Optimized Design Of Acoustic Radiation Of Composite Cylindrical Shell Structure

Cylindrical shell structure is widely used in ship,submarine and underwater vehicle engineering.Especially the stiffened ring-ribbed cylindrical shell structure is often used in submarines,and its acoustic and vibration characteristics are directly related to the acoustic stealth performance of submarines.At present,the internal structure of submarine is neglected,and the sound and vibration characteristics of cylindrical shells with different ring ribs are studied under the action of an excitation force.In this paper,finite element method(FEM),boundary element method(BEM)and other numerical methods are used to study the acoustic and vibration characteristics of ring-ribbed cylindrical shell structure.ANSYS and LMS Virtual Lab finite element software are used to carry out joint simulation,and then the acoustic and vibration characteristics of different ring-ribbed cylindrical shell structures are analyzed.The structure optimization of viscoelastic materials is also carried out,which has important theoretical reference and universal engineering application value.The main work of this paper is as follows:(1)Firstly,based on the sound-vibration theory of cylindrical shell structure,different ring-ribbed cylindrical shells are calculated.In this paper,five ring-ribbed cylindrical shells with 0,1,3,5 and helical ring ribs are used for sound-vibration analysis.The sound pressure level radiated by 3 ring-ribbed cylindrical shells is the highest,but by changing the shape of the ring-ribbed pillar,it can become a cylindrical shell with helical ring-ribbed pillars.The sound pressure level radiated by the three ring-ribbed cylindrical shells is lower than that radiated by different numbers of ring-ribbed pillars.The noise reduction effect is obvious.(2)According to the ring-ribbed cylindrical shell structure with the lowest sound pressure level calculated,the outer surface of the shell is divided into plates and the respective sound contribution of each plate is analyzed.Local dampers are laid at the plate locations with high sound contribution,and their sound radiation characteristics are analyzed and compared with those of the global damped helical ring ribbed cylindrical shell.The influence of different cylindrical shell structures on the sound and vibration characteristics of the shell is further studied.(3)The damping layer thickness of cylindrical shell is optimized.First,the sound radiation characteristics of helical ring ribbed cylindrical shells with different damping layer thicknesses are calculated,then the optimized objective function is fitted according to the characteristics,and the lowest damping layer thickness of sound radiation is calculated using genetic algorithm.In this paper,the method of theoretical calculation is adopted.Firstly,the correctness of the theoretical model is verified.Then,based on this theory,the acoustic-vibration characteristics of different ring-ribbed cylindrical shells under excitation force are discussed.Meanwhile,the acoustic contribution of ring-ribbed cylindrical shells with the smallest sound pressure level to external radiation is studied.Damping materials are laid to reduce the noise where the sound contribution is high.It has certain reference value for the research of cylindrical shell structure noise reduction,and targeted local laying damping can reduce the use of materials and save costs better.