The vibroacoustical characteristics of an annular flow duct system, which consists of two infinite concentric cylindrical elastic thin steel shells (hereafter referred to as a double shell simply) coupled by the entra...The vibroacoustical characteristics of an annular flow duct system, which consists of two infinite concentric cylindrical elastic thin steel shells (hereafter referred to as a double shell simply) coupled by the entrained axial uniform water flow, is investigated. By using a fully coupled model between fluid and shells, the dispersion behaviour is analyzed for the system, vibrating in the n = 0 and n = 1 circumferential modes. The impact of the flow on the dispersion curves is also discussed for the system.展开更多
To take into account the influence of uncetainties on the dynamic response of the vibro-acousitc structure, a hybrid modeling technique combining the finite element method（FE）and the statistic energy analysis（SEA）...To take into account the influence of uncetainties on the dynamic response of the vibro-acousitc structure, a hybrid modeling technique combining the finite element method（FE）and the statistic energy analysis（SEA） is proposed to analyze vibro-acoustics responses with uncertainties at middle frequencies. The mid-frequency dynamic response of the framework-plate structure with uncertainties is studied based on the hybrid FE-SEA method and the Monte Carlo（MC）simulation is performed so as to provide a benchmark comparison with the hybrid method. The energy response of the framework-plate structure matches well with the MC simulation results, which validates the effectiveness of the hybrid FE-SEA method considering both the complexity of the vibro-acoustic structure and the uncertainties in mid-frequency vibro-acousitc analysis. Based on the hybrid method, a vibroacoustic model of a construction machinery cab with random properties is established, and the excitations of the model are measured by experiments. The responses of the sound pressure level of the cab and the vibration power spectrum density of the front windscreen are calculated and compared with those of the experiment. At middle frequencies, the results have a good consistency with the tests and the prediction error is less than 3. 5dB.展开更多
Multisource unstable impulsive excitations, time varying transmission path, concentrated mode, dispersion and reverberation that are important characteristics of reciprocating machines such as diesel engines result in...Multisource unstable impulsive excitations, time varying transmission path, concentrated mode, dispersion and reverberation that are important characteristics of reciprocating machines such as diesel engines result in wide band non stationary vibroacoustic responses which influence the effective extraction of vibroacoustic signatures and become a key factor to limit diesel engines’ vibration diagnosis. In this paper, a serial theoretical deduction on the unstable dynamic properties of diesel engines was made; the mechanism of non stationary vibroacoustic responses was elucidated. Based upon that, the wavelet packet technique was introduced. The reason for the existence of frequency aliasing in the Paley series from wavelet packets’ decomposition was analyzed, and the wavelet packet frequency shifting algorithm was given. Experiments on 190 serial diesel engines verify the given method’s significant validity in vibroacoustic signature extraction and reciprocating machines’ vibration diagnosis.展开更多
Locally resonant metamaterial plates with subwavelength bandgaps can be exploited for the simultaneous control of structural vibrations and acoustic radiation.The present work theoretically investigates the vibroacous...Locally resonant metamaterial plates with subwavelength bandgaps can be exploited for the simultaneous control of structural vibrations and acoustic radiation.The present work theoretically investigates the vibroacoustic characteristics of a metamaterial plate with periodic lateral local resonance.The high accuracy of the presented method is evident from the consistency of the cross mobility of the metamaterial plate calculated with the finite element technique.The modal superposition approach and Rayleigh integral technique are adopted to formulate the mean square velocity and acoustic radiation power in terms of the structural deflection and sound pressure to capture the vibroacoustic coupling characteristics of the metamaterial plate and the surrounding environment.Large vibration suppression and sound reduction with high radiation efficiency can be observed within the frequency ranges of interest.The near-field sound intensity and far-field acoustic pressure distributions inside and outside the bandgaps are plotted and analyzed.The results from this work can be utilized to set design guidelines for metamaterial design to achieve prescribed vibroacoustic characteristics.展开更多
In this paper,we consider the model updating problem of the undamped vibroacoustic system with no spill-over(MUP-UVA),which is to update the original system to a new system such that some“unstable”eigenvalues are re...In this paper,we consider the model updating problem of the undamped vibroacoustic system with no spill-over(MUP-UVA),which is to update the original system to a new system such that some“unstable”eigenvalues are replaced by some newly measured ones.Based on the spectral decomposition of the undamped vibroacoustic system,a necessary and sufficient condition is derived such that the updated system can preserve no spill-over,and a set of parametric solutions of MUP-UVA is characterized.Furthermore,a gradient optimization algorithm for the minimum norm solution of MUP-UVA is proposed and the performance of the algorithm is illustrated by several numerical experiments.展开更多
In this investigation,the analysis of the nonlinear vibroacoustic and sound transmission loss behaviors of plates made of functionally graded material is presented.It is assumed that the properties of the functionally...In this investigation,the analysis of the nonlinear vibroacoustic and sound transmission loss behaviors of plates made of functionally graded material is presented.It is assumed that the properties of the functionally graded plates are in the form of the simple power law scheme and continuous along the thickness,under thermal load and incident oblique plane sound wave as well as the first-order shear deformation theory.For this purpose,first,using Hamilton’s principle,the nonlinear partial differential equations of motion are derived by the displacement field function approach and by considering the nonlinear von K´arm´an strain-displacement relations.To solve the equations,using the Galerkin method,the nonlinear partial differential equations of motion lead to Duffing equation.Then,using the homotopy analysis method,the equation of the transverse movement of the plate is solved semi-analytically to obtain the nonlinear frequencies.Finally,the nonlinear vibration and acoustic response of functionally graded plates are studied by considering the variation of the important parameters such as aspect ratio,dimensionless amplitude,volume fraction power of functionally graded material,external acoustic pressure,incidence and azimuthal angles,temperature changes,phase portrait,sound transmission loss,velocity and average mean square velocity of drive point and sound power level of the functionally graded plate.Results show increasing the incidence angle leads increase in hardening effects and sound transmission loss,but growing the azimuthal angle does not have much effect on the frequency-response and sound transmission loss in the absence of the external mean flow.Also,increasing temperature changes lead to decrease in hardening effects and sound transmission loss.展开更多
Deep-sea submersibles are significant mobile platforms requiring multi-functional capabilities that are strongly determined by the constituent materials.Their cylindrical protective cover can be advanced by designing ...Deep-sea submersibles are significant mobile platforms requiring multi-functional capabilities that are strongly determined by the constituent materials.Their cylindrical protective cover can be advanced by designing their sandwiched cellular materials whose physical properties can be readily parameterized and flexibly tuned.Porous honeycomb materials are capable of possessing tuned positive,negative,or zero Poisson’s ratios(PPR,NPR,and ZPR),which is expected to produce distinct physical performance when utilized as a cellular core of cylindrical shells for the deep-sea submersibles.A novel cylindrical meta-structure sandwiched with the semi-re-entrant ZPR metamaterial has been designed as well as its similarly-shaped sandwich cylindrical shell structures with PPR and NPR honeycombs.The mechanical and vibroacoustic performance of sandwich cylindrical shells with cellular materials featuring a full characteristic range of Poisson’s ratios are then compared systematically to explore their potential for engineering applications on submerged pressure-resistant structures.The respective unit cells are designed to feature an equivalent load-bearing capability.Physical properties of pressure resistance,buckling,and sound insulation are simulated,respectively,and the orders of each property are then generalized by systematic comparison.The results indicate that the PPR honeycomb core takes advantage of higher structural strength and stability while the ZPR one yields better energy absorption and sound insulation behavior.The NPR one yields moderate properties and has the potential for lower circumferential deformation.The work explores the application of cellular materials with varied Poisson’s ratios and provides guidance for the multi-functional design of sandwich cylindrical meta-structures.展开更多
The loading method of the external excitations generated by the equipment directly affects the predicted result of the mechanical noise which should be the same under different excitation forms for the given equipment...The loading method of the external excitations generated by the equipment directly affects the predicted result of the mechanical noise which should be the same under different excitation forms for the given equipment.In this paper,general load criteria are proposed to define forces/moments as the standard form and convert other forms of loads in the low-frequency domain.As the most typical form to charac-terize equipment excitation,acceleration load loading methods for different conditions are investigated.The equivalent formula between ideal accelerations and generalized forces establishes the first load cri-terion.The second load criterion is proposed to address the issue of an average acceleration loading,in which the phase and amplitude distribution are both absent,and cannot apply to the load identification.The upper and lower limits of the mechanical noise can be determined by the vibroacoustic transfer func-tion of the three load models,and the energy-averaged value is used to represent the mechanical noise.Furthermore,the third criterion is used to handle the case where the acceleration load is given by the results of a bench test.According to the equipment source descriptor invariance,the conversion method is achieved between the bench test and the real ship based on the transfer function of a load model,and the mechanical noise is predicted by an equivalent energy method.Finally,a three-parameter method to quantitatively evaluate the well-fitting of experimental and numerical results,and the load criteria are well validated by underwater acoustic experiments of an experimental model.展开更多
In this paper,an asymmetric vibroacoustic system that can passively realize nonreciprocal transmission of acoustic energy is reported.This experimental system consists of a waveguide,a strongly nonlinear membrane,and ...In this paper,an asymmetric vibroacoustic system that can passively realize nonreciprocal transmission of acoustic energy is reported.This experimental system consists of a waveguide,a strongly nonlinear membrane,and three acoustic cavities with different sizes.The theoretical modeling of the system is verified by experiments,and parametric analysis is also carried out.These intensive studies reveal the nonreciprocal transmission of acoustic energy in this prototype system.Under forward excitation,internal resonance between the two nonlinear normal modes of the vibroacoustic system occurs,and acoustic energy is irreversibly transferred from the waveguide to the nonlinear membrane.However,under backward excitation,there is no internal resonance in the system.Energy spectra and wavelet analysis are used to highlight the mechanism of nonreciprocal transfer of acoustic energy.Consequently,nearly unidirectional(preferential)transmission of acoustic energy transfer is shown by this system.The nonreciprocal acoustic energy transfer method illustrated in this paper provides a new way to design the odd acoustic element.展开更多
文摘The vibroacoustical characteristics of an annular flow duct system, which consists of two infinite concentric cylindrical elastic thin steel shells (hereafter referred to as a double shell simply) coupled by the entrained axial uniform water flow, is investigated. By using a fully coupled model between fluid and shells, the dispersion behaviour is analyzed for the system, vibrating in the n = 0 and n = 1 circumferential modes. The impact of the flow on the dispersion curves is also discussed for the system.
基金Science and Technology Support Planning of Jiangsu Province(No.BE2014133)the Open Foundation of Key Laboratory of Underw ater Acoustic Signal Processing(No.UASP1301)the Prospective Joint Research Project of Jiangsu province(No.BY2014127-01)
文摘To take into account the influence of uncetainties on the dynamic response of the vibro-acousitc structure, a hybrid modeling technique combining the finite element method（FE）and the statistic energy analysis（SEA） is proposed to analyze vibro-acoustics responses with uncertainties at middle frequencies. The mid-frequency dynamic response of the framework-plate structure with uncertainties is studied based on the hybrid FE-SEA method and the Monte Carlo（MC）simulation is performed so as to provide a benchmark comparison with the hybrid method. The energy response of the framework-plate structure matches well with the MC simulation results, which validates the effectiveness of the hybrid FE-SEA method considering both the complexity of the vibro-acoustic structure and the uncertainties in mid-frequency vibro-acousitc analysis. Based on the hybrid method, a vibroacoustic model of a construction machinery cab with random properties is established, and the excitations of the model are measured by experiments. The responses of the sound pressure level of the cab and the vibration power spectrum density of the front windscreen are calculated and compared with those of the experiment. At middle frequencies, the results have a good consistency with the tests and the prediction error is less than 3. 5dB.
基金National Natural Science Foundation ofChina (No.5 9775 0 2 4
文摘Multisource unstable impulsive excitations, time varying transmission path, concentrated mode, dispersion and reverberation that are important characteristics of reciprocating machines such as diesel engines result in wide band non stationary vibroacoustic responses which influence the effective extraction of vibroacoustic signatures and become a key factor to limit diesel engines’ vibration diagnosis. In this paper, a serial theoretical deduction on the unstable dynamic properties of diesel engines was made; the mechanism of non stationary vibroacoustic responses was elucidated. Based upon that, the wavelet packet technique was introduced. The reason for the existence of frequency aliasing in the Paley series from wavelet packets’ decomposition was analyzed, and the wavelet packet frequency shifting algorithm was given. Experiments on 190 serial diesel engines verify the given method’s significant validity in vibroacoustic signature extraction and reciprocating machines’ vibration diagnosis.
基金supported by the National Natural Science Foundation of China(No.52001131 and No.52071152).
文摘Locally resonant metamaterial plates with subwavelength bandgaps can be exploited for the simultaneous control of structural vibrations and acoustic radiation.The present work theoretically investigates the vibroacoustic characteristics of a metamaterial plate with periodic lateral local resonance.The high accuracy of the presented method is evident from the consistency of the cross mobility of the metamaterial plate calculated with the finite element technique.The modal superposition approach and Rayleigh integral technique are adopted to formulate the mean square velocity and acoustic radiation power in terms of the structural deflection and sound pressure to capture the vibroacoustic coupling characteristics of the metamaterial plate and the surrounding environment.Large vibration suppression and sound reduction with high radiation efficiency can be observed within the frequency ranges of interest.The near-field sound intensity and far-field acoustic pressure distributions inside and outside the bandgaps are plotted and analyzed.The results from this work can be utilized to set design guidelines for metamaterial design to achieve prescribed vibroacoustic characteristics.
基金supported by the Research Foundation of Education Department of Hunan Province(Grant No.23A0266)Hunan Provincial Natural Science Foundation(Grand No.2025JJ50034)Hunan Provincial Key Laboratory of Mathematical Modeling and Analysis in Engineering(Grant No.2017TP1017).
文摘In this paper,we consider the model updating problem of the undamped vibroacoustic system with no spill-over(MUP-UVA),which is to update the original system to a new system such that some“unstable”eigenvalues are replaced by some newly measured ones.Based on the spectral decomposition of the undamped vibroacoustic system,a necessary and sufficient condition is derived such that the updated system can preserve no spill-over,and a set of parametric solutions of MUP-UVA is characterized.Furthermore,a gradient optimization algorithm for the minimum norm solution of MUP-UVA is proposed and the performance of the algorithm is illustrated by several numerical experiments.
文摘In this investigation,the analysis of the nonlinear vibroacoustic and sound transmission loss behaviors of plates made of functionally graded material is presented.It is assumed that the properties of the functionally graded plates are in the form of the simple power law scheme and continuous along the thickness,under thermal load and incident oblique plane sound wave as well as the first-order shear deformation theory.For this purpose,first,using Hamilton’s principle,the nonlinear partial differential equations of motion are derived by the displacement field function approach and by considering the nonlinear von K´arm´an strain-displacement relations.To solve the equations,using the Galerkin method,the nonlinear partial differential equations of motion lead to Duffing equation.Then,using the homotopy analysis method,the equation of the transverse movement of the plate is solved semi-analytically to obtain the nonlinear frequencies.Finally,the nonlinear vibration and acoustic response of functionally graded plates are studied by considering the variation of the important parameters such as aspect ratio,dimensionless amplitude,volume fraction power of functionally graded material,external acoustic pressure,incidence and azimuthal angles,temperature changes,phase portrait,sound transmission loss,velocity and average mean square velocity of drive point and sound power level of the functionally graded plate.Results show increasing the incidence angle leads increase in hardening effects and sound transmission loss,but growing the azimuthal angle does not have much effect on the frequency-response and sound transmission loss in the absence of the external mean flow.Also,increasing temperature changes lead to decrease in hardening effects and sound transmission loss.
基金support provided by the China Postdoctoral Science Foun-dation(No.2021M692043)Shanghai Postdoctoral Excellence Program(No.2021200)+1 种基金Lingchuang Research Project of China National Nuclear Corporation and the fund of ScienceTechnol-ogy on Reactor System Design Technology Laboratory is gratefully acknowledged.
文摘Deep-sea submersibles are significant mobile platforms requiring multi-functional capabilities that are strongly determined by the constituent materials.Their cylindrical protective cover can be advanced by designing their sandwiched cellular materials whose physical properties can be readily parameterized and flexibly tuned.Porous honeycomb materials are capable of possessing tuned positive,negative,or zero Poisson’s ratios(PPR,NPR,and ZPR),which is expected to produce distinct physical performance when utilized as a cellular core of cylindrical shells for the deep-sea submersibles.A novel cylindrical meta-structure sandwiched with the semi-re-entrant ZPR metamaterial has been designed as well as its similarly-shaped sandwich cylindrical shell structures with PPR and NPR honeycombs.The mechanical and vibroacoustic performance of sandwich cylindrical shells with cellular materials featuring a full characteristic range of Poisson’s ratios are then compared systematically to explore their potential for engineering applications on submerged pressure-resistant structures.The respective unit cells are designed to feature an equivalent load-bearing capability.Physical properties of pressure resistance,buckling,and sound insulation are simulated,respectively,and the orders of each property are then generalized by systematic comparison.The results indicate that the PPR honeycomb core takes advantage of higher structural strength and stability while the ZPR one yields better energy absorption and sound insulation behavior.The NPR one yields moderate properties and has the potential for lower circumferential deformation.The work explores the application of cellular materials with varied Poisson’s ratios and provides guidance for the multi-functional design of sandwich cylindrical meta-structures.
文摘The loading method of the external excitations generated by the equipment directly affects the predicted result of the mechanical noise which should be the same under different excitation forms for the given equipment.In this paper,general load criteria are proposed to define forces/moments as the standard form and convert other forms of loads in the low-frequency domain.As the most typical form to charac-terize equipment excitation,acceleration load loading methods for different conditions are investigated.The equivalent formula between ideal accelerations and generalized forces establishes the first load cri-terion.The second load criterion is proposed to address the issue of an average acceleration loading,in which the phase and amplitude distribution are both absent,and cannot apply to the load identification.The upper and lower limits of the mechanical noise can be determined by the vibroacoustic transfer func-tion of the three load models,and the energy-averaged value is used to represent the mechanical noise.Furthermore,the third criterion is used to handle the case where the acceleration load is given by the results of a bench test.According to the equipment source descriptor invariance,the conversion method is achieved between the bench test and the real ship based on the transfer function of a load model,and the mechanical noise is predicted by an equivalent energy method.Finally,a three-parameter method to quantitatively evaluate the well-fitting of experimental and numerical results,and the load criteria are well validated by underwater acoustic experiments of an experimental model.
基金supported by the National Natural Science Foundation of China(No.51875522)the“One Belt One Road”Program through Zhejiang Province,and the Zhejiang University of Technology-Institute of Applied Physics,Russian Academy of Sciences Joint Research Laboratory of Innovative Technology of Acoustics and Vibration(No.2018C04018).
文摘In this paper,an asymmetric vibroacoustic system that can passively realize nonreciprocal transmission of acoustic energy is reported.This experimental system consists of a waveguide,a strongly nonlinear membrane,and three acoustic cavities with different sizes.The theoretical modeling of the system is verified by experiments,and parametric analysis is also carried out.These intensive studies reveal the nonreciprocal transmission of acoustic energy in this prototype system.Under forward excitation,internal resonance between the two nonlinear normal modes of the vibroacoustic system occurs,and acoustic energy is irreversibly transferred from the waveguide to the nonlinear membrane.However,under backward excitation,there is no internal resonance in the system.Energy spectra and wavelet analysis are used to highlight the mechanism of nonreciprocal transfer of acoustic energy.Consequently,nearly unidirectional(preferential)transmission of acoustic energy transfer is shown by this system.The nonreciprocal acoustic energy transfer method illustrated in this paper provides a new way to design the odd acoustic element.
