Wave Propagation in an Elastic Beam or Plate on an Elastic Foundation

1962 ◽  
Vol 29 (3) ◽  
pp. 459-464 ◽  
Author(s):  
J. R. Lloyd ◽  
Julius Miklowitz
Keyword(s):  
Wave Propagation ◽  
Elastic Foundation ◽  
Elastic Plate ◽  
High Frequency ◽  
Wave Train ◽  
Elastic Beam ◽  
Frequency Spectra ◽  
Short Waves ◽  
Exact Theory ◽  
Good Agreement

Presented is an analysis of wave propagation in an infinite elastic plate or beam on an elastic foundation, based on a comparison of frequency spectra (or wave-train solutions) from the exact equations and existing approximate bending theories. A distinct similarity is found between the spectrum representing the more exact theory of bending and the Rayleigh-Lamb spectrum for symmetric waves in a free elastic plate, including the existence of complex branches. Good agreement between the approximate theories and the exact equations is found for soft foundations under the usual restrictions on high-frequency, short waves.

scholarly journals Novel Simulation Technique of Electromagnetic Wave Propagation in the Ultra High Frequency Range within Power Transformers

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4236 ◽  
Author(s):  
Takahiro Umemoto ◽  
Stefan Tenbohlen
Keyword(s):  
Wave Propagation ◽  
High Frequency ◽  
External Noise ◽  
Detection Sensitivity ◽  
Power Transformers ◽  
Optimal Placement ◽  
Ultra High Frequency ◽  
The Time Domain ◽  
Attenuation Characteristics ◽  
Good Agreement

Diagnoses of power transformers by partial discharge (PD) measurement are effective to prevent dielectric failures of the apparatus. Ultra-high frequency (UHF) method has recently received attention due to its various advantages, such as the robustness against external noise and the capability of PD localization. However, electromagnetic (EM) waves radiated from PD tend to suffer attenuation before arriving at UHF sensors, because active part of the transformer disturbs the EM wave propagation. In some cases, that results in poor detection sensitivity. To understand propagation and attenuation characteristics of EM waves and to evaluate the detection sensitivity quantitatively, a computational approach to simulate the EM wave propagation is important. Although many previous researches have dealt with EM wave simulation for transformers, validations of those simulations by comparing with the experimental ones have seldom been reported. In this paper, cumulative energies, signal amplitudes and propagation times of EM waves were measured using a 630 kVA transformer. EM wave propagation was computed using the time-domain finite integration technique and the results were compared with the experimentally obtained ones. These simulation results showed good agreement with the experimental ones. The results can serve as guidelines to improve the efficiency of UHF PD detection and offer the possibility to achieve optimal placement of UHF sensors in power transformers.

Bending Solid Elastic Waves with Arbitrary Angles by Bricks

2012 ◽  
Vol 161 ◽  
pp. 26-29 ◽  
Author(s):  
Jin Hu ◽  
Xiang Yang Lu
Keyword(s):  
Wave Propagation ◽  
Numerical Simulations ◽  
Elastic Waves ◽  
High Frequency ◽  
Elastic Beam ◽  
Transformation Method ◽  
Isotropic Materials ◽  
Engineering Practices

Transformation method provides an efficient way to control wave propagation by materials. Recently, this method has been extended to control elastic waves in solids in case of high frequency or small material gradient. An important device in practice, elastodynamic beam bender with isotropic materials, can be designed by this method. In this paper, we will explore some characteristics of the isotropic elastodynamic beam bender and show that it can be used as bricks to guide the solid elastic beam to arbitrary angles, providing more flexibility in engineering practices. Examples are conceived and validated by numerical simulations.

On the Vibration of an Elastic Plate on an Elastic Foundation

1967 ◽  
Vol 42 (5) ◽  
pp. 1202-1202
Author(s):  
David H. Y. Yen ◽  
S. C. Tang
Keyword(s):  
Elastic Foundation ◽  
Elastic Plate

Wave Propagation in a Micropolar Elastic Plate with Voids

2005 ◽  
Vol 11 (6) ◽  
pp. 849-863 ◽  
Author(s):  
S. K. Tomar
Keyword(s):  
Wave Propagation ◽  
Attenuation Coefficient ◽  
Elastic Material ◽  
Elastic Plate ◽  
Lamb Wave ◽  
Specific Model ◽  
Present Formulation ◽  
Numerical Computations ◽  
Lamb Wave Propagation ◽  
Symmetric And Antisymmetric Modes

Frequency equations are obtained for Rayleigh–Lamb wave propagation in a plate of micropolar elastic material with voids. The thickness of the plate is taken to be finite and the faces of the plate are assumed to be free from stresses. The frequency equations are obtained corresponding to symmetric and antisymmetric modes of vibrations of the plate, and some limiting cases of these equations are discussed. Numerical computations are made for a specific model to solve the frequency equations for symmetric and antisymmetric modes of propagation. It is found that both modes of vibrations are dispersive and the presence of voids has a negligible effect on these dispersion curves. However, the attenuation coefficient is found to be influenced by the presence of voids. The results of some earlier works are also deduced from the present formulation.

Hypersonic Velocity, Absorption and Relaxation in Molten CSNO3

1977 ◽  
Vol 32 (1) ◽  
pp. 57-60 ◽  
Author(s):  
H. E. Gunilla Knape ◽  
Lena M. Torell
Keyword(s):  
Relaxation Time ◽  
High Frequency ◽  
Viscosity Coefficient ◽  
Sound Waves ◽  
Frequency Range ◽  
Ultrasonic Velocities ◽  
Hypersonic Velocity ◽  
Frequency Shifts ◽  
Bulk Viscosity Coefficient ◽  
Good Agreement

Abstract Brillouin spectra of molten CSNO3 were investigated for scattering angles between 40 and 140° and in a temperature interval of 420-520 °C. An Ar+ singlemode laser was used for excitation and the total instrumental width was ~265 MHz. The measured frequency shifts and linewidths of the Brillouin components were used to determine velocities and attenuations of thermal sound waves in the frequency range 2.3-7.0 GHz. A dispersion of 4-5% was found between the present hyper­ sonic velocities and reported ultrasonic velocities. A considerable decrease in attenuation with frequency was observed in the investigated frequency range, with the value at high frequency ap­ proaching the classical attenuation. The results are in good agreement with Mountain's theory of a single relaxation time. The relaxation time of the bulk viscosity coefficient was calculated to 1.2×10-10S.

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