas they decrease with increasing edge distance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.324-327
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• 1995

In this research, FEM solution to analysis near field of high Tc superconductor microstrip antenna is presented. This method uses the interpolation function with vector edge triangular element. The advantage of this element is elimination of spurious solutions which are attributed to the lack of enforcement of the divergence condition. The solutions of this method will be used to have a good fundamental data for next reaserch about analysis of HTS microstrip array antenna etc.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.935-937
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• 1993

This paper presents a three dimensional automatic mesh generation scheme for the boundary element method, and this scheme can be applicable to practical problems of complex shape. The geometry of the problem is expressed as an assemblage of linear Coon's surfaces, and each surface is made up of four edge curves which are defined in the form of a parametric function. Curves are automatically segmented according to their characteristics. With these segments of curves, interior points and triangular mesh elements are generated in the parametric plane using Lindholm's method, and then their projection on the real surface forms the initial mesh. The refinement of initial mesh is performed so that the discrete triangular planes are close to the real continuous surfaces. The bisection method is used for the refinement. Finally, interior points in the refined mesh are rearranged so as to make each element be close with an equilateral triangle. An attempt has been made to apply the proposed method to a DY(Deflection Yoke) model.

• Steel and Composite Structures
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• v.2 no.6
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• pp.411-428
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• 2002

Non-linear large-displacement elasto-plastic finite element analyses are used to propose design recommendations for the eaves bracket of a cold-formed steel portal frame. Owing to the thinness of the sheet steel used for the brackets, such a structural design problem is not trivial as the brackets need to be designed against failure through buckling; without availability of the finite element method, expensive laboratory testing would therefore be required. In this paper, the finite element method is firstly used to predict the plastic moment capacity of the eaves bracket. Parametric studies are then used to propose design recommendations for the eaves bracket against two potential buckling modes of failure: (1) buckling of the stiffened free-edge into one-half sine wave, (2) local plate buckling of the exposed triangular bracket area.The results of full-scale laboratory tests on selected geometries of eaves bracket demonstrate that the proposed design recommendations are conservative. The use of the finite element method in this way exploits modern computational techniques for an otherwise difficult structural design problem.

• Interaction and multiscale mechanics
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• v.6 no.2
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• pp.237-255
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• 2013

In this paper, a meshfree-enriched finite element method (ME-FEM) is introduced for the large deformation analysis of nonlinear path-dependent problems involving contact. In linear ME-FEM, the element formulation is established by introducing a meshfree convex approximation into the linear triangular element in 2D and linear tetrahedron element in 3D along with an enriched meshfree node. In nonlinear formulation, the area-weighted smoothing scheme for deformation gradient is then developed in conjunction with the meshfree-enriched element interpolation functions to yield a discrete divergence-free property at the integration points, which is essential to enhance the stress calculation in the stage of plastic deformation. A modified variational formulation using the smoothed deformation gradient is developed for path-dependent material analysis. In the industrial metal forming problems, the mortar contact algorithm is implemented in the explicit formulation. Since the meshfree-enriched element shape functions are constructed using the meshfree convex approximation, they pose the desired Kronecker-delta property at the element edge thus requires no special treatments in the enforcement of essential boundary condition as well as the contact conditions. As a result, this approach can be easily incorporated into a conventional displacement-based finite element code. Two elasto-plastic problems are studied and the numerical results indicated that ME-FEM is capable of delivering a volumetric locking-free and pressure oscillation-free solutions for the large deformation problems in metal forming analysis.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.3 s.180
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• pp.39-46
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• 2006

In this work a dynamic cutting force model in ball end milling of inclined surface is introduced. To represent the complex cutting geometry in ball end milling of inclined surface, workpiece is modeled with Z-map method and cutting edges are divided into finite cutting edge elements. As tool rotates and vibrates, a finite cutting edge element makes two triangular sub-patches. Using the number of nodes in workpiece which are in the interior of sub-patches, instant average uncut chip thickness is derived. Instant dynamic cutting forces are computed with the chip thickness and cutting coefficients. The deformation of cutting tool induced by cutting farces is also computed. With iterative computation of these procedures, a dynamic cutting force model is generated. The model is verified with several experiments.

• Transactions of Materials Processing
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• v.15 no.6 s.87
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• pp.445-452
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• 2006

In most of automobile body panel manufacturing, trimming process is generally performed before flanging. To find feasible trimming line is crucial in obtaining accurate edge profile after flanging. Section-based method develops blank along manually chosen section planes and find trimming line by generating loop of end points. This method suffers from inaccurate results of edge profile. On the other hand, simulation-based method can produce more accurate trimming line by iterative strategy. In this study, new fast simulation-based method to find feasible trimming line is proposed. Finite element inverse method is used to analyze the flanging process because final shape after flanging can be explicitly defined and most of strain paths are simple in flanging. In utilizing finite element inverse method, the main obstacle is the initial guess generation for general mesh. Robust initial guess generation method is developed to handle genera] mesh with very different size and undercut. The new method develops final triangular mesh incrementally onto the drawing tool surface. Also in order to remedy mesh distortion during development, energy minimization technique is utilized. Trimming line is extracted from the outer boundary after finite element inverse method simulation. This method has many advantages since trimming line can be obtained in the early design stage. The developed method is verified by shrink/stretch flange forming and successfully applied to the complex industrial applications such as door outer flanging process.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.3 s.73
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• pp.259-269
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• 2006

In this paper, the stress intensity factor, energy release rate and crack opening displacement are computed using the finite element method for axisymmetric viscoelastic cylinders with the penny-shaped and circumferential cracks. The triangular elements with quarter point nodes are used to describe the stress singularity around the crack edge. The analytical solutions are also derived by using the elastic-viscoelastic correspondence principle and compared with the numerical results to show the validity and accuracy of the presented method. Viscoelastic materials are assumed to behave elastically in dilatation and like a three-parameter standard linear solid.