• Proceedings of the KSME Conference
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• 2001.06d
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• pp.828-833
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• 2001

In this study, an analysis tool to assess the susceptibility of steam generator tubes due to the flow-induced vibration was developed. The fluid-elastic instability analysis of the U-tube bundle for CE-type steam generator was accomplished. The effective mass distribution along the U-tube was obtained to calculate the natural frequency and dynamic mode shape. Finally, stability ratios for selected tubes are obtained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.190-197
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• 1998

Equations of motions of a pretwisted rotating blade with a concentrated mass in an arbitrary position are derived. The flapwise and chordwise equations are coupled to each other due to the pretwist angle of the blade. As the angular speed, hub radius ratio, pretwist angle and concentrated mass vary, the vibration characteristics of the blade change. It is found that eigenvalue lociveering phenomena occur between two closing loci due to the pretwist angle. The effect of the pretwist angle on the critical angular speed and location of the concentrated mass on the natural frequencies are also investigated.

• Structural Engineering and Mechanics
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• v.51 no.6
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• pp.1017-1036
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• 2014

Steel tubes have an efficient shape with large second moment of inertia relative to their light weight. One of the main problems of these members is their low buckling resistance caused from having thin walls. In this study, steel foams with high strength over weight ratio is used to fill the steel tube to beneficially modify the response of steel tubes. The linear eigenvalue and plastic collapse FE analysis is done on steel foam filled tube under pure compression and three point bending simulation. It is shown that steel foam improves the maximum strength and the ability of energy absorption of the steel tubes significantly. Different configurations with different volume of steel foam and composite behavior is investigated. It is demonstrated that there are some optimum configurations with more efficient behavior. If composite action between steel foam and steel increases, the strength of the element will improve, in a way that, the failure mode change from local buckling to yielding.

• Journal of Industrial Technology
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• v.28 no.B
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• pp.135-141
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• 2008

In this paper, the Proper Orthogonal Decomposition (POD) method, which is a statistical analysis technique to find the modal characteristics of a structure, is adapted to identify the modal parameters of a tall chimney structure. A wind force time history, which is applied to the structure, is obtained by a wind tunnel test of a scale down model. The POD method is applied on the wind force induced responses of the structure, and the true normal modes of the structure can be obtained. The modal parameters including, natural frequency, mode shape, damping ratio and kinetic energy of the structure can be estimated accurately. With these results, it may be concluded that the POD method can be applied to obtain accurate modal parameters from the wind-induced building responses.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.6
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• pp.71-76
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• 2003

Optimal design of panel with trapezoidal type stiffeners was studied using linear and nonlinear deformation theories. Also analysis method was using closed-form analysis and finite difference energy methods, respectively. Various bucking load factors are obatined for stiffened laminated composite panel with trapezoidal type stiffeners and various aspect ratios, which are made from Carbon/Epoxy USN 125 prepreg and are simply-supported on four edges under uniaxial compression. Optimal design analyses are carried out by the nonlinear search optimizer, ADS.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.118-125
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• 2003

In this study, we carried out the finite element analysis for the screw of centrifuge that is the weakest part of the centrifuge for sewage management. Centrifugal force caused by rotation with velocity of 4000rpm was applied at the screw. Structural analysis was done with respect to the change of the ratio of blade pitch($R_P$), shaft diameter($R_D$) and extended hole($R_E$). When the area of circular hole is equal to that of extended holes, maximum equivalent stresses in the screw with circular and extended circular hole were compared. And then natural frequency analysis was executed for the same model. Three mode shapes were used to explain the vibration characteristics of each screw. Convergence study was accomplished fur more accurate results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.57-60
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• 2005

Modal parameters of a structure are the important factor to control the missile maneuver. In general, a dummy structure is used for the modal test of missile structure instead of the real warhead and propellant because there may be the danger of a explosion by the electric shock of test equipment, such as the exciter and the power amplifier. However, the modal testing of a real missile structure is required to acquire the modal parameters and to analyze the missile performance accurately. The new test system and technique are developed to get rid of the danger and secure the safety during the testing. This test system is made of with the computer network system and controlled remote from test site. Using His new test system, the modal test of real missile structure is performed successfully and its validity is proven.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.1
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• pp.87-93
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• 2001

이 논문은 사하중에 의한 정적 처짐을 갖는 변단면 보의 자유진동에 관한 연구이다. 사하중이 작용하는 변단면 보의 자유진동을 지배하는 상미분방정식을 유도하고 이를 수치해석하여 최 저차 3개 모드의 고유진동수 및 진동형을 산출하였다. 수치해석 예제에서는 선형 변단면과 등분포 사하중을 채택하였다. 지점조건으로는 회전-회전, 회전-고정, 고정-고정 보를 채택하였다. 수치해석의 결과로 하중강도, 세장비 및 단면비가 고유진동수에 미치는 영향을 분석하였다. 사하중의 영향을 고려한 경우와 고려하지 않은 경우의 진동형을 서로 비교하였다.

• Journal of KSNVE
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• v.9 no.1
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• pp.149-162
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• 1999

A method for the analysis of free vibrations of steel and plain weave composite cylindrical shells with a longitudinal, interior rectangular plate is developed by using the receptance method. This method is based on the ratio of a deflection (or slope) response to a harmonic force(or moment) at the joint. In this study, after getting the free vibration characteristics of the simply supported plate and shell, the frequency equation of the combined system is obtained by considering the continuity condition at the joint between the plate and the shell. The numerical results are compared with published results and experiment results in order to show the validate of the formulation, and shown that the analytical results agreed with those from other methods. The effects of the location and the thickness of the plate on the natural frequencies are also investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.571-575
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• 2000

The physical properties of the spatial model, mass, stiffness and damping matrix, can be defined by a specific natural frequency, damping ratio and mode shape. These modal parameters can be determined from a set of frequency response function(FRF) measured by exciting the structure and measuring the responses at various points around the structure. In this paper, The Transfer Matrix is obtained by experimental modal analysis for the 3-story scaled building model which TMD is installed on top and the physical properties of the spatial model is determined using the residue matrix and the location of poles from FRF measurement using polynomial curve fitting methods.