• Title/Summary/Keyword: forced vibration system

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Nonlinear dynamic responses of cracked atomic force microscopes

  • Alimoradzadeh, M.;Akbas, S.D.
    • Structural Engineering and Mechanics
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    • v.82 no.6
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    • pp.747-756
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    • 2022
  • This study presents the nonlinear free and forced vibrations of a cracked atomic force microscopy (AFM) cantilever by using the modified couple stress. The cracked section of the AFM cantilever is considered and modeled as rotational spring. In the frame work of Euler-Bernoulli beam theory, Von-Karman type of geometric nonlinear equation and the modified couple stress theory, the nonlinear equation of motion for the cracked AFM is derived by Hamilton's principle and then discretized by using the Galerkin's method. The semi-inverse method is utilized for analysis nonlinear free oscillation of the system. Then the method of multiple scale is employed to investigate primary resonance of the system. Some numerical examples are presented to illustrate the effects of some parameters such as depth of the crack, length scale parameter, Tip-Mass, the magnitude and the location of the external excitation force on the nonlinear free and forced vibration behavior of the system.

Torsional Vibration Analysis of a Multi-Stage Reduction Gear System (다단 감속치차계의 비틀림진동 해석)

  • 이동환;김영철;최상규;이안성
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1996.10a
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    • pp.307-312
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    • 1996
  • A torsional vibration analysis of a multi-stage reduction gear box connected to a gas turbine system is presented. For a free vibration analysis the Modified Hibner Branch Method, so called "Blank Matrix Method", and the .lambda.-Matrix Method are used in the modeling and the eigenvalue solution, respectively. Also, a short circuit forced analysis of the system is performed, utilizing the energy method modeling. It is shown that the results of the free vibration analysis have the same tendency as those of the short circuit analysis. analysis.

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Accuracy of incidental dynamic analysis of mobile elevating work platforms

  • Jovanovic, Miomir L.J.;Radoicic, Goran N.;Stojanovic, Vladimir S.
    • Structural Engineering and Mechanics
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    • v.71 no.5
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    • pp.553-562
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    • 2019
  • This paper presents the results of a study into the dynamic behaviour of a support structure of a mobile elevating work platform. The vibrations of the mechanical system of the observed structure are examined analytically, numerically, and experimentally. Within the analytical examination, a simple mathematical model is developed to describe free and forced vibrations. The dynamic analysis of the mechanical system is conducted using a discrete dynamic model with a reduced number of vibrational degrees of freedom. On the basis of the expression for the system energy, and by applying Lagrange's equations of the second kind, differential equations are derived for system vibrations, frequencies are determined, and the laws of forced platform vibration are established. At the same time, a nonlinear FEM model is developed and the laws of free and forced vibration are determined. The experimental and numerical part of the study deal with the examination of the real structure in extreme conditions, taking into account: the lowest eigenfrequency, forced actions that could endanger the general stability, the maximal amplitudes, and the acceleration of the work platform. The obtained analytical and numerical results are compared with the experiments. The experimental verification points to the adverse behaviour of the platform in excitation cases - swaying. In such a situation, even a relatively small physical force can lead to unacceptably high amplitudes of displacement and acceleration - exceeding the usual work values.

A Study on the Design of Propeller Shaft for Reduction of Torsional Vibration (비틀림짙동 저감을 위한 추진축 설계에 관한 연구)

  • 최은오;안병민;홍동표;정태진
    • Transactions of the Korean Society of Automotive Engineers
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    • v.7 no.7
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    • pp.221-228
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    • 1999
  • A full-time four wheel drive vehicle is driven literally full time by the front and the rear wheels. Front and rear drive shafts are rotated rapidly in the extremely torsional state, which can cause various vibration and noise problems. The purpose of this study is to reduce the vibration and the noise of the full -time four wheel drive vehicle. In this paper, both the causes and the methods for reduction of torsional vibration are suggested. For this study, the characteristics of the torsional vibration are analyzed by free and forced torsional vibration simulation. And this paper described the influence upon the torsional vibration with emphasis shafting system. The validity of simulation models is checked by the field test. The forced vibration simulation with the variations of shaft design factors are performed by the checked models. According to the simulation , the resonance region shifts and the torque fluctuation varies in the system,. Finally, the methods and the effects for the torsional vibration reduction in driveline are proposed.

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A Study on the Coupled Forced Lateral Vibration of Multi-Supported Shafting by the Transfer Matrix Method (전달매트릭스법에 의한 다지점지지계의 연성강제감쇠 횡진동 계산에 관한 연구)

  • 이돈출;박병학;전효중
    • Journal of Advanced Marine Engineering and Technology
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    • v.14 no.2
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    • pp.35-47
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    • 1990
  • The natural frequency of lateral vibration for ship's propulsion shafting tends to become lower as the relative stiffness of supproted system of the propulsion shafting decreases and the weight of shafting increases. Especially, the propulsion shafting of high-power ships such as car ferries, roll-on/roll-off, and container ships are susceptible to lateral vibration for their resonant speeds are happened to be in ordinary operating speed ranges. So far, many papers on the lateral vibration of ship's propulsion shaftings are published but they treated mainly special cases and not explained explicitly the calculation process. In this paper, the calculation processes of undamped and also forced damped lateral vibration by the transfer matrix method are presented and the calculation programs are developed. With the developed computer programs, a ship's propulsion shafting which was introduced on the published paper is analyzed for its lateral vibration and also the lateral vibration of the main drive shaft for a lathe is calculated to show the availiability of developed computer programs.

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A multiple scales method solution for the free and forced nonlinear transverse vibrations of rectangular plates

  • Shooshtari, A.;Khadem, S.E.
    • Structural Engineering and Mechanics
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    • v.24 no.5
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    • pp.543-560
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    • 2006
  • In this paper, first, the equations of motion for a rectangular isotropic plate have been derived. This derivation is based on the Von Karmann theory and the effects of shear deformation have been considered. Introducing an Airy stress function, the equations of motion have been transformed to a nonlinear coupled equation. Using Galerkin method, this equation has been separated into position and time functions. By means of the dimensional analysis, it is shown that the orders of magnitude for nonlinear terms are small with respect to linear terms. The Multiple Scales Method has been applied to the equation of motion in the forced vibration and free vibration cases and closed-form relations for the nonlinear natural frequencies, displacement and frequency response of the plate have been derived. The obtained results in comparison with numerical methods are in good agreements. Using the obtained relation, the effects of initial displacement, thickness and dimensions of the plate on the nonlinear natural frequencies and displacements have been investigated. These results are valid for a special range of the ratio of thickness to dimensions of the plate, which is a characteristic of the Multiple Scales Method. In the forced vibration case, the frequency response equation for the primary resonance condition is calculated and the effects of various parameters on the frequency response of system have been studied.

Vibration experiment of precision stage that use laser vibrator (비접촉식 진동측정 장치를 이용한 정밀 스테이지의 진동특성 평가시험)

  • Lee, Jae-Woo;Lee, Kang-Wook;Yim, Hong-Jae
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.11a
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    • pp.1224-1230
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    • 2007
  • In this study, a new modal test method is presented to evaluate vibration characteristic of the nano imprint stage system. Since it is difficult to measure vibration level without contacting the machine component, non contacting modal test method, laser scanning system is ultrared. Finite element analysis results are compared with the modal test results.

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Forced vibration of the hydro-elastic system consisting of the orthotropic plate, compressible viscous fluid and rigid wall

  • Akbarov, Surkay D.;Huseynova, Tarana V.
    • Coupled systems mechanics
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    • v.8 no.3
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    • pp.199-218
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    • 2019
  • This paper studies the forced vibration of the hydro-elastic system consisting of the anisotropic (orthotropic) plate, compressible viscous fluid and rigid wall within the scope of the exact equations and relations of elastodynamics for anisotropic bodies for describing of the plate motion, and with utilizing the linearized exact Navier-Stokes equations for describing of the fluid flow. For solution of the corresponding boundary value problem it is employed time-harmonic presentation of the sought values with respect to time and the Fourier transform with respect to the space coordinate on the coordinate axis directed along the plate length. Numerical results on the pressure acting on the interface plane between the plate and fluid are presented and discussed. The main aim in this discussion is focused on the study of the influence of the plate material anisotropy on the frequency response of the mentioned pressure. In particular, it is established that under fixed values of the shear modulus of the plate material a decrease in the values of the modulus of elasticity of the plate material in the direction of plate length causes to increase of the absolute values of the interface pressure. The numerical results are presented not only for the viscous fluid case but also for the inviscid fluid case.

Characteristics of Forced Vibration System According to the Frequency of External Exciting Force (외부 가진력의 주파수에 따른 강제진동시스템의 특성)

  • Kim, Jong-Do;Yoon, Moon-Chul
    • Journal of Convergence for Information Technology
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    • v.11 no.9
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    • pp.130-137
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    • 2021
  • The characteristics of forced vibration by an external excitation force having a frequency were analyzed according to the amplitude and frequency of the excitation force. To obtain displacement, velocity, and acceleration, numerical analysis was performed to obtain the frequency response, and in particular, each FRF(Frequency Response Function) was analyzed to reveal the location of the system natural frequency and excitation frequency in the frequency domain. In the vibration model caused by external excitation, the natural frequency and distribution of the surrounding excitation mode in displacement, velocity and acceleration FRF. The FRF was also shown in the power spectrum and FRF of real and imaginary parts. The external excitation force was approximated with the excitation force of a sine wave by giving the amplitude and frequency, the mode generated by this excitation force could be distinguished. After numerical analysis by changing the equivalent mass, damping and stiffness, the forced vibration response characteristics by external excitation force were systematically analyzed.

On the particularities of the forced vibration of the hydro-elastic system consisting of a moving elastic plate, compressible viscous fluid and rigid wall

  • Akbarov, Surkay D.;Panakhli, Panakh G.
    • Coupled systems mechanics
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    • v.6 no.3
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    • pp.287-316
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    • 2017
  • This paper studies the particularities of the forced vibration of the hydro-elastic system consisting of a moving elastic plate, compressible viscous fluid and rigid wall. This study is made by employing the discrete-analytical solution method proposed in the paper by the authors (Akbarov and Panakhli (2015)). It is assumed that in the initial state the fluid flow is caused by the axial movement of the plate and the additional lineally-located time-harmonic forces act on the plate and these forces cause additional flow field in the fluid and a stress-strain state in the plate. The stress-strain state in the plate is described by utilizing the exact equations and relations of the linear elastodynamics. However, the additional fluid flow field is described with linearized Navier-Stokes equations for a compressible viscous fluid. Numerical results related to the influence of the problem parameters on the frequency response of the normal stress acting on the plate fluid interface plane and fluid flow velocity on this plane are presented and discussed. In this discussion, attention is focused on the influence of the initial plate axial moving velocity on these responses. At the same, it is established that as a result of the plate moving a resonance type of phenomenon can take place under forced vibration of the system. Moreover, numerical results regarding the influence of the fluid compressibility on these responses are also presented and discussed.