An Experimental Study of a Novel Impact Damper in Free Vibration of Structures

2014 ◽  
Author(s):  
Mohamed Gharib ◽  
Mansour Karkoub ◽  
Muhammad Tahir Bin Yousaf ◽  
Mohammad AlGammal
Keyword(s):  
Single Unit ◽  
Free Vibrations ◽  
Control Device ◽  
Experimental Investigations ◽  
Passive Vibration Control ◽  
Single Degree Of Freedom ◽  
Impact Damper ◽  
Single Degree ◽  
Particle Chain ◽  
Structure Vibration

A Linear Particle Chain (LPC) impact damper is a newly developed passive vibration control device. It is an extension for the commonly used conventional (single unit) impact damper. In this paper, experimental investigations are conducted to examine the efficacy of the LPC impact damper in attenuating the free vibrations of single degree of freedom structures. The experiments’ outcomes clearly indicate the significant effect of the LPC impact damper in suppressing the structure vibration compared to the conventional impact dampers.

Shock-Based Experimental Investigation of the Linear Particle Chain Impact Damper

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Mohamed Gharib ◽  
Mansour Karkoub
Keyword(s):  
Frame Structure ◽  
Primary System ◽  
Mass Ratio ◽  
Linear Arrangement ◽  
Single Degree Of Freedom ◽  
Impact Damper ◽  
Single Degree ◽  
Particle Chain ◽  
The Common ◽  
Freely Moving

Impact dampers (IDs) provide an effective, economical, and retrofittable solution to the vibration problem in several engineering applications. An ID typically consists of a single or multiple masses constrained between two or more stops and attached to a primary system to be controlled. The latest developed type in the IDs family is the linear particle chain (LPC) ID. It consists of a linear arrangement of two sizes of freely moving masses, constrained by two stops. The high number of impacts among the damper masses leads to rapid energy dissipation compared to the common IDs. This paper presents an experimental study on the effectiveness of the LPC ID in reducing the vibrations of a single degree-of-freedom (SDOF) frame structure under different shock excitations. Prototypes of the LPC and conventional IDs with different geometric parameters are fabricated. The structure is excited by either an impact at the top floor or pulses at its base. The damping effect of the LPC ID is compared with that of conventional IDs. The experimental outcomes clearly show that the LPC ID can effectively reduce the response of simple structures under shock excitation. Additional investigations are conducted to examine the LPC ID sensitivity to the main damper parameters, such as the chain length, damper mass ratio, and damper clearance.

Forced Vibration of Systems With Nonlinear, Nonsymmetrical Characteristics

1957 ◽  
Vol 24 (3) ◽  
pp. 435-439
Author(s):  
S. Mahalingam
Keyword(s):  
Approximate Solution ◽  
Linear System ◽  
Nonlinear Vibration ◽  
Forced Vibration ◽  
Free Vibrations ◽  
Frequency Function ◽  
Vibration Absorber ◽  
Single Degree Of Freedom ◽  
Nonlinear Vibration Absorber ◽  
Single Degree

Abstract A one-term approximate solution is given for the amplitudes of steady forced vibration of a single-degree-of-freedom system with a nonlinear (nonsymmetrical) spring characteristic. The method is similar to that of Martienssen (1), but the construction uses a modified curve (or “frequency function”) in place of the actual spring characteristic, the curve being so chosen that it gives the correct frequency for free vibrations. The method is extended to deal with a nonlinear vibration absorber fitted to a linear system.

On the Natural Modes and Their Stability in Nonlinear Two-Degree-of-Freedom Systems

1959 ◽  
Vol 26 (3) ◽  
pp. 377-385
Author(s):  
R. M. Rosenberg ◽  
C. P. Atkinson
Keyword(s):  
Free Vibrations ◽  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Natural Modes ◽  
Theoretical Predictions ◽  
Stability Chart ◽  
The Stability ◽  
Two Parameters ◽  
Two Degree Of Freedom

Abstract The natural modes of free vibrations of a symmetrical two-degree-of-freedom system are analyzed theoretically and experimentally. This system has two natural modes, one in-phase and the other out-of-phase. In contradistinction to the comparable single-degree-of-freedom system where the free vibrations are always orbitally stable, the natural modes of the symmetrical two-degree-of-freedom system are frequently unstable. The stability properties depend on two parameters and are easily deduced from a stability chart. For sufficiently small amplitudes both modes are, in general, stable. When the coupling spring is linear, both modes are always stable at all amplitudes. For other conditions, either mode may become unstable at certain amplitudes. In particular, if there is a single value of frequency and amplitude at which the system can vibrate in either mode, the out-of-phase mode experiences a change of stability. The experimental investigation has generally confirmed the theoretical predictions.

On Free Vibrations With Combined Viscous and Coulomb Damping

1980 ◽  
Vol 102 (4) ◽  
pp. 283-286 ◽  
Author(s):  
P. H. Markho
Keyword(s):  
Decay Curve ◽  
Closed Form Solution ◽  
Free Vibrations ◽  
Form Solution ◽  
Forced Response ◽  
Experimental Plot ◽  
Damping Force ◽  
Single Degree Of Freedom ◽  
Coulomb Damping ◽  
Single Degree

A closed-form solution of the governing, nonlinear equation for free vibrations of a single-degree-of-freedom system, without stops, under combined viscous and Coulomb damping is first obtained. This is much less involved than forced-response considerations of the same system (with or without stops) the solution of which problem was first obtained by Den Hartog [1]. This note contains the first derivation, as far as the author is aware of, of the equation for the amplitude decay curve (or envelope) for such a system vibrating freely under no-stop conditions. This equation is presented in a form which enables the components of the damping force to be determined from the system’s experimental plot (or record) of displacement versus time.

A Novel Impact Damper Consisting of a Linear Chain of Particles

2012 ◽  
Author(s):  
Mohamed Gharib ◽  
Saud Ghani
Keyword(s):  
Kinetic Energy ◽  
Passive Control ◽  
Linear Chain ◽  
Control Device ◽  
Contact Forces ◽  
Primary System ◽  
Small Ball ◽  
Impact Damper ◽  
Particle Chain ◽  
The Impact

Passive control is preferred due to its simplicity and low power consumption. A common passive control device is the Impact Damper which consists of a freely moving mass constrained by two stops inside a container mounted on the primary system. Researchers attempted to develop the impact damper for many decades. Their objective was to decrease the high accelerations, contact forces and noise levels. In this paper, a novel type impact damper consisting of linear chain of different sizes spherical balls is introduced. The Linear Particle Chain (LPC) impact damper is based on dissipating the kinetic energy of the primary system by placing a small ball between each two large balls in the chain arrangement. The small ball will have numerous collisions with the larger balls when the primary system is excited. This behavior leads to dissipate part of the kinetic energy at each collision with the large balls. The LPC impact damper is validated by comparing its responses with the single unit conventional impact damper. The free vibration of a single degree of freedom system equipped with the damper is studied. It has been shown that the LPC impact damper is more efficient than the conventional impact damper. A parametric study is conducted to investigate the effective number of balls and the efficient geometry of the impact damper to be used in a specific available space in the primary system.

On the Vibration Isolation of Flexible Structures

2006 ◽  
Vol 74 (3) ◽  
pp. 415-420 ◽  
Author(s):  
Y. Q. Tu ◽  
G. T. Zheng
Keyword(s):  
Vibration Isolation ◽  
Flexible Structures ◽  
Vibration Absorber ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Isolation Frequency ◽  
Vibration Attenuation ◽  
Vibration Transmissibility ◽  
Structure Vibration ◽  
Modal Space

Although the study of vibration isolation has a very long history, when an isolated structure is so flexible that it cannot be properly approximated with a rigid body or a single-degree-of-freedom model, its vibration isolation brings about some new questions and problems. By transforming the dynamic equation of motion of the coupled structure formed by the isolator and the isolated structure into the modal space and following the tradition of studying features of the vibration transmissibility across the isolator, questions and problems associated with the flexible structure vibration isolation are studied. It is found from the study that a lower isolation frequency and a higher damping level can both increase the isolation effectiveness, the isolated structure is a vibration absorber to the isolator, and a combination of the vibration isolation and the vibration attenuation can be more effective in mitigating the vibration. A numerical example of the whole spacecraft vibration isolation has proved the above conclusions.

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