• Advances in Computational Design
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• v.5 no.2
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• pp.177-193
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• 2020

In the present research, dynamic analysis of functionally graded (FG) graphene-reinforced beams under thermal loading has been carried out based on finite element approach. The presented formulation is based on a higher order refined beam element accounting for shear deformations. The graphene-reinforced beam is exposed to transverse periodic mechanical loading. Graphene platelets have three types of dispersion within the structure including uniform-type, linear-type and nonlinear-type. Convergences and validation studies of derived results from finite element approach are also presented. This research shows that the resonance behavior of a nanocomposite beam can be controlled by the GPL content and dispersions. Therefore, it is showed that the dynamical deflections are notably influenced by GPL weight fractions, types of GPL distributions, temperature changes, elastic foundation and harmonic load excitation frequency.

• 한국전산유체공학회:학술대회논문집
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• 1996.05a
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• pp.68-73
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• 1996

The full incompressible Navier-Stokes equations are numerically integrated to solve the unsteady channel flow using a new numerical scheme of second-order accuracy developed by the authors. It is well known that in spite of the symmetry in the boundary condition and geometry, asymmetry can develop with time-dependency in a channel with sudden expansion. The instability of the shear flow and the cross-channel pressure contribute to such asymmetric flow. In this paper, we successfully generated a channel flow in which vortex waves were propagated downstream due to the harmonically oscillating inlet flow. The structure of the eddies and wall vorticity are parametrically investigated.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.592-595
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• 2011

A numerical investigation on a suction vortices, free vortices and subsurface vortices behavior in the model sump system with multi-intakes is performed A test model sump and piping system were designed based on Froude similitude for the prototype of the recommended structure layout by HI-9.B Standard for Pump Intake Design of the Hydraulic Institute. A numerical analysis of three dimensional multiphase flows through the model sump is performed by using the finite volume method of the CFX code with multi-block structured grid systems. A ${\kappa}-{\omega]$ ShearStressTransportturbulencemodelandthe Rayleigh-Plesset cavitation model are used for solving turbulence cavitating flow. From the numerical analysis, several types of vortices are reproduced and their formation, growing shedding and detailed vortex structures are investigated. To reduce abnormal vortices, an anti-vortex device is considered and its effect is investigated and discussed.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.18 no.2
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• pp.137-143
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• 2009

This paper presents the fabrication of inchworm motor for high precision actuator system of large displacement and high force. The inchworm motor consists of a extend actuator that provides displacement of tool guide and two clamping actuators which provide the holding force. In order to avoid the PZT fracture, design of pre-load housing was conducted by flexure hinge structure, because PZT actuator has low tensile and shear. To design the pre-load housing and optimize the clamping mechanism, the static and dynamic analysis were conducted by finite element method. From these results, a prototype of the inchworm motor was fabricated and dynamic characteristic with respect to the various frequency was tested. The maximum velocity of the inchworm motor was $41.1{\mu}m/s$ at 16Hz.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.6
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• pp.745-750
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• 2011

A jig vise is a device to clamp workpiece precisely, which is widely used for various machine tools and manufacturing purpose. A new elastic structured jaw-wedge of jig vise is developed, in this paper, so as to satisfy the clamping requirement and the suppression effect of upright movement of workpiece. The advanced design parameters of jaw-wedge are derived step by step considering the stress distribution and the displacement profiles of ANSYS analysis, and it could find the optimum model which shows the uniform displacement profiles and exhibits the non-concentrated stress distribution of jaw neck. As a result, it is ascertained that an jaw-wedge developed in this study is the simple elastic structure which is effective for automatic multiple clamping purpose without the danger of shear crack or bucking of jaw.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.331-338
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• 2005

The grain structure, dislocation density and second phase particles in various regions including the stir zone(SZ), thermo-mechanically affected zone(TMAZ), and heat affected zone(HAZ) of a friction stir weld 6.35mm thick aluminum 7075-T651 alloy were investigated and compared with the base metal. The microstruectures of nugget zone were compared according to tool rotation speeds and tool transition speeds. The hardness profiles of nugget zone were increased, while decreasing rotation speed and increasing welding speed. The optimal microstructure was gained at the low rotation speed 800rpm and th high welding speed 124mm/min. The nugget microstructures of fracture surface, transgranular dimple and quasicleavage type were showed different fracture type with the HAZ, shear fracture type.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1721-1730
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• 2000

An eccentric degenerated shell element with geometric non-linearity for the precise and efficient analysis of stiffened shell structures is developed. To deal with the eccentricity, we define the e ccentric shell and the master shell that constitute one combined shell. It is assumed that the sections remain plane after deformation. The internal force vector and the tangent stiffness matrix based on the virtual work principle in the natural coordinate system are derived. To enhance the robustness of the element, assumed strain method for transverse shear and membrane strains is used. Through numerical experiments the effectiveness of the proposed element is demonstrated.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1696-1701
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• 2003

This paper deals with a vibration control analysis of a rotating composite blade, modeled as a tapered thinwalled beam induced by heat flux. The displayed results reveal that the thermally induced vibration yields a detrimental repercussions upon their dynamic responses. The blade consists of host graphite epoxy laminate with surface and spanwise distributed transversely isotropic (PZT-4) sensors and actuators. The controller is implemented via the negative velocity and displacement feedback control methodology, which prove to overcome the deleterious effect associated with the thermally induced vibration. The structure is modeled as a composite thin-walled beam incorporating a number of nonclassical features such as transverse shear, secondary warping, anisotropy of constituent materials, and rotary inertias.

• Proceeding of KASS Symposium
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• 2005.05a
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• pp.205-212
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• 2005

In order for utilization of the concrete filled tubular, It Is necessary to scrutinize interfacial characteristics between heterogeneous materials, and be performed to various analytical studies on the composite structure. In this paper, this analytic study is carried on using ABAQUS Package/ Version 5.8-1, and the variables aye the relations between the coefficient of friction and the contact pressure for analyzing the behavior on the contact surface, through modifying the analytic methods and improving some problems. It is used to subdivided analytical methods in this research which categorize into four regions and can obtain closer effect for the bond behavior. Four categories compose of the chemical bond and mechanical bond legions replaced the full-interaction before yielding, and the pure friction and moving-down regions after yielding.

• Journal of Korean Association for Spatial Structures
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• v.2 no.2 s.4
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• pp.59-67
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• 2002

In this study, a method that estimates stiffness and mass matrices of shear building from modal test data is presented. This method applied of building depends on the number of measurement points that are less in number than the total structural degrees of freedom, and on the first two orders of structural mode measured. By means of this method it is possible to use modal data of unmeasurable points to estimate total stiffness and mass matrices of structure. Some examples are studied in this paper, and its result shows that this method is reliable.