• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.5
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• pp.404-411
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• 2007

new domain/boundary decomposition method is suggested to perform efficient finite element analyses of contact problems. A penalty method is used for connecting an interface or contact interfaces with neighboring subdomains that satisfy continuity conditions. As a result, the derived effective stiffness matrices are always positive definite, and computational efficiency can be improved to a considerable degree. Moreover, any complex-shaped domain can be divided into independently modeled subdomains without considering the conformity of meshes along the interface. Using a computer code based on the present method, these advantageous features are confirmed through a set of numerical examples.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.846-852
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• 2004

This paper proposes a method to calculate the characteristics of a coupled hydrodynamic journal and thrust bearing of a HDD spindle motor. The governing equations for the journal and thrust bearings are the two dimensional Reynolds equations in ${\theta}z$ and $r\theta$ planes, respectively. Finite element method is appropriately applied to analyze the coupled journal and thrust bearing by satisfying the continuity of mass and pressure at the interface between the journal and thrust bearings. The pressure in a coupled bearing is calculated by applying the Reynolds boundary condition and compared with that by using the Half-Sommerfeld boundary condition. The static characteristics are obtained by integrating the pressure along the fluid film. The flying height of spindle motor is measured to verify the proposed analytical result. This research shows that the proposed method can describe HDB in a HDD system more accurately and realistically than the separate analysis of a journal or thrust bearing.

• Structural Engineering and Mechanics
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• v.54 no.4
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• pp.607-622
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• 2015

This paper presents a comparative study of analytical method and finite element method (FEM) for analysis of a continuous contact problem. The problem consists of two elastic layers loaded by means of a rigid circular punch and resting on semi-infinite plane. It is assumed that all surfaces are frictionless and only compressive normal tractions can be transmitted through the contact areas. Firstly, analytical solution of the problem is obtained by using theory of elasticity and integral transform techniques. Then, finite element model of the problem is constituted using ANSYS software and the two dimensional analysis of the problem is carried out. The contact stresses under rigid circular punch, the contact areas, normal stresses along the axis of symmetry are obtained for both solutions. The results show that contact stresses and the normal stresses obtained from finite element method (FEM) provide boundary conditions of the problem as well as analytical results. Also, the contact areas obtained from finite element method are very close to results obtained from analytical method; disagree by 0.03-1.61%. Finally, it can be said that there is a good agreement between two methods.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.309-314
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• 2001

In this study, the nonlinear soil structure interaction analysis method based on finite element and boundary element method is developed. In the seismic region, the nonlinearity of near field soil has to be considered for more exact reflection of soil-structure interaction effect. Thus, nonlinear finite element program coupled with boundary elements is developed for nonlinear soil-structure interaction analysis. Using the developed numerical algorithm, the nonlinear soil-structure interaction analysis is performed and responses due to dynamic forces and seismic excitation are investigated. The developed method is verified by comparing with previous studies.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.475-480
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• 2007

For the propagation of elastic waves in unbounded domains, absorbing boundary conditions at the fictitious numerical boundaries have been proposed. In this paper we focus on both first- and second-order paraxial boundary conditions(PBCs) in the framework of variational approximations which are based on paraxial approximations of the scalar and elastic wave equations- We propose a penalty function method for the treatment of PBCs and apply these into finite element analysis. The numerical verification of the efficiency is carried out through comparing PBCs with Lysmer-Kuhlemeyer' s boundary conditions.

• Journal of Power System Engineering
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• v.10 no.4
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• pp.83-89
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• 2006

Curved beams are more efficient in transfer of loads than straight beams because the transfer is effected by bending, shear and membrane action. The finite element method is a versatile method for solving structural mechanics problems and curved beam problems have been solved using this method by many author. In this study, a new three-noded hybrid-mixed curved beam element is proposed to investigate the in-plane flexural vibration behavior of arches depending on the curvature, aspect ratio and boundary conditions, etc. The proposed element including the effect of shear deformation is based on the Hellinger-Reissner variational principle, and employs the quadratic displacement functions and consistent linear stress functions. The stress parameters are then eliminated from the stationary condition of the variational principle so that the standard stiffness equations are obtained. Several numerical examples confirm the accuracy of the proposed finite element and also show the dynamic behavior of arches with various shapes.

• Structural Engineering and Mechanics
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• v.81 no.4
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• pp.461-479
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• 2022

A finite element method analysis framework is introduced for the free vibration analyses of functionally graded porous beam structures by employing two variables trigonometric shear deformation theory. Both Young's modulus and material density of the FGP beam element are simultaneously considered as grading through the thickness of the beam. The finite element approach is developed using a nonlocal strain gradient theory. The governing equations derived here are solved introducing a 3-nodes beam element. A comprehensive parametric study is carried out, with a particular focus on the effects of various structural parameters such as the dispersion patterns of GPL reinforcements and porosity, thickness ratio, boundary conditions, nonlocal scale parameter and strain gradient parameters. The results indicate that porosity distribution and GPL pattern have significant effects on the response of the nanocomposite beams.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.589-596
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• 2010

In this study, we calculate the welding residual stresses for a butt-welded thin-walled plate by carrying out three-dimensional finite-element analyses. To study the effect of mechanical boundary conditions on the welding residual stresses, various boundary conditions are considered. The welding residual stresses obtained in the measurements and finite-element analyses are validated by comparing them with the welding residual stress profiles in the R6 code. The results of this study are used to analyze the influence of residual stress on the crack formation in thin-section weldments.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.03a
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• pp.196-202
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• 1995

Drawbead formulation is the first process together with a binder wrap process in a sheet metal forming process. The purpose of a drawbead is to control the flow of the metal into the die in panel press forming. To simulate the drawbead formation process, an elasto-plastic finite element formulation is derived from the equilibrium equation an drelated boundary conditions considering the proper contact conditons. The developed finite element program is applied to drawbead formation in the plane strain condition. The simulation of drawbead formation produces the distribution fo stress and strain along the bead and the resultant elongation of the sheet in the cavity region with respect to various cavity dimensions of the sheet as well as the punch force of a drawbead and the amount of draw-in with respect to the stroke fo a drawbead. The numerical resutls provides the fundamental information as a boundary condition to analyze the complex binder wrap phenomena and panel press forming in simple way.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.832-834
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• 2017

In this paper, the finite element models for composite lattice structures were verified through natural frequency test. Finite element models of composite lattice structure were generated using beam, shell and solid element. Natural frequencies were measured using impact test method under free-boundary condition. The natural frequencies of finite element analysis for shell and solid element showed a good agreement with experimental results. But beam element did not show a good agreement with experimental results, because beam element could not consider the degradation of mechanical properties of non-intersection parts for composite lattice structure.