• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.10b
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• pp.51-58
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• 2000

The purpose of this study is the optimum modification of dynamic characteristics of stiffened plate structure. In the method of the optimization ,finite element method (FEM), sensitivity analysis and optimum structural modification method are used. To begin with, using FEM, the dynamic characteristics of stiffened plate structure is analyzed. Next, rate of change of dynamic characteristic by the change of design variable is calculated using the sensitivity analysis. Then, amount of change of design variable is calculated using this sensitivity value and optimum structural modification method. The change of natural frequency is made to be an objective function. Thickness of plate and cross section moment become a design variable. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate structure.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1463-1465
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• 2003

In this paper, we studied on the growing characteristics of dendrite structure of melted wire deteriorated by over current. Electric wire was melted by Jolue's heat. By using HSIS(High Speed Imaging System), we found out a lot of melted parts of wire were dispersed and radiated. Electric wire had narrow melted areas in case of short fusing time. A lot of very small dots generated around the grain of copper cross-section and they were changed into dendrite structure. Dendrite structure appeared at the values lower than 2.5[A/sec]. In case of very short fusing time, fusing current was calculated by empirical formula. The Preece equation was not enough to analyze a variety of characteristics of melted wire because it did not consider melting time, atmosphere, etc.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.3
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• pp.187-194
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• 1999

In this study, a series of items on the safety and stability of cracked main structure in subway are investigated and analyzed. Cracks due to dry contraction under the construction can be found when a tensile stress of cross section is higher than tensile strength at a value of coefficient of dry contraction $200{\times}10^{-6}$. It is concluded that there is no problems when load carrying capacity, that is, an ability of resisting loads of structure is enough in this analytical model. Also, it is concluded that this model has a desirable serviceability because a width of bending crack is lower than allowable one.

• Journal of Aerospace System Engineering
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• v.4 no.3
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• pp.24-28
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• 2010

The purpose of this study is to define available microwave absorbing structure for aircraft from in the X-band(8.2~12.4GHz) frequencies. The electromagnetic wave absorption or shielding techniques is an important issue not only for military purpose but also for commercial purposes. Aircraft Radar Absorbing Structure(RAS) is absorbed or scattered propagation waves from the enemy radar. There are absorbing technologies at shaping design techniques and using Radar Absorbing Materials(RAM). RAM is more important because shaping design can't include perfect radar absorbing performance. In this study, based on material properties was introduced RAM and to analyze the each characteristics. Finally, we comparison appropriate RAM for aircraft.

• Advances in materials Research
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• v.13 no.2
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• pp.87-102
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• 2024

This paper is focused on the delamination analysis of a multilayered beam structure loaded in torsion under strain-path control. The beam under consideration has a rectangular cross-section. The layers of the beam are made of different viscoelastic materials which exhibit continuous inhomogeneity in longitudinal direction. Since the delamination is located inside the beam structure, the torsion moments in the two crack arms are obtained by modeling the beam as an internally static undetermined structure. The strain energy stored in the beam is analyzed in order to derive the strain energy release rate (SERR). Since the delamination is located inside the beam, the delamination has two tips. Thus, solutions of the SERR are obtained for both tips. The solutions are verified by analyzing the beam compliance. Delamination analysis with bending-torsion coupling is also performed. The solutions derived are timedependent due to two factors. First, the beam has viscoelastic behavior and, second, the angle of twist of the beam-free end induced by the external torsion moment changes with time according to a law that is fixed in advance.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.3
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• pp.255-263
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• 2017

This paper presents a beam element capable of conducting material and geometric nonlinear analysis for applications requiring the ultimate behavioral analysis of structures with composite cross-sections. The element formulation is based on co-rotational kinematics to simulate geometrically nonlinear behaviors, and it uses the fiber section method to calculate the stiffness and internal forces of the element. The proposed element was implemented using an in-house numerical program in which an arc-length method was adopted to trace severe nonlinear responses(such as snap-through or snapback), as well as ductile behavior after the peak load. To verify the proposed method of element formulation and the accuracy of the program that was used to employ the element, several numerical studies were conducted and the results from these numerical models were compared with those of three-dimensional continuum models and previous studies, to demonstrate the accuracy and computational efficiency of the element. Additionally, by evaluating an example case of a frame structure with a composite member, the effects of differences between composite material properties such as the elastic modulus ratio and strength ratio were analyzed. It was found that increasing the elastic modulus of the external layer of a composite cross-section caused quasi-brittle behavior, while similar responses of the composite structure to those of homogeneous and linear materials were shown to increase the yield strength of the external layer.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.319-322
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• 2002

In this paper, an experimental study is carried out to find out structural behavior of upper slab in concrete box girder bridges. The major variables in the tests are the cross-section of upper slab including haunch dimensions. The strains of concrete and steel bars and the deflections of slabs are measured automatically during the tests. The test results indicate that the size of haunches has much influence on the structural behavior of box girders. The appropriate haunch dimensions are suggested from the present study.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.82-85
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• 2003

In this paper, we present the analysis of electromagnetic scattering from arbitrarily shaped three-dimensional conducting objects coated with a dielectric material. The integral equation treated here is the combined field integral equation. Numerical results of radar cross section for coated conducting structure are presented and compared with other available solutions.

• Journal of Mechanical Science and Technology
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• v.18 no.2
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• pp.246-252
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• 2004

The modal characteristics of rotating structures vary with the rotating speed. The material and the geometric properties of the structures as well as the rotating speed influence the variations of their modal characteristics. Very often, the modal characteristics of rotating structures need to be specified at some rotating speeds to meet their design requirements. In this paper, rotating cantilever beam is chosen as a design target structure. Optimization problems are formulated and solved to find the optimal shapes of rotating beams with rectangular cross section.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.175-179
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• 2017

This study is based on the real structure which is installed earlier in the field. The model is simplified, and thereafter, optimization process was done with a variation of cross-section and rise of the arch model.