Российский фонд
фундаментальных
исследований

Физический факультет
МГУ им. М.В.Ломоносова
 

F

Fan Jun

 

Zhou Fulin, Wang Bin, Fan Jun, Peng Zilong «Theoretical and Numerical Studies on in vacuo Structural Admittance of an Infinite, Coated Cylindrical Shell» Акустический журнал, 65, № 1, с. pp. 14-22 (2019)

Studying the interaction of sound with a coated cylindrical shell immersed in water is essential for improving existing underwater target detection and classification algorithms. According to the impedance theory of sound scattering, in vacuo structural admittance describes the relationship between the sonar-induced forces and the resulting vibration on the surface, which can be used to solve the problem of the acoustic scattering and radiation. In this work, we investigate numerically and theoretically the structural admittance of a coated cylindrical shell. Analytical expressions of the structural admittance are derived for different external forces: a plane acoustic wave, a normal point force, and a random noise field. The structural admittance is also numerically evaluated. The results show that the structural admittance is independent of exterior medium and fluid loading. According to the impedance theory of sound scattering, the scattered field of a coated cylindrical shell is calculated by combining the structural-, acoustic-, and internal-admittance matrices. Because of the non-local property of structural surface admittance, we build an algebraic model of a coated object by nonlinear curve fitting and study a local approximation of the structural admittance. We also find that simplifying the large matrices is useful for research on structural vibrations. Thus, this work presents a systematic study of the acoustic scattering characteristics of structural admittance of an infinite, coated cylindrical shell.

Акустический журнал, 65, № 1, с. pp. 14-22 (2019) | Рубрика: 07.11

Tong Yunzhe  Wei Wang, Fan Jun, Wang Bin «Acoustic Scattering from a Cylindrical Shell with Double Internal Rigid Plates» Акустический журнал, 65, № 1, с. pp. 7-13 (2019)

The acoustic scattering from an infinite cylindrical shell with double internal rigid plates at normal incidence is studied by theoretical and experimental approaches. The two rigid plates are attached to the shell along lines parallel to the shell axis symmetrically. The dominant feature of frequency-angle spectra is the interference fringes caused by the reflection waves of attachments in the illuminated region and specular reflection. For a cylindrical shell with double internal plates, there may be several attachments in the illuminated region simultaneously. There will be bright spots when two interference fringes caused by two attachments in the illuminated region intersect, while only interference fringes can be observed for one attachment in the illuminated region. Theoretical and experimental results show that the number of attachments in illuminated region can significantly affect the scattering characteristics, and it is a prominent feature to identify the location of internal plates.

Акустический журнал, 65, № 1, с. pp. 7-13 (2019) | Рубрика: 04.04

Fan Yanping

 

Fan Yanping, Ji Xiaojun «A Novel Rotation Speed Measurement Method Based on Surface Acoustic Wave» Акустический журнал, 64, № 1, с. pp. 122-128 (2018)

This paper presents an original passive wireless rotation speed measurement method based on surface acoustic wave (SAW) technology. A theoretical analysis was conducted on the principle of SAW rotation speed measurement and a numerical analysis on the SAW response energy pulses with different rotation angles and resonance frequencies was performed. Numerical calculation results showed that when the distance and the effective length of the antenna connected to SAWR vary with the rotation angle, the energy of acquired SAW response varies periodically. The rotation speed was estimated by searching the crossing points of the SAW response energy pulses and its mean value line. The SAW rotation speed measurement system was set up and the high performance SAW resonators were fabricated on a quartz substrate. The proposed measurement system was tested with a maximum error of 0.6 rpm, indicating that the system is capable of measuring rotation speeds from 10 to 100 rpm. Experimental results verified the validity and feasibility of presented rotation speed measurement method.

Акустический журнал, 64, № 1, с. pp. 122-128 (2018) | Рубрика: 06.13

Fu Lin

 

Wu Delin, Dai Yuyu, Chen Hao, Zhou Yinqiu, Fu Lin, Wang Xiuming «Mode analysis of trilaminar bender bar transducers using an approximation method» Акустический журнал, 63, № 5, с. pp. 617-624 (2017)

Based on the vibration theory of a thin plate, an analytical treatment of the trilaminar bender bar with piezoelectric elements and inert substrate of various lengths is presented for mode analysis. Resonance frequency and effective electromechanical coupling coefficient are calculated by this method. The impacts of the geometries of the bender bar on the performance of its fundamental and third-order flexural mode are investigated in detail under rigid boundary conditions. It is shown that resonance frequency is extremely sensitive to the thickness of inert substrate. Moreover, the effective electromechanical coupling coefficient has peaks as the length of piezoelectric elements varies. The peaks are achieved when the length of piezoelectric elements equals the length between two nodes having zero strains in the x-direction. The trilaminar bender bar will be effectively excited when the strains on the piezoelectric element are in the same phase, which is important to disclose the vibration mechanisms of this kind of transducer. Also, analytical results are compared with the ones of numerical simulation. The results suggest that effective electromechanical coupling coefficient shares similar patterns with electrical conductance, which can be used to characterize transducer performance to a certain extent. It also demonstrates that the analytical treatment provides an efficient alternative way for optimizing the bender bar transducer design.

Акустический журнал, 63, № 5, с. pp. 617-624 (2017) | Рубрика: 06.14