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.

Gimaltdinov I.K., Kochanova E.Y. «Propagation of Detonation Waves in Bubbly Liquids in Suddenly Widening Channels» Акустический журнал, 65, № 3, с. pp. 246-252 (2019)

The propagation of detonation waves in a channel filled with a bubbly liquid that suddenly widens is investigated. Possible scenarios for the dynamics of detonation waves after their transition to the widening part of the channel are analyzed. The influence of the volume content of a combustible gas and the geometric parameters of the channel on the propagation and breakdown of the detonation wave has been established.

Laidoudi F., Boubenider F., Mebarki M., Medjili F., Bettine F. «Numerical Investigation of Quasi-Lamb Modes in c–Tilted ZnO/SiC Composite Membrane for High Performance Pressure Micro-Sensor» Акустический журнал, 65, № 3, с. pp. 253-262 (2019)

Using the finite element method, we have studied the Lamb modes characteristics propagation in c tilted ZnO/SiC thin film composite membrane. Phase velocity dispersion curves, electromechanical coupling factors and the mass loading effect on the fundamental quasi Lamb modes are theoretically investigated for different rotating angle (0], τ°, 90°), τ being the angle of rotation, and for different h_ZnO/λ values. To develop high performance pressure micro-sensor based on thin film piezoelectric ZnO on amorphous SiC (range 0.1 to 100 Pa) the anti-symmetric fundamental qA0 mode phase shift is studied for pressure sensing.

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.