• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.4
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• pp.375-387
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• 2004

A new finite element model will be presented to analyze the nonlinear behavior of RC beams and slabs strengthened by a patch repair. The numerical approach is based on the p-version degenerate shell element including theory of anisotropic laminated composites, theory of materially and geometrically nonlinear plates. In the nonlinear formulation of this model, the total Lagrangian formulation is adopted with large deflections and moderate rotations being accounted for in the sense of von Karman hypothesis. The material model is based on hardening rule, crushing condition, plate-end debonding strength model and so on. The Gauss-Lobatto numerical quadrature is applied to calculate the stresses at the nodal points instead of Gauss points. The validity of the proposed p-version nonlinear finite element model is demonstrated through the load-deflection curves, the ultimate loads, and the failure modes of RC beams or slabs bonded with steel plates or FRP plates compared with available result of experiment and other numerical methods.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.8
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• pp.777-783
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• 2012

Vibration intensity has been used to identify the location of a vibration source in a vibrating system. By using vectors representation, the source of the power flow and the vibration energy transmission paths can be revealed. However, due to the large surface area of a plate-like structure, clear transmission paths cannot be achieved using the vectors representation. Experimentally, for a large surface object, the number of measured points will also be increased. This requires a lot of time for measurement. In this study, streamlines representation is used to clearly indicate the power flow transmission paths at all surface plate for FEM and experiment. To clearly improve the vibration intensity transmission paths, streamlines representation from experimental works and FEM computations are compared. Improved transmission paths visualization for both FEM and experiment are shown in comparison to conventional vectors representation. These streamlines visualization is useful to clearly identify vibration source and detail energy transmission paths especially for large surface plate-like structures. Not only that, this visualization does not need many measured point either for experiment or FEM analysis.

• The Journal of the Acoustical Society of Korea
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• v.42 no.3
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• pp.227-232
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• 2023

Underwater noise pollution has a significant impact on the marine environment. This study proposed a simple approach to estimate the acoustic radiation efficiency of structures with air bubble layers. The method considered the insertion loss caused by the air bubble layer through post-processing of numerical results, assuming that insertion loss is equivalent to attenuation as demonstrated by previous studies. The proposed approach was validated by comparing it with a fully coupled analysis for plate structure models. The commercial finite element program COMSOL Multiphysics was used for the acoustic-structure interaction analysis, and the acoustic characteristics of air bubble layer for the fully coupled analysis was simulated by on the Commander and Prosperetti theory. The trends indicated good agreement between the simple approach and the fully coupled analysis in terms of radiation efficiency. It is confirmed that the proposed method is providing insight into the principal mechanism of underwater noise reduction for the bubble layer on the wedge-shaped structure.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.163-168
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• 1991

During Compression molding of polymeric composite materials, the flow characteristics should be obtained. Understanding the flow states may be useful for determination of optimum molding conditions, charge pattern etc. So far, for obtaining the flow analysis, no-slip boundary condition was applied on the mold surface. However, The study under consideration of the slip was conducted by Barone and Caulk. They have introduced the nondimensional parameter which is the ratio of viscous to friction resistance and governs the frictional condition. But the method for determining the parameter could not be proposed. In our work, the parameter which explains the interfacial friction is measured under a variety of molding conditions. Two-dimensional rectangular part and circular hollow disk are simulated with the measured parameter using the finite element method. Effects of the parameter on shapes of flow fronts are also presented.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.113-116
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• 1998

This study should investigate to what extent the electric field of a vacuum interrupter might be influenced by the electric potential of floating arc shield. The electric potentials of floating shield and electric fields of a vacuum interrupter are analysed by a finite element method against variation of gap distances from 1mm to 12mm. The electric potentials of floating shield was increased with the gap distance, which is because the relative position of shield is closer to fixed contact so that the capacitance distribution inside interrupter is varied. The calculated results show that the maximum value of electric field of a vacuum interrupter with floating shield is nearly same to that without shield at shorter gap distance(below 5mm), however at larger gaps a significant increment of electric field is achieved in interrupter with shield companying with model without shield, which is due to the influence of charged floating shield.

• Composites Research
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• v.26 no.1
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• pp.36-41
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• 2013

In this study, low velocity impact analysis on composite sandwich structure was performed. Sandwich structure configuration is made of Carbon-Epoxy face sheets and foam cores. For validating study, the results of an experimental and a finite element method analysis were compared previously. From the finite element method analysis results of sandwich panel, it was confirmed that the results of analysis was reasonable. Impactor velocity to initiate damage was estimated, and in order to investigate the damage at the predicted velocity, impact analysis using finite element method was performed. According to the impact analysis results of sandwich panel, it was confirmed that the damage was generated at the estimated impact velocity. Finally, The comparison of the numerical results with those measured by the experiment showed good agreement.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.1
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• pp.14-28
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• 1992

For a planar curve-sided paned with constant or linear density distributions of source or doublet in the singularity methods, Cantaloube and Rehbach(1986) show that the surface integral can be transformed into contour integral by using Stokes' formulas. As an extension of their formulations, this paper deals with a planar polygonal panel for which we derive the closed-forms of the potentials and the velocities induced by the singularity distributions. Test calculations show that the analytical evaluation of the closed-forms is superior to numerical integration(suggested by Cantaloube and Rehbach) of the contour integral. The compact and explicit expressions may produce accurate values of matrix elements of simultaneous linear equations in the singularity methods with much reduced computer tiome.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.3
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• pp.213-220
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• 2000

The method of photoelasticity allows one to obtain principal stress differences and principal stress directions in a photoelastic model. In the classical approach, the photoelastic parameters are measured manually point by point. The previous methods require much time and skill in the identification and measurement of photoelastic data. Fringe phase shifting method has been recently developed and widely used to measure and analyze fringe data in photo-mechanics. This paper presents the test results of photoelastic fringe phase shifting technique for the stress analysis of a circular disk under compression and an edge-cracked plate subjected to tensile load. The technique used here requires four phase stepped photoelastic images obtained from a circular polariscope by rotating the analyzer at $0^{\circ}$, $45^{\circ}$, $90^{\circ}$ and $135^{\circ}$. Experimental results are compared with those or FEM. Good agreement between the results can be observed. However, some error may be included if the technique is used to general direction which is not parallel to isoclinic fringe.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.439-440
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• 2016

본 연구에서는 상용차의 무시동시 에어컨용 전력변환기의 열분포를 조사하였다. 유한요소법(PEM : Finite Element Method)기반의 열 분포 시뮬레이션을 한 후, 이 결과를 바탕으로 실험을 수행하였으며, 방열판 및 MOSFET의 열 분포 결과를 서로 비교 분석하였다.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.154.2-154.2
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• 2005