Российский фонд
фундаментальных
исследований

Физический факультет
МГУ им. М.В.Ломоносова
 

D

Dai Yuxiang

 

Dai Yuxiang, Yan Shouguo, Zhang Bixing «Acoustic Field Excited by Single Force with Arbitrary Direction in Semi-Infinite Elastic Space» Акустический журнал, 65, № 3, с. pp. 235-245 (2019)

In this paper, the acoustic field excited by a single force with arbitrary direction in a semi-infinite elastic space is studied and its mathematical expressions are obtained. It shows that there are many complex behaviors when the elastic wave reaches the free boundary. The numerical simulation shows that there are several kinds of waves in the semi-infinite elastic space: direct P wave, direct SV wave, SP wave propagating along the free surface which can generate Head wave and Rayleigh wave. The forming mechanism of the SP wave and Rayleigh wave is specially studied. The waveforms at the observation point on the free surface of the semi-infinite space contain only direct P wave and direct SV wave when the SV wave incident angle is within the critical reflection angle. However, if the incident angle from the source to the observation point is exceeding to the critical reflection angle, not only direct P and direct SV wave but also the SP wave and Rayleigh wave are all be generated. It is focused on the relationships of the direction of single force to the excitation intensity of each wave. The relationship of each wave packet to the single force and observation direction is obtained and analyzed.

Акустический журнал, 65, № 3, с. pp. 235-245 (2019) | Рубрика: 04.05

Dai Yuyu

 

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

Deldar H.

 

Deldar H., Bidokhti A.A., Chegini V. «An Investigation of the Effects of Internal Waves on Sound Propagation in a Stratified Medium with a Sloping Bed» Акустический журнал, 64, № 1, с. pp. 58-63 (2018)

Internal waves usually cause temporal and spatial changes of density and consequently affect the acoustic wave propagation in the ocean. The purpose of this study is a laboratory investigation of the effects of internal waves generated by oscillation of a cylinder in a large stratified glass tank with a sloping bed on the sound waves propagation. Results showed that sound waves are affected by internal waves that depend on the slope angle to the direction of internal wave propagation angle ratio. When the ratio is subcritical or supercritical, the acoustic signal is much reduced as compared to the case with no sloped bottom. This can be explained in terms of the internal waves energy reaching the sloped bed and their reflections.

Акустический журнал, 64, № 1, с. pp. 58-63 (2018) | Рубрика: 07.03

Dervisoglu Ahmet

 

Sahin Timur, Dervisoglu Ahmet «High resolution optical spectroscopy of a B-type abundance standard candidate in Ori OB1 – HD 35039» Письма в Астрономический журнал: Астрономия и космическая физика, 45, № 8, с. 585 (2019)

We present LTE analysis of high resolution optical spectra for the B-type abundance standard candidate HD 35039 (HR 1765, 22 Ori) with an ambigous binary nature. The spectra were obtained with the 3.9-m Anglo-Australian Telescope (AAT) and the UCLES spectrograph.

Письма в Астрономический журнал: Астрономия и космическая физика, 45, № 8, с. 585 (2019) | Рубрика: 18

Ding S.S.

 

Ding S.S., Jin S.J., Luo Z.B., Chen J., Lin L. «Researches on the ultrasonic scattering attenuation of carbon fibre reinforced plastics with 2D real morphology void model» Акустический журнал, 63, № 4, с. pp. 490-495 (2017)

In order to investigate the ultrasonic propagation in carbon fibre reinforced plastics with complex void morphology, the effective mathematical model needs to be established. The current models are oversimplified on void morphology, leading to the significant inconsistency of theoretical calculation with experimental results. In view of the problem, a real morphology void model (RMVM) was established with the idea of image-based modeling. The void morphology was extracted by digital image processing technology, and the material properties were assigned subsequently. As a result of the complex and random void morphology in RMVMs, a non-unique corresponding relationship was verified between porosity P and ultrasonic attenuation coefficient α. In the scatterplot of simulation, about 66 percent of points were plotted within the ±10% error band of fitting line, while almost all the data located at the ±20% error zone. The simulation results showed good consistency with experiments, and it proved the validity of RMVM. The investigation provides a novel model to explore the ultrasonic scattering mechanism for the composite materials containing random voids.

Акустический журнал, 63, № 4, с. pp. 490-495 (2017) | Рубрика: 06.02

Dou Yihua

 

Li Suobin, Dou Yihua, Chen Tianning, Wan Zhiguo, Ju Luyan, Zhang Fan, Cui Xiao Xiao «Forming Low-Frequency Complete Vibration Bandgaps in a thin Nonmetallic Elastic Metamaterial Plate» Акустический журнал, 65, № 3, с. pp. 322-333 (2019)

Low-frequency vibration-bandgaps in elastic metamaterials open new possibilities to minimize low-frequency vibration and noise. Unfortunately, fabricating a complete vibration bandgap for low frequencies still represents a challenging engineering task. In this paper, a new type of a low-frequency complete vibration bandgap in a thin non-metal elastic metamaterial plate is introduced and investigated numerically. The proposed elastic metamaterial plate consists of decoupling-resonators, which are deposited on a 2D, locally resonant phononic-crystal plate, made of an array of rubber fillers, which are embedded in a nonmetallic plate. The dispersion relationship, the power-transmission spectrum, and the displacement fields for the eigenmode are calculated using the finite element method. It is shown that coupling between the local resonance mode of the decoupling-resonators and the Lamb-wave mode of the epoxy plate, consistent with the modal superposition principle, is responsible for the formation of vibration bandgaps. Moreover, the equivalent spring-mass system for the coupling-resonators can be decoupled by introducing a rubber filler. In addition, both longitudinal and the transverse elastic wave bandgaps can be tuned to the same low-frequency range. As a result, a novel kind of low-frequency complete vibration bandgap, which can damp a low-frequency elastic wave, is produced. Furthermore, the effects of the decoupling-resonators on the vibration bandgap are investigated. It is now possible that an elastic metamaterial plate can be dampen with complete low-frequency vibration bandgaps, which can potentially be used for commercial noise and vibration reduction.

Акустический журнал, 65, № 3, с. pp. 322-333 (2019) | Рубрика: 06.15

Dunai L.

 

Dunai L., Lengua I., Iglesias M., Peris-Fajarnés G. «Buffeting-Noise Evaluation in Passenger Vehicle BMV 530d» Акустический журнал, 65, № 5, с. pp. 578-582 (2019)

In this paper we exhibit the results and evaluation of the buffeting-noise effect in a BMW 530d model vehicle. The buffeting noise was studied in real measurement conditions in an outdoors highway at different speeds. We evaluate different listening positions inside the vehicle to demonstrate that the buffeting-noise effect is independent from the listener position.

Акустический журнал, 65, № 5, с. pp. 578-582 (2019) | Рубрика: 10.06