A Nonlinear Acoustic Resonator

2007 ◽  
Author(s):  
Umar Farooq ◽  
Shahin S. Nudehi
Keyword(s):  
Vibration Suppression ◽  
Perturbation Technique ◽  
Helmholtz Resonator ◽  
Acoustic Resonator ◽  
Wide Frequency Range ◽  
Frequency Range ◽  
Vibration Absorption ◽  
Membrane Attachment ◽  
Nonlinear Acoustic ◽  
System Frequency

An acoustic resonator of Helmholtz type with a membrane attached to one of its ends is studied in this work. A membrane possesses a geometric nonlinearity of cubic type. This work examines that when attached to the resonator, a membrane can be exploited to attenuate vibrations for a variable frequency range in an acoustical system. This can be viewed as a parallel to vibration absorption for the structural systems. The coupled nonlinear mathematical model of Helmholtz resonator with a membrane attachment is investigated by applying a perturbation technique to obtain a set of second order differential equations. These equations are then numerically solved. The simulations of system frequency response show that the vibration suppression could be achieved for a wide frequency range.

scholarly journals A Tuned Mass Damper with Nonlinear Magnetic Force for Vibration Suppression with Wide Frequency Range of Offshore Platform under Earthquake Loads

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
Qiong Wu ◽  
Wei Zhao ◽  
Weiguo Zhu ◽  
Rencheng Zheng ◽  
Xilu Zhao
Keyword(s):  
High Speed ◽  
Permanent Magnets ◽  
Vibration Suppression ◽  
Wide Frequency Range ◽  
Offshore Platform ◽  
Offshore Platforms ◽  
Frequency Range ◽  
Response Characteristics ◽  
Narrow Frequency Band ◽  
Dynamic Performances

Tuned mass dampers (TMDs) are applied to ensure the safety and stability of offshore platforms; however, linear dampers are effective for a single resonance frequency, providing vibration suppression only within a narrow frequency band. Therefore, this paper proposed a magnetic TMD with two pairs of permanent magnets on both sides of the structures, which can generate a nonlinearly repulsive force, making the magnetic TMD reliable and robust in damping the oscillations of structures with wide frequency range under seismic excitations. A comprehensively numerical and experimental study was processed to investigate the dynamic performances of the proposed magnetic TMD, by application of a 1 : 200-scale prototype of the offshore platform. The results verified that the performance of the magnetic TMD can be significantly improved than that of the linear TMD, meanwhile maintaining high-speed response characteristics. The experimental results indicated that the displacement, acceleration, and frequency responses of the offshore platform can be significantly reduced; furthermore, the evaluation indices showed that the magnetic TMD system is credible in reducing the overall vibration levels and maximum peak values.

scholarly journals Detection and localization of multiple small damages in beam

2021 ◽  
Vol 13 (1) ◽  
pp. 168781402098732
Author(s):  
Ayisha Nayyar ◽  
Ummul Baneen ◽  
Syed Abbas Zilqurnain Naqvi ◽  
Muhammad Ahsan
Keyword(s):  
Frequency Response ◽  
Natural Frequencies ◽  
Signal To Noise Ratio ◽  
Moving Average ◽  
A Priori ◽  
Damage Index ◽  
High Signal ◽  
Frequency Range ◽  
Spatial Locality ◽  
System Frequency

Localizing small damages often requires sensors be mounted in the proximity of damage to obtain high Signal-to-Noise Ratio in system frequency response to input excitation. The proximity requirement limits the applicability of existing schemes for low-severity damage detection as an estimate of damage location may not be known  a priori. In this work it is shown that spatial locality is not a fundamental impediment; multiple small damages can still be detected with high accuracy provided that the frequency range beyond the first five natural frequencies is utilized in the Frequency response functions (FRF) curvature method. The proposed method presented in this paper applies sensitivity analysis to systematically unearth frequency ranges capable of elevating damage index peak at correct damage locations. It is a baseline-free method that employs a smoothing polynomial to emulate reference curvatures for the undamaged structure. Numerical simulation of steel-beam shows that small multiple damages of severity as low as 5% can be reliably detected by including frequency range covering 5–10th natural frequencies. The efficacy of the scheme is also experimentally validated for the same beam. It is also found that a simple noise filtration scheme such as a Gaussian moving average filter can adequately remove false peaks from the damage index profile.

Installation for testing electronic voltmeters over a wide frequency range

1976 ◽  
Vol 19 (10) ◽  
pp. 1525-1526
Author(s):  
A. M. Fedorov ◽  
V. V. Krestovskii ◽  
V. S. Kiselev ◽  
S. A. Razumovskii ◽  
V. A. Shcheglov
Keyword(s):  
Wide Frequency Range ◽  
Frequency Range

Analysis of Dielectric Spectra of Water with Conductive Impurities in a Wide Frequency Range

2018 ◽  
Vol 60 (11) ◽  
pp. 1893-1900 ◽  
Author(s):  
V. A. Zhuravlev ◽  
V. I. Suslyaev ◽  
A. V. Zhuravlev ◽  
E. Yu. Korovin
Keyword(s):  
Wide Frequency Range ◽  
Frequency Range ◽  
Dielectric Spectra
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