• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.5
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• pp.199-208
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• 2011

The purpose of this study is to evaluate of the strength and deformation capacity of metallic dampers with the variable slit shape. For this purpose, 12 metallic damper specimens were prepared and shear testing was performed. According to the test results, the S shaped metallic damper with the strut height of 200mm and angle of $60^{\circ}$ shows better hysteretic performance than any other specimens. By making a comparison between the yield strength in test and the proposed strength formula, test results shows larger yield strength than calculation method.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1045-1050
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• 2007

Equations of motion of rotating cantilever curved beams are derived based on a dynamic modeling method developed in this paper. The Kane's method is employed to derive the equations of motion. Different from the classical linear modeling method which employs two cylindrical deformation variables, the present modeling method employs a non-cylindrical variable along with a cylindrical variable to describe the elastic deformation. The derived equations (governing the stretching and the bending motions) are coupled but linear. So they can be directly used for the vibration analysis. The coupling effect between the stretching and the bending motions which could not be considered in the conventional modeling method is considered in this modeling method. The natural frequencies of the rotating curved beams versus the rotating speed are calculated for various radii of curvature and hub radius ratios.

• Journal of Welding and Joining
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• v.19 no.6
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• pp.652-657
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• 2001

To analyze and predict crack initiation position and propagation directions on the spot welded area are very important for strength design of the automobile body structure. It is necessary to test by method considering random loads with variable amplitude for strength design of vehicle body structure, because driving cars are actually subjected to random loads with variable amplitude in the road. Although this condition, nearly all tests haute been performed under constant load conditions in the laboratory because it is impossible to replay like an actual conditions. In this study, using in-plane bending type specimens, the overload factor affecting on the fatigue strength, crack initiation and propagation directions of spot-welded specimens have been studied.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.405-410
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• 2000

Generally, it is known that the reduced integration, modified shape function anisoparametric and non-conforming element can minimize the error induced by stiffness locking phenomenon in the finite element analysis. In this study, new anisoparametric curved beam elements are introduced by using different shape functions in each displacement field. When these shape functions are substitute for functional, we can expect that the undulate stress patterns are not appeared or minimized because there is no unmatched coefficient in the constrained energy equation. As a result of numerical test, the undulate stress patterns are disappeared, and displacement and stress are coincide with the exact solutions.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2002.11a
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• pp.89-93
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• 2002

One of the primary factors like plate structure in ship is redundancy structure that is comparable with ocean structure and frame structure. The more component material becomes buckling collapsed locally the less structure stiffness becomes accordingly. As a result, by increasing the load distribution of my other subsidiary structure continually component member collapses, therefore the structure could be in danger of collapse. So, in order to interpret this phenomenon precisely, the study on boundary condition of the ship's plate and post-buckling analysis must be considered In this study, the rectangular plate is compressed by the in-plane load Buckling & Ultimate strength characteristics are applied o be the elasto-plasticity large deformation by ansys code with F.E.M method On this basis, elasto-plasticity of the plain plate are investigated. This study proved elasto-plasticity behaviour of the ship's plate in accordance with boundary condition based on the series analysis in case of the compressive load operation

• Journal of the Society of Naval Architects of Korea
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• v.33 no.3
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• pp.66-80
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• 1996

Recently, HT steel has been widely used in structure, and this enables to reduce the plate thickness. To use the HT steel effectively for a ship hull, the plate thickness becomes thin so that plate buckling may take place. Therefore, precise assessment of the behaviour of plat above primary buckling load is important. The plate under the load, that is called, secondary buckling load may undergo abrupt changes in wave form after primary buckling. This is very important when the collapse strength of the whole structures is considered. From this point of view, this paper discusses secondary buckling behaviour of thin plate under inplane compressive loading. A elastic large deflection analysis of plates with initial imperfection is performed assuming uniaxial compression, respectively, and the influence of secondary buckling is investigated. It is known that square plate is not influenced by non-symmetrical deflection coefficient but influenced by symmetrical deflection coefficient. Also, it has been found that rectangular plate($\alpha$=a/b) is influenced by all deflection coefficient, and the reduction of inplane stiffness of the plate after primary buckling is continued.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.47-60
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• 2007

In this paper, we investigate the natural frequencies and buckling loads of functionally graded material (FGM) plates and shells, using a quasi-conforming shell element that accounts for the transverse shear strains and rotary inertia. The eigenvalue of the FGM plates and shells are calculated by varying the volume fraction of the ceramic and metallic constituents using a sigmoid function, but their Poisson's ratios of the FGM plates and shells are assumed to be constant. The expressions of the membrane, bending and shear stiffness of FGM shell element are more complicated combination of material properties than a homogeneous element. In order to validate the finite element numerical solutions, the Navier's solutions of rectangular plates based on the first-order shear deformation theory are presented. The present numerical solutions of composite and sigmoid FGM (S-FGM) plates are proved by the Navier's solutionsand various examples of composite and FGM structures are presented. The present results are in good agreement with the Navier's theoretical solutions.

• Composites Research
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• v.26 no.2
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• pp.91-98
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• 2013

A three-dimensional finite analysis method was proposed to predict the failure of composite double-lap bolted joints, which is based on the stiffness degradation method using damage variables and Hashin's three-dimensional failure criteria. Ladeveze's theory using damage variables to consider the matrix/shear damage was combined with stiffness degradation in fiber direction. Four different failure modes were considered including matrix compression/shear, matrix tension/shear, fiber compression, and tension failures. The friction between bolt and composite and the clamping force were considered using a commercial finite element software ABAQUS. The damage model was incorporated using the user-defined subroutine of the software. The predicted result was verified with the existing test result for bearing tension double shear and showed the deviation ranging 7~16% from test results.

• Composites Research
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• v.21 no.6
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• pp.1-7
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• 2008

The main objective of this study is to investigate the effect of salt water on the mechanical properties of a high modulus carbon-epoxy composite. Specimens were made of a carbon-epoxy composite UPN139B of SK Chemical and tested under inplane tension and shear after 0, 1, 3, 6, 9, and 12 months immersion in 3.5% salt water. Acceleration technique such as temperature elevation was not used. The tensile strengths and modulli in fiber and matrix direction did not show any remarkable degradation until 12 months immersion. In contrast to the tensile properties, shear strength and modulus started to gradually decrease up to about 10% of values of dry specimens after 12 months immersion. It was confirmed through the test that the material UPN139B can be an effective material for the shell structures in salt water to resist against the external pressure buckling because of the high fiber directional modulus and corrosion resistance.

• Composites Research
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• v.21 no.3
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• pp.1-8
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• 2008

The main objective of this study is to investigate the effect of salt water on the mechanical properties of a carbon-epoxy composite material. Specimens were made of a carbon-epoxy composite USN125 and tested under inplane tension and shear after 0, 0.5, 1, 2, 3, 6, 9, and 12 months immersion in 3.5% salt water. Waterproof painting and acceleration technique were not applied. The tensile strengths and moduli in fiber and matrix directions did not show any remarkable degradation until 12 months immersion. In contrast to the tensile properties, shear strength and modulus started to degrade from the early stage of the immersion time and gradually decreased to 36% and 46% of dry values, respectively, after 12 months immersion.