Study On The Vibroacoustic Characteristics Of Sandwich Plate With Corrugated Cores Based On Structural-Acoustic Coupling Effect

Benefiting from its simple topology,low manufacturing costs and excellent mechanical properties,the metallic sandwich plate with corrugated cores is widely used in constructing aircraft fuselage,high speed train cabin and ship bulkhead.Analyzing the dynamic properties and understanding the sound transmission mechanism of this kind of structure is of great significance for the lightweight and noise reduction design of modern high speed transportation system.According to the geometric topology and structural properties of the sandwich panel,in this thesis,a theoretical model targeting at a typical H shaped sandwich beam system is constructed,in which the fully structural-acoustic coupling effect is taken into consideration.Based on the theoretical model,a detailed vibro-acoustic analysis is performed to investigate the basic dynamic behaviors of the coupled system.After that,in order to overcome the computation efficiency bottleneck of conventional finite element method in solving middle and high frequency structuralacoustic coupling problem,a numerical method is proposed based on the basic concepts of the wave based method.The vibro-acoustic properties of a complete sandwich plate with corrugated cores are studied by using this method.And,a parametric study is implemented to investigate the influence of the in-cavity acoustic medium and structure design parameters on the vibro-acoustic characteristics of the sandwich plate.Furthermore,a structural-acoustic optimization is performed targeting at the sound transmission loss of the sandwich plate to find out the priori design parameter in different frequency ranges.At last,a series of experiments is carefully designed and performed to verify the conclusions revealed by the numerical investigation and the numerical method itself.The main works and conclusions of this thesis are expatiates as follows:(1)By using the analytical modal function of Euler-Bernoulli beam and rectangular acoustic cavity in associate with envelope rectangle technique,the theoretical vibro-acoustic model of the H shaped beam system is constructed.The basic behaviors of structural-acoustic coupling effect are revealed and explained in detail.Considering the two main dynamic effect of the acoustic cavity on the coupled system,known as the added stiffness effect and added mass effect,a principle of distinction is proposed according to the ratio between the global stiffness of the beam system and the aerostatistic stiffness of the acoustic cavities.(2)The particular solutions to the governing equations of dynamic response of the sandwich panel on the structural-acoustic coupling boundaries and boundaries under external plane wave excitation are derived first.Associating with the structural and acoustical wave function sets,a numerical method targeting at efficiently solving the vibro-acoustic response of the sandwich panel is constructed.Verified numerically and experimentally,this method has been proven to be much more efficient than conventional FEM under the same precision conditions.(3)The detailed vibro-acoustic properties of the sandwich plate with corrugated cores are analyzed and the concrete manifestations of the structural-acoustic coupling effect are revealed.A parametric study is implemented to investigate the influence of the in-cavity acoustic medium density and structure design parameters on the vibro-acoustic characteristics of the sandwich plate,which gives a deeper understanding of the sound transmission mechanism of the sandwich plate.By comparing the experimental results with the previously revealed conclusions,the basic vibro-acoustic characteristics of the sandwich plate and the effects of the design parameters given by the numerical investigation are verified.(4)A structure-acoustic optimization targeting at maximize the frequency averaged sound transmission loss under constraint of structural stiffness and weight is conducted in three different frequency ranges.The optimization history is analyzed statistically,according to the results,in the low frequency range,the thickness of the face panel,the thickness of the core panel and the inclined angle of the stiffeners have strong effect on the sound transmission loss of the sandwich plate.As for the high frequency range,the priori parameter is the thickness of the face panel.At the same time,the actual sound transmission loss of the optimization model is also tested by the experiment,and the A-STL of the optimized specimen turns out to be much higher than the control group in the targeting frequency range.All the results show that the numerical method proposed previously is reliable and effective.This thesis gives a detailed analysis and research on the vibro-acoustic properties of the sandwich plate with corrugated cores from five aspects including theoretical modeling,numerical modeling and investigation,characteristic analysis,structure-acoustic optimization and experimental study.The revealed conclusions enrich the sound transmission theorem of complex structural-acoustic coupling system at some degree,and,offer valuable references to the vibro-acoustic design of such sandwich structure.