Vibro-acoustic Analysis Research Articles

Vibro-acoustic characteristics analysis of the rotary composite plate and conical–cylindrical double cavities coupled system

PurposeThe purpose of the study is to obtain and analyze vibro-acoustic characteristics.Design/methodology/approachA unified analysis model for the rotary composite laminated plate and conical–cylindrical double cavities coupled system is established. The related parameters of the unified model are determined by isoparametric transformation. The modified Fourier series are applied to construct the admissible displacement function and the sound pressure tolerance function of the coupled systems. The energy functional of the structure domain and acoustic field domain is established, respectively, and the structure–acoustic coupling potential energy is introduced to obtain the energy functional. Rayleigh–Ritz method was used to solve the energy functional.FindingsThe displacement and sound pressure response of the coupled systems are acquired by introducing the internal point sound source excitation, and the influence of relevant parameters of the coupled systems is researched. Through research, it is found that the impedance wall can reduce the amplitude of the sound pressure response and suppress the resonance of the coupled systems. Besides, the composite laminated plate has a good noise reduction effect.Originality/valueThis study can provide the theoretical guidance for vibration and noise reduction.

The Vibroacoustic Characteristics Analysis of Transformer Core Faults Based on Multi-Physical Field Coupling

Power transformers play an important role in the safe and reliable operation of the whole power grid. Once a fault occurs, it will endanger the normal operation of the transformer, and even result in power grid accidents. Accurate and practical methods of transformer fault monitoring and type identification have attracted extensive attention in the field of electrical engineering. However, it is difficult to obtain a large number of measurement data for different fault types on a large power transformer. The vibroacoustic characteristics of transformer faults have significant asymmetry. For the power transformer in service, it is complex and uneconomic to obtain the vibroacoustic signals under different fault conditions. To handle this problem, this paper proposes simulation methods of several common transformer core faults, based on multi-physical field coupling, and then analyzes the vibroacoustic signals generated by the operating transformer. Finally, it verifies the results of acoustic and vibration signals under several faults, through physical experiments. The results show that the transformer fault simulation method is reasonable and accurate. Furthermore, a change in the transformer core state will cause a change in the transformer vibroacoustic characteristics, and different types of core faults can be distinguished by the analysis of vibroacoustic characteristics.

Vibro-acoustic analysis of double-walled cylindrical shells through a novel semi-analytic method

A novel semi-analytic model is developed for vibro-acoustic analysis of immersed double-walled cylindrical shells coupled by annular plates and annular fluid between two shells. For structural model, it is firstly divided to inner shell, outer shell and annular plates, and the inner and outer shells are further divided to narrow shell segments. By utilizing Flügge shell theory and power series method, all shell segments and annular plates are uniformly analyzed as conical shells, and they are rapidly assembled to the overall structural model via boundary conditions and continuity conditions between segments. For acoustic model, interior annular fluid region and exterior infinite fluid region are separately analyzed via the Helmholtz surface integral equation. Two surface integrals are simplified to two line integrals after expanding surface sound pressure and velocity as Fourier series, so the pressure is further expressed as displacements of all segments. Through adding the pressure to the continuity conditions, the structural model is coupled with acoustic model. High efficiency and accuracy are demonstrated via comparing vibro-acoustic results of present method with ones in the literature or calculated by coupled finite element-boundary element method. Furthermore, effects of annular plates, annular fluid and excitation on vibro-acoustics of double-walled shells are discussed.

The vibro-acoustic analysis of a matching layer attached on a 1–3 piezoelectric composite transducer

The vibro-acoustic analysis of a matching layer attached on a 1–3 piezoelectric composite transducer

A semi-analytic model for vibro-acoustic analysis of functionally graded shells of revolution

A semi-analytic model with wider applications is developed for vibro-acoustics of submerged functionally graded material (FGM) shells of revolution, and independent or coupled FGM shells are specific cases. For structural model, the shell is divided to many narrow segments treated as conical shells. Materials vary continuously in thickness direction according to the four-parameter power-law distributions about volume fractions of two constituents. Based on the first-order shear deformation theory (FSDT), differential equations are solved via expanding displacements as power series and Fourier series in meridional and circumferential directions, respectively. Continuity and boundary conditions are assembled to vibration governing equation. For acoustic model, Helmholtz integral equation is simplified to one line integral after expanding velocity and acoustic pressure as Fourier series in circumferential direction, and the pressure is further expressed as displacements of the shell. Then, structural and acoustic models are coupled as adding the acoustic pressure to continuity conditions. Through comparing results of developed model with the ones of literature and coupled finite element–boundary element method for some FGM shells, rapid convergence and high accuracy are demonstrated. Furthermore, discrepancies between vibro-acoustic responses of FGM, homogeneous and layered shells are slight, and effects of heavy fluid become more obvious as the volume fraction of the material with large stiffness decreases.

Диагностирование газораспределительного механизма на основе контроля виброколебаний его элементов

The operability and efficiency of the engines significantly depend on the periodic diagnostics of their technical condition. Currently, vibration-based damage detection (measurement of vibration characteristics of structures and mechanisms) is a promising area of research activity. The features of monitoring and diagnostics of internal combustion engines using vibroacoustic analysis are considered. In the article a method has been developed for determining the main malfunctions of the gas distribution mechanism (tightness of the valve-seat coupling, thermal gap in the valve actuator, valve opening and closing phases), consisting in measuring and analyzing vibroacoustic pulses caused by the operation of individual engine elements. The maximum amplitude (peak) and the moment of occurrence of vibration pulses are used as signal parameters. A vibration pulse from the impact of the piston on the elastic tip placed in the combustion chamber is taken as the reference signal of the TDC of the piston of the cylinder under study. The speed of rotation of the crankshaft up to 600 min-1 (does not exceed the frequency of scrolling by the starter) does not lead to the appearance of dangerous stresses in any of the elements of the engine and the device. At the same time, the tip made of Bflex plastic, as the most malleable element, can be repeatedly used. To ensure a trouble-free diagnostic process, calculations were carried out using the software – Solid Works Simulation and the finite element method (FEM) built into it. To calculate the stresses, the solver finds the displacements at each node, and then calculates the deformations and the final stress. As a result of the study, the proposed diagnostic method allows to achieve an accuracy of up to 96 %

FE analysis of urethane foam using X-ray CT data

Polyurethane foam for sound absorption is used to reduce noise in automobiles, houses, home appliances, etc. The Biot-Allard model is generally used to calculate the sound absorption characteristics of urethane foam, which is used as a sound absorbing and insulating material for automobiles. Biot parameters used in calculations are measured with a dedicated measuring instrument, but it is difficult to connect them to actual material development. In order to clarify the sound absorption mechanism, 3D data of the urethane skeleton was obtained using an X-ray CT device. The FE model of the skeleton and surrounding air was created from the 3D data of the skeleton, and vibroacoustic analysis was performed. We report the results of comparison between the results of normal incidence sound absorption coefficient measurement using acoustic tubes and the calculation results of the FE model, and the results of various parameter studies.

Vibro-acoustic analysis of metal and non-metal gears used in a powertrain

Gearbox (Powertrain) is one of the prime sources of noise in any Automobile. The noise can be broadly divided into two types. First is the one that occurs due to meshing of gears and second due to the inefficient design of the gearbox casing. This paper focuses majorly on the former problem and compares the results for analytical methods of vibration measurement. Modal analysis is carried out on a 5-speed synchromesh manual gearbox using ANSYS to find out modes of vibrations. The amplitude of noise is then calculated for one specific modal frequency (the one showing maximum deflection) using Acoustics module of COMSOL Multiphysics Software for 4 different gear materials.

Experimentally validated vibro-acoustic modeling of 3D bio-printed grafts for potential use in human tympanic membrane regeneration

Three-dimensional (3D) bioprinting is a pioneering field of tissue engineering obtaining a special role in most medical engineering fields. Otology is a medicine branch that needs bioprinting technology to receive aids for the reconstruction of aesthetic necessities of the ear and treating hearing loss diseases due to several pathological reasons such as tympanic membrane (TM) perforation. In this work, computational dynamic simulations of 3D printed TM grafts are presented. The main purpose of numerical modeling of these experimentally validated composite scaffolds is to demonstrate the worth of simulation in shortening the design time and decreasing testing costs of biomedical engineering projects. The simulated 3D printed TM grafts were fabricated in two main architectural categories using three different polymeric materials of polydimethylsiloxanes (PDMS), flex polylactic acid (PLA), and polycaprolactone (PCL) with uniform infilling of fibrincollagen composite hydrogels. As a numerical and dynamic validation study, firstly, a finite element (FE) simulation of the artificial TM grafts is carried out for a vibro-acoustic analysis by the COMSOL Multiphysics software package. Then a comparative study of results obtained from the dynamic modeling is performed with a set of existing data taken from experimental validation test results from digital optoelectronic holography (DOEH) and laser Doppler vibrometry (LDV). Observations show a good correlation between the acoustic behaviors of in vitro tested 3D printed TM grafts and computational models in both frequency domain motion and normalized velocity patterns. Satisfying correlation between acoustic properties of simulated TM grafts and experimental test results shows potential applications of printed TM grafts in tympanoplasty.

Coupled vibro-acoustic analysis of submerged double cylindrical shells with stringers, rings, and annular plates in a symplectic duality system

A wave propagation analysis model of a submerged double cylindrical shell with stringers, rings, and annular plates is established in a symplectic duality system, accounting for acoustic-structure coupling. First, the vibration problem of the double cylindrical shell with stringers is introduced into the symplectic duality system by the Hamiltonian function. The wave propagation parameters and wave shape matrices with symplectic orthogonal relations are obtained by solving a symplectic eigenvalue problem. Then, according to the wave propagation relations, the wave amplitudes are derived by accounting for unknown forces, moments, and pressures induced by the rings, annular plates, and fluid. Finally, the vibration and acoustic responses are obtained through the wave shape matrices and wave amplitudes. In this study, the wave propagation parameters and wave shape matrices are calculated in the symplectic dual space, and the axial thickness discontinuity induced by the rings and annular plates is addressed through the cutting of the wave propagation path. Consequently, the convergence is not affected by the number of rings and annular plates, and the method achieves higher calculation accuracy and efficiency compared with the modal superposition method based on analytical beam functions. The parameter analysis indicates that proper combinations of the number and thickness of the annular plates can significantly reduce the vibro-acoustic responses for the same total mass of the annular plates, while changing the number of rings and stringers cannot. When the inner and outer cylindrical shells lose the same mass, altering the thickness of the outer shell has a greater impact.

Vibro-Acoustic Energy Transmission Analysis of the Acoustic Cavity with Multiple Partial Partitions

The general dynamic characteristics of the acoustic cavity with multiple partial partitions are presented in this thesis. A theoretical model has been developed for predictions, and several configurations are analyzed. To describe the apertures on the interface of subcavities, the virtual air panel assumption is introduced into the improved Fourier series system. The governing equations of the coupling system are derived by using the energy principle. The results obtained with the proposed model are firstly compared with the numerical calculations based on the finite element method (FEM). Subsequently, a configuration made up from a rigid cavity partitioned by a partial steel panel has been specifically built, and the forced responses of the coupling system have been measured for comparison and model validation. The present results are excellent over most of the studied frequency range. Furthermore, the visualizations of the interior sound intensity field of the acoustic cavity with three partial partitions under different frequencies are researched to illustrate the energy transmission paths and vibro-acoustic coupling mechanism of the complicated system. The obtained results are believed to be helpful in the optimal design of the vibro-acoustic coupling system with optimal sound insulation capacity.

Vibro-Acoustic Formulation of Elastically Restrained Shear Deformable Orthotropic Plates Using a Simple Shear Deformation Theory

A method is presented for vibro-acoustic analysis of elastically restrained orthotropic shear deformable plates subjected to excitation forces at different locations. The vibration of the shear deformable plate is formulated on the basis of the Ritz method and a simple first-order shear deformation theory in which 4 rather than 5 displacement components are used to simulate the deformation of the plate. The accuracy of the modal characteristics (natural frequency and mode shape) of an orthotropic plate predicted using the proposed method is verified by those obtained using other methods. The vibration responses of the plate are used in the first Rayleigh integral to construct the sound pressure level (SPL) curves of the plate subjected to excitation forces at different locations. The suitability of the present method for sound radiation analysis is validated by comparing the SPL curve obtained using the present method with those obtained using the other methods. The effects of different system parameters on the SPL curve of the plate are studied by means of several numerical examples. It has been shown that excitation location has significant effects on the smoothness of the SPL curve.

Sound Enhancement of Orthotropic Sound Radiation Plates Using Line Loads and Considering Resonance Characteristics

A new vibro-acoustic method is presented to analyze the sound radiation behavior of orthotropic panel-form sound radiators using strip-type exciters to exert line loads to the panels for sound radiation. The simple first-order shear deformation theory together with the Ritz method is used to formulate the proposed method that makes the vibro-acoustic analysis of elastically restrained stiffened orthotropic plates more computationally efficient than the methods formulated on the basis of the other shear deformation theories. An elastically restrained orthotropic plate consisting of two parallel strip-type exciters was tested to measure the experimental sound pressure level curve for validating the effectiveness and accuracy of the proposed method. The resonance characteristics (natural frequency and mode shape) detrimental to sound radiation are identified in the vibro-acoustic analysis of the orthotropic plate. For any orthotropic sound radiation plate, based on the detrimental mode shapes, a practical procedure is presented to design the line load locations on the plate to suppress the major sound pressure level dips for enhancing the smoothness of the plate sound pressure level curve. For illustration, the sound radiation enhancement of orthotropic plates with different fiber orientations for aspect ratios equal to 3, 2, and 1 subjected to one or two line loads is conducted using the proposed procedure. The results for the cases with two line loads perpendicular to the fiber direction and located at the nodal lines of the major detrimental mode shape may find applications in designing orthotropic panel-form speakers with relatively smooth sound pressure level curves.

Using fibrincollagen composite hydrogel and silk for bio-inspired design of tympanic membrane grafts: A vibro-acoustic analysis

Tympanic membrane (TM) is vulnerable to a variety of middle ear diseases. In some cases, reconstruction or repair of the TM is essential for recovering the hearing. Although there are many kinds of materials and therapeutics for TM reconstruction, tissue engineering of the TM is still in its initial steps of advancement. Treatment of damaged TM is usually carried out by otology-related techniques such as myringoplasty and tympanoplasty. Most of the novel tympanoplasty methods employ artificial grafts made of biomaterials and polymers for scaffolds. One biomaterial candidate for design and fabrication of synthetic grafts is spider silk, which has excellent mechanical and acoustic characteristics. On the other hand, the structural function of the spider web is also one of the potential inspirations for designing tissue-engineered grafts on micro-scale explorations. In this study, a bio-inspired design and analysis of silky TM grafts are carried out employing finite element modeling and vibro-acoustic investigation. A comparative and statistical analysis is also performed with experimentally validated data to check the suitability of the materials and design. The numerical study shows that the proposed bio-inspired models are appropriate for TM graft design and fabrication. The effects of inspired architecture and materials on obtaining an optimum design for TM grafts are put into evidence via a parametric study, and pertinent conclusions are outlined.

A Compact and Highly Sensitive Voice-Eavesdropping Microresonator

A compact cantilever-based voice-eavesdropping microresonator is proposed. The dynamic vibration of the cantilever-microresonator system induced by an applied acoustic pressure is converted into a modulation of the cavity resonances. Then, the resonance-shift-induced optical transmission change is utilized to detect the applied acoustic signals. The enhancement of both the vibration and optical response makes the proposed system highly sensitive and have better performance than many other optical acoustic sensors. The noise equivalent pressure of the proposed system at 900 Hz is 52 μPa/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> . The system has a favorable broad frequency response range covering 0∼6 kHz. Experimental results prove that the system can acquire and reconstruct a voice signal 7 m away with high sensitivity and reliability, which can meet a variety of needs, such as indoor eavesdropping. Furthermore, the system is easy to fabricate, has low power consumption and is fairly tunable in terms of the frequency response range and sensitivity. This microcavity-based novel acoustic sensor is promising for opening up new possibilities in intrusion detection, voice eavesdropping and many other vibro-acoustic analysis applications.

Vibro-acoustic analysis of combined elliptical–cylindrical–elliptical shells immersed in acoustic medium

The vibro-acoustic behaviors of combined elliptical–cylindrical–elliptical​ shells (CECES) is studied by the spectral-energy boundary element approach. The Jacobian orthogonal polynomials and the variational principles are employed to establish the dynamic model of the CECES. The Kirchhoff–Helmholtz integral equation is used to calculate the exterior sound radiation of the CECES. The Chebyshev polynomials and the Fourier series are adopted to express the acoustic variables along the meridional direction and the circumferential direction of the CECES, respectively. In this case, the two-dimensional Helmholtz integral formulation is simplified to a one-dimensional problem. By using the spectral boundary element and Chebyshev collocation points to discretize the acoustic boundary, the mathematical difficulties of traditional boundary element method which needs physical points to integrate can be overcome. Furthermore, to solve the problem of singularity and frequency non-uniqueness in the acoustic solution, the CHIEF method is used. The full vibro-acoustic coupling model is established by considering the work due to the external field acting on the CECES surface. By comparing to the acoustic responses obtained by the coupled BEM/FEM, the present method is proved to have enough accuracy for predicting the vibro-acoustic behaviors of CECES. Furthermore, study on the influence of the circumferential wave modes, boundary condition and acoustic medium on vibro-acoustic behaviors of the CECES is made by several numerical examples, which contributes to the preliminary design of the CECES.

Acoustic analysis of impact sound on vibrating circular membranes

A finite element method (FEM) - boundary element method (BEM) model is developed to compute the sound generated by of a force acting on a circular membrane (drumhead). A vibro-acoustic analysis that combines modal FEM analysis, a FEM steady state dynamic analysis (SSD), considering harmonic loading and boundary element acoustics, is performed. The drumhead vibrates due to the force impact and the sound is emitted in the air. The vibration of structural response is initially computed, and the obtained results are set to be the boundary conditions of the acoustic analysis in the vibro-acoustic simulation. The radiated sound can be computed at any point of the solution domain. Various materials used by drumhead manufacturers are tested and a parametric analysis focusing on the mesh density of the models is presented. The impact sound and the acoustical characteristics of the simulated test cases are evaluated. The Rayleigh method is also applied to the acoustic simulations and is further compared to the BEM simulation results. The outcomes of this study may be further used as reverse engineering inputs, to machine learning models for the estimation of the physical and mechanical parameters of drumheads from audio signals.

Vibroacoustic analysis of a thin laminated composite plate with surface-boned piezoelectric patches and subjected to general boundary conditions

In this paper, a semi-analytical model is proposed to deal with the vibroacoustic problems of laminated composite plates with surfaced-boned piezoelectric patches and subjected to general boundary condition using the modified Fourier series method. Based on Kirchhoff plate theory, the dynamic equation of the laminated composite plate is derived using Hamilton's principle. In order to satisfy general boundary conditions, the displacement solution of the plate is expressed in the form of two-dimensional Fourier series and serval auxiliary functions. The acoustic response of the laminated composite plate due to a harmonic concentrated force is obtained with the Rayleigh integral. Besides, the mass and stiffness contribution of the piezoelectric patch are taken into consideration in the present study. Through enough convergent studies and comparative studies, the convergence, accuracy and universality of the proposed method are validated. The developed semi-analytical model can be used for efficient and accurate analysis and design of laminated composite plates equipped with shunted piezoelectric patches. Finally, the effects of the resistor and inductor shunt damping circuits on the vibration and acoustic response is discussed.

Comparison of noise generated from simplex and duplex configurations of drum brake using non-linear vibro-acoustic models

The drum brakes used on the rear wheels of automobiles have various configurations. These contribute to the differences in kinematic (geometry) and dynamic (contact, friction) aspects, eventually leading to significantly different vibration and acoustic response. This work attempts to estimate the difference in the vibro-acoustic noise generated by the drum brake's simplex and duplex variants using a combination of non-linear analytical vibration models and a numerical acoustic model. Four degrees-of-freedom lumped parameter models developed for the simplex and the duplex configurations with conformal contact predict the contact and reaction forces during braking. These forces act as the sources for the finite element based acoustic models developed for the two configurations to obtain the sound pressure to force transfer functions. The sound pressure levels are estimated by the product of the predicted forces with the respective transfer functions in the frequency domain. The sound pressure levels of the simplex and duplex drum brakes are quantitatively compared under different braking conditions, and the results are presented. It is expected that this vibro-acoustic analysis will help in designing quieter drum brakes.

Transient Vibroacoustic Analysis of Functionally Graded Plates

Abstract This paper presents the vibroacoustic response of pure functionally graded (FG) plates under transient loading of mechanical nature. The functionally graded plate is modeled using the conventional first-order shear deformation theory (FSDT) to incorporate the effects of transverse shear and rotary inertia. The mid-surface variables are determined using the finite element method. Transient structural response is determined using Newmark Beta time marching scheme and the acoustic pressure in the free field is obtained using the time-domain Rayleigh integral. The effective material properties of the FG plate and the transient response of both the structural and acoustic fields have been computed in matlab. The influence of the volume fraction index, thickness ratio, and boundary conditions of pure FG plate on its transient vibroacoustic response is investigated by a detailed parametric study.