• Transactions of Materials Processing
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• v.14 no.8 s.80
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• pp.718-724
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• 2005

An efficient finite element method has been introduced for analysis of metallic sandwich plates subject to bending moment. A full model 3-point bending FE-analysis shows that the plastic behavior of inner structures appears only at the load point. The unit structures of sandwich plates are defined to numerically calculate the bending stiffness and strength utilizing the recurrent boundary condition for pure bending analysis. The equivalent models with the same bending stiffness and strength of full models are then designed analytically. It is demonstrated that the results of both models are almost the same and the FE-analysis method incorporating the equivalent models can reduce the computation time effectively. The dominant collapse modes are face buckling and face yielding. Since the inner dimpled structures prevent face buckling, sandwich plates with inner dimpled shell structure can absorb more energy than other types of sandwich plates during the bending behavior.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2287-2289
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• 1999

In this paper, a new method for calculating capacitance in multi-electrode system with arbitrarily shape is presented. This new approach based on divergence theorem and Gauss's law is achieved by Surface-Contacted Element(SCE) for Gaussian surface. To evaluate capacitance in multi-electrode system, two dimensional finite element method using only the elements which is contacted one nod (PE: Point-Element) or two nod (FE: Face-Element) with surface is employed. The proposed SCE method has short computing time to calculate capacitance which is because it uses only SCE elements and needs one calculation loop while exiting FEM method in servral loops. This method is verified by application in calculating capacitance using potential detection device model which is composed with anode, cathode, and floating electrode.

• Korean Journal of Materials Research
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• v.28 no.10
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• pp.595-600
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• 2018

This study investigates the microstructural properties of CoCrFeMnNi high entropy alloy (HEA) oxynitride thin film. The HEA oxynitride thin film is grown by the magnetron sputtering method using nitrogen and oxygen gases. The grown CoCrFeMnNi HEA film shows a microstructure with nanocrystalline regions of 5~20 nm in the amorphous region, which is confirmed by high-resolution transmission electron microscopy (HR-TEM). From the TEM electron diffraction pattern analysis crystal structure is determined to be a face centered cubic (FCC) structure with a lattice constant of 0.491 nm, which is larger than that of CoCrFeMnNi HEA. The HEA oxynitride film shows a single phase in which constituting elements are distributed homogeneously as confirmed by element mapping using a Cs-corrected scanning TEM (STEM). Mechanical properties of the CoCrFeMnNi HEA oxynitride thin film are addressed by a nano indentation method, and a hardness of 8.13 GPa and a Young's modulus of 157.3 GPa are obtained. The observed high hardness value is thought to be the result of hardening due to the nanocrystalline microstructure.

• Transactions of Materials Processing
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• v.29 no.3
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• pp.163-171
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• 2020

We present a multi-step cold drawing for a non-equiatomic Co₁₀Cr₁₅Fe₂₅Mn₁₀Ni₃₀V₁₀ high entropy alloy (HEA) with a simple face-centered cubic (FCC) crystal structure. The distribution of strain in the cold-drawn Co₁₀Cr₁₅Fe₂₅Mn₁₀Ni₃₀V₁₀ HEA wires was analyzed by the finite element method (FEM). The effective strain was expected to be higher as it was closer to the surface of the wire. However, the reverse shear strain acted to cause a transition in the shear strain behavior. The critical effective strain at which the shear strain transition behavior is completely shifted was predicted to be 4.75. Severely cold-drawn Co₁₀Cr₁₅Fe₂₅Mn₁₀Ni₃₀V₁₀ HEA wires up to 96% of the maximum cross-sectional reduction ratio were successfully manufactured without breakage. With the assistance of electron back-scattering diffraction and transmission electron microscope analyses, the abundant deformation twins were found in the region of high effective strain, which is a major strengthening mechanism for the cold-drawn Co₁₀Cr₁₅Fe₂₅Mn₁₀Ni₃₀V₁₀ HEA wire.

• Journal of the Korean Society for Railway
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• v.7 no.3
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• pp.186-192
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• 2004

Using the finite element method, rail-wheel contact model has been analyzed for mechanical loads due to passengers and payload of the train. This paper presents an investigation on how tapered wheel and inclined rail surfaces affect the contact stress and displacement of rail-wheel contacting surface under mechanical loads. For a numerical analysis, the tapered faces of the wheel are considered as 2.5% and 5.5%. And two models of the tilted rail are also considered as 40：1 and 20：1 at the bottom of the rail. The computed results based on the contact stress and displacement FE analysis indicate that the tilting ratio of the rail, 20：1 with a tapered face of the wheel, 2.5% may be more stable compared to that of 40：1 tilting model and 5.5% tapered wheel face.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.7 s.262
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• pp.739-746
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• 2007

Recently, models in STL files are widely used in reverse engineering processes, CAD systems and analysis systems. However the models have poor geometric quality and include only triangles, so the models are not suitable for the finite element analysis. This paper presents a general method that generates finite element mesh from STL file models. Given triangular meshes, the method estimates triangles and makes clusters which consist of triangles. The clusters are merged by some geometric indices. After merging clusters, the method applies plane meshing algorithm, based on domain decomposition method, to each cluster and then the result plane mesh is projected into the original triangular set. Because the algorithm uses general methods to generate plane mesh, we can obtain both tri and quad meshes unlike previous researches. Some mechanical part models are used to show the validity of the proposed method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.04a
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• pp.149-156
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• 1998

In suspension bridges, the axial farces in the wires are transferred by side pressure on the semicircular face, and further from the strand shoe through rods to a base plate fixed to the massive concrete part of the anchor block. For prefabricated strands the most common way of anchoring is by socketing the ends of the strands. In this study, strand shoe and hanger socket are analyzed far various load conditions using Finite Element Method. The finite element models are built using MSC/PATRAN and analysis is carried out using MSC/NASTRAN. Results are again completely processed using MSC/PATRAN. From the results of the analysis, trends of deformation and stress distribution are reviewed and important factors to consider in the design of strand shoe and hanger socket are discussed.

• Advances in aircraft and spacecraft science
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• v.9 no.6
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• pp.507-523
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• 2022

This study is aimed to accurately predict the vibration response of two types of functionally graded sandwich plates, one with FGM core and another with FGM face sheets. The gradation in FGM layer is quantified by exponential method. An efficient zig-zag theory is used and the zigzag impacts are established via a linear unit Heaviside step function. The present theory fulfills interlaminar transverse stress continuity at the interface and zero condition at the top and bottom surfaces of the plate for transverse shear stresses. Nine-noded C-0 FE having 8DOF/node is utilized throughout analysis. The present model is free from the obligation of any penalty function or post-processing technique and hence is computationally efficient. Numerical results have been presented on the free vibration behavior of sandwich FGM for different end conditions, lamination schemes and layer orientations. The applicability of present model is confirmed by comparing with published results. Several new results are also specified, which will serve as the benchmark for future studies.

• Steel and Composite Structures
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• v.27 no.1
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• pp.123-133
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• 2018

Steel-concrete-steel (SCS) sandwich composite structure with corrugated-strip connectors (CSC) has the potential to be used in buildings and offshore structures. In this structure, CSCs are used to bond steel face plates and concrete. To overcome executive problems, in the proposed system by the authors, shear connectors are one end welded as double skin composites. Hence, this system double skin with corrugated-strip connectors (DSCS) is named. In this paper, finite element model (FEM) of push-out test was presented for the basic component of DSCS. ABAQUS/Explicit solver in ABAQUS was used due to the geometrical complexity of the model, especially in the interaction of the shear connectors with concrete. In order that the explicit analysis has a quasi-static behavior with a proper approximation, the kinetic energy (ALLKE) did not exceed 5% to 10% of the internal energy (ALLIE) using mass-scaling. The FE analysis (FEA) was validated against those from the push-out tests in the previous work of the authors published in this journal. By comparing load-slip curves and failure modes, FEMs with suitable analysis speed were consistent with test results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.6
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• pp.118-126
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• 2011

The objective of this paper is to study the structural behavior of Composite Basement Wall (CBW) according to shear span-to-depth ratio through an experiment and predict the nonlinear behavior of CBW by using ADINA program widely has been being used for FE analysis. Especially, this study focuses on the part of CBW in which the Reinforced Concrete (RC) is under compression stress; At the region of CBW around each floor, RC part stresses by compressive force when lateral press by soil acts on the wall. The contact condition between RC wall and steel (H-Pile) including stud connector is main factor in the analysis since it governs overall structural behavior. In order to understand the structural behavior of CBW whose RC part is under compressive stress, an experimental work and finite element analysis were performed. Main parameter in the test is shear span-to-depth ratio. For simplicity in analysis, reinforcements were not modeled as a seperated element but idealized as smeared to concrete. All elements were modeled to have bi-linear relation of material properties. Three type of contact conditions such as All Generate Option (AGO), Same Element Group Option with Tie(SEGO-T) and Same Element Group Option with Not tie(SEGO-NT) were considered in the analysis. For each analysis, the stress flow and concentration were reviewed and analysis result was compared to test one. From the test result, CBW represented ductile behavior by contribution of steel member even if it had short shear span-to-depth ration which is close to "1". The global composite behavior of CBW whose concrete wall was under compressive stress could be predicted by using contact element in ADINA program. Especially, the modeling by using AGO and SEGO-T showed more close relation on comparing with test result.