Constant Mass Metastructure with Vibration Absorbers of Linearly Varying Natural Frequencies

2017 ◽  
pp. 153-158
Author(s):  
Katherine K. Reichl ◽  
Daniel J. Inman
Keyword(s):  
Natural Frequencies ◽  
Vibration Absorbers ◽  
Constant Mass

Structural Optimization of Cantilever Mechanical Elements

1986 ◽  
Vol 108 (4) ◽  
pp. 427-433 ◽  
Author(s):  
Eugene I. Rivin
Keyword(s):  
Structural Optimization ◽  
Natural Frequencies ◽  
Superior Performance ◽  
Vibration Absorbers ◽  
Stability Margins ◽  
Dynamic Vibration ◽  
Robot Arms ◽  
Limited Effectiveness ◽  
Mass Ratios ◽  
Dynamic Vibration Absorbers

Naturally limited stiffness of cantilever elements due to lack of constraint from other structural components, together with low structural damping, causes intensive and slow-decaying transient vibrations as well as low stability margins for self-excited vibrations. In cases of dimensional limitations (e.g., boring bars), such common antivibration means as dynamic vibration absorbers have limited effectiveness due to low mass ratios. This paper describes novel concepts of structural optimization of cantilever components by using combinations of rigid and light materials for their design. Two examples are given: tool holders (boring bars) and robot arms. Optimized boring bars demonstrate substantially increased natural frequencies, together with the possibility of greatly enhanced mass ratios for dynamic vibration absorbers. Machining tests with combination boring bars have been performed in comparison with conventional boring bars showing superior performance of the former. Computer optimization of combination-type robot arms has shown a potential of 10–60 percent reduction in tip-of-arm deflection, together with a commensurate reduction of driving torque for a given acceleration, and a higher natural frequencies (i.e., shorter transients). Optimization has been performed for various ratios of bending and joint compliance and various payloads.

On the Usage of Dynamic Vibration Absorbers for Reduction of Forced Vibrations of a System of Coupled Rigid Bodies

2009 ◽  
Author(s):  
Dmitry Chebanov ◽  
Alexander M. Kovalev ◽  
Irina A. Bolgrabskaya ◽  
Vladimir F. Shcherbak
Keyword(s):  
Forced Vibrations ◽  
Rigid Bodies ◽  
Vibration Absorbers ◽  
Constant Mass ◽  
External Perturbations ◽  
Dynamic Vibration ◽  
Dynamic Vibration Absorbers ◽  
Controlled Motion ◽  
A Chain ◽  
Chain Links

In this paper we study the problem of neutralizing the forced vibrations of a chain of heavy rigid bodies coupled by one-degree-of-freedom joints using dynamic vibration absorbers. Each absorber is modeled by a system that has a constant mass and is capable of making instantaneous changes in its stiffness. We propose and analyze several strategies for introducing the absorbers that differ from each other by the number of absorbers attached and the way they are positioned on the chain links. In particular, we suggest a way to choose the parameters of the absorbers so that their controlled motion totally compensates the effect of the external perturbations.

Size-dependent free vibration of axially functionally graded tapered nanorods having nonlinear spring constraint with a tip nanoparticle

2019 ◽  
Vol 25 (21-22) ◽  
pp. 2769-2783 ◽  
Author(s):  
Arian Bahrami ◽  
Ali Zargaripoor ◽  
Hamidreza Shiri ◽  
Nima Khosravi
Keyword(s):  
Literature Review ◽  
Natural Frequencies ◽  
Nonlocal Parameter ◽  
Nonlocal Theory ◽  
Functionally Graded ◽  
The Other ◽  
Constant Mass ◽  
Axial Vibration ◽  
Nonlinear Spring ◽  
Size Dependent

According to the present literature review, the axial vibration of the axially functionally graded (FG) tapered nanorod with attached nonlinear spring has not been addressed so far. In this study, the axial vibration of the FG tapered nanorod is studied based on Eringen’s nonlocal theory, in which one end of the nanorod is clamped and the other end is attached to a nonlinear spring and a nanoparticle. The influence of different parameters such as the nonlinear spring constant, mass of the nanoparticle, and the nonlocal parameter on the natural frequencies is presented in detail. The solutions via Tables can be utilized as a reliable reference for evaluating the validity of future researches. The presented nonlocal solutions can be helpful for those who are interested in designing micro/nano electromechanical systems.

Nonlinear Dynamics of Flexible Rotating Shafts With Centrifugal Pendulum Vibration Absorbers

2015 ◽  
Author(s):  
Mustafa A. Acar ◽  
Steven W. Shaw ◽  
Brian F. Feeny
Keyword(s):  
Torsional Vibration ◽  
Perturbation Methods ◽  
Natural Frequencies ◽  
Rotation Speed ◽  
Vibration Modes ◽  
Vibration Absorbers ◽  
Engine Order ◽  
Centrifugal Pendulum Vibration Absorbers ◽  
Rotating Shafts ◽  
Practical Implications

We consider the nonlinear vibration response of rotating flexible shafts fitted with centrifugally driven pendulum vibration absorbers (CPVAs) that are used to address engine-order torsional vibrations. The model used to represent the behavior of the flexible shaft consists of two lumped inertial elements with an interconnecting stiffness element, which captures the rigid body and fundamental torsional vibration modes of the rotor. The absorbers are centrifugally driven pendulums fitted to a rotor element, such that their natural frequencies scale with the rotor speed, and can thus tuned to a given order of rotation. Previous analysis of a linearized version of this coupled rotor-absorber system revealed frequency veering behavior as the rotation speed varies, and showed that one can detune the absorber to eliminate key system resonances. In this paper the behavior of the system is analyzed for large absorber amplitudes using perturbation methods and numerical simulations. It is shown that the absorbers remain effective in reducing torsional vibration when moving through large amplitudes, and that the resonance avoidance is similarly robust. This has practical implications for the tuning of absorbers in certain applications.

Validation of a Modeling Tool for In-Plane Longitudinal Resonators with Zigzag Topology

2019 ◽  
Vol 11 (02) ◽  
pp. 1950013
Author(s):  
Bowei Chen ◽  
Oleg Shiryayev ◽  
Nader Vahdati ◽  
Ameen El-Sinawi
Keyword(s):  
Elastic Waves ◽  
Experimental Validation ◽  
Natural Frequencies ◽  
Frequency Tuning ◽  
Finite Element Models ◽  
Vibration Absorbers ◽  
Longitudinal Vibrations ◽  
Resonant Frequencies ◽  
Modeling Tool ◽  
Proposed Model

Metastructures are viewed as a promising means for suppressing elastic waves and unwanted vibrations. Metastructures comprise of elementary cells with embedded resonators, which act as vibration absorbers. Design and frequency tuning of individual resonators inside the metastructure allows to achieve effective suppression of vibrations over a relatively wide frequency bandwidth, which makes metastructures superior compared to conventional passive vibration absorbers. This paper describes numerical and experimental validation of a modeling tool for design of planar resonators with elastic elements arranged in a zigzag configuration for suppression of longitudinal vibrations. Zigzag topology is advantageous due to its ability to provide higher compliance within a limited space, so as to achieve low resonant frequencies. Natural frequencies predicted by the proposed model agree well with predictions provided by detailed finite element models and experimental measurements.

Design of Vibration Absorbers for Structures Subject to Multiple-Tonal Excitations

2005 ◽  
Vol 128 (1) ◽  
pp. 106-114 ◽  
Author(s):  
P. W. Wang ◽  
C. C. Cheng
Keyword(s):  
Natural Frequencies ◽  
Vibration Absorber ◽  
Vibration Absorbers ◽  
Systematic Method ◽  
Rotating Speed ◽  
Rotary Machine ◽  
Eccentric Rotor ◽  
Vibration Attenuation ◽  
Impedance Technique ◽  
Multiple Frequencies

The purpose of this paper is to introduce a systematic method of designing a vibration absorber that affects vibration attenuation at multiple frequencies. This vibration absorber is a nonprismatic beam with natural frequencies intentionally designed to coincide with the frequencies of excitation, e.g., the rotating speed of a rotary machine and its harmonic orders. Therefore, it can reduce the vibration response due to rotor eccentric, rotor shaft bending, mechanical looseness, etc. The thickness profile of the nonprismatic beam can be approximated discretely by a large amount of block masses. Each block mass behaves as an elastic structure member, and its thickness can be determined systematically using the impedance technique proposed in this paper. A design is given to demonstrate the methodology, and the result is experimentally validated.

Design and Optimization of Broadband Vibration Absorbers for Noise Control

2001 ◽  
Author(s):  
Emily S. Heinze ◽  
Michael D. Grissom ◽  
Ashok Belegundu
Keyword(s):  
Natural Frequencies ◽  
Mode Shapes ◽  
Vibration Absorber ◽  
Vibration Absorbers ◽  
Analysis Algorithm ◽  
Design And Optimization ◽  
Forcing Function ◽  
Modal Model ◽  
Practical Design ◽  
Base Structure

Abstract A general and practical approach is presented for optimizing structural additions to a base structure for broadband dynamic objectives when the base structure is excited by an arbitrary forcing function. The mode shapes and natural frequencies of the base structure are first found using a commercial finite element code or an experimental modal analysis. The mode shapes are used as basis shapes to reduce the size of the equations. The structural additions are then added as impedances into the reduced modal model. An efficient analysis algorithm is presented to reduce the computational burden for broadband analysis and optimization loops. The power transferred into a Broadband Vibration Absorber (BBVA) from a base structure is maximized as an example application. The numerical results are experimentally verified demonstrating the practical design capabilities of the method.

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