Vibro-acoustic Characteristic Research Of Acoustic Black Hole Stiffened Plate

Vibration and noise control of ships had attracted much attention.In recent years,vibration and noise reduction in the marine industry had been put forward with higher requirements.Acoustic black hole had been widely studied and applied to different scenarios due to its special structure and as an efficient method of structural bending wave control.In this thesis,the acoustic black hole was applied to the structure of the ship platform.A new type of acoustic black hole stiffener structure was designed,which had combined the energy gathering effect of the acoustic black hole,the vibration damping effect of the reinforcement rib and the energy dissipation performance of the damping layer.Therefore,it was effortless to realize the efficient aggregation and effective dissipation of the vibration energy of the ship platform structure.The specific research work in this thesis started from the perspective of power flow to verify the concentrated energy effect of acoustic black hole.The thesis had described vibroacoustic characteristics of acoustic black hole stiffener plate and the influence of different acoustic black hole’s parameters on the vibroacoustic properties.In this thesis,the energy transfer and distribution characteristics of acoustic black hole stiffener plates were analyzed in depth,and the influence of stiffeners on energy transfer and vibrational reduction characteristics was explored.The distributed acoustic black hole stiffened plate structure was proposed to optimize the vibration and noise performance of the structure at low frequencies.The main research work and innovation points were as follows.1.The energy aggregation effect of acoustic black holes was verified.This thesis took two-dimensional elastic sheet as an example to introduce the theory of bending wave propagation in two-dimensional elastic structure.The above theory was illustrated the energy aggregation effect of acoustic black hole structures.Using the finite element model of twodimensional acoustic black hole plate,the theory that the curved wave propagation of acoustic black hole in the time domain had the energy aggregation effect was verified.2.Analysis of acoustic and vibroacoustic characteristics of acoustic black hole stiffened plate and the influence of structural parameters on the acoustic and vibroacoustic characteristics were discussed.This thesis was introduced the derivation process of vibroacoustic theory of two-dimensional flat plate structure,which provided a theoretical basis for the analysis of acoustic black hole stiffener plate.By establishing the acoustic vibroacoustic properties of acoustic black hole in the classic thesis,the correctness of the finite element simulation of the vibro-acoustic characteristics in this thesis was verified by calculation result.Vibro-acoustic theory was used to analyze the vibroacoustic radiation properties of acoustic black hole stiffener plate.The calculation result showed that the acoustic black hole stiffened plate has better vibration and noise reduction effect than the ordinary stiffened plate,and the sound power level reduction had reached 8～20 d B.That leaded to a weakened coupling to the sound field and an increasing in the level of vibration resistance in the structural system.Acoustic black hole stiffener plate’s structural parameters on the influence of vibro-acoustic characteristics was analyzed,which had the greatest influence on the vibro-acoustic characteristics.3.The vibration energy transfer and distribution characteristics of acoustic black hole stiffener plates were studied.Based on the basic theories of structure-based sound intensity and power flow vector visualization,this thesis analyzed the energy transfer and distribution characteristics of acoustic black hole stiffener plate,and established a finite element model of acoustic black hole stiffener plate after discretization.The calculation result showed that the vibration energy could carry a large number of bending waves,weakening the propagation of the bending waves could improve the vibration damping effect of the structure,and the visual power flow vector diagram visually showed the energy transfer and distribution of the structure.The acoustic black hole stiffener plate with additional damping layer had a high level of vibration control effect compared with ordinary stiffened plate after further analysis of the stiffened plate-damping coupling system.The influence of stiffeners on vibration transmission characteristics was explored.The result showed that stiffener could block the transfer of structural energy due to the change of the center of gravity of the structure,weakened the transmission of bending waves,and made its vibration damping effect better.4.A distributed acoustic black hole stiffener plate was proposed to optimize the performance of low-frequency vibration and noise reduction.In this thesis,the distributed acoustic black hole stiffener structure was proposed to improve the vibration and noise control ability of the acoustic black hole stiffener plate before the cut-off frequency,and the distributed structure was better in vibration and noise reduction at low frequencies through calculation.