A Theoretical Prediction of Natural Frequency of a Ferromagnetic Beam Plate With Low Susceptibility in an In-Plane Magnetic Field

1998 ◽  
Vol 65 (1) ◽  
pp. 121-126 ◽  
Author(s):  
You-He Zhou ◽  
Kenzo Miya
Keyword(s):  
Magnetic Field ◽  
Theoretical Model ◽  
Natural Frequency ◽  
Magnetic Force ◽  
Damping Ratio ◽  
Theoretical Models ◽  
Energy Functional ◽  
Magnetoelastic Interaction ◽  
Magnetic Damping ◽  
Theoretical Predictions

In order to simulate the experimental phenomenon of increase of natural frequency to a cantilevered ferromagnetic beam plate in in-plane magnetic fields, a theoretical model for behaving the magnetoelastic interaction is proposed in this paper based on the variational principle of energy functional of the system. It is found that the expression of magnetic force is distinctly different from those of the existing theoretical models in publications, and the experimental phenomenon is successfully simulated by this theoretical model. After the increase of natural frequency is quantitatively considered in the predictions of magnetic damping, the theoretical predictions of magnetic damping ratio are agreement with the corresponding experimental data well.

Simulation research on low frequency sound absorption of monostable metamaterials

2021 ◽  
Vol 263 (6) ◽  
pp. 648-652
Author(s):  
Tuo Xing ◽  
Xianhui Li ◽  
Xiaoling Gai ◽  
Zenong Cai ◽  
Xiwen Guan
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Theoretical Model ◽  
Finite Element Simulation ◽  
Sound Absorption ◽  
Magnetic Force ◽  
Low Frequency ◽  
Low Frequencies ◽  
Element Simulation ◽  
Simulation Results

The monostable acoustic metamaterial is realized by placing a flexible panel with a magnetic proof mass in a symmetric magnetic field. The theoretical model of monostable metamaterials has been proposed. The method of finite element simulation is used to verify the theoretical model. The magnetic force of the symmetrical magnetic field is simplified as the relationship between force and displacement, acting on the mass. The simulation results show that as the external magnetic force increases, the peak sound absorption shifts to low frequencies. The theoretical and finite element simulation results are in good agreement.

Modeling of Eddy Current Damper Composed of Spherical Magnet and Conducting Shell

2006 ◽  
Author(s):  
Yoshihisa Takayama ◽  
Atsuo Sueoka ◽  
Takahiro Kondou
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
Magnetic Force ◽  
Eddy Currents ◽  
Reaction Force ◽  
Damping Force ◽  
Magnetic Damping ◽  
Conducting Plate ◽  
Direction Of Movement ◽  
Eddy Current Damper

If a conducting plate moves through a nonuniform magnetic field, eddy currents are induced in the conducting plate. The eddy currents produce a magnetic force of drag, known as Fleming's left-hand rule. This rule means that a magnetic field perpendicular to the direction of movement generates a magnetic damping force. We have fabricated the eddy current damper composed of the spherical magnet and the conducting shell. The spherical magnet produces the axisymmetric magnetic field, and the shape of the conducting shell appears to combine a semispherical shell conductor and a cylinder conductor. When the eddy current damper works, the conducting shell is fixed in space, and the spherical magnet moves under the conducting shell. In this case, since there are magnetic flux densities perpendicular to the direction of movement, eddy currents flow inside the conducting shell, and then a magnetic force is produced. The reaction force of this magnetic force acts on the spherical magnet. In our study, eddy current dampers composed of a magnet and a conducting plate have been modeled using infinitesimal loop coils. As a result, magnetic damping forces are obtained. Our modeling has three merits as follows: the equation of a magnetic damping force is simple in the equation, we can use the static magnetic field obtained using FEM, the Biot-Savart law or experiments and the equation automatically satisfies boundary conditions using infinitesimal loop coils. In this study, we explain simply the principle of this method, and model an eddy current damper composed of a spherical magnet and a conducting shell. The analytical results of the modeling agree well with the experimental results.

Development and Design of the Dynamic Vibration Absorber Using Magneto-Rheological Elastomer for the Weight and Power Consumption Saving

2019 ◽  
Author(s):  
Osamu Terashima ◽  
Mika Nakata ◽  
Toshihiko Komatsuzaki
Keyword(s):  
Magnetic Field ◽  
Power Consumption ◽  
Natural Frequency ◽  
Damping Ratio ◽  
Wide Band ◽  
Test Results ◽  
Dynamic Vibration Absorber ◽  
Small Power ◽  
Dynamic Absorber ◽  
Magneto Rheological

Abstract In this study, a broadband frequency tunable dynamic absorber was designed and fabricated based on the primary design principle of a mass damper. A magneto-rheological elastomer that can change the relative stiffness when an external magnetic field is applied was used to control the natural frequency of the movable mass of the absorber. A coil to generate the magnetic field was also used as a movable mass to decrease the total weight and to create a constant closed loop of the magnetic force. The hammer impact test results show that the present absorber could change its natural frequency with minimal electric power and had a constant damping ratio. Experimental results of vibration absorbing of an acrylic flat plate show that the proposed absorber could change the natural frequency of the movable mass and reduce the vibration over a wide band by constantly applying the optimum current to the coil in the device with a small power consumption (less than 10 W). Therefore, the proposed absorber works effectively. Further, a technique to determine the electric current applied to the coil automatically based on the phase difference of the vibrational acceleration of the movable mass and the vibrating objective was also presented.

A Theoretical and Experimental Investigation of a Gas Operated Bearing Damper for Turbomachinery: Part II — Experimental Results and Comparison With Theory

1993 ◽  
Author(s):  
Padmanabhan Sundararajan ◽  
John M. Vance
Keyword(s):  
Experimental Investigation ◽  
High Temperature ◽  
Theoretical Model ◽  
Natural Frequency ◽  
Experimental Results ◽  
Experimental Measurements ◽  
Vibration Damper ◽  
Theoretical Predictions ◽  
Present Design ◽  
Gas Damper

Abstract This is the second of two papers describing results of a research project directed at developing a gas operated vibration damper for high temperature turbomachinery applications. This part presents the experimental measurements made on three variations of the gas damper hardware and compares them with the theoretical predictions presented in Part I. It is found that the isentropic theoretical model predicts the damper characteristics quite well. A maximum damping of 13.2 Ib-s/in was measured for a single actuator at a natural frequency of 100 hz using the present design and the results suggest that significantly higher damping levels are possible with design modifications.

A Gas-Operated Bearing Damper for Turbomachinery—Theoretical Predictions Versus Experimental Measurements: Part II—Experimental Results and Comparison With Theory

1995 ◽  
Vol 117 (4) ◽  
pp. 750-756 ◽  
Author(s):  
P. Sundararajan ◽  
J. M. Vance
Keyword(s):  
High Temperature ◽  
Theoretical Model ◽  
Natural Frequency ◽  
Experimental Results ◽  
Experimental Measurements ◽  
Vibration Damper ◽  
Research Project ◽  
Theoretical Predictions ◽  
Present Design ◽  
Gas Damper

This is the second of two papers describing results of a research project directed at developing a gas-operated vibration damper for high-temperature turbomachinery applications. This part presents the experimental measurements made on a gas damper hardware and compares them with the theoretical predictions given in Part I. It is found that the isentropic theoretical model predicts the damper characteristics quite well. A maximum damping of 2310 N-s/m (13.2 lb-s/in.) was measured at a natural frequency of 118 Hz using the present design and the results suggest that significantly higher damping levels are possible with design modifications.

The Magnetic Viscous Damping Effect on the Natural Frequency of a Beam Plate Subject to an In-Plane Magnetic Field

2009 ◽  
Vol 77 (1) ◽  
Author(s):  
Jui-Lin Lee ◽  
Chun-Bo Lin
Keyword(s):  
Magnetic Field ◽  
Natural Frequency ◽  
Magnetic Force ◽  
Ferromagnetic Material ◽  
Transverse Magnetic ◽  
Force Model ◽  
Viscous Damping ◽  
Damping Effect ◽  
Soft Ferromagnetic ◽  
Uniform External Magnetic Field

Several magnetic force models were developed to interpret various phenomena of a soft ferromagnetic beam plate subjected to a uniform external magnetic field with different incident angles. In this paper, a new transverse magnetic force model for the interface between a ferromagnetic material and the air is derived with the continuation of magnetoelastic stress across the material boundary. It is noted that both the normal and the tangential components of magnetic field on the material boundary are considered in this model. By applying such a transverse magnetic force and the effect of magnetic viscous damping, a new theoretical model is constructed in this study to predict the natural frequency of a soft ferromagnetic beam plate placed in an in-plane magnetic field. The numerical results of the present study are displayed graphically and compared with the experimental data, which appeared in literature to assure the exactness of the present work.

scholarly journals Analysis of Magnetic and Hydraulic Forces in an Oriented Real Matrix of a High Gradient Magnetic Separator

1985 ◽  
Vol 1 (4) ◽  
pp. 173-182 ◽  
Author(s):  
V. Hencl ◽  
K. Jahoda ◽  
E. Madai
Keyword(s):  
Magnetic Field ◽  
Magnetic Force ◽  
Theoretical Models ◽  
Attractive Force ◽  
Suspension Flow ◽  
Real Matrix ◽  
Magnetic Separator ◽  
High Gradient ◽  
Gradient Separation ◽  
The Magnetic Field

The application of existing theoretical models for the computation of magnetic and hydraulic forces in a real oriented matrix consisting of regularly arranged rods and wires indicates that these models produce no exact results. The differences between computations and measurements of force effects documented by Maxwell lead to the conclusion that it is necessary to start with different physical assumptions when modelling a high–gradient separation process. First of all, the magnetic field of the rods or wires system differs from the magnetic field of a single rod. Second, the particle need not be attracted to the rod surface, it is brought there by the suspension stream and the magnetic force must hold it, so that it is not entrained by the streaming suspension. As the layer of attracted particles grows, the magnetic attractive force on the surface of the growing layer decreases until the magnetic attractive force is in equilibrium with the entraining force of suspension flow.

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.

scholarly journals Heat Flux of a Transferred Arc Driven by a Transverse Magnetic Field

2009 ◽  
Vol 2009 ◽  
pp. 1-5 ◽  
Author(s):  
Naomi Matsumoto ◽  
Takashi Usami ◽  
Ikumi Kuno ◽  
Takeo Yamamoto ◽  
Masaya Sugimoto ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Flux ◽  
Theoretical Model ◽  
Magnetic Flux ◽  
Field Experiments ◽  
Transverse Magnetic ◽  
Magnetic Flux Density ◽  
Dc Magnetic Field ◽  
Transferred Arc ◽  
Theoretical Predictions

Theoretical consideration of a magnetically driven arc was performed to elucidate the variation of heat flux with an imposed DC magnetic field. Experiments were conducted to confirm the validity of the theoretical model. The heat flux decreased concomitantly with increased imposed magnetic flux density. Theoretical predictions agreed with experimental results.

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