• 제목/요약/키워드: Natural frequency and mode

검색결과 1,009건 처리시간 0.028초

곡선보의 모우드 해석 (Modal Analysis of Curved Beam.)

  • 김영문;유기표
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 2000년도 가을 학술발표회논문집
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    • pp.349-354
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    • 2000
  • The modal analysis based on deformations is the method to drived dynamic responsed from superposition of natural frequency and mode shape. In order to free vibration analysis of the structures, Aluminum-made model is used in experiment. The dynamic characteristic of the structures are determined from acceleration measurements using impulse hammer. Experimenrt input and output signal are derive from impact hammer and the one accerometer. This paper present three methods for calculating the natural frequencies and mode shapes of the structure with theory value and finite element analysis, experiment. The results were good approximated about natural frequency and mode shape.

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하중을 받고 회전하는 승용차 타이어의 고유진동수 측정에 관한 실험적 연구 (A Experimental study on natural frequency measurement of passenger car tire under the load and rotation)

  • 김병삼;홍동표;김동현
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 1993년도 추계학술대회 논문집
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    • pp.601-606
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    • 1993
  • The natural frequency measurement of passenger car tire under the load and rotation are studied. In order to obtain theoretical natural frequency and mode shape, the plane vibration of a tire is modeled to that of circular beam. By using the Tickling method based on Hamilton's principle, theoretical results are determined by considering tension force due to tire inflation pressure, rotational velocity and tangential, radial stiffness. Modal parameters varying the inflation pressure, load, rotational velocity are determined experimentally by using frequency response function method. The results show that experimental conditions are parameter for shifting of natural frequency.

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회전하는 유체이송 외팔 파이프의 동특성 해석 (The Dynamic Characteristics of Rotating Cantilever Pipe Conveying Fluid)

  • 윤한익;손인수
    • 한국소음진동공학회논문집
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    • 제13권1호
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    • pp.26-32
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    • 2003
  • The vibrational system of this study is consisted of a rotating cantilever pipe and the flow in the pipe. The equation of motion is derived by using Lagrange equation. The influences of the rotating angular velocity and the velocities of fluid flow in the pipe have been studied on the dynamic characteristics of a rotating cantilever pipe by numerical method. The tip-amplitude of axial vibration and maximum tip-deflection of axial direction of cantilever pipe are directly proportional to the velocity of fluid and rotating angular velocity of pipe In the steady state. respectively The bending tip-amplitude of cantilever pipe is inversely proportional to the velocity of fluid in the steady state. When the rotating angular velocity is 5 rad/s, the velocity of fluid increase with increasing the natural frequency of axial vibration at second mode and third mode, but the natural frequency axial direction of first mode is decreased. The natural frequency of lateral direction is decreased due to increase of the rotating angular velocity. It identifies that the Influence of velocity of fluid give much variation lower mode of vibration in lateral direction. And the Influence of velocity of fluid give much variation higher mode of vibration in axial direction.

축으로 고정된 승용차용 레디얼 타이어의 3차원 진동특성 (3-D Vibration Characteristics of Radial Tire for Passenger Car under Fixed Axle)

  • 김용우;남진영
    • 한국소음진동공학회논문집
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    • 제12권3호
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    • pp.228-235
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    • 2002
  • Two kinds of experimental modal analyses have been performed on a radial tire for passenger car under fixed axle. One is the modal analysis to obtain three-dimensional modes of tire using accelerometers and the other is the one to identify cavity resonance frequency using a pressure sensor. From the first analysis, we have obtained three-dimensional natural modes and their decomposed 3-D modes in each direction, which make it possible to grasp the features of the modes that cannot be identified in the conventional 2-D modes and to classify the vibrationall modes into symmetric, non-symmetric, and antisymmetric modes in a simple way by using the experimental results. From the second experimental analysis, the cavity resonance frequency is found. Coomparing the results of the two analyses, we have Identified the three-dimensional mode of the cavity resonance. We also haute shown that natural frequencies of structural vibration depends on inflation Pressure while the cavity resonance does not.

하부구조의 고유진동수비에 따른 래티스돔의 동적응답특성에 관한 연구 (A Study on Dynamic Response Property of Latticed Domes according to Natural Frequency Ratio of Substructure)

  • 이영락;석근영;강주원
    • 한국공간구조학회논문집
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    • 제16권3호
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    • pp.59-66
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    • 2016
  • This study analyze the dynamic response property of latticed domes according to natural frequency ratio of substructure. Through eigenvalue analysis, it is was confirmed that the half-open angle $30^{\circ}$ and $45^{\circ}$ dominate vibration mode of the vertical direction and the half-open angle $60^{\circ}$ and $90^{\circ}$ dominate vibration mode of the horizontal direction. Through the dynamic response analysis, it is was confirmed that the first frequency about total structure largely appears about the vertical and the horizontal direction regardless of half-open angle.

Exact solutions for free vibration of multi-step orthotropic shear plates

  • Li, Q.S.
    • Structural Engineering and Mechanics
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    • 제9권3호
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    • pp.269-288
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    • 2000
  • The governing differential equations for free vibration of multi-step orthotropic shear plates with variably distributed mass, stiffness and viscous damping are established. It is shown that a shear plate can be divided into two independent shear bars to determine the natural frequencies and mode shapes of the plate. The jk-th natural frequency of a shear plate is equal to the square root of the square sum of the j-th natural frequency of a shear bar and the k-th natural frequency of another shear bar. The jk-th mode shape of the shear plate is the product of the j-th mode shape of a shear bar and the k-th mode shape of another shear bar. The general solutions of the governing equations of the orthotropic shear plates with various boundary conditions are derived by selecting suitable expressions, such as power functions and exponential functions, for the distributions of stiffness and mass along the height of the plates. A numerical example demonstrates that the present methods are easy to implement and efficient. It is also shown through the numerical example that the selected expressions are suitable for describing the distributions of stiffness and mass of typical multi-storey buildings.

수중 동축원통쉘 구조물의 경계조건 변화에 따른 동특성 시험 (An Experimental Study. on Dynamic Characteristics of Submerged Co-axial Cylinderical Shells)

  • 박진호;류정수;김태룡;심우건
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2001년도 춘계학술대회논문집
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    • pp.668-674
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    • 2001
  • An experimental study was performed for two types of co-axial cylindrical shell structures in order to establish the relationship between in-air dynamic characteristics and in-water ones and to observe hydrodynamic mass effects on their mode shapes when submerged. The outer cylinders are prepared with two kinds to get more insights on the fluid-structure interaction phenomena: one is flexible, which means that the outer cylinder has almost same stiffness as the inner one, and the other is a rigid one whose stiffness is more than ten times of the inner one's(it might be regarded as the scaled-down model of the reactor internals). The finite element. analyses were also implemented to support the experimental results. The results show that the natural frequencies of a co-axial cylindrical shell structure in water are remarkably lower than those in air due to the fluid mass effects. In case of the flexible-to-flexible cylinders, there exist in-phase and out-of-phase mode shapes and they are affected by the annular gap between the. co-axial cylinders. For the in-phase mode the in-water natural frequency decreases exponentially as the gap increases, while it slightly increases in case of the out-of-phase mode due to the squeezing effect of the gap fluid. In the flexible-to-rigid case, the normalized natural frequency(in-water frequency/in-air one) of the inner cylinder(core barrel model) ranges between in-phase and out-of-phase mode frequencies of the flexible-to-flexible co-axial cylindrical structure having identical dimensions. Also the normalized natural frequency of the inner cylinder of the flexible-to-rigid one moves from near of the in-phase mode frequency into the out-of-phase mode value of the flexible-to-flexible case as circumferential mode number(n) increases.

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해상 풍력 발전용 구조물 변화에 따른 고유진동해석 (A Study of Natural Frequency on Offshore Wind Turbine Structural Change)

  • 이강수;이정탁;손충렬
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2007년도 춘계학술대회논문집
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    • pp.1008-1016
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    • 2007
  • The purpose of this paper is to investigate the Natural Frequency behavior characteristic of Wind Turbine Tower model, and calculated the stress values of thrust load, wave load, wind load, current load, and gravity load. The offshore Jacket Type Tower which was installed in Vitenam South China Sea is used for the study. Natural frequency and mode shape are calculated with commercial program using the measured vibration. The finite element analysis is performed with commercial F.E.M program(ANSYS) on the basis of the natural frequency and mode shape.

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상부 돔구조와 하부구조간의 고유진동수비에 따른 동적응답특성 (Dynamic Response Property according to Natural Frequency Ratio between Dome Structure and Substructure)

  • 이영락;김광일;강주원
    • 한국공간구조학회논문집
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    • 제15권2호
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    • pp.113-120
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    • 2015
  • This study investigate the dynamic response changes of rib dome structure according to property changes of Substructure. Eigenvalue analysis is conducted in first natural frequency of rib dome versus substructure and searched in the dominant mode of horizontal and vertical direction. Resonance frequency by each first natural frequency of the rib dome structure, substructure and total structure is applied for a seismic wave. That is analyzed about maximum displacement response ratio and maximum acceleration response ratio.

수직-수평부 단면적비에 따른 동조액체기둥형 감쇠장치의 고유진동수 산정식 제안 (Proposition to Natural Frequency of Liquid Column Vibration Absorber with Vertical-Horizontal Area Ratio)

  • 우성식;이상현;정란;이정우;조승호
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2008년도 춘계학술대회논문집
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    • pp.653-658
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    • 2008
  • LCVA has an advantage that its natural frequency can be easily controlled by changing the area ratio of the vertical column and horizontal part. The previous studies investigated the dynamic characteristics of the LCVA under harmonic load. This study experimentally obtained the first and second mode natural frequencies of the LCVA from shaking table tests using white noise and compared the values with the ones by previous study. Test results show that the measured first mode natural frequency of the LCVA has a different value compared with calculated one. The effective length($L_e$) was revised using by power equation. In the Case01 to 19, the standard deviation($s_r$) is 4.7292 and the coefficient of correlation(r) is 0.9856. In the Case21 to 61, the standard deviation ($s_r$) is 14.2143 and the coefficient of correlation(r) is 0.9935. The second mode frequency increases with the increasing area ratio, which is due to the sloshing motion effect resulting from the large area of the vertical column.

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