Research On Vibro-acoustic Characteristics Of Composite Plate And Shell Structures Coupled With Acoustic Cavity Under Elastic Boundary Conditions

In engineering practice,with the wide application of composite materials,it is more and more important to analyze the vibration characteristics of composite plate and shell structures and the vibro-acoustic characteristics of the coupled system composed of the plate and shell structures and the surrounding sound field.There are abundant research results on vibration characteristics of single-form plate and shell structures,but there is no universal unified modeling method to simplify the research process.For the composite structure-acoustic coupling system,mechanical wave will produce energy dissipation and waveform conversion at the coupling interface,which makes the study of vibro-acoustic coupling mechanism extremely complex and relatively scarce.Therefore,a unified analysis model of vibration characteristics for composite shallow shells is established from the structural domain.On this basis,the sound field is introduced to establish the vibro-acoustic characteristics analysis model of composite laminated plate and enclosed acoustic cavity.Firstly,according to the first-order shear deformation theory and the two-dimensional improved Fourier series method,a unified analysis model for vibration characteristics of composite shallow shells under elastic boundary conditions is established.As long as the curvature of the foundation model of shallow shell structure is changed,the panel,cylindrical,spherical or hyperbolic parabolic structures can be easily obtained.The displacement functions of shallow shells are invariably expressed as cosine function multiplication and superposed by complementary polynomials.The introduction of complementary polynomials can effectively eliminate the potential discontinuity or jumping phenomena at the boundaries.Based on artificial virtual spring technology,five sets of springs are uniformly arranged at the boundary of shallow shell structures to simulate the elastic boundary conditions.The Rayleigh-Ritz energy method is used to find the extremum of the energy functional of shallow shell structures under elastic boundary conditions,and then the equation of vibration characteristics could be obtained.Then,according to the elastic theory of composite materials and the basic principle of enclosed sound field,the vibro-acoustic characteristics analysis model of moderately thick laminated plate-cavity coupling system is established.The extrusion potential energy at the coupling surface of the elastic plate and the acoustic cavity is introduced into the energy functional of the structure and the acoustic field to obtain the overall energy functional of the coupling system.The Rayleigh-Ritz energy method is used to obtain the vibro-acoustic characteristics of the coupled system.By introducing the point force of the structure and the point sound source inside the acoustic cavity,the influence of the plate vibration on the sound pressure response and the influence of the sound pressure on the vibration response of the plate structure are further studied.Finally,the modal testing platform of rectangular plate structure and the vibro-acoustic testing platform of plate-cavity coupling system are built under clamped boundary condition.By comparing the experimental results with the theoretical analysis results,the correctness of the vibro-acoustic characteristic analysis model established by the present method is further verified.The results obtained by the finite element simulation software,existing literature and experiment are compared with those obtained by the present method to verify the correctness of the analysis model established in this paper.On this basis,some important parameters,such as geometric parameters,material parameters and boundary conditions,are studied.The influence of relevant parameters on structural vibration characteristics and vibro-acoustic characteristics of coupled system are obtained,which provides theoretical basis and technical support for vibration and noise reduction.