| Composite materials have the characteristics of high specific strength,high specific rigidity,and strong designability.They have a wide range of application prospects in the field of ship and ocean engineering.The use of composite materials for ship structures has become a general trend.Acoustic stealth performance is a key indicator of ship’s survivability and combat effectiveness.The research on ship structure vibro-acoustic problem has important theoretical significance and engineering value.Aiming at the quantitative acoustic design requirements of composite materials in the application of ship structures,this paper takes an axisymmetric shell structure as the research object,and carries out the following research work around the underwater vibro-acoustic problem of composite shell structures:Aiming at the vibration problem of composite material axisymmetric shell structure,the generalized spectrum method is used to establish a composite material structure vibration analysis model suitable for arbitrary boundary conditions and layering methods.First,based on the first-order shear deformation lamination theory considering the transverse shear deformation and the moment of inertia,the dynamic equation of the axisymmetric shell in the curved coordinate system is derived.Then the spectral polynomial expansion is carried out in the solution domain to reduce the structural dynamics problem to a functional variational problem.The high-order spectral polynomial has the advantages of fast convergence,stable and reliable calculation.Finally,the correctness and accuracy of the generalized spectrum method are verified by comparing the results from the literature and the vibration test results of the glass fiber cylindrical shell.For complex composite shell structures,the coupling relationship between discrete structures is established by using the displacement coordination conditions of the structural coupling interface,and the overall dynamic model of the composite shell is established by combining the dynamic equations of the substructures.The influence of relevant parameters on the vibration of the composite structure is systematically analyzed.Aiming at the external acoustic radiation of composite axisymmetric structures,a structural acoustic radiation model based on the generalized spectrum-spectrum boundary element method is established.Based on the establishment of the composite material structure vibration analysis model by the generalized spectrum method,the spectrum boundary element method is used to expand the relative variables of the boundary integral equation by polynomial expansion of the high-order spectrum function,and the sound field equation that does not depend on unit division is obtained.For the external sound radiation problem of axisymmetric structures,the sound pressure,normal displacement,Green function and its partial derivatives in the boundary integral equation are expanded along the circumferential coordinates by Fourier polynomials in the cylindrical coordinate system.Through mathematical simplification,the one-dimensional and semi-analytical vibro-acoustic coupling sound field equation can be obtained.For shell structures immersed in light and heavy fluids,a strong coupling method is used to solve the vibro-acoustic problem.Numerical results verify the correctness of the method,and the effects of boundary conditions,material properties,and layering methods on the acoustic radiation characteristics of composite shells are studied.The generalized spectrum-spectral boundary element method is further extended to the vibro-acoustic analysis of the hemispherical shell-cylindrical shell-hemispherical shell combined shell structure.Based on the theory of first-order shear deformation laminated shells,the sound radiation problems of isotropic homogeneous materials and orthotropic composite materials hemispherical shell-cylindrical shell-hemispherical shell are analyzed,and the effects of different loads and ply angles on the acoustic radiation of the composite shell are discussed. |
