scholarly journals Numerical Simulation Analysis and Experimental Research on Damping Performance of a Novel Magnetic Fluid Damper

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Wenrong Yang ◽  
Dejie Wei ◽  
Jianzheng Su ◽  
Xiaorui Yang ◽  
Qingxin Yang
Keyword(s):  
Magnetic Field ◽  
Magnetic Fluid ◽  
Simulation Analysis ◽  
Damping Ratio ◽  
Low Frequency ◽  
Operating Characteristics ◽  
Damping Force ◽  
Rolling Ball ◽  
High Rise ◽  
Field Coupling

Considering the low-frequency and large-amplitude vibration characteristics of the high-rise structure, a tuned magnetic fluid rolling-ball damper is proposed to suppress the vibration of the structure. By adjusting the external magnetic field to control the natural rolling frequency of the ball, the purpose of tuning vibration reduction is achieved. Firstly, the working principle of the damper is theoretically analysed, a three-dimensional (3D) magnetic-fluid-solid multiphysical field coupling mathematical model of the damper is established and the governing equations of multiphysical field coupling are derived. Secondly, the magnetic field distribution and operating characteristics of the damper are simulated and analysed. Finally, the effectiveness of the model is verified by experiments, and the damping performance of the damper with two kinds of magnetic fluid is tested and compared. The results show that the magnetic-fluid-solid multiphysical field coupling model can accurately simulate the working characteristics of the damper. The maximum damping force of the damper is about 12% of the elastic force of the structure, which can increase the damping ratio of the structure by about two times, effectively reduce the vibration response time, and suppress the vibration of the high-rise structure.

A Coupled System of a Magnet and Magnetic Fluid in a U-Tube under Reciprocating Traveling Magnetic Field

2010 ◽  
Vol 670 ◽  
pp. 207-214 ◽  
Author(s):  
Yasushi Ido ◽  
Koichi Hayashi ◽  
Takahiro Kunitomo
Keyword(s):  
Magnetic Field ◽  
Magnetic Fluid ◽  
Vibration Mode ◽  
Low Frequency ◽  
Coupled System ◽  
The Other ◽  
Reciprocating Motion ◽  
Vibration Properties ◽  
Short Cylinder ◽  
Traveling Magnetic Field

A coupled system of a magnet and magnetic fluid is used as a piston in a U-tube. Applying reciprocating travelling magnetic field produces reciprocating motion of the coupled system. In this study, vibration properties of the coupled system are investigated experimentally. Three types of vibration mode of the coupled system appear and the mode depends on the frequency and intensity of travelling magnetic field and the shape of the magnet. Basically the coupled system follows the travelling magnetic field in the range of low frequency, while the system cannot follow the travelling field when the frequency of the travelling magnetic field is high. However, when the magnet is sphere or short cylinder, the other type of vibration appears in the range of low frequency and the coupled system intermittently tracks the travelling magnetic field.

Model of Eddy Current Damping Mechanism for the Suppression of Beam Vibrations

Aerospace ◽  
2004 ◽  
Author(s):  
Henry A. Sodano ◽  
Jae-Sung Bae ◽  
Daniel J. Inman ◽  
W. Keith Belvin
Keyword(s):  
Magnetic Field ◽  
Theoretical Model ◽  
Eddy Current ◽  
Damping Ratio ◽  
Power Supplies ◽  
Damping Force ◽  
Electromagnetic Damping ◽  
Eddy Current Damping ◽  
Eddy Current Damper ◽  
External Power

The movement of a conductor through a stationary magnetic field or a time varying magnetic field through a stationary conductor generates electromagnetic forces that can be used to suppress the vibrations of a flexible structure. In the present study, a new electromagnetic damping mechanism is introduced. This mechanism differs from previously developed electromagnetic braking systems and eddy current dampers because the system investigated in the following manuscript uses the radial magnetic flux of a permanent magnet to generate the electromagnetic damping force rather than the flux perpendicular to the magnet’s face as done in other studies. One important advantage of the proposed mechanism is that it is simple and easy to be applied. Additionally, a single magnet can be used to damp the transverse vibrations that are present in many structures. Furthermore, it doesn’t require any electronic devices or external power supplies, therefore functioning as a non-contacting passive damper. A theoretical model of the system is derived using electromagnetic theory, enabling us to estimate the electromagnetic damping force induced on the structure. The proposed eddy current damper was constructed and experiments were performed to verify the precision of the theoretical model. It is found that the proposed eddy current damping mechanism increases the damping ratio by up to 150 times and provides sufficient damping force to quickly suppress the beam’s vibration.

Research on the low-frequency pressure generator based on magnetic fluid

2019 ◽  
Vol 33 (16) ◽  
pp. 1950173 ◽  
Author(s):  
Wenrong Yang ◽  
Yao Zhai ◽  
Xiaorui Yang
Keyword(s):  
Magnetic Field ◽  
Magnetic Fluid ◽  
Excitation Frequency ◽  
Low Frequency ◽  
Magnetic Core ◽  
Input Current ◽  
Manufacturing Cost ◽  
Solenoid Coil ◽  
Output Pressure ◽  
Pressure Generator

To solve the problems that the existing pressure generators require high mechanical excitation frequency, need large manufacturing cost and are hard to control, a kind of pressure generator with low-frequency based on magnetic fluid is proposed in this paper. Magnetic fluid possesses the advantages of both magnetism of solid magnetic material and fluidity of liquid. The first-order buoyancy of magnetic fluid changes with low frequency alternating magnetic field. Based on this, the superimposed magnetic field is generated by electrifying the conical solenoid coil connected with the long solenoid coil with magnetic core in parallel. Magnetic field and magnetic force in the model are analyzed, then the relationship between input current and output pressure is calculated. In addition, the experimental platform is built and the performance of the device is tested. The result shows that the pressure generator can produce the corresponding pressure signal according to the input current.

scholarly journals Statistical Significance of Earth’s Electric and Magnetic Field Variations Preceding Earthquakes in Greece and Japan Revisited

Entropy ◽  
2018 ◽  
Vol 20 (8) ◽  
pp. 561 ◽  
Author(s):  
Nicholas Sarlis
Keyword(s):  
Magnetic Field ◽  
Statistical Significance ◽  
Low Frequency ◽  
Lead Times ◽  
Operating Characteristics ◽  
Complexity Measures ◽  
Natural Time ◽  
Experimental Findings ◽  
Precursory Phenomena ◽  
Magnetic Field Variations

By analyzing the seismicity in a new time domain, termed natural time, we recently found that the change of the entropy under time reversal (Physica A2018, 506, 625–634) and the relevant complexity measures (Entropy2018, 20, 477) exhibit pronounced variations before the occurrence of the M8.2 earthquake in Mexico on 7 September 2017. Here, the statistical significance of precursory phenomena associated with other physical properties and in particular the anomalous variations observed in the Earth’s electric and magnetic fields before earthquakes in different regions of the world and in particular in Greece since 1980s and Japan during 2001–2010 are revisited (the latter, i.e., the magnetic field variations are alternatively termed ultra low frequency (ULF) seismo-magnetic phenomena). Along these lines we employ modern statistical tools like the event coincidence analysis and the receiver operating characteristics technique. We find that these precursory variations are far beyond chance and in addition their lead times fully agree with the experimental findings in Greece since the 1980s.

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