• Proceedings of the KSME Conference
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• 2001.06a
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• pp.710-715
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• 2001

Rubber is used extensively in many industries because of its large reversible elastic deformation, excellent damping and energy absorption characteristics, and wide availability. It becomes very important to predict the fatigue life of rubber components. But a great deal of time and cost are necessary for the fatigue test of rubber components. In this study the fatigue life of rubber components is evaluated by performing the fatigue test of a specimen and FE analysis. The fatigue life of Jang-gu type specimen which is considered as a simple rubber component is predicted and compared with experimental results. Its material is natural rubber of which hardness is 60 and used for the engine mount of commercial vehicles.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.134-137
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• 2005

In this paper, a continuous contact treatment has been considered during FE-analysis of the sheet metal forming processes. Because the simulation is usually performed stepwise, the status of contact can change suddenly. In case of implicit scheme, the increment of punch stroke can be chosen as large value. For exact assessment of contact force and friction force between die and sheet, the continuous contact treatment is proposed. The virtual surface of sheet metal is modeled by NURBS curves or surfaces in order to calculate exact contact area and penetration depth. From the geometrical evaluation of contact behavior, additional contact pressure is imposed to the element. The deformation of bending process and hydroforming process are analyzed based on this scheme.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.905-909
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• 2001

The significance of casting/forging process for reducing the production cost of large components is being noted in these days. This casting/forging process is a method of forging a workpiece preformed by casting into the final shape. In this study, the casting/forging process has been applied in manufacturing a large aluminum flange in order to determine the optimum forging condition of the aluminum flange. The optimum range of forging temperature of Al 5083 was from $420^{\circ}C$ to $450^{\circ}C$. The suitable strain rate was 1.5 $sec^{-1}$. The deformation amount of a preform in a forging process is key role in the mechanical properties of casting/forging products. In order to find the change of mechanical properties according to effective stain of cast aluminum billets, a hot upsetting test were performed with rectangular blocks and then a uniaxial tensile test was performed with specimens cut from the upsetted billets. The tensile strength and the elongation of cast/upsetted aluminum billets were increased largely until the effective strain was 0.7. FE analysis was performed to determine the configurations of cast preform and die for an aluminum flange. In the FE analysis, the forging load-limit was fixed 1500ton for the low equipment cost. The cast preform was designed so that the effective stain around the neck of a flange exceeds 0.7. In the forging experiment for an aluminum flange, it was confirmed that the optimal configuration of the cast preform predicted by FE analysis was very useful. The cast/forged products using designed preform were made perfectly without any defects.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.2
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• pp.553-563
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• 1996

An algorithm for automatic mesh generation of two-dimensional arbitrary planar domain is proposed by using Delaunay triangulation algorithm. An efficient algorithm is proposed for the construction of Delaunay triangulation algorithm over convex planar domain. From the definition of boundary, boundary nodes are first defined and then interior nodes are generated ensuring the Delaunay property. These interior nodes and the boundary nodes are then linked up together to produce a valid triangular mesh for any finite element analysis. Through the various example, it is found that high-quality triangular element meshes are obtained by Delaunay algorithm, showing the robustness of the current method. The proposed mesh generation scheme has been extended to automatic remeshing, which is applicable to FE analysis including large deformation and large distortion of elements.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.895-906
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• 2014

A fundamental study of the dynamically penetrating anchor (DPA - colloquially known as torpedo anchor) embedded into deep seabed was conducted using measurement data and numerical approaches. Numerical simulation of such a structure penetration was often suffered by severe mesh distortion arising from very large soil deformation, complex contact condition and nonlinear soil behavior. In recent years, a Coupled Eulerian-Lagrangian method (CEL) has been used to solve geomechanical boundary value problems involving large deformations. In this study, 3D finite element analyses using the CEL formulation are carried out to simulate the construction process of dynamic anchors. Through comparisons with results of field measurements, the CEL method in the present study is in good agreement with the general trend observed by in-situ measurements and thus, predicts a realistic large deformation movement for the dynamic anchors by free-fall dropping, which the conventional FE method cannot. Additionally, the appropriate parametric studies needed for verifying the characteristic of dynamic anchor are also discussed.

• Korea-Australia Rheology Journal
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• v.18 no.2
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• pp.109-118
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• 2006

A finite-element method was employed to analyze axisymmetric unsteady motion of a deformable bubble near the wall. In the present study a deformable bubble in a Newtonian medium near the wall was considered. In solving the governing equations a structured mesh generator was used to describe the collapse of highly deformed bubbles with the Arbitrary Lagrangian Eulerian (ALE) method being employed in order to capture the transient bubble boundary effectively. In order to check the accuracy of the present FE analysis we compared the results of our FE solutions with the result of the collapse of spherical bubbles in a large body of fluid in which solutions can be obtained using a 1D FE analysis. It has been found that 1D and 2D bubble deformations are in good agreement for spherically symmetric problems confirming the validity of the numerical code. Non-spherically symmetric problems were also solved for the collapse of bubble located near a plane solid wall. We have shown that a microjet develops at the bubble boundary away from the wall as already observed experimentally. We have discussed the effect of Reynolds number and distance of the bubble center from the wall on the transient collapse pattern of bubble.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.1
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• pp.1-17
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• 2024

Analyzing the tunnel excavation behavior and its effect on the surrounding ground involves large deformation behavior. Therefore, in order to properly simulate the tunnel excavation process and rigorously investigate the actual effect of excavation on surrounding ground and tunnel structure large deformation analysis method is required. In this study, two major numerical approaches capable of considering large deformations behavior were applied to investigate the effect of tunnel boring machine excavation on the surrounding ground: coupled Eulerian-Lagrangian (CEL) and the automatic remeshing (AR) method. Relative performance of both approaches was evaluated through the ground response due to TBM excavation. The ground response will be quantified by estimating the range of the excavation damaged zone (EDZ). By comparing the results, the range of the EDZ will be suggested on the vertical and horizontal direction along the TBM excavation surface. Based on the computed results, it was found that the size of EDZ around the excavation surface and the tendencies was in good agreement among the two approaches. Numerical results clearly show that the size of the EDZ around the tunnel tends to be larger for rock with higher RMR rating. The size of the EDZ is found to be direct proportional to the tunnel diameter, whereas the depth of the tunnel is inversely proportional due to higher confinement stress around the excavation surface.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.3
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• pp.467-473
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• 2017

This paper focuses on the investigation of three-dimensional (3D) warping effect on the stiffness constants of composite beams with closed section profiles. A finite element (FE) cross-sectional analysis is developed based on the Reissner's multifield variational principle. The 3D in-plane and out-of-plane warping displacements, and sectional stresses are approximated as linear functions of generalized sectional stress resultants at the global level and as FE shape functions at the local sectional level. The classical elastic couplings are taken into account which include transverse shear and Poisson deformation effects. A generalized Timoshenko level $6{\times}6$ stiffness matrix is computed for closed section composite beams with and without warping. The effect of neglecting the 3D warping on stiffness constants is shown to be significant indicating large errors as high as 93.3%.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.9
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• pp.1438-1443
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• 2001

The significance of the casting/forging process for reducing the production cost of large components is being noted in these days. This casting/forging process is a method of forging a workpiece preformed by casting into the final shape. In this study, the casting/forging process has been applied in manufacturing a large aluminum flange in order to reduce press capacity and material cost. Firstly, a hot compression test was performed with cast cylindrical billets in order to determine the optimum forging condition of the aluminum flange. The optimum range of forging temperature of Al 5083 was from 420$\^{C}$ to 450$\^{C}$. The suitable strain rate was 1.5 sec(sup)-1. The deformation amount of a preform of a preform in a forging process is a key role in the mechanical properties of casting/forging products. In order to find the change of mechanical properties according to effective stain of cast aluminum billets, a hot upsetting test were performed with rectangular blocks and then a uniaxial tensile test was performed with specimens cut from the upsetted billets. The tensile strength and the elongation of cast/upsetted aluminum billets were increased largely until the effective strain was 0.7. FE analysis was performed to determine the configurations of case preform and die for an aluminum flange. In the FE analysis, the forging load-limit was fixed 1500ton for low equipment cost. The cast preform was designed so that the effective stain around the neck of a flange exceeded 0.7. From the result of FE analysis, optimal configurations of the cast preform and the die were designed for a large flange. The filling and solidification analysis for a sound cast-preform was carried out with MAGMA soft. In the forging experiment for an aluminum flange, it was confirmed that the optimal configuration of the cast preform predicted by FE analysis was very useful. The cast/forged products using designed preform were made perfectly without any defects.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.6.2-6.2
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• 2009

Ultra-fine grained (UFG) Al alloys, which have submicron grain structures, are expected to show outstanding high strength at ambient temperature and excellent superplastic deformation at elevated temperatures and high strain rate. In order to get the UFG microstructure, various kind of severe plastic deformation (SPD) processes have been developed. Among these processes, accumulative roll bonding (ARB) process is a promising process to make bulky Al sheets with ultrafine grained structure continuously. The purpose of the present study is to clarify the grain refinement mechanism during the ARB process and to investigate on the effects of ultra-fine grained structure on the mechanical properties. In addition, UFG AA8011 alloy (Al-0.72wt%Fe-0.63wt%Si) manufactured by the ARB had fairly large tensile elongation, keeping on the strength. In order to clarify the reason for the increase of elongation in the UFG AA8011 alloy, detailed microstructural and crystallographic analysis was performed by TEM/Kikuchi-line and SEM/EBSP method. The unique tensile properties of the UFG AA8011 alloy could be explained by enhanced dynamic recovery at ambient temperature, owing to the large number of high angle boundaries and the Al matrix with high purity.