• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.647-651
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• 2000

This paper deals with the dynamic stability of a vertical cantilevered pipe conveying fluid and having two attached masses. Some valves or other mechanical components in pipe systems can be regarded as attached lumped masses. Governing equations are derived by energy expressions, and numerical technique using Galerkin's method is applied to discretize the equations of small motion of the pipe. Effects of attached masses on the dynamic stability of a vertical cantilevered pipe conveying fluid are investigated for various locations and magnitudes of the attached lumped masses.

• 한국정밀공학회지
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• 제25권5호
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• pp.121-131
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• 2008

In this paper, the dynamic stability of a cracked simply supported pipe conveying fluid with an attached mass is investigated. Also, the effect of attached masses on the dynamic stability of a simply supported pipe conveying fluid is presented for the different positions and depth of the crack. Based on the Euler-Bernoulli beam theory, the equation of motion can be constructed by the energy expressions using extended Hamilton's principle. The crack section is represented by a local flexibility matrix connecting two undamaged pipe segments. The crack is assumed to be in the first mode of a fracture and to be always opened during the vibrations. Finally, the critical flow velocities and stability maps of the pipe conveying fluid are obtained by changing the attached masses and crack severity. As attached masses are increased, the region of re-stabilization of the system is decreased but the region of divergence is increased.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.127-131
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• 2000

The paper presents both theoretical and experimental study for dynamic instabilities of a vertical cantilevered pipe with two attached lumped masses conveying fluid. The two attached lumped masses can be considered as valves or some mechanical parts in real pipe system. Eigenvalue behaviors depending on the flow velocity are investigated for the change of positions and magnitudes of an attached lumped mass and a tip mass. In order to verify appropriaty of numerical solutions, experiments were accomplished. Theoretical predictions have a good agreement with experimental ones.

• 한국소음진동공학회논문집
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• 제11권6호
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• pp.208-215
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• 2001

The paper presents both theoretical and experimental study fur dynamic instabilities of a vortical cantilevered pipe with two attached lumped masses conveying fluid. The two attached lumped masses can be considered as valves or some mechanical paras in real pipe systems. Eigenvalue behaviors depending on the flow velocity are investigated for the change of Positions and magnitudes of an attached lumped mass and a tip mass. In order to verify appropriate of numerical solutions, experiments were accomplished. Theoretical predictions have a good agreement with experimental ones.

• 소음진동
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• 제10권2호
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• pp.280-290
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• 2000

The paper deals with vibration suppression and dynamic stability of a vertical cantilevered pipe conveying an internal flowing fluid and having an attached mass. Real pipe systems may have some valves or mechanical attached parts, which can be regarded as attached lumped masses. The effect of attached mass on the dynamic stability of a cantilevered pipe conveying fluid is investigated for different locations and magnitudes of the attached mass. The flow rate was controlled through motor pump output and measured by a flow meter. Experimental resutls in the vicinity of flutter fluid velocity were compared with theoretical predictions. It has been found that the experimental results are in substantial agreement with the theoretical predictions. Finally, in order to suppress the vibration of the pipe subjected to a disturbance, and control technique using an internal flowing fluid is introduced.

• 전산구조공학
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• 제10권1호
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• pp.149-158
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• 1997

본 논문은 첨가질량이 있는 양단 단순지지 타단 자유단의 경계조건을 갖는 특별 직교 이방성 적층복합판에 대한 적용례로 제시한다. 구조물 설계시 설계자들은 구조물의 정확한 고유진동수를 계산할 필요성을 느끼나 정확한 해답을 얻기란 매우 어렵다. Pretlove는 유효질량 개념을 사용하여 첨가질량을 갖는 보의 해석 방법을 발표하였다. 그러나 이 방법은 단순보의 경우에만 유용할 뿐이다. 그러므로 본 논문에선 해석법이 간단하고, 정확하며, 임의의 경계조건과 단면을 가진 판의 해석에 매우 효과적인 김덕현의 방법으로 첨가질량이 있는 적층복합판의 고유진동수를 계산하였다.

• Structural Engineering and Mechanics
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• 제61권5호
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• pp.685-691
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• 2017

The free transverse vibrations of axially functionally graded (AFG) cantilever beams with concentrated masses attached at different points are studied in this paper. The material properties of the AFG beam, consisting of metal and ceramic, vary continuously in the axial direction according to an established law form. Approximated solutions for the title problem are obtained by means of the Ritz Method. The influence of the material variation on the natural frequencies of vibration of the functionally graded beam is investigated and compared with the influence of the variation of the cross section. The phenomenon of dynamic stiffening of beams can be observed in various situations. The accuracy of the procedure is verified through results available in the literature that can be represented by the model under study.

• Structural Engineering and Mechanics
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• 제66권6호
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• pp.703-711
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• 2018

In this paper is studied the effect of considering the theory of Timoshenko in the vibration of AFG beams that support ground masses. As it is known, Timoshenko theory takes into account the shear deformation and the rotational inertia, provides more accurate results in the general study of beams and is mandatory in the case of high frequencies or non-slender beams. The Rayleigh-Ritz Method is employed to obtain approximated solutions of the problem. The accuracy of the procedure is verified through results available in the literature that can be represented by the model under study. The incidence of the Timoshenko theory is analyzed for different cases of beam slenderness, variation of its cross section and compositions of its constituent material, as well as different amounts and positions of the attached masses.

• 산업기술연구
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• 제15권
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• pp.169-174
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• 1995

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and tower structures, with irregular cross-sections and with arbitrary boundary conditions was developed and reported by D. H. Kim in 1974. IN this paper, the result of application of this method to the laminated plates with axial forces and with attached point mass/masses is presented. Both $N_x$ and $N_y$ forces are considered. The solution for the laminated plates with arbitrary boundary conditions and irregular section can be obtained by simply obtaining the deflection influence coefficients by any method. The effect of neglecting the mass of the plates on the natural frequency, as the ratio of the point mass/masses to the plate mass increases, is thoroughly studied. The influence of $N_x$ and $N_y$ is also carefully investigated.

• 산업기술연구
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• 제15권
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• pp.71-75
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• 1995

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and tower structures, with irregular cross-sections and with arbitrary boundary conditions was developed and reported by D. H. Kim in 1974. This method has been developed for two-dimensional problems including the laminated composite plates and was proved to be very effective for the plates with arbitrary boundary conditions and irregular sections. In this paper, the result of application of this method to the clamped composite plates with non-uniform cross-section and with attached point mass/masses is presented.