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.

Passive Multi-Degree-of-Freedom Structural Control Using LPC Impact Dampers

2015 ◽  
Author(s):  
Mohamed Gharib ◽  
Mansour Karkoub
Keyword(s):  
Structural Control ◽  
Flexible Structures ◽  
Tall Buildings ◽  
Degree Of Freedom ◽  
Frame Structure ◽  
Linear Arrangement ◽  
Impact Damper ◽  
Particle Chain ◽  
The Impact ◽  
Partial Damage

Excessive vibration is one of the main reasons leading to partial damage and in some cases collapse of tall buildings and structures. Impact dampers provide an effective, economical, and easy to install solution to the vibration problem in several applications. The latest developed type in the impact dampers family is the Linear Particle Chain (LPC) impact damper. It consists of a linear arrangement of two sizes of freely moving masses, constrained by two stops. This paper presents the results of an experimental investigation on the effectiveness of the LPC impact damper in damping the vibrations of a multi-degree-of-freedom system under different types of excitations. A prototype of the LPC impact dampers is fabricated and tested in our lab using a three-story frame structure. The experimental outcomes clearly show that the LPC impact damper can effectively attenuate the free and forced vibrations of flexible structures.

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.

Performance of Particle Dampers Under Random Excitation

1996 ◽  
Vol 118 (4) ◽  
pp. 614-621 ◽  
Author(s):  
A. Papalou ◽  
S. F. Masri
Keyword(s):  
Wide Band ◽  
Small Mass ◽  
Random Excitation ◽  
Primary System ◽  
Mass Ratio ◽  
Impact Damper ◽  
Mean Square Response ◽  
Small Model ◽  
Particle Dampers ◽  
Auxiliary Mass

An experimental and analytical study is made of the performance of particle dampers under wide-band random excitation. A small model, provided with a nonlinear auxiliary mass damper, was used to investigate the major system parameters that influence the performance of particle dampers: total auxiliary mass ratio, particle size, container dimension, and the intensity and direction of the excitation. It is shown that properly designed particle dampers, even with a relatively small mass ratio, can considerably reduce the response of lightly damped structures. An approximate analytical solution, which is based on the concept of an equivalent single unit-impact damper, is presented. It is shown that the approximate solution can provide an adequate estimate of the root-mean-square response of the randomly excited primary system when provided with a particle damper that is operating in the vicinity of its optimum range of parameters.

Tunable-with-energy intense modal interactions induced by geometric nonlinearity

2020 ◽  
pp. 095440622090862
Author(s):  
Alireza Mojahed ◽  
Lawrence A Bergman ◽  
Alexander F Vakakis
Keyword(s):  
Geometric Nonlinearity ◽  
Degree Of Freedom ◽  
Primary System ◽  
Energy Relation ◽  
Initial Angle ◽  
Modal Interactions ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Energy Transfers ◽  
Wave Tailoring

Modal interactions are distinct features of nonlinear systems that can be exploited in applications such as vibration and shock mitigation, targeted (irreversible) energy transfers (TET), and acoustic/stress wave tailoring. For such applications, different types of nonlinearities, e.g. hardening, softening, smooth, non-smooth, material or geometric, have been considered. In this work, we examine the geometric nonlinearity resulting from an initially inclined element consisting of a linear spring and a viscous damper connected in parallel, having an initial angle of inclination, [Formula: see text]. Because of its inclined configuration, this element possesses strong (and doubly tunable with respect to [Formula: see text] and energy) geometrically nonlinear stiffness and damping effects, despite the linear constitutive laws governing its constituent components. First, we consider a single-degree-of-freedom linearly grounded oscillator attached to the nonlinear inclined element. Omitting dissipative effects, we investigate the frequency–energy relation of this system by employing the canonical action-angle transformation and show that, depending on the initial angle of inclination and the energy-level, the resulting nonlinearity can be tuned to be softening, hardening or a combination of both. Next, we explore the efficacy of the geometric nonlinearity to induce strong modal interactions by considering a three-degree-of-freedom lightly damped primary system that is weakly coupled to a single-degree-of-freedom lightly damped attachment with the inclined nonlinear element, subjected to impulsive excitation. Varying [Formula: see text] and the input energy, we demonstrate strong modal energy-exchanges between the modes of the primary system and the nonlinear attachment over broad energy-dependent spans of [Formula: see text]. We show that the passive self-adaptiveness of the nonlinear damping and the hardening–softening geometric nonlinearity can induce narrowband or broadband frequency TET, including high-to-low frequency energy transfers. Interestingly, over a definitive range of [Formula: see text], these modal interactions may be limited only between the nonlinear mode of the attachment and the highest-frequency linear mode of the primary system, inducing strong high-frequency targeted energy transfer to the primary system.

Study on Applicability of Equivalent Single Degree of Freedom Methods for Single Column Pier with Uniform Cross Section

2011 ◽  
Vol 255-260 ◽  
pp. 1716-1720
Author(s):  
Liang Chen
Keyword(s):  
Cross Section ◽  
Fundamental Mode ◽  
Degree Of Freedom ◽  
Mass Ratio ◽  
Shape Functions ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Single Column ◽  
Simplified Method ◽  
Uniform Cross Section

Applicability of the simplified method based on equivalent single-degree-of-freedom (ESDOF) for single-column pier with uniform cross-section is investigated in this paper. The modal participating mass ratio of pier’s fundamental mode is taken as an index to evaluate the applicability of the simplified method. Based on the fundamental mode shape functions selected deliberately in the first step, equations to evaluate the modal participating mass ratio of pier fundamental mode is obtained. Using the proposed equations, it is convenient to evaluate applicability of the simplified method with the height of the pier and the ratio of the linear mass along the column to the dumped mass at the top of the pier. Finally, the index is verified in the different nonlinear range of piers.

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.

scholarly journals Optimization of Multiple Tuned Mass Damper (MTMD) Parameters for a Primary System Reduced to a Single Degree of Freedom (SDOF) through the Modal Approach

2021 ◽  
Vol 11 (4) ◽  
pp. 1389
Author(s):  
Piotr Wielgos ◽  
Robert Geryło
Keyword(s):  
Degrees Of Freedom ◽  
Research Work ◽  
System Optimization ◽  
Degree Of Freedom ◽  
Primary System ◽  
Single Degree Of Freedom ◽  
Modal Approach ◽  
Single Degree ◽  
Novel Approach ◽  
The Impact

The research paper presents a novel approach toward constructing motion equations for structures with attached MTMDs (multiple tuned mass dampers). A primary system with MDOF (multiple dynamic degrees of freedom) was reduced to an equivalent system with a SDOF (single degree of freedom) through the modal approach, and equations from additional MTMDs were added to a thus-created system. Optimization based on ℌ2 and ℌ∞ for the transfer function associated with the generalized displacement of an SDOF system was applied. The research work utilized GA (genetic algorithms) and SA (simulated annealing method) optimization algorithms to determine the stiffness and damping parameters for individual TMDs. The effect of damping and stiffness (MTMD tuning) distribution depending on the number of TMDs was also analyzed. The paper also reviews the impact of primary system mass change on the efficiency of optimized MTMDs, as well as confirms the results of other authors involving greater MTMD effectiveness relative to a single TMD.

scholarly journals Leading-Edge Flutter of Supercavitating Hydrofoils

1980 ◽  
Vol 24 (03) ◽  
pp. 135-146
Author(s):  
C. Brennen ◽  
K. T. Oey ◽  
C. D. Babcock
Keyword(s):  
Leading Edge ◽  
Bubble Collapse ◽  
Hydrodynamic Load ◽  
Mass Ratio ◽  
Secondary Effects ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Flutter Speed ◽  
Cavity Closure ◽  
Collapse Process

This paper presents the results of experiments and analysis of the phenomenon of leading-edge flutter which has been observed to occur for supercavitating hydrofoils. The experiments confirmed the existence of such a single-degree-of-freedom flutter involving chordwise bending and indicated that for long, natural (or vapor-filled) cavities the reduced flutter speed, UF/ωFc, was in the range 0.15 to 0.23. Secondary effects observed were the variation with the angle of attack (a minimum flutter speed occurred at 10 deg) and with a foil mass ratio. Shorter cavities typically yielded lower flutter speeds due to a complex interaction between the bubble collapse process occurring in the cavity closure region and the unsteady hydrodynamic load on the foil. Finally, a relatively simple theoretical analysis for supercavitating hydrofoils with elastic axes aft of midchord is presented. This linear analysis yields reduced flutter velocities somewhat lower than those observed.

scholarly journals Optimization of Multiple Tuned Mass Damper (MTMD) Parameters for a Primary System Reduced to a Single Degree of Freedom (SDOF) Through the Modal Approach

2020 ◽  
Author(s):  
Piotr Wielgos ◽  
Robert Geryło
Keyword(s):  
Degrees Of Freedom ◽  
Research Work ◽  
System Optimization ◽  
Degree Of Freedom ◽  
Primary System ◽  
Single Degree Of Freedom ◽  
Modal Approach ◽  
Single Degree ◽  
Stiffness And Damping ◽  
The Impact

The research paper presents a new approach towards constructing motion equations for structures with attached MTMDs (multiple tuned mass dampers). A primary system, with MDOF (multiple dynamic degrees of freedom) was reduced to an equivalent system with a SDOF (single degree of freedom) through the modal approach, and equations from additional MTMDs were added to a thus-created system. Optimization based on H2 and H∞ for the transfer function associated with the generalized displacement of an SDOF system. The research work utilized GA (genetic algorithms) and SA (simulated annealing method) optimization algorithms to determine the stiffness and damping parameters for individual TMDs. The effect of damping and stiffness (MTMD tuning) distribution depending on the number of TMDs was also analyzed. The paper also reviews the impact of primary system mass change on the efficiency of optimized MTMDs, as well as confirms the results of other authors involving greater MTMD effectiveness relative to a single TMD.

Vibration of Satellite Subsystem During Orbiter Lift-Off

1993 ◽  
Vol 8 (3) ◽  
pp. 167-176 ◽  
Author(s):  
Gina Lee-Glauser ◽  
Goodarz Ahmadi
Keyword(s):  
Response Spectra ◽  
Degree Of Freedom ◽  
Mass Ratio ◽  
Acceleration Response ◽  
Single Degree Of Freedom ◽  
Lump Parameter Model ◽  
Single Degree ◽  
Acceleration Response Spectra ◽  
Lift Off ◽  
Sinusoidal Excitation

Vibrations of a satellite and one of its sensitive subsystems during orbiter lift-off are studied. A single degree-of-freedom representation of the subsystem and a five degree-of-freedom lump parameter model of the satellite are considered. Deflection and acceleration response spectra of the satellite and its subsystem subject to sinusoidal excitation and the STS - 41 lift-off accelerations are evaluated. The significance of the subsystem and primary satellite interaction is investigated. The effect of mass ratio and damping coeficient of the subsystem on the peak deflection and acceleration response spectra of the satellite and its subsystem are examined.

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