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 Evidence for Stable High-Temperature Ferromagnetism in Fluorine-Treated C60

2013 ◽  
Vol 2013 ◽  
pp. 1-5
Author(s):  
Rajen Patel ◽  
Frank J. Owens
Keyword(s):  
Magnetic Field ◽  
High Temperature ◽  
Magnetic Force Microscopy ◽  
Room Temperature ◽  
Magnetic Force ◽  
Ac Susceptibility ◽  
Ferromagnetic Material ◽  
Molecular Orbital Calculations ◽  
Force Microscopy ◽  
Field Dependent

It is shown by magnetic field dependent ac susceptibility, magnetic force microscopy, and ferromagnetic resonance that exposure of C60 to fluorine at 160°C produces a stable ferromagnetic material with a Curie temperature well above room temperature. The exposure to fluorine is accomplished by decomposing a fluorine-rich polymer, trifluorochloroethylene [F2C–CFCl]n, which has C60 imbedded in it. Based on previous experimental observations and molecular orbital calculations, it is suggested that the ferromagnetism is arising from crystals of C60–F.

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.

Vibration and Dynamic Instability of a Beam-Plate in a Transverse Magnetic Field

1969 ◽  
Vol 36 (1) ◽  
pp. 92-100 ◽  
Author(s):  
F. C. Moon ◽  
Yih-Hsing Pao
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Mathematical Model ◽  
Natural Frequency ◽  
Dynamic Instability ◽  
Critical Value ◽  
Transverse Magnetic ◽  
Axial Forces ◽  
Oscillating Magnetic Field ◽  
Theoretical Results

Experiments show that the natural frequency of a beam-plate in a transverse static magnetic field decreases to near zero as the field attains a critical value which causes the same plate to buckle statically. Under an oscillating magnetic field the beam-plate is observed to become unstable and perform parametrically excited oscillations. A mathematical model based on a quasistatic solution for the magnetization in the deformed plate is proposed. The theoretical results agree very well with the experimental data. It is shown that the phenomena are analogous to those for a beam-column under static and dynamic axial forces.

A modified magnetic force model and experimental validation of a tri-stable piezoelectric energy harvester

2020 ◽  
Vol 31 (7) ◽  
pp. 967-979 ◽  
Author(s):  
Guangqing Wang ◽  
Haiqiang Wu ◽  
Wei-Hsin Liao ◽  
Sujuan Cui ◽  
Zexiang Zhao ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Separation ◽  
Magnetic Dipole ◽  
Magnetic Force ◽  
Energy Harvester ◽  
Separation Distance ◽  
Force Model ◽  
Point Dipole ◽  
Transition Mechanism ◽  
Piezoelectric Energy

Nonlinear tri-stable piezoelectric energy harvesters with magnetic field coupling have attracted many researchers’ interest in ambient vibration energy harvesting and conversion. In such a tri-stable piezoelectric energy harvester, the nonlinear magnetic force generated by the external magnetic field is mainly calculated by the equivalent magnetic dipole method. However, this method will give highly erroneous results when the magnetic separation distance is small. This study presents a modified magnetic force model to precisely calculate the nonlinear magnetic force exerted on the tip of the cantilever beam. Unlike the equivalent magnetic dipole method regarding the magnet as a point dipole at its body center, this model only considers the surface magnetization current of the left and right surfaces of the magnets and replaced them by the one of the center point dipoles on these associated surfaces. With this model, the nonlinear magnetic force, the potential energy, and the transition mechanism of the tri-stable piezoelectric energy harvester are numerically investigated. Experimental validations are consequently performed to testify the numerical results. Compared with the equivalent magnetic dipole method, the modified magnetic force model has a much higher accuracy to be more applicable for different magnetic separation distances, especially when the magnetic separation distance is small.

Radio Measurements of Coronal Magnetic Fields

1994 ◽  
Vol 144 ◽  
pp. 21-28 ◽  
Author(s):  
G. B. Gelfreikh
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Transverse Magnetic ◽  
Radio Sources ◽  
Radio Waves ◽  
Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

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