Showing papers on "Vibration published in 1984"
Book•
01 Dec 1984
TL;DR: A survey of the technology of modal testing, a new method for describing the vibration properties of a structure by constructing mathematical models based on test data rather than using conventional theoretical analysis.
Abstract: A survey of the technology of modal testing, a new method for describing the vibration properties of a structure by constructing mathematical models based on test data rather than using conventional theoretical analysis. Shows how to build a detailed mathematical model of a test structure and analyze and modify the structure to improve its dynamics. Covers techniques for measuring the mode, shapes, and frequencies of practical structures from turbine blades to suspension bridges.
2,525 citations
TL;DR: In this paper, a model was developed to describe the vibration produced by a single point defect on the inner race of a rolling element bearing under constant radial load, incorporating the effects of bearing geometry, shaft speed, bearing load distribution, transfer function and the exponential decay of vibration.
792 citations
TL;DR: In this article, the authors reviewed the use of high-frequency resonance for vibration monitoring of rolling element bearings by the highfrequency resonance technique and showed that the procedures for obtaining the spectrum of the envelope signal are well established, but that there is an incomplete understanding of the factors which control the appearance of this spectrum.
751 citations
TL;DR: In this article, an inexpensive and realistic procedure is developed for estimating the lateral dynamic stiffness and damping of flexible piles embedded in arbitrarily layered soil deposits, where material and radiation damping due to waves emanating at different depths from the pile-soil interface are rationally taken into account; the overall equivalent damping at the top of the pile is then obtained as a function of frequency by means of a suitable energy relationship.
Abstract: An inexpensive and realistic procedure is developed for estimating the lateral dynamic stiffness and damping of flexible piles embedded in arbitrarily layered soil deposits. Starting point is the determination of the pile deflection profile for a static force at the top using any reasonable method—beam‐on‐Winkler foundation, finite elements, well‐instrumented pile load tests in the field, etc. Material as well as radiation damping due to waves emanating at different depths from the pile‐soil interface are rationally taken into account; the overall equivalent damping at the top of the pile is then obtained as a function of frequency by means of a suitable energy relationship. The method is applied to study the dynamic behavior of three different piles embedded in two idealized and one actual layered soil deposit; the results of the method, obtained by hand computations, compare favorably with the results of three dimensional dynamic finite element analyses.
310 citations
TL;DR: In this article, the dynamic behavior of rigid-block structures resting on a rigid foundation subjected to horizontal harmonic excitation is examined, and several possible modes of steady-state response are detected, and analytical procedures are developed for determining the amplitudes of the predominant modes and for performing stability analyses.
Abstract: The dynamic behavior of rigid-block structures resting on a rigid foundation subjected to horizontal harmonic excitation is examined. For slender structures, the nonlinear equation of motion is approximated by a piecewise linear equation. Using this approximation for an initially quiescent structure, safe or no-toppling and unsafe regions are identified in an excitation amplitude versus excitation frequency plane. Furthermore, several possible modes of steady-state response are detected, and analytical procedures are developed for determining the amplitudes of the predominant modes and for performing stability analyses. It is shown that the produced stability diagrams can be beneficial to assessing the toppling potential of a rigid-block structure under a given amplitude-frequency combination of harmonic excitation; in this manner the integration of the equation of motion is circumvented.
225 citations
Book•
30 Jun 1984TL;DR: In this paper, the Asymptotic Method in the Theory of Random Vibrations of Continuous Systems is used for the planning of Vibration Measurements in Structures under RandomVibrations.
Abstract: 1 - Random Loadings Acting on Mechanical Systems.- 2 - Methods in the Theory of Random Vibrations.- 3 - Random Vibrations of Linear Continuous Systems.- 4 - The Asymptotic Method in the Theory of Random Vibrations of Continuous Systems.- 5 - Parametrically Excited Random Vibrations.- 6 - Random Vibrations of Nonlinear Systems.- 7 - Reliability and Longevity under Random Vibrations.- 8 - The Planning of Vibration Measurements in Structures under Random Vibrations.- References.
184 citations
TL;DR: In this paper, a non-linear equation of the free motion of a heavy elastic cable about a deformed initial configuration is developed, which is obtained via a Galerkin procedure, an approximate solution is pursued through a perturbation method.
Abstract: Continuum non-linear equations of free motion of a heavy elastic cable about a deformed initial configuration are developed. Referring to an assumed mode technique one ordinary equation for the cable planar motion is obtained via a Galerkin procedure, an approximate solution of which is pursued through a perturbation method. Suitable nondimensional results are presented for the vibrations in the first symmetric mode with different values of the cable properties. Which procedure is the proper one to account consistently for the non-linear kinematical relations of the cable in one ordinary equation of motion is discussed.
178 citations
TL;DR: In this article, a simple model was developed to obtain radiation damping coefficients of soil-foundation systems, for both plane-strain and axisymmetric loading conditions, and the results were in very good accord with available rigorous solutions for strip footings, circular footings and piles, resting on or embedded in a homogeneous space and subjected to vertical and horizontal vibration.
Abstract: A simple model is developed to obtain radiation damping coefficients of soil‐foundation systems, for both plane‐strain and axisymmetric loading conditions. Despite the simplifying assumptions made, the obtained closed‐form results are in very good accord with available rigorous solutions for strip footings, circular footings and piles, resting on or embedded in a homogeneous space and subjected to vertical and horizontal vibration. The models are readily extended to a class of realistic inhomogeneous media, for which no exact solutions are presently available. Considerable insight is provided on the nature of radiation damping and its dependence on frequency, and an analogy is drawn with the propagation of sound from a loudspeaker.
164 citations
TL;DR: In this paper, the free vibration analysis of joined conical-cylindrical shells is presented, where the governing equations of vibration of a conical shell, including a cylindrical shell as a special case, are written as a coupled set of first order differential equations by using the transfer matrix of the shell.
129 citations
01 Apr 1984
TL;DR: In this article, a method for analyzing the free vibration of combined linear undamped dynamical systems attached at discrete points is presented, which uses separation of variables to exhibit the harmonic motion of the system and to derive a generalized differential equation for the normal modes.
Abstract: A method for analyzing the free vibration of combined linear undamped dynamical systems attached at discrete points is shown. The method uses separation of variables to exhibit the harmonic motion of the system and to derive a generalized differential equation for the normal modes. Green’s functions for the vibrating component systems are used to solve the generalized differential equation and derive the characteristic equation for the natural frequencies of the system. The characteristic equation can then be solved for the exact natural frequencies and exact normal modes. The method is demonstrated for two types of dynamical systems involving beams and oscillators. For two particular systems, approximate natural frequencies determined through a Galerkin’s method and the finite element method are compared to the exact natural frequencies. The generalized orthogonality relation for each system is derived.
95 citations
TL;DR: In this paper, the Rayleigh-Ritz method is used to determine the natural frequencies in transverse vibration of rectangular plates with elastically restrained edges, which can be applied to a wide range of elastic restraint conditions, any aspect ratio and for higher modes in addition to the fundamental.
TL;DR: Thresholds for sensation of continuous sinusoidal skin displacements were determined in 7 different test points in the glabrous skin area of the right hand of 11 human subjects and it was proposed that the detection of the type of stimuli used was based on activity in 3 different mechanoreceptive systems.
TL;DR: In this paper, a liquid container filled with two immiscible liquids is proposed to dampen the motion of the interface of a cantilever beam in which the liquid theory is derived and a mathematical mechanical model is presented.
TL;DR: In this article, a method for the analysis of the influence of spindle speed variation on the course of self-excited vibration has been presented, based on self-frequency of selfexcited vibrations on the stability of machining, and dependence of this frequency on workpiece rotational speed.
TL;DR: Partial differential equations of motion suitable to study moderately large free oscillations of an clastic suspended cable arc are obtained in this paper, where an integral procedure is used to eliminate the spatial dependence and to reduce the problem to one ordinary differential equation which shows quadratic and cubic nonlincarities.
TL;DR: In this paper, the modal frequencies and damping ratios of three degrees of freedom were measured and analyzed for different types of vibrations induced by dry friction by means of a model apparatus described in Part 1.
Abstract: Different types of vibrations induced by dry friction are investigated by means of a model apparatus described in Part 1. The structural model is obtained from the measurement of the modal frequencies and damping ratios of three degrees of freedom. The oscillations in the normal and frictional forces, as well as the slider vibrations, have been measured and analyzed. As the normal load is increased, four different regions of vibrations are observed corresponding to the four friction regimes discussed in a companion paper. Small oscillations are encountered at low values of the normal load and they are possibly caused by random surface irregularities. The vibration characteristics are changed when transition occurs from steady state friction. When the normal load is further increased, self-excited periodic vibrations are produced. The spectra of the oscillations are related to the modal frequencies. Self-excited vibrations are analyzed on the basis of the experimental data. 12 references, 6 figures, 1 table.
TL;DR: In this paper, a developed simulator on a rotational vibration and a strain at a root of a tooth, on a power transmission spur gear, is presented, which solves a differential equation with one degree of freedom in consideration of the behaviour of the stiffness around tooth tip meshing.
Abstract: This paper introduces a developed simulator on a rotational vibration and a strain at a root of a tooth, on a power transmission spur gear. The simulator solves a differential equation with one degree of freedom in consideration of the behaviour of the stiffness around tooth tip meshing. The stiffness function is discussed and determined with static and dynamic meshing tests under load. The developed simulator has one more distinctive feature that the errors of the gears are put into the simulator with a newly developed automatic gear accuracy measuring instrument. The simulated outputs depict precisely the experimental behaviours. Through the development of this simulator, the the discussion becomes easier on the effectiveness of a spur gear for the decrease of vibration.
TL;DR: In this paper, two-dimensional equations of motion or piezoelectric crystal plates, obtained from the three dimensional equations of linear PDE by expansion in power series of the thickness coordinate of the plate, are solved for forced vibrations of electroded SC-cut quartz plates.
TL;DR: The nonlinear transfer of energy among modes of different frequencies on a vibrating string is investigated both theoretically and experimentally in this paper, where it is shown that at least one of the end supports has finite mechanical admittance if there is to be any mode coupling.
Abstract: The nonlinear transfer of energy among modes of different frequencies on a vibrating string is investigated both theoretically and experimentally. The nonlinearity is associated with the well‐known variation of string tension caused by the vibration modes, but it is essential that at least one of the end supports has finite mechanical admittance if there is to be any mode coupling. If the nonrigid bridge support has zero admittance in a direction parallel to the string, the coupling is of third order in the mode amplitudes. For a more realistic model in which the string changes direction as it passes over a bridge of finite admittance there are additional coupling terms of second order. The first mechanism gives driving terms of frequency 2ωn±ωm where ωn and ωm are, respectively, the angular frequencies of the nth and mth modes present on the string, while the second mechanism gives driving terms of angular frequencies 2ωn and 2ωm. Analysis shows that modes absent from the initial excitation of the string...
TL;DR: In this paper, the authors examined the effect of vibration transmission between the catching region and the hub of a web and found that the amount of that same type of vibration appearing at the hub was correlated with the distance over which the signal was transmitted (63±11 mm).
Abstract: Orbweaving spiders build an elaborate web to trap aerial prey. The web transmits vibration cues about the presence and location of entangled prey to the spider, which is usually waiting at the hub of the web. This paper examines the web as a medium for vibration transmission between the prey-catching region and the hub. Three types of vibration are propagated along a radius: longitudinal (motion directed along the strand's axis), transverse (motion perpendicular to the strand and to the web), and lateral (motion perpendicular to the strand and in the plant of the web). The web was stimulated in the middle of the preycatching region with one type of vibration, and the amount of that same type of vibration appearing at the hub was measured. In an empty web longitudinal vibration reaches the hub with almost no attenuation over the frequency range of 1 to 10,000 Hz (Fig. 3). Transverse vibration is attenuated by ∼15 dB at 1 Hz and transmission drops more or less linearly to ∼35 dB attenuation at 10 kHz. Lateral vibration is attenuated ∼23 dB between 1 and ∼200 Hz, and attenuation increases to ∼40 dB between 1 and 10 kHz. Individual webs (Fig. 4) show resonance effects (peaks and troughs in transmission) above ∼1 kHz. The distance over which the signal was transmitted (63±11 mm) was not correlated with the amount of attenuation. The three types of vibration vary in directionality (Fig. 5), that is, in how greatly the amplitude of the stimulated radius differs from that of its nonstimulated neighbors at the hub. Longitudinal vibration is the most directional and consequently it may play the dominant role in the spider's choice of radius to run out along to reach trapped prey. In a web containing the spider and/or prey, the web/object system tends to resonate at frequencies that depend on the weight of the objects, their position in the web, and the types of vibration (Fig. 6). A 200 mg spider at the hub of the web will oscillate at ∼10 Hz for longitudinal and lateral vibration, and at ∼4 Hz for transverse vibration. A 1 to 2 mg insect in the catching zone oscillates at ∼100 Hz for longitudinal vibration but a 100 mg insect oscillates at only ∼4 Hz for transverse vibration. Generally, resonance effects due to web loading will be confined to frequencies below a few hundred Hz. The presence of a spider at the hub modifies the transmission curves derived from the empty web. For longitudinal vibration, signals from the prey-catching zone to the spider's tarsus (Fig. 7) are attenuated by several dB below ∼300 Hz and by ∼20 dB/decade above this frequency. For transverse and lateral vibration, transmission to the spider could not be measured and must be estimated from that obtained in the empty web. Qualitative aspects of vibration transmission across web crossings are discussed using the physical properties of radial and sticky-spiral strands (Table 1).
TL;DR: Based on the internal structure of oligoprotein as well as the basic physical characteristics+ of vibrations, it is deduced that the low-frequency vibrations possess some exceptional functions in transmitting biological information at the molecular level.
TL;DR: In this paper, the damping effects of various kinds of state of matter, such as neutron stars, are discussed and it is shown that damping in quark matter is more efficient than in π-condensate.
TL;DR: In this paper, higher-order vibration-rotation perturbation calculations for the X 3 molecular model employing a sequential contact transformation procedure are presented for a general molecule because the principal Coriolis interaction is diagonal in the quantum numbers (V 1, V 2 ).
TL;DR: The Sydney Tower, the tallest building in Australia, is one of the first buildings with the installation of a large scale tuned mass damper (TMD) as discussed by the authors, which reduces wind-induced motions by 8 shock-absorbers installed tangentially to the tank and anchored to the floor of the turret.
Abstract: The Sydney Tower, the tallest building in Australia, is 820ft (250m) high and with the base of the structure anchored on the roof of a 15 storey building, it stands 1000ft (305m) above street level The tower is one of the first buildings with the installation of a large scale tuned mass damper (TMD) The doughnut-shaped water tank near the top of the turret, which normally serves as the tower’s water and fire protection supply, was incorporated into the design of the TMD to reduce wind-induced motions Energy associated with relative movements between the tower and the water tank is dissipated by 8 shock-absorbers installed tangentially to the tank and anchored to the floor of the turret A secondary TMD of similar design was later installed on the intermediate anchorage ring to further increase the damping level, particularly in the second mode Full scale measurements were taken to determine the natural frequencies of vibration and damping Dampings of the tower were determined for different damper configurations The natural frequencies of vibration were found to be 010 Hz and 050 Hz for the first mode and second mode respectively Significant increases in damping levels, particularly in second mode, are produced by the water tank tuned mass damper and the secondary damper
TL;DR: In this paper, the design of the design parameters of passive vibration absorbers attached to a long cantilevered beam is studied, motivated by the need for conducting p arametric analysis of dynamics and control for spaceshuttle-attached l ong beams.
Abstract: The selection of the design parameters of passive vibration absorbers attached to a long cantilevered beam is studied. This study was motivated by the need for conducting p arametric analysis of dynamics and control for spaceshuttle-attached l ong beams. An optimization scheme using a quadratic cost f unction is introduced yiedding the optimal sizing of the tip vibration absorber. Analytical s olutions for an optimal absorber are presented for the case of one beam vibrational mode coupled with the absorber dynamics, and results are extended to cover the m ultiple mode case. An algorithm is developed to make an initial estimate of optimal tuning parameters which m inimize the quadratic error cost function. Examples are given to illustrate the design concept.
TL;DR: In this paper, the non-linear vibration of a clamped-clamped beam at large displacement amplitudes is examined and the amplitude dependence of the fundamental mode shape and its derivatives and the spatially-dependent harmonic distortion of the transverse displacement is examined.
TL;DR: In this article, the effects of initial geometric imperfections on large-amplitude vibrations of cylindrical panels simply supported along all four edges are considered for each pair of parallel edges.
Abstract: This papers deals with the effects of initial geometric imperfections on large-amplitude vibrations of cylindrical panels simply supported along all four edges. In-plane movable and in-plane immovable boundary conditions are considered for each pair of parallel edges. Depending on whether the number of axial and circumferential half waves are odd or even, the presence of geometric imperfections (taken to be of the same shape as the vibration mode) of the order of the shell thickness may significantly raise or lower the linear vibration frequencies. In general, an increase (decrease) in the linear vibration frequency corresponds to a more pronounced soft-spring (hard-spring) behavior in nonlinear vibration.
TL;DR: In this paper, a general theory was developed which describes the interdependence of the small-amplitude internal motion and reorientation of a molecule in an anisotropic environment.
TL;DR: In this article, structural optimization techniques are applied to vibration reduction of helicopter rotor blades in forward flight, where the objective function minimized consists of the oscillatory vertical hub shears or the hub rolling moments at one particular advance ratio.
Abstract: Modern structural optimization techniques are applied to vibration reduction of helicopter rotor blades in forward flight. The objective function minimized consists of the oscillatory vertical hub shears or the hub rolling moments at one particular advance ratio. The behavior constraints are the frequency placements of the blade and the requirement that aeroelastic stability margins, in hover, remain unaffected by the optimization process. The aeroelastic stability and response analysis is based on a fully coupled flap-lag-torsional analysis of the blade. Numerical results are presented for some typical soft-in-plane hingeless rotor configurations indicating a 15-40 percent reduction in vibration levels, as well as a blade which is 20 percent lighter than the initial design. These results imply that structural optimization techniques can yield substantial practical benefits in the design process of rotor systems.
TL;DR: In this paper, a method for determining cross sections and other dynamical information based on the use of accurate coupled channel nonreactive wave functions in an evaluation of the distorted wave reactive scattering amplitude is developed for three-dimensional atom-diatom reactive collisions and applied to the H+H2 reaction.
Abstract: A method for determining cross sections and other dynamical information based on the use of accurate coupled channel nonreactive wave functions in an evaluation of the distorted wave reactive scattering amplitude is developed for three‐dimensional atom–diatom reactive collisions and applied to the H+H2 reaction. The nonreactive wave functions are obtained by using a truncated expansion in asymptotic vibration/rotation states to generate coupled channel equations in terms of the full Hamiltonian. Explicit reduction of the distorted wave scattering matrix expression to a real valued three‐dimensional integral is given and methods for simplifying the calculation through the use of parity decoupling, even/odd decoupling, and the coupled states approximation are introduced. The application to H+H2 considers the Porter–Karplus potential surface. Comparison of reaction probabilities, opacity functions, differential and integral cross sections with corresponding results from exact quantum calculations indicates t...