Showing papers on "Vibration published in 1983"
TL;DR: In this paper, the authors review the theory and the empirical evidence of damping of simple nuclear excitations, including the particle states and vibrational states, and compare theory and empirical evidence.
Abstract: The authors review the theory and the empirical evidence of damping of simple nuclear excitations. The excitations considered are the particle states and vibrational states. The particle damping phenomena include the fragmentation of single-particle levels, the systematics of neutron strength functions, and the optical absorption of elastic scattering. Information on the known collective vibrational states is summarized and compared with theory. A theoretical model that has found considerable success is based on a damping mechanism in which the simple excitations mix with the surface vibrations. This implies that the surface damping dominates for excitation energies below about 15 MeV. There is a close relation between the single-particle damping and the damping of collective vibrations. However, the vibrational damping is strongly suppressed by the coherence between the particle and the hole. While the model reproduces many of the observed features of the data rather well, it tends to underpredict the spreading width by as much as a factor of 2. Thus other degrees of freedom, not well understood at present, may play a role in the damping.
419 citations
TL;DR: In this article, an extended active suspension concept involving a high-gain load leveler as well as active damping is analyzed, and the realization of active or semi-active damping forces through electrical or hydraulic means is briefly discussed.
Abstract: Low order, linearized dynamic models of road vehicle suspension systems are analyzed to provide insight into the benefits of suspensions incorporating generalized velocity feedback compared with conventional passive suspensions. Damping forces from passive dampers are supplemented by forces generated by an active element requiring a power supply. A simple criterion is developed which indicates whether or not the introduction of activedamping forces will result in significant benefit for pneumatic tired vehicles. An extended active suspension concept involving a high-gain load leveler as well as active damping is analyzed. The realization of active or semi-active damping forces through electrical or hydraulic means is briefly discussed.
302 citations
TL;DR: In this article, a simple experiment was carried out to demonstrate the phenomenon of Anderson localization in an acoustical context, where the propagation of vibration in a structure which is not entirely regular is impeded by the irregularities, giving rise on the average to an exponential decay of vibration level away from the driving point, even in the absence of any dissipation.
Abstract: This article describes the theory and a simple experiment carried out to demonstrate the phenomenon of Anderson localization in an acoustical context. This is an effect whereby the propagation of vibration in a structure which is not entirely regular is impeded by the irregularities, giving rise on the average to an exponential decay of vibration level away from the driving point, even in the absence of any dissipation. The structure used in the experiment was a stretched string with masses attached to it. This string was studied with regular spacings of the masses and after the masses had been moved in a controlled way to provide a small degree of irregularity. In both cases, the transmission of energy from end to end of the string was measured as a function of frequency, and also the mode shapes in the second and fourth passbands were measured so as to demonstrate the underlying physics of the localization phenomenon, in which the individual modes making up each passband change from being extended throughout the structure in the regular case to being localized in specific areas of the structure in the presence of irregularity. All measurements yielded satisfactory agreement with the theoretical predictions.
241 citations
TL;DR: Forced vibrations of an elastic beam with non-linear boundary conditions are shown to exhibit chaotic behavior of the strange attractor type for a sinusoidal input force as mentioned in this paper, where the beam is clamped at one end, and the other end is pinned for the tip displacement less than some fixed value and is free for displacements greater than this value.
Abstract: Forced vibrations of an elastic beam with non-linear boundary conditions are shown to exhibit chaotic behavior of the strange attractor type for a sinusoidal input force The beam is clamped at one end, and the other end is pinned for the tip displacement less than some fixed value and is free for displacements greater than this value The stiffness of the beam has the properties of a bi-linear spring The results may be typical of a class of mechanical oscillators with play or amplitude constraining stops Subharmonic oscillations are found to be characteristic of these types of motions For certain values of forcing frequency and amplitude the periodic motion becomes unstable and nonperiodic bounded vibrations result These chaotic motions have a narrow band spectrum of frequency components near the subharmonic frequencies Digital simulation of a single mode mathematical model of the beam using a Runge-Kutta algorithm is shown to give results qualitatively similar to experimental observations
225 citations
TL;DR: In this article, a model for predicting the across-wind response of constant-diameter circular cylinders vibrating in a mode of uniform amplitude and subject to uniform flow is presented.
208 citations
TL;DR: In this paper, a high-rise building was designed and modeled using linear elastic (and also nonlinear) degrading stiffness idealizations, and three different techniques were used to design an optimum tuned-mass damper (TMD) for the prototype.
Abstract: A realistic prototype high-rise building was designed and modeled using linear elastic (and also nonlinear) degrading stiffness idealizations. Using an effective damper mass ratio of 0.026, three different techniques were used to design an optimum tuned-mass damper (TMD) for the prototype. All were found to give essentially the same design. The response of the idealized prototype building to a strong ground motion was computed with and without a TMD. The TMD did not reduce the prototype's maximum response. Based on these results, vibration absorbers do not seem effective in reducing the maximum seismic response of tall buildings.
139 citations
135 citations
117 citations
TL;DR: In this article, a new multimode linear theory for the computation of cross-spectra of bridge response to turbulent wind excitations is presented, where the average wind velocity is used to formulate the self-excited loads.
Abstract: Spectral analysis of random vibration is used to develop a new multimode linear theory for the computation of cross‐spectra of bridge response to turbulent wind excitations. New interpretations are given to previous works in the literature, and the results compared. The comparison enables a direct utilization of previously obtained experimental results, as well as clarification of the implication and limitation of previously proposed simplified procedures. Since the average wind velocity is used to formulate the self‐excited loads, with the effects of turbulence on these loads neglected in the analysis, the present theory may not be applicable at the proximity of flutter instabilities.
100 citations
TL;DR: In this article, a computationally fast and efficient least-squares method to minimize the vibration of any general rotor-bearing system by the application of external control forces is presented, which provides a wide range of statistical information, and the sensitivity of the optimum response to changes in the control forces.
Abstract: This paper presents a computationally fast and efficient least-squares method to minimize the vibration of any general rotor-bearing system by the application of external control forces. The D-optimality concept is used to optimize the force locations. The proposed method provides a wide range of statistical information, and the sensitivity of the optimum response to changes in the control forces. Magnetic bearings can be applied to implement the open-loop adaptive vibration control strategies outlined in the paper. These components can also be used to inject a multi-frequency test signal as required for identification studies.
99 citations
Patent•
03 Aug 1983
TL;DR: A ventilated disc brake rotor as mentioned in this paper is a type of brake rotor in which spacing between and/or radial length of cooling fins are varied around the rotor for frequency and amplitude modulated damping of vibration harmonics.
Abstract: A ventilated disc brake rotor in which spacing between and/or radial length of cooling fins are varied around the rotor for frequency and/or amplitude modulated damping of vibration harmonics, and for balancing the rotor.
TL;DR: In this paper, an electrical control method of absorbing arm vibrations of industrial robots is described, where dampers are composed as electric manners by utilizing arm acceleration feedback to actuators of an industrial robot Acceleration signals are fed back to the corresponding actuators passed through phase compensation circuits.
Abstract: This paper describes an electrical control method of absorbing arm vibrations of industrial robots Arm vibration problems are divided into two categories: resonance vibration phenomenon depending on actuator velocity and transient oscillations caused by acceleration change of actuators Because resonance frequency of an industrial robot changes more than double due to the arm posture, mechanical vibration absorbing methods may not be easily utilized The method applied in this paper is to compose dampers as electric manners by utilizing arm acceleration feedback to actuators of an industrial robot Acceleration sensors are attached on three axes which construct a robot arm Acceleration signals are fed back to the corresponding actuators passed through phase compensation circuits By experiments applied to an industrial robot, this method has been proved to be effective in eliminating both resonance and transient vibrations According to this control, a smart motion industrial robot which does not have resonance characteristics and operates speedily and smoothly has been realized
01 Jan 1983
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, the authors focus on two methods of controlling the vibration radiated by the transit structure and modify the design of transit car bogies such that the wheel/rail forces are reduced.
TL;DR: A uniform linear beam in a uniform linear ambient medium is studied in this article, where the beam performs stationary harmonic damped nonsynchronous space vibration in simultaneous tension, torsion, bending and shear in the presence of a large static axial load.
Abstract: A uniform linear beam in a uniform linear ambient medium is studied. The beam performs stationary harmonic damped nonsynchronous space vibration in simultaneous tension, torsion, bending and shear in the presence of a large static axial load. Hysteretic and viscous dampings of the beam material and ambient medium are considered. Generalized complex Kolousek functions are derived. A 12 × 12 complex symmetric stiffness matrix is established for a supported beam member excited at its ends by prescribed harmonic translations and rotations which have the same frequency but may be out of phase. This matrix allows for an exact analysis of nonproportionally damped built-up beam structures, thus avoiding assumed mode shapes and lumped or consistent masses. A general notation is suggested. Numerical examples are given, including applications of the computer program SFVIBAT-DAMP.
TL;DR: In this article, a Lagrange-type formulation for finite element analysis of non-linear vibrations of immovably supported beams is presented and two equations of motion coupled in axial and transverse displacements are derived by using Lagrange's equations.
TL;DR: In this article, the effects of air and gas pressure on the vibration of miniature quartz tuning forks are investigated, and it is shown that the resonant frequency appears to vary quite linearly with the gas pressure.
TL;DR: In this article, an efficient optimal design algorithm for minimizing the vibratory response of a multi-degree of freedom system under sinusoidal loading over several excitation frequencies is presented.
TL;DR: In this paper, a methode analytique for the re-conception automatisee des caracteristiques modales des systemes mecaniques non amortis is presented.
Abstract: On presente une methode analytique pour la re-conception automatisee des caracteristiques modales des systemes mecaniques non amortis. La methode est basee sur une perturbation du systeme propre et les termes non lineaires sont traites de facon a pouvoir tenir compte de grands changements
TL;DR: In this article, the effects of teeth, windings, impregnation and wedges on the natural frequencies and vibration response of stators on the basis of experiments and simulation through numerical computation of the natural frequency and vibration responses of ring and segmented-core stators having totally impregnated formed coils.
Abstract: In order to reduce electromagnetic acoustic noise in motors, it is essential to understand the vibration behaviour of the stators so as to prevent resonance between the electromagnetic forces and the stators. This paper presents an assessment of the effects of teeth, windings, impregnation and wedges on the natural frequencies and vibration response of stators on the basis of experiments and simulation through numerical computation of the natural frequencies and vibration response of ring- and segmented-core stators having totally impregnated formed coils. The results show that assessment of the Young's modulus of the insulating layers of the impregnated windings and the wedges is the most important, and that the insulating layers of the windings can be reasonably dealt with as having a value of about 30% of the converged equivalent Young's modulus, and the wedges as having a value of 100% of that of their material.
TL;DR: In this paper, the collective vibrational motions in the solid DNA fiber have been found from the wave vector dependence of the low frequency Raman spectra, and the main part of low frequency modes have been assigned to the αxz(αyz) component of the Raman tensor from the polarized Raman Spectroscopy.
Abstract: The collective vibrational motions in the solid DNA fiber have been found from the wave vector dependence of the low frequency Raman spectra. The main part of the low frequency modes have been assigned to the αxz(αyz) component of the Raman tensor from the polarized Raman spectroscopy.
TL;DR: In this article, it was shown that the mode shape of the vibration can vary with the amplitude as well as the frequency, and that the amplitude frequency relation is strongly affected by constraints imposed on the mode shapes in an approximate solution.
Abstract: In the study of natural vibrations of non-linear elastic systems it is shown that the mode shape of the vibration can vary with the amplitude as well as the frequency, and that the amplitude frequency relation is strongly affected by constraints imposed on the mode shape in an approximate solution. A method is developed which assumes the approximate solution in the form of a truncated series in which, instead of the set of coefficients, the set of functions of spatial variables is unknown and then determined by a procedure that can be regarded as a generalization of the Ritz method. The problem of variations of the normal mode shapes and of the associated natural frequencies with the amplitude is illustrated by two examples of beams with non-linear boundary conditions, and the amplitude-frequency relation is compared to that corresponding to the a priori assumed linear normal mode solution. Further possible consequences of the mode shape amplitude variations in forced, resonant motion of nonconservative systems are also indicated.
TL;DR: In this article, a high-order triangular membrane finite element is combined with a fully conforming triangular plate bending element to solve the geometrically nonlinear problems of plates where the membrane and flexural behaviors are coupled and the effect of the inplane boundary conditions is as significant as the flexural boundary conditions.
Abstract: A high-order triangular membrane finite element is combined with a fully conforming triangular plate bending element to solve the geometrically nonlinear problems of plates where the membrane and flexural behaviors are coupled and the effect of the inplane boundary conditions is as significant as the flexural boundary conditions. Each of the three orthogonal displacement components is represented by a two-dimensional polynomial of the same quintic order with no bias against one another giving the element a total of 54 degrees of freedom. The nonlinear stiffness matrices are formulated and a Newton-Raphson iteration procedure is used. Examples include the analyses of plane stresses of a parabolically loaded square plate, large deflections of a square plate under lateral pressure, postbuckling of a square plate, linear free vibration of a buckled rectangular plate, large amplitude free vibration of a square plate with and without inplane stresses. Various flexural and inplane boundary conditions are considered. Results are compared with those obtained by alternative finite element methods, analytical approximate methods, and an experiment. Physical interpretations of the results and explanations of the discrepancies among various solutions are provided. The results indicate that the present development is capable of accurately solving a wide variety of geometrically nonlinear plate problems.
TL;DR: In this paper, a general theory and analysis of the nonlinear free coupled vertical-torsional vibrations of suspension bridges with horizontal decks is presented, and approximate solutions are developed by using the method of multiple scales via a perturbation technique.
Abstract: A general theory and analysis of the nonlinear free coupled vertical-torsional vibrations of suspension bridges with horizontal decks are presented. Approximate solutions are developed by using the method of multiple scales via a perturbation technique. The amplitude-frequency relationships for any single set of coupled vertical-torsional modes are presented for three cases: (1) when the large-amplitude vertical vibration is dominating the motion, (2) when large-amplitude torsional vibration is dominating, and (3) when one of the linear natural frequencies of vertical vibration is equal to, or approximately equal to, another linear natural frequency of torsional vibration, and the two modes are strongly coupled; this contrasts with the linear solution, which predicts that the two modes are uncoupled.
TL;DR: In this article, the effects of the groove dimensions on the frequency of free-free, square beams with a rectangular groove are discussed and the results are compared with those obtained by the simple beam theory.
TL;DR: In this paper, the free vibrations and forced vibrations of a system comprising two elastically connected parallel upper and lower beams having unequal masses and unequal flexible rigidities were analyzed using a generalised method of finite integral transformation and the Laplace transformation.
Abstract: The free vibrations and forced vibrations of a system comprising two elastically-connected parallel upper and lower beams having unequal masses and unequal flexible rigidities are analysed using a generalised method of finite integral transformation and the Laplace transformation. The natural frequencies and the amplitude ratios for the normal modes of vibration are presented; it is also shown that a system comprising a lower beam and coupling springs can be used as a dynamic vibration absorber to reduce the vibrations of an upper beam that is subjected to a periodic force.