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• The nonlinear vibro-acoustic problem of a buckled beam is studied. • A finite element method in an arbitrary Lagrangian-eulerian framework is adopted. • Effects of acoustic pressure on beam vibration are discussed. • Sound radiation efficiencies of quadrupole and dipole directivity patterns are much different. • Internal resonance can be used to adjust acoustic directivity patterns. Although the nonlinear vibration of buckled beam has been thoroughly studied, its acoustic radiation does not get much attention. This paper deals with the nonlinear vibro-acoustic problem of an internally resonant buckled beam immersed in an infinite fluid. A finite element method based on an arbitrary Lagrangian-Eulerian framework is adopted to analyze the nonlinear interaction between the large-deformed buckled beam and the finite-amplitude acoustic waves in the fluid. The effects of acoustic pressure excitation, external harmonic excitation, and internal resonance on the vibro-acoustic responses of the buckled beam are discussed in the first and second primary resonances. It is found that the amplitude of the acoustic pressure can be comparable to the amplitude of the external harmonic force. This leads to an increase in the critical harmonic excitation amplitude for the occurrence of quasi-periodic responses and an increase in the second mode frequency component of quasi-periodic responses compared to the case neglecting the acoustic pressure excitation on the beam. Saturation phenomena are discovered in the second mode frequency components of beam displacement and acoustic pressure. Due to the 2:1 internal resonance, different time-frequency characteristics, quadrupole acoustic directivity patterns with low radiation efficiency, and dipole acoustic directivity patterns with high radiation efficiency can be observed at different harmonic excitation amplitudes and frequencies. Understanding these phenomena will help design loudspeakers and recognize sound sources. [Display omitted] [ABSTRACT FROM AUTHOR]

• A hybrid multi-scale/arbitrary Lagrangian-Eulerian finite element method is proposed. • The novel method is used for predicting nonlinear structural-acoustic responses. • The novel method offers valuable insights into structural-acoustic interaction mechanisms. This paper introduces a novel hybrid multi-scale/arbitrary Lagrangian-Eulerian finite element method (HMS/ALE-FEM) for addressing the nonlinear vibro-acoustic problem of a large-deformed beam in an infinite fluid. In the HMS/ALE-FEM, the vibrational response of the beam is tackled through modal superposition and a temporal multi-scale approach, while the acoustic wave emitted from the beam is addressed using the arbitrary Lagrangian-Eulerian finite element method (ALE-FEM). An alternating frequency/time domain technique is employed to handle the displacement and velocity of the moving mesh and the acoustic pressure on the beam surface. To validate the HMS/ALE-FEM, it is compared against the finite element method for beam response and the ALE-FEM for acoustic response, serving as a reference method. Taking the nonlinear vibro-acoustic problem of a buckled beam with 2:1 internal resonance as an example, the results of the HMS/ALE-FEM are compared with those of the reference method. The results show that the HMS/ALE-FEM is in good agreement with the reference method under different harmonic excitation amplitudes and frequencies. Due to the 2:1 internal resonance, double modes can be generated, and the second mode amplitudes of both beam displacement and acoustic pressure remain constant as the excitation amplitude varies. Notably, the HMS/ALE-FEM provides direct access to mode amplitude and phase information for beam displacement and acoustic pressure on the beam surface, offering valuable insights into fluid-structure interaction mechanisms in both single- and double-mode scenarios. [ABSTRACT FROM AUTHOR]

• A tunable sound absorber is proposed to dissipate energy of different intensities. • The neck and cavity are synchronously controlled and simultaneous tuning. • Relations between geometric parameters and impedance are established. • Energy dissipation mechanism is revealed under different sound excitations. • Absorption states and bandwidth are provided in the complex frequency plane. Noise reduction problem has been studied for decades with various novel sound absorbers proposed. Most existing absorbers are designed with fixed parameters, which cannot preserve a high absorption coefficient for acoustic waves with different sound pressure levels. This work designs a tunable sound absorber with a synchronously controlled neck and cavity to accommodate acoustic waves with different intensities. A nonlinear impedance model of the acoustic absorber based on an equivalent fluid method is established to quantify the relationship between the geometrical parameters, the levels of incident sound pressures, and the impedance of the absorber. Experiments on sound absorption performance are carried out to confirm the design and theoretical analysis of the absorber. The results show that the proposed absorber can maintain perfect sound absorption at designed frequencies by enlarging the cavity depth when the intensity of the acoustic wave increases. The sound reflection coefficient of the absorber is analyzed in a complex frequency plane. It is found that the sound absorption bandwidth of the absorber can be broadened with an increase in the sound excitation intensity as a larger cavity depth improves the upper bound of the sound absorption bandwidth. Physical insights into the energy dissipation mechanism of the absorber subject to different levels of sound excitation are provided. This work establishes a new approach to realizing perfect noise suppression performance of the absorber under different sound pressure levels without remanufacturing. [ABSTRACT FROM AUTHOR]

This paper presents a semi-analytical method for the vibro-acoustic analysis of a functionally graded shell of revolution immersed in an infinite light or heavy fluid. The structural model of the shell is formulated on the basis of a modified variational method combined with a multi-segment technique, whereas a spectral Kirchhoff–Helmholtz integral formulation is employed to model the exterior fluid field. The material properties of the shell are estimated by using the Voigt׳s rule of mixture and the Mori–Tanaka׳s homogenization scheme. Displacement and sound pressure variables of each segment are expanded in the form of a mixed series using Fourier series and Chebyshev orthogonal polynomials. A set of collocation nodes distributed over the roots of Chebyshev polynomials are employed to establish the algebraic system of the acoustic integral equations, and the non-uniqueness solution is eliminated using a combined Helmholtz integral equation formulation. Loosely and strongly coupled schemes are implemented for the structure-acoustic interaction problem of a functionally graded shell immersed in a light and heavy fluid, respectively. The present method provides a flexible way to account for the individual contributions of circumferential wave modes to the vibration and acoustic responses of functionally graded shells of revolution in an analytical manner. Numerical tests are presented for sound radiation problems of spherical, cylindrical, conical and coupled shells. The individual contributions of the circumferential modes to the radiated sound pressure and sound power of functionally graded shells are observed. Effects of the material profile on the sound radiation of the shells are also investigated. [ABSTRACT FROM AUTHOR]

This paper is focused on the nonlinear aerothermoelastic analysis of composite laminated panels having non-smooth frictional boundaries and simultaneously subject to combined supersonic aerodynamic, thermal and random acoustic loads. The Reddy's third-order shear deformation plate theory with zig-zag effects is employed to formulate the structural model of the panels. The von Karman strain relationships are considered in order to take into account the geometrical nonlinearities of the panels. The aerodynamic loads and the random acoustic loads acting on the panel are characterized by the quasi-steady first-order piston theory and the Gaussian band-limited white noise, respectively. A four-node finite element is developed to establish the aerothermoelastic models of the panels, and the non-smooth frictional boundaries of the panels are represented by a number of macro-slip friction models. The effects of the aerodynamic forces, acoustic loads, thermal forces and the spatial location of the frictional boundaries on the nonlinear aerothermoelastic responses (including the stable limit-cycle oscillations, chaotic and random vibration responses) of composite laminated panels are examined. The effects of non-uniform distribution of the temperature on the aerothermoelastic behaviors of composite laminated panels are discussed. • Numerical model of composite panels with friction boundaries in multi-fields is established.The numerical model of composite panel with friction boundaries in multi-fields is established. • Physical insight into nonlinear dynamic responses of composite panels in multi-fields is provided. • Effects of normal loads and friction coefficients of boundaries on flutter of composite panels are analyzed. • Effects of non-uniform distributed temperature on flutter of composite panels are discussed. [ABSTRACT FROM AUTHOR]

• An energy approach is proposed for vibration of fluid-filled FGP cylindrical shells under arbitrary boundary conditions. • Domain participating techniques for structural and 3D fluid domains are proposed, naturally reinforcing interface constrains. • Various porosities of the shell and fluid-structure interactions are considered. • Effects of material properties and boundary conditions on vibration behaviors of FGP shells are presented. • Added mass factor are introduced and effects of material properties on fluid-structure coupling are revealed. In this paper, a novel energy approach is proposed for fully coupled fluid-structure problems of functionally graded porous (FGP) fluid-filled cylindrical shells under arbitrary boundary conditions. Kinds of continuous FG materials are considered including various patterns in which the voids distributed. A modified variational principle is developed in fluid domain as well as in structural domain, naturally reinforcing the restrains on the boundaries and interfaces between adjacent subdomains. Energy functions in structural and fluid domain are deduced based on the first-order shear deformable shell theory (FSDT) and Helmholtz equation, respectively. The fluid-structure interactions are successfully introduced with the work done by the sound pressure and displacement continuous conditions at fluid-structural interface. A semi-analytical solution is obtained by expanding the displacement and sound pressure components analytically in the circumferential direction and numerically in the axial direction. Good convergence, high accuracy, superior efficiency and flexibility in using admissible functions are demonstrated by comparing reasonably many proposed results with those in literatures or obtained by FEM/BEM. Numerous examples are developed to examine the effects of material properties and boundary conditions on free vibration of FGP cylindrical shells with and without water. With added mass factor introduced, the influences of the key parameters on the fluid-structure coupling are also presented. The slight dependences of the added mass factor on material and boundary conditions greatly broaden the applied scope of the numerical results. [ABSTRACT FROM AUTHOR]

• A multilayer structure aiming for high-intensity sound absorption is designed. • Equivalent fluid model is established to predict the sound absorption coefficient. • The designed absorption layers generate micro-vortices and dissipate extra energy under high sound excitations. • Absorption bandwidth of the structure is broadened by grouping more units. • Sound pressure inside the fairing is reduced under high sound environment by using proposed absorbers. Although small-amplitude sound absorption problems have been comprehensively studied over the past decades, the high-intensity sound absorption problem in the low-frequency range remains unresolved. This paper is concerned with the design of a multilayer structure consisting of a main pore and hierarchical absorption layers to realize perfect absorption of high-intensity sound energy in the low-frequency range. The multilayer structure has enhanced energy dissipation ability in the high-intensity noise excitation environment due to vortex shedding in the sub-slits of the structure. An analytical model based on the equivalent fluid method is established for computing the nonlinear sound absorption coefficient of the structure. Effects of geometrical parameters on the sound absorption coefficient of the multilayer structure are investigated. It is found that under high-intensity sound excitation (e.g., 140 dB), the resistance of the multilayer structure grows along with the sound amplitude and renders a higher absorption coefficient, leading to great sound energy attenuation for high-intensity acoustic waves. The effective sound absorption coefficient of the designed structure is also studied by experiments based on an impedance tube. Noise reduction of a scaled-down payload fairing equipped with multilayer structures is investigated by experiments in a high-intensity sound pressure reverberation chamber in order to confirm the great noise control performance of the proposed structure. The results show that the sound pressure levels inside the fairing can be significantly suppressed by the multilayer structure in broadband, and the maximum reduction of the average sound pressure level is more than 17.5 dB. [Display omitted] [ABSTRACT FROM AUTHOR]