Study On The Dynamic Modeling And Vibration Characteristics Of Cylindrical Shell Covered With Porous Materials

As a kind of functional material with excellent sound and energy absorbing performance,saturated porous plates and shells are widely used in the field of aerospace,machinery,construction,petroleum,chemical and other biomedical engineering applications.The basic theories and the analysis of acoustic and vibration characteristics of saturated porous media have been always concerned by scholars.In order to make the function of the covered layer more comprehensive,covered structure gradually develop from a single layer of viscoelastic material to the complex multilayer structure.And the double-layer complex acoustic shell structures composed of homogeneous elastic material layer and porous layer,with a function of damping,sound insulation and absorption,have great application prospect.So far,there are few researches about the vibration properties of cylindrical porous shell.Both the theoretical analysis and the design methods of this kind structure need further study for it still exist some weaknesses.In this article,a new semi-analytical method with high computational precision and high efficiency is established for a cylindrical porous shell of both single layer and double-layer.The first-order differential equation of cylindrical porous shell structure under harmonic excitation is proposed.In the equations,there are 12 state variables which contain displacements,internal forces,the force and torque variables in respected with the fluid pressure.So the model can be applied to various boundary conditions conveniently.In this paper,the fluid displacements are derived from the fluid motion equations of Biot theory,which considering the fluid displacement of three directions.And the governing equations can be solved by combining the boundary conditions and the extended homogeneous capacity precision integration method which has high precision.So the model has high accuracy and can be widely applied.Finally,numerical results are given for verifying the correctness and effectiveness of the present model by applying the MATLAB software and the finite element model.The influence of the material parameters and boundary conditions on the transverse vibrations of the structure had also been discussed.In the work of the model for a single layer thin cylindrical porous shell,the numerical model for analysis the vibration behavior of double-layer thin cylindrical shell covered with porous materials is proposed by considering the continuity conditions and the superposition principle of the junction.The model present can be applied to the analysis of multi-layer complex structure for its modeling principle is simpler.And it can also offer theoretical and technical references for analysis the influence of different types of acoustic layer parameters on the vibration characteristics of cylindrical shells.Finally,the main work and research efforts of this article are summarized briefly.And the author also gave prospects of the application and the future research direction of the theoretical model presented by this paper.