Vibration Reduction of a Floating Roof by Dynamic Vibration Absorbers

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
M. Utsumi
Keyword(s):  
Damping Ratio ◽  
Earthquake Ground Motion ◽  
Primary System ◽  
Vibration Absorbers ◽  
Long Period ◽  
Dynamic Vibration ◽  
Time Integral ◽  
Sloshing Frequency ◽  
Dynamic Vibration Absorbers ◽  
Tuning Frequency

This paper investigates the use of dynamic vibration absorbers as a means to reduce the vibration of a floating roof due to sloshing caused by long-period earthquakes. It is shown that the damping ratio of the primary system caused by the dynamic vibration absorbers increases with rising filling level, hence increasing the probability of liquid overspilling, although the ratio of the vibration absorbers’ mass to the liquid mass decreases as the filling level rises. We also study dynamic vibration absorbers that can be more easily tuned to the filling-level dependent sloshing frequency. A feature of these vibration absorbers is that they use time-integral feedback of the primary structure’s displacement near the tuning frequency unlike ordinary vibration absorbers. Computer simulation is carried out using a sinusoidal wave function and an actual earthquake ground motion record as the excitation applied to the tank.

Parameters optimization of dynamic vibration absorber based on grounded stiffness, inerter, and amplifying mechanism

2021 ◽  
pp. 107754632110382
Author(s):  
Peng Sui ◽  
Yongjun Shen ◽  
Shaopu Yang ◽  
Junfeng Wang
Keyword(s):  
Analytical Solution ◽  
Vibration Isolation ◽  
Damping Ratio ◽  
Vibration Absorber ◽  
Primary System ◽  
Vibration Absorbers ◽  
Stiffness Ratio ◽  
Dynamic Vibration Absorber ◽  
Dynamic Vibration ◽  
Dynamic Vibration Absorbers

In the field of dynamics and control, some typical vibration devices, including grounded stiffness, inerter and amplifying mechanism, have good vibration isolation and reduction effects, especially in dynamic vibration absorber (DVA). However, most of the current research studies only focus on the performance of a single device on the system, and those DVAs are gradually becoming difficult to meet the growth of performance demand for vibration control. On the basis of Voigt dynamic vibration absorber, a novel dynamic vibration absorber model based on the combined structure of grounded stiffness, inerter, and amplifying mechanism is presented, and the analytical solution of the optimal design formula is derived. First, the motion differential equation of the system is established, and the normalized amplitude amplification factor of the displacement is calculated. It is found that the system has three fixed points unrelated to the damping ratio. The optimal frequency ratio is obtained based on the fixed-point theory. In order to ensure the stability of the system, it is found that inappropriate inerter coefficient will cause the system instable when screening optimal grounded stiffness ratio. Accordingly, the best working range of inerter is determined. Finally, optimal grounded stiffness ratio and approximate optimal damping ratio are also obtained. The influence of inerter coefficient and magnification ratio on the response of the primary system is analyzed. The correctness of the derived analytical solution is verified by numerical simulation. Compared with other dynamic vibration absorbers, it is verified that presented model has superior vibration absorption performance and provides a theoretical basis for the design of a new type of dynamic vibration absorbers.

Analysis of Parallel Damped Dynamic Vibration Absorbers

1969 ◽  
Vol 91 (1) ◽  
pp. 282-287 ◽  
Author(s):  
A. V. Srinivasan
Keyword(s):  
Vibration Absorber ◽  
Vibration Absorbers ◽  
Dynamic Vibration Absorber ◽  
Main Mass ◽  
Dynamic Vibration ◽  
Frequency Comparison ◽  
Dynamic Vibration Absorbers ◽  
Tuning Frequency ◽  
Comparison Of The Results ◽  
Operational Range

The analysis of parallel damped dynamic vibration absorbers is presented. The system considered is essentially a modification of the conventional damped vibration absorber and consists of adding, in parallel, a subsidiary undamped absorber mass in addition to the damped absorber mass. The analysis clearly shows that it is possible to obtain an undamped antiresonance in a dynamic absorber system which exhibits a well-damped resonance. While the bandwidth of frequencies between the damped peaks is not significantly increased, the amplitudes of the main mass are considerably smaller within the operational range of the absorber. The damped absorber mass and the main mass attain null simultaneously so that the vibratory force is transmitted directly to the undamped absorber. Numerical results are presented for the special case when the absorber masses have the same magnitude. Two cases of tuning have been considered: (a) when the absorber masses are tuned to the frequency of the main mass, and (b) when the absorber masses are tuned to the so-called favorable tuning frequency. Comparison of the results with those of the conventional absorber indicates that the parallel damped dynamic vibration absorber has definite advantages over the conventional damped vibration absorber.

Parametric Selection of Dynamic Vibration Absorbers for Resonant Suppression of Structure-Absorber Systems

2015 ◽  
Vol 723 ◽  
pp. 31-35
Author(s):  
Lin Liu ◽  
Huang Cheng Fang
Keyword(s):  
Frequency Tuning ◽  
Damping Ratio ◽  
Structural Vibration ◽  
Vibration Absorbers ◽  
Practical Applications ◽  
Dynamic Vibration ◽  
Magnification Factors ◽  
Modal Damping ◽  
Dynamic Vibration Absorbers ◽  
Selection Of

The selection of absorber parameters is of utmost significance for structural vibration control by dynamic vibration absorbers. Based on the classical frequency tuning approach by Den Hartog, optimal damping ratio is derived in close form by equating the dynamic magnification factors of the structural motion at three particular frequencies of interest. In addition, by maximizing the two identical modal damping ratios through root locus in the first quadrant of complex plane, the corresponding absorber damping ratio is derived and proposed as the upper bound of the absorber damping ratio for practical applications.

Optimal Design of Double-Mass Dynamic Vibration Absorbers Minimizing the Mobility Transfer Function

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Toshihiko Asami ◽  
Yoshito Mizukawa ◽  
Tomohiko Ise
Keyword(s):  
Transfer Function ◽  
Vibration Suppression ◽  
Optimal Solution ◽  
Algebraic Solution ◽  
Primary System ◽  
Vibration Absorbers ◽  
Dynamic Vibration ◽  
Double Mass ◽  
Dynamic Vibration Absorbers ◽  
The Absolute

Although the vibration suppression effects of precisely adjusted dynamic vibration absorbers (DVAs) are well known, multimass DVAs have recently been studied with the aim of further improving their performance and avoiding performance deterioration due to changes in their system parameters. One of the present authors has previously reported a solution that provides the optimal tuning and damping conditions of the double-mass DVA and has demonstrated that it achieves better performance than the conventional single-mass DVA. The evaluation index of the performance used in that study was the minimization of the compliance transfer function. This evaluation function has the objective of minimizing the absolute displacement response of the primary system. However, it is important to suppress the absolute velocity response of the primary system to reduce the noise generated by the machine or structure. Therefore, in the present study, the optimal solutions for DVAs were obtained by minimizing the mobility transfer function rather than the compliance transfer function. As in previous investigations, three optimization criteria were tested: the H∞ optimization, H2 optimization, and stability maximization criteria. In this study, an exact algebraic solution to the H∞ optimization of the series-type double-mass DVA was successfully derived. In addition, it was demonstrated that the optimal solution obtained by minimizing the mobility transfer function differs significantly at some points from that minimizing the compliance transfer function published in the previous report.

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.

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