Showing papers on "Dynamic Vibration Absorber published in 1980"

Differential and Difference Sensitivities of Natural Frequencies and Mode Shapes of Mechanical Structures

Abstract: A method, based upon the theory of the adjoint structures, is formulated for calculating the derivatives of natural frequencies and normalized mode shapes with respect to structural parameter changes in terms of local mass, stiffness, or damping, starting with data obtained by experimental processing techniques such as modal analysis. The method applies for statically or kinematically undeterminate structures, which is not the case for most classical methods of sensitivity analysis. The method is extended to obtain large-change sensitivities and frequency response sensitivities to structural nonparameter changes (e.g., the addition of a damped vibration absorber). Two examples demonstrate the procedure and the usefulness of the sensitivity analysis. HE dynamic analysis of complex mechanical equipment and the prediction of the dynamic behavior of a modified mechanical structure has turned out to be a difficult way of reaching the objectives of such analysis. However, modal analysis techniques and computer-interfaced testing equip- ment have contributed to a solution of those problems. Furthermore, modal analysis results (complex modal displacements, natural frequencies, damping values) may be used in system synthesis methods1>2 to predict mathematically the effect of structural changes on the dynamic behavior. The objective of this paper is to present a * 'sensitivity analysis" using experimental data, obtained by modal analysis, for computational assessment of the most effective parameter change in order to obtain a desired dynamic behavior. The sensitivities give the influence of the building element parameters on the natural frequencies and mode shapes of the mechanical structures. They provide us with an answer to the question of where to change, e.g., to obtain a maximum shift of a specific natural frequency or to reduce most effectively the modal displacements in certain points for a specific mode. The assumption of linear and statically or kinematically determinate structures simplifies the calculation of the sen- sitivities.3"5 Van Belle6'7 developed a more general method, called the theory of adjoint structures, for the sensitivity analysis of mechanical structures, yielding equations still valuable for statically or kinematically undeterminate structures. In this paper, the method based upon the theory of adjoint structures is extended to obtain sensitivities in the case of viscously damped systems and expressions for the sensitivities are derived, using finite instead of infinitesimal changes.

Rotating body sympathetic vibration absorber

Abstract: In a vibration absorber for resonance vibrations of rotating bodies, in particular rail wheels, comprising several oscillatory plates which establish a damping mass; intermediate layers of damping material separating the plates from each other; a fastener connecting the plates with the rotating body at at least one point and an intermediate layer of damping material coupling the plates over a large remaining area to the rotating body the geometric dimensions of the plates and the intermediate layers and the Shore hardness of the damping material of the intermediate layers is selected such that all plates oscillate at a natural frequency of the rotating body to be damped, but with the amplitudes and phases of the vibrations of the individual plates differing in such a manner, with respect to one another, that the damping material is as strongly distorted as possible.

Fixed position variable frequency pendular-type vibration absorber

Abstract: A variable frequency vibration absorber adapted to be fixedly mounted in a fixed vibration prone system to coact with the system principal vibration excitation source to control system vibration. The vibration absorber is bifilar in construction and the natural frequency thereof is varied in proportion to the frequency of the vibration being generated by the principal system excitation source.

Shock and vibration damping arrangement for vehicles

Abstract: not available for EP0027869Abstract of corresponding document: US4368900A mass such as a vehicle or craft, for example an aircraft, is cushioned against landing shocks and vibrations by an electronically controlled shock and vibration absorber system. For this purpose an electrical control signal is produced which takes into account several coefficients through the adjustment of potentiometers in a control circuit which continuously controls the damping characteristic curve of the shock and vibration absorber system.

Minimizer system of vibrational movements of a mass

Abstract: A mass such as a vehicle or craft, for example an aircraft, is cushioned against landing shocks and vibrations by an electronically controlled shock and vibration absorber system. For this purpose an electrical control signal is produced which takes into account several coefficients through the adjustment of potentiometers in a control circuit which continuously controls the damping characteristic curve of the shock and vibration absorber system.

Fixed position, fixed frequency pendular-type vibration absorber with frequency linearization

Abstract: A fixed frequency vibration absorber adapted to be fixedly mounted in a fixed vibration prone system. The vibration absorber is of the pendular-type with two dynamic masses suspended in pendular fashion from a base member, and with at least one coil spring acting upon the masses to establish and linearize the vibration absorber natural frequency.

Vibration absorber of vehicle

Abstract: PURPOSE: To efficiently absorb any low frequncy vibration generated on a vehicle, by elastically supporting a such as a radiator on a front end of a vehicle body so that its inherent vibration frequency becomes a prescribed value to have the part actuated as a dynamic damper. CONSTITUTION: A heavy weight part 1 such as a radiator or a battery on a front end of a vehicle body is mounted so that its inherent vibration frequency is kept within the range of 20W30Hz, by means of an elastic body 21, etc. is suppressed by a dynamic damper, so that vibrations of a steering post 8 and a seat 9 can be reduced. COPYRIGHT: (C)1982,JPO&Japio

Resonance oscillation absorber for rotating bodies

Abstract: Die Erfindung betrifft einen Schwingungsabsorber fur Resonanzschwingungen rotierender Korper. The invention relates to a vibration absorber for resonant vibrations of rotating bodies. Der Schwingungsabsorber setzt sich aus mehreren schwingungsfahigen Platten zusammen, die voneinander durch Zwischenlagen aus Dampfungsmaterial getrennt sind und an einer Stelle miteinander und mit dem rotierenden Korper starr verbunden und im ubrigen Bereich grosflachig an dem rotierenden Korper angekoppelt sind. The vibration absorber is composed of a plurality of oscillatory plates which are separated from each other by intermediate layers of damping material and are rigidly connected at one point with each other and with the rotating body and is coupled in the remaining region over a large area on the rotating body. Die Platten und die Zwischenlagen sind bezuglich ihrer geometrischen Abmessungen und der Shoreharte des Dampfungsmaterials derart aufeinander abgestimmt, das samtliche Platten mit der zu dampfenden Resonanzfrequenz des rotierenden Korpers schwingen und die Amplituden und die Phasen der Schwingungen der einzelnen Platten so zueinander liegen, das das Dampfungsmaterial moglichst stark verformt wird. The plates and the intermediate layers are keyed with reference to their geometric dimensions and the Shore hardness of the damping material to each other such that all the plates vibrate with the to be damped resonant frequency of the rotating body and the amplitudes and the phases of vibrations of the individual plates are built so that the damping material as possible is greatly deformed.

Vibration proofing bush and manufacture thereof

Abstract: PURPOSE:To obtain an effective combination of a vibration absorbing effect and a vibration restricting effect by a direct adhering by vulcanizing of a rubber or a rubberlike vibration absorber of a resilient material having a plurality of recesses and a groove communicating these recesses to inner and outer cylinders. CONSTITUTION:The vibration absorber 3 having two recesses (a) and (b) each opened at one end or both ends by which the releasing after molding is facilitated and a groove 4' which communicates these recesses is secured to the inner and outer cylinders 1 and 2 by direct adhering by vulcanizing. The outer peripheral surface of the vibration absorber 3 exluding the parts of recesses (a) and (b) and groove 4' which are molded by the arrangement of a die piece and die disc and including the entire periphery on the lefthand in the drawing and the inner peripheral surface thereof are vulcanized and adhered to the inner surface of the outer cylinder 2 and the outer surface of the inner cylinder 1 respectively at the same time of the vulcanizing and molding of the vibration absorber itself. After this molding process, the vibration absorber 3 thus jointed with the inner and outer cylinders is pulled out of the die. Then a vibration restricting liquid is poured into the recesses (a) and (b) and groove 4', which are sealed with a rubber sealing ring 5 thereafter.

Vibrationnproof system for track

Abstract: PURPOSE:To prevent the vibration of a monorail track and to eliminate a vibration pollution and an operational trouble, by hanging a vibration absorber at a track. CONSTITUTION:A vibration absorber 14 is composed of a weight 15, a spring 16 and a dash pot 17, and is located at a middle of foundations 12 of a track 11 after establishing a constant and coefficiency of the dash pot 17 on a basis of the relations to the track 11. And thus, vibtation of the track 11 produced when a train 13 runs is absorbed most efficiently. As a result of the vibration absorber 14 absorbing the vibration of the track 11 in such a manner as described above, the vibration, which is transmitted to the ground through the foundations 12, is reduced sharply. This allows the vibration produced when a train runs to be efficiently absorbed without shortening a distance between adjacent foundations 12, which support the track 11, and without increasing the rigidity of the track 11. Constructing at an extremely favourable cost may thus result.

Vibrationnproof tool shank

Abstract: PURPOSE:To manufacture a vibration-proof tool shank, by making a vibration absorber from a hard alloy consisting of a hard part and a high-melting-point part and by providing the vibration absorber on at least part of the shank. CONSTITUTION:A tip 4 is attached to the front end of the tool shank 1. The vibration absorber 2 is tightened on the shank by a holder 3 and a screw 5. The vibration absorber 2 is made from the hard alloy represented by a general formula (M1a, M2b)(C1-x-y, Ny, Ox)z where M1 denotes at least one of Ti, Zr and Hf, M2 denotes at least one of Cr, Mo and W, a+b=1, 0.1<=a<=0.7, 0.05<=x+y<0.6, 0.05< x<=0.5, 0<=y<=0.5 and 0.1<=z<=0.5.

Overhead electrical conductor system including subspan oscillation and aeolian vibration absorber for single and bundle conductors

Abstract: In a vibration absorber for use with aerially suspended conductors and cables, there is described an improved vibration absorber wherein wind or turbulence induced vibrations resulting in travelling waves on conductors and cables are absorbed so as to prevent damage to or failure of conductors and related hardware due to fatigue. Known devices, particularly dampers and spacer dampers, attempt to control merely the amplitude of the waves produced on the conductor and are therefore ineffective in preventing the formation of such waves and the damage that may result. In this invention, a vibration absorber comprises a piston and cylinder device whereby a travelling wave displaces the piston or the cylinder relative to one another causing a fluid contained within the cylinder to be displaced through an orifice in the piston. The absorbing system thus defined has a mechanical dissipative impedance of value R to inhibit the reflection of a wave propagated on the conductor whereby the wave is absorbed. The value of R is in the range of 0.5√TM to 3.0√TM where T is the tension of the conductor and M is the mass of the conductor per unit length.

Subharmonic steady vibrations of a non-linear damper with two degrees of freedom and viscous damping

Abstract: The steady-state. 13 subharmonic vibrations of a dynamic damper (or vibration absorber) with two degrees of freedom, sinusoidal forcing function and internal viscous damping. are presented. The study of these oscillations leads to the determination of suitable “form functions” of the solutions, by following a methodology recently introduced by Nocilla for studying the harmonic vibrations of non-linear systems with one and two degrees of freedom. The proposed theory. which is valid even if the non-linearity is large, gives satisfactory results in all the cases in which the subharmonic component is predominant in the steady-state oscillation of the system.

Method of absorbing vibration of machine foundation or the like

Abstract: PURPOSE:To maintain the static or dynamic balance of a system as a whole and absorb the vibration of a rigid body, by providing two dynamic vibration absorbers which are different in various constants and lacated in different positions on the rigid body. CONSTITUTION:When a vibrating rigid body 10 such as a machine foundation vibrates on a spring 13, dynamic vibration absorbers 11, 12 are provided in two positions to absorb the vibration. The dynamic vibration absorbers 11, 12 are conventionally composed of mass parts 14, 15, springs 16, 17 and dampers 18, 19 and different in various constants such as the mass, spring stiffness and viscosity. The natural frequency of each dynamic vibration absorber is set near the frequency of a stationary vibration source. The dynamic vibration absorbers 11, 12 are mounted in such positions on the right and left or rear and front or the like of a rotary vibrating machine that a foundation system including the machine is statically balanced. This results in enabling the enlargement of the absorbed vibration frequency range, absorption of higher mode of vibration, etc.

Vibration of a clamped circular plate driven by a noncentral force

Abstract: Expressions are stated for the transmissibility and for the driving‐point impedance of an internally damped circular plate of radius a with a clamped boundary that is driven by a vibratory point force at an arbitrary distance μa from the plate center. Expressions are also stated for the plate transmissibility and driving‐point impedance when the plate is loaded at the arbitrary driving point either by a lumped mass, by a dynamic vibration absorber, or simultaneously by a lumped mass and a dynamic absorber. In all cases, representative calculations of transmissibility and impedance are plotted versus the square root of frequency. These curves clearly show the dependence of transmissibility and impedance on the plate damping factor, the value of the parameter μ, and the extent of the mass loading. They also show the effectiveness of the dynamic absorber, which varies with the value assigned to μ.

Bifilar analysis study, volume 1

Abstract: A coupled rotor/bifilar/airframe analysis was developed and utilized to study the dynamic characteristics of the centrifugally tuned, rotor-hub-mounted, bifilar vibration absorber. The analysis contains the major components that impact the bifilar absorber performance, namely, an elastic rotor with hover aerodynamics, a flexible fuselage, and nonlinear individual degrees of freedom for each bifilar mass. Airspeed, rotor speed, bifilar mass and tuning variations are considered. The performance of the bifilar absorber is shown to be a function of its basic parameters: dynamic mass, damping and tuning, as well as the impedance of the rotor hub. The effect of the dissimilar responses of the individual bifilar masses which are caused by tolerance induced mass, damping and tuning variations is also examined.

The transient behaviour of the dynamic vibration absorber for linear frequency rise

Abstract: The applicability of the Frahm dynamic vibration absorber is generally restricted to the case of constant forcing frequency; it may happen, however, that this condition is fulfilled only after a certain instant, prior to which the frequency is increasing, e.g. linearly. The analysis of the transient behaviour shows that in such a situation the main mass can undergo oscillations much broader than those predictable by the constant frequency scheme.