• Title, Summary, Keyword: Free vibration

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Free Vibration Analysis of Thermoelastic Structure (열탄성 구조물의 자유진동 특성)

  • Cho, Hee-Keun;Park, Young-Won;Park, Ki-Young;Lee, Kyoung-Don
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.12
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    • pp.201-208
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    • 2000
  • A numerical analysis algorithm for thermally loaded structures has been proposed and compared with the general free vibration approach to determine the characteristics of thermal load effects in vibration structures. The field of numerical inspection includes free vibration analysis, transient heat transfer analysis and thermal stress analysis. The key point of the analysis of thermally loaded structure is the method of parallel time integration between transient heat transfer and free vibration simultaneously. The results of the study demonstrate the computation of the specific total external force vector and stiffness matrix. The proposed analysis method can be applied to both heated and cooled structure vibration analysis.

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Free Vibration Characteristics of a String with Time-Varying Length (길이가 변하는 현의 자유진동 특성)

  • 이승엽;박상규
    • Journal of KSNVE
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    • v.9 no.5
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    • pp.906-913
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    • 1999
  • Time-dependent period and energy of free vibration of a string, whose length varies with time at a constant rate, are investigated by a traveling wave method. When the string length is increased, the vibration period increase, but the free vibration energy decrease with time. However, when the string undergoes retraction, the vibration energy increases with time. String tension together with non-zero instantaneous velocity at the moving boundary results in energy variation. Analytical solutions by the traveling wave method are compared with previous results using the perturbation method and Kotera's approach.

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Theory and Experiments of Free Vibration Characteristics for the Composite Beam with Transverse Open Cracks (크랙이 있는 복합재료 보 자유진동특성의 이론과 실험적 입증)

  • 하태완
    • Journal of the Korea Institute of Military Science and Technology
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    • v.5 no.2
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    • pp.217-227
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    • 2002
  • Theoretical and experimental free vibration characteristics of cantilevered laminated composite beams with single or multiple transverse non-propagating open cracks are investigated. The presence of intrinsic cracks in beams modifies the flexibility and in turn free vibration characteristics of the structures, and the existence of the multiple cracks in an anisotropic composite beam affects the free vibration characteristics in a more complex fashion compared with the beam with a single crack. Also the experimental results are well coincide with the numerical results in the decrease of natural frequencies and the transformation of mode shapes because of intrinsic cracks in the composite or aluminum beams. It is revealed that non-destructive crack detection(NDT) or vibration based inspection(VBI) is possible by analyzing the free vibration responses of cracked composite beams.

Free Vibration Analysis of Helical Springs (헬리컬 스프링의 자유진동 해석)

  • 김월태;정명조;김현수;이영신
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.977-983
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    • 2003
  • Free vibration analysis of helical springs was performed by the use of the commercial finite element analysis program, ANSYS. The investigation of national frequency was focused on the effect of various parameters such as boundary conditions, spring indices, number of coil turns and helix angles which are considered to affect the free vibration of a spring. The finite element method was validated by comparison with the result of a previouosly published literature. The similarity of frequency trend was shown among three boundary conditions: clamped-clamped, free-free, simpliy supported-simply supported but there was no similarity in light of mode shapes among them. Several modes showed similar frequencies on and near the frequencies identified by the natural frequency formula of Wahl. Natural frequencies increased with spring indices and number of turns decreasing and with helix angles increasing. The results investigated by finiete element method were compared with the experemental result and theoretical result and showed a good agreement among them.

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A Study on the Behavior of a Noise & Vibration-Free Screw Pile Method by Means of numerical analysis (무소음.무진동 스크류말뚝공법의 수치해석에 의한 거동 연구)

  • Kim, Young-Pil;Jung, Ho-Young;Ha, Young-Min;Oh, Seung-Ryul;Choi, Yong-Kyu
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.30-37
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    • 2009
  • In doing the foundation work in the downtown, the popular complaints by means of Noise and vibration have been became heavy burden. Therefore, the noise & vibration-free screw PHC pile method will contribute to the foundation work by removal of the popular complaints and improvement of the constructability. In this paper, the load bearing capacity and displacement characteristics of the noise & vibration-free screw PHC pile were analyzed. The noise & vibration-free screw PHC pile's behavior was better well than the existing PHC pile's one.

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Free Vibration Analysis of Double Cylindrical Shells Using Transfer of Influence Coefficent (영향계수의 전달에 의한 2중 원통형 셸의 자유진동해석)

  • Choi, Myung-Soo;Yeo, Dong-Jun
    • Journal of the Korea Society For Power System Engineering
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    • v.21 no.5
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    • pp.48-54
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    • 2017
  • The transfer influence coefficient method which is an vibration analysis algorithm based on the transfer of influence coefficient is applied to the free vibration analysis of double cylindrical shells. After the computational programs for the free vibration analysis of double cylindrical shells were made using the transfer influence coefficient method and the transfer matrix method, we compared the results using the transfer influence coefficient method with those by the transfer matrix method. The transfer influence coefficient method provided the good computational results in the free vibration analysis of double cylindrical shells. In particular, The results of the transfer influence coefficient method are superior to those of the transfer matrix method when the stiffness of internal springs connecting a inside cylindrical shell and a outside cylindrical shell is very large.

A study on characteristics of blast vibration waveform by vibration time history analysis (진동이력분석을 응용한 발파 진동파형의 특성에 관한 연구)

  • 김진수;임한욱
    • Tunnel and Underground Space
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    • v.9 no.1
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    • pp.36-47
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    • 1999
  • For cautious controlled blasting, it is necessary to understand characteristics of the blasting vibration. In this study, a series of tests were carried out to investigate the several characteristics of blasting vibration waveform by vibration time history analysis. Separation between impulse vibration and free vibration from blasting vibration, duration time, effects of overlap of free vibration upon the level of vibration and changes of waveform according to increase of charge weight per delay etc. were studied with waveform analysis.

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Static and free vibration behaviour of orthotropic elliptic paraboloid shells

  • Darilmaz, Kutlu
    • Steel and Composite Structures
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    • v.23 no.6
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    • pp.737-746
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    • 2017
  • In this paper the influence of aspect ratio, height ratio and material angle on static and free vibration behaviour of orthotropic elliptic paraboloid shells is studied by using a four-node hybrid stress finite element. The formulation of the element is based on Hellinger-Reissner variational principle. The element is developed by combining a hybrid plane stress element and a hybrid plate element. A parametric study is carried out for static and free vibration response of orthotropic elliptic paraboloid shells with respect to displacements, internal forces, fundamental frequencies and mode shapes by varying the aspect and height ratios, and material angle.

A hybrid 8-node hexahedral element for static and free vibration analysis

  • Darilmaz, Kutlu
    • Structural Engineering and Mechanics
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    • v.21 no.5
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    • pp.571-590
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    • 2005
  • An 8 node assumed stress hexahedral element with rotational degrees of freedom is proposed for static and free vibration analyses. The element formulation is based directly on an 8-node element. This direct formulation requires fewer computations than a similar element that is derived from an internal 20-node element in which the midside degrees of freedom are eliminated by expressing them in terms of displacements and rotations at corner nodes. The formulation is based on Hellinger-Reissner variational principle. Numerical examples are presented to show the validity and efficiency of the present element for static and free vibration analysis.

Free vibration analysis of composite conical shells using the discrete singular convolution algorithm

  • Civalek, Omer
    • Steel and Composite Structures
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    • v.6 no.4
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    • pp.353-366
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    • 2006
  • The discrete singular convolution (DSC) algorithm for determining the frequencies of the free vibration of single isotropic and orthotropic laminated conical shells is developed by using a numerical solution of the governing differential equations of motion based on Love's first approximation thin shell theory. By applying the discrete singular convolution method, the free vibration equations of motion of the composite laminated conical shell are transformed to a set of algebraic equations. Convergence and comparison studies are carried out to check the validity and accuracy of the DSC method. The obtained results are in excellent agreement with those in the literature.