• Interaction and multiscale mechanics
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• v.6 no.2
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• pp.83-105
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• 2013

In this paper, a multi-scale meshfree-enriched finite element formulation is presented for the analysis of acoustic wave propagation problem. The scale splitting in this formulation is based on the Variational Multi-scale (VMS) method. While the standard finite element polynomials are used to represent the coarse scales, the approximation of fine-scale solution is defined globally using the meshfree enrichments generated from the Generalized Meshfree (GMF) approximation. The resultant fine-scale approximations satisfy the homogenous Dirichlet boundary conditions and behave as the "global residual-free" bubbles for the enrichments in the oscillatory type of Helmholtz solutions. Numerical examples in one dimension and two dimensional cases are analyzed to demonstrate the accuracy of the present formulation and comparison is made to the analytical and two finite element solutions.

• Structural Engineering and Mechanics
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• v.25 no.4
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• pp.467-480
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• 2007

Two methods were developed for analyzing problems with two adjacent sub-domains modeled by different kinds of elements in finite element method. Each sub-domain can be defined independently without the consideration of equivalent division with common nodes used for the interface. These two methods employ an individual interface to accomplish the compatibility. The MLSA method uses the moving least square approximation which is the basic formulation for Element Free Galerkin Method to formulate the interface. The displacement field assumed by this method does not pass through nodes on the common boundary. Therefore, nodes can be chosen freely for this method. The results show that the MLSA method has better approximation than traditional methods.

• Structural Engineering and Mechanics
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• v.33 no.3
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• pp.325-337
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• 2009

Structural damage detection, damage localization and severity estimation of jacket platforms, based on calculating modal strain energy is presented in this paper. In the structure, damage often causes a loss of stiffness in some elements, so modal parameters; mode shapes and natural frequencies, in the damaged structure are different from the undamaged state. Geometrical location of damage is detected by computing modal strain energy change ratio (MSECR) for each structural element, which elements with higher MSECR are suspected to be damaged. For each suspected damaged element, by computing cross-modal strain energy (CMSE), damage severity as the stiffness reduction factor -that represented the ratios between the element stiffness changes to the undamaged element stiffness- is estimated. Numerical studies are demonstrated for a three dimensional, single bay, four stories frame of the existing jacket platform, based on the synthetic data that generated from finite element model. It is observed that this method can be used for damage detection of this kind of structures.

• Structural Engineering and Mechanics
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• v.22 no.1
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• pp.1-16
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• 2006

This paper presents a virtual boundary element-equivalent collocation method (VBEM) for the plane magnetoelectroelastic solids, which is based on the fundamental solutions of the plane magnetoelectroelastic solids and the basic idea of the virtual boundary element method for elasticity. Besides all the advantages of the conventional boundary element method (BEM) over domain discretization methods, this method avoids the computation of singular integral on the boundary by introducing the virtual boundary. In the end, several numerical examples are performed to demonstrate the performance of this method, and the results show that they agree well with the exact solutions. So the method is one of the efficient numerical methods used to analyze megnatoelectroelastic solids.

• Journal of Korean Association for Spatial Structures
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• v.21 no.2
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• pp.81-88
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• 2021

In this paper, nonlinear finite element analysis was conducted based on the experimental results on buckling restrained brace. The reliability of the analytical model was verified by comparing the results of experimental studies with hysteresis loop, bi-linear curve, cumulative energy dissipation capacity, and equivalent viscous damping. A valid finite element model has been secured and will be used as basic data for finite element analysis of buckling restrained braces in the future.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.06b
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• pp.141-146
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• 1999

In the stage of process design, many factors affecting tool life should be considered. Wear, Damage Accumulation and excessive die Stress are those. Most Engineer think wear and damage accumulation affection deeply to the cold forging dies and wear for the hot forging dies. In this report, the example that wear and stress distribution affect tool life in hot forging together will be introduced and the way to solve that problem using Finite Element Method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1992.03a
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• pp.115-130
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• 1992

The analysis of thermoplastic automotive bumpers needs not only characterizations of the thermomechanical properties of thermoplastic materials but also the finite element method which can solve the problems with a large deflection, an elastic-inelastic deformation, and a change of a contact state. This paper describes the modeling techniques in the finite element analysis in order to get a good prediction of thermoplastic bumper behaviors. Simplification effects of a complex geometry of thermoplastic bumpers are studied by comparing the results from static loading tests and the finite element analysis.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.351-354
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• 2003

Titanium alloys are a vital element for developing advanced structural components, especially in aerospace applications. However, process design for successful forming of titanium alloy is a difficult task, which is to be achieved within a very narrow range of process parameters. Presented in this paper is a finite element - based optimal design technique as applied to ductile fracture minimization process design in backward extrusion of titanium alloys.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.10a
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• pp.149-156
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• 1994

The thermomechanical elasto-plastic problems in hot forging of the porous metals are analyzed using the thermo-elasto-plastic finite element method. This finite element program has been formulated using the yield condition advanced by Lee and Kim and developed using the thermo-elasto-plastic time integration procedure. Thermomechanical responses and densification behaviors of the porous metals during hot forging are calcucated at various initial relative densities, strain rates and temperatures. The calculated results are in good agreement with experimental data.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.10a
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• pp.173-181
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• 1994

Process design is one of the most important fields in metal forming, where the finite element method has appeared a useful method for industrial applications. In this study, a program using the rigid plastic finite element has been developed for preform design in three-dimensional plastic deformation. The surface integration for calculation of the friction between die and workpiece has been implemented with care in numerical treatment. The developed program is applied to a precision coining process for designing an optimal punch.