• Title, Summary, Keyword: Free vibration

Search Result 1,868, Processing Time 0.043 seconds

Vibration Characteristics of the Axially Moving Continuum with Time-Varying Length: Spagetti Problem (축방향으로 이동하며 길이가 변하는 연속체의 진동특성: 스파게티 문제에 응용)

  • 사재천;이승엽;이민형
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • /
    • pp.385-392
    • /
    • 2001
  • Time-dependent frequency and energy of free vibration of the Spagetti problem, that is the axially moving continuum with time-varying length, are investigated. Exact expressions for the natural frequency and time-varying vibration energy are derived by dealing with traveling waves. When the string length is increased, the vibration period increases, but the free vibration energy varies as a function of both translating velocity and boundary velocity of the continuum. 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.

  • PDF

Using fourth order element for free vibration parametric analysis of thick plates resting on elastic foundation

  • Ozdemir, Y.I.
    • Structural Engineering and Mechanics
    • /
    • v.65 no.3
    • /
    • pp.213-222
    • /
    • 2018
  • The purpose of this paper is to study free vibration analysis of thick plates resting on Winkler foundation using Mindlin's theory with shear locking free fourth order finite element, to determine the effects of the thickness/span ratio, the aspect ratio, subgrade reaction modulus and the boundary conditions on the frequency paramerets of thick plates subjected to free vibration. In the analysis, finite element method is used for spatial integration. Finite element formulation of the equations of the thick plate theory is derived by using higher order displacement shape functions. A computer program using finite element method is coded in C++ to analyze the plates free, clamped or simply supported along all four edges. In the analysis, 17-noded finite element is used. Graphs are presented that should help engineers in the design of thick plates subjected to earthquake excitations. It is concluded that 17-noded finite element can be effectively used in the free vibration analysis of thick plates. It is also concluded that, in general, the changes in the thickness/span ratio are more effective on the maximum responses considered in this study than the changes in the aspect ratio.

Free Vibration Analysis of Arches With General Boundary Condition (일반 경계조건 아치의 자유진동해석)

  • 이태은;이종국;이병구
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • /
    • pp.995-999
    • /
    • 2001
  • This paper deals with the free vibrations of arches with general boundary condition. Based on the dynamic equilibrium equations of a arch element acting the stress resultants and the inertia forces, the governing differential equation is derived for the in-plane free vibration of such arches. Differential equations are solved numerically to calculate natural frequencies. In numerical examples, the parabolic arch is considered. The effects of the arch rise to span length ratio, the slenderness ratio, the vertical spring coefficient and the rotational spring coefficient on the natural frequencies are analyzed.

  • PDF

Vibration analysis of functionally graded material (FGM) grid systems

  • Darilmaz, Kutlu
    • Steel and Composite Structures
    • /
    • v.18 no.2
    • /
    • pp.395-408
    • /
    • 2015
  • The paper considers the free vibration analysis of FGM grid systems. Up to now, very little work has been done on this type of system and the paper aspires to fill this gap. Based on the hybrid-stress finite element formulation free vibration solutions for FGM grid systems of various aspect ratios, different types of gradations functions, and support conditions are determined. The tabulation of these results, not available thus far, should be useful to designers and researchers who may use them.

On the Forced Vibration in the Nonlinear Symmetric Structure by Using the Normal Modes (정규모우드를 활용한 비선형 대칭구조물의 강제진동해석)

  • 박철희;최성철
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • /
    • pp.21-28
    • /
    • 1994
  • The forced vibration with the symmetric boundary condition in nonlinear structure is studied by utilizing the characteristic of the free vibration which have two modes with the similar natural frequency. Two linear modes exist to have no concern with the amplitude. It is found that the normal mode or elliptic orbit as the newly coupled modes is generated in accordance with changing the stability. It is also known that responses for forced vibration having the small external force and damping are near mode of free vibration and the stability for each response is determined according to the stability for each response is determined according to the stability in mode of free vibration. Finally the stability and bifurcation are analyzed in proportion to increment of external force and damping.

  • PDF

Free vibration analysis of cantilever cylindrical tanks

  • Hadid, H.A.;Hasson, D.A.
    • Structural Engineering and Mechanics
    • /
    • v.3 no.1
    • /
    • pp.25-34
    • /
    • 1995
  • General free vibration characteristics of cantilevered circular cylindrical tanks are analyzed using the integral equations technique with the cubic spline functions. For computations, the partial differential equations for thin shallow shells as given by Flugge's have been employed after the addition of the inertia forces. The application of the method is illustrated with a numerical examples of tanks which are free at the top edge and fixed at the bottom. The results obtained by this method have been compared with the available results and a good agreement was found.

Determination of Construction Method for Noise & Vibration-Free Screw Concrete Piles (무소음.무진동 스크류콘크리트말뚝의 시공법 설정)

  • Choi, Yong-Kyu;Kim, Dong-Chul;Kim, Sung-Su;Nam, Moom-S.
    • Proceedings of the Korean Geotechical Society Conference
    • /
    • /
    • pp.360-368
    • /
    • 2010
  • Noise and vibration triggered by pile driving in a construction site not only give hard time to the surrounding areas but could also cause residents nearby to file civil complaints to the extent of bringing construction to a halt. To deal with this issue, construction engineers have worked strenuously to develop low noise & low vibration pile methods. A noise & vibration-free screw concrete pile method proposed in this study is one of the successful outputs. It penetrates pile underground by rotating and pressing in body of the pile to avert noise and vibration while maximizing bearing capacity. A prototype of noise and vibration-free precast screw pile method was manufactured, which is not seen anywhere in Korea and elsewhere, and have undergone pilot tests twice to determine construction method.

  • PDF

Buckling and vibration behavior of a non-uniformly heated isotropic cylindrical panel

  • Bhagata, Vinod S.;Pitchaimani, Jeyaraj;Murigendrappa, S.M.
    • Structural Engineering and Mechanics
    • /
    • v.57 no.3
    • /
    • pp.543-567
    • /
    • 2016
  • This study attempts to address the buckling and free vibration characteristics of an isotropic cylindrical panel subjected to non-uniform temperature rise using numerical approach. Finite element analysis has been used in the present study. The approach involves three parts, in the first part non-uniform temperature field is obtained using heat transfer analysis, in the second part, the stress field is computed under the thermal load using static condition and, the last part, the buckling and pre-stressed modal analysis are carried out to compute critical buckling temperature as well as natural frequencies and associated mode shapes. In the present study, the effect of non-uniform temperature field, heat sink temperatures and in-plane boundary constraints are considered. The relation between buckling temperature under uniform and non-uniform temperature fields has been established. Results revealed that decrease (Case (ii)) type temperature variation field influences the fundamental buckling mode shape significantly. Further, it is observed that natural frequencies under free vibration state, decreases as temperature increases. However, the reduction is significantly higher for the lowest natural frequency. It is also found that, with an increase in temperature, nodal and anti-nodal positions of free vibration mode shapes is shifting towards the location where the intensity of the heat source is high and structural stiffness is low.

Semi-analytical solutions of free and force vibration behaviors of GRC-FG cylindrical shells

  • Lei, Zuxiang;Tong, Lihong
    • Steel and Composite Structures
    • /
    • v.32 no.5
    • /
    • pp.687-699
    • /
    • 2019
  • In this paper, free and force vibration behaviors of graphene-reinforced composite functionally graded (GRC-FG) cylindrical shells in thermal environments are investigated based on Reddy's third-order shear deformation theory (HSDT). The GRC-FG cylindrical shells are composed of piece-wise pattern graphene-reinforced layers which have different volume fraction. Based on the extended Halpin-Tsai micromechanical model, the effective material properties of the resulting nanocomposites are evaluated. Using the Hamilton's principle and the assumed mode method, the motion equation of the GRC-FG cylindrical shells is formulated. Using the time- and frequency-domain methods, free and force vibration properties of the GRC-FG cylindrical shell are analyzed. Numerical cases are provided to study the effects of distribution of graphene, shell radius-to-thickness ratio and temperature changes on the free and force vibration responses of GRC-FG cylindrical shells.