• International Journal of Highway Engineering
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• v.11 no.1
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• pp.195-201
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• 2009

In this paper, the critical strains for pavement design were calculated from both Layered Elastic Program (LEP) and Finite Element Method (FEM) and the case studies which give similar critical responses were compared. Although FEM has been realized as a superior model, LEP is more favorable to pavement design due to its simplicity and thus, the technique to calculate the correct critical responses using LEP is significant. This study showed that KENLAYER can possibly estimate the critical responses close to ones obtained from TTIPAVE, which considers nonlinear cross-anisotropic behavior of unbound base materials, by adjusting the stress point locations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.340-343
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• 2007

In this paper, we present our method to reduce vibration of the base plate of a refrigerator by avoiding resonance between base plate and compressor operation. To verify the modes of the base plate, FE models of the base plate with free-free condition and applied boundary condition were built and validated by results from experimental modal analysis. Operating Deflection Shape analysis was applied to find the sensitive area on the base plate during compressor operation. In optimization process, Finite Difference Method - based sensitivity analysis is used to detect the most sensitive area. Finally, based on this numerical result, we will make beads on the base plate to reduce vibration of refrigerator.

• Journal of applied mathematics & informatics
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• v.22 no.1_2
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• pp.67-82
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• 2006

In this paper, we present a finite difference method for the implementation of the rotation of a circular cylinder in the incompressible flow field by solving the two-dimensional unsteady Navier-Stokes equations. The approach is to use staggered grid method so that the accuracy and order of convergence of the associated algorithms can be maintained. The proposed method is easy to be implemented and is effective. A set of simulations for the flow dynamics is provided to show the computational results.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.18 no.2
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• pp.221-227
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• 2009

The study of the solidification process of welded metal is carried out using the finite element method, which is the basic study for optimal design. In the analysis of temperature, the welded zone is cooled as the result of heat conduction to the base metal and heat transfer to the circumference. In the early phase of the temperature in base metal zone is little changed. But after the rise in temperature the whole area is cooled gradually and uniformly with the lapse of 10 seconds, and a temperature change is hardly occurred in the radial direction but in the axial direction.

• Geomechanics and Engineering
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• v.18 no.4
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• pp.391-406
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• 2019

The aim of this paper was to study the influence of the footing shape and the effect of the roughness of the foundation base on the bearing capacity of shallow foundations on rock masses. For this purpose the finite difference method was used to analyze the bearing capacity of various types and states of rock masses under the assumption of Hoek-Brown failure criterion, for both plane strain and axisymmetric model, and considering smooth and rough interface. The results were analyzed based on a sensitivity study of four varying parameters: foundation width, rock material constant (mo), uniaxial compressive strength and geological strength index. Knowing how each parameter influences the bearing capacity depending on the footing shape (circular vs strip footing) and the footing base interface roughness (smooth vs rough), two correlation factors were developed to estimate the percentage increase of the ultimate bearing capacity as a function of the footing shape and the roughness of the footing base interface.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.3
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• pp.86-91
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• 2022

The mechanical structures mounted on vehicles or aircrafts are subject to random accelerations, such as earthquakes, at the base, and their responses have been calculated through spectrum analysis. However, this method poses a challenge during the synthesis of the responses owing to the loss of the vibration phase. It is necessary to evaluate the time history results to obtain the exact responses; therefore, an efficient technique is proposed to solve this issue. The present technique involves constructing a superelement using the sub-structuring method and finding solutions for this superelement. The finite element model (FEM) was substituted by a superelement, which was simplified into one element with selected nodes. Comparing the numerical results of the superelement with the time history responses for the original finite element model, the two solutions agree well despite the fact that the computation time of the proposed technique has been greatly shortened.

• Advances in concrete construction
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• v.6 no.3
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• pp.269-283
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• 2018

This study presents the effects of geometrical dimensions of concrete gravity dams on the seismic response considering different base width/dam height (L/H) ratios. In the study, a concrete gravity dam with the height of 200 m is selected and finite element models of the dam are constituted including five different L/H ratios such as 0.25, 0.5, 0.75, 1.00, 1.25. All dams are modeled in ANSYS software considering dam-reservoir-foundation interaction. 1989 Loma Prieta earthquake records are applied to models in upstream-downstream direction and linear time history analyses are performed. Dynamic equilibrium equations of motions obtained from the finite element models of the coupled systems are solved by using Newmark time integration algorithm. The seismic response of the models is evaluated from analyses presenting natural frequencies, mode shapes, displacements and principal stresses. The results show that the L/H ratios considerably affect the seismic response of gravity dams. Also, the model where L/H ratio is 1.00 has more desirable results and most appropriate representation of the seismic response of gravity dams.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.369-372
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• 2006

Monolithic forging of cask is required continuously. Body-base monolithic forging of cask has advantage of an economical manufacturing process and better reliability for nuclear applications. Through the finite element analysis and parametric study of design variables, those are die angle, groove length and flange thickness, the optimal dimensions of preform and die sets are determined in order to develop a suitable forging process for body-base monolithic forging. To verify the result of finite element analysis, the physical model of 1/30 scale of actual product using plasticine was carried out. The result of this experiment, deformed shapes were very similar to the finite element analysis. As a result of this work, the special piercing method was developed using blank material consisting of a flange, groove and squared part.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.876-886
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• 1994

Process design in superplastic forming to produce a Nickel-base jet engine disk has been carried out using the rigid-viscoplastic finite element method. This study aims at deriving systematic procedures in forging of superalloy engine disk, and develops a simple scheme to control strainrate within a range of superplastic deformation during the forging operation. The new process, a pancake type preform being used, is designed to have less manufacturing time, and more even distribution of effective strain in the final product, while the conventional superplastic forging of an engine disk has been produced from a cylindrical billet. The jet engine company, Pratt & Whitney, provided the basic information on the manufacturing process of superplastic forging of a jet engine disk.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.472-478
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• 2000

The vibration of the hard disk drive (HDD) systems, which comprises flexible disks, flexible shafts, bearings, and base structures, are analyzed by a finite element method (FEM) to cope with complicated coupling effects between them. The natural frequencies and mode shapes of the uncoupled, axial and bending coupled vibrations are calculated. Modal testing of the HDD systems is performed to validate the finite element analysis (FEA) results. Good agreement was obtained between the computed and experimental results. Sizing design sensitivity analysis (DSA) of the system was performed with the thickness of base structure and bearing stiffness as design variables. The DSA results tell how can I increase or decrease eigenvalue of the system effectively.