| Submarine,as an important strategic weapon for maintaining national security,must have good stealth performance to ensure safety.It is clear that an underwater sound-absorbing structure which has good performance is of great significance for improving the stealth ability of submarines.This dissertation,based on the traditional design concept of underwater sound-absorbing structures with cavities and parallel arrangement,disscus about the design of an underwater sound-absorbing structure which has gradual cavities.Moreover,this structure has several other advantage,such as better low-frequent and broadband sound absorption and better pressure resistance.this paper aims to achieve better lowfrequency,broadband sound absorption and pressure resistance performance,and designs underwater sound-absorbing structures with gradual cavities.First of all,the first part of this article discusses the reasons for choosing the interpolation cavity structure as the cavity type of the underwater sound absorption structure theoretically,building the genetic algorithm for its structural optimization design.It also explores a new manufacturing process of the underwater sound absorption structure and introduces the test condition for the underwater sound absorption performance testing,which can be used in experiment to verify the finite element simulation model of the underwater soundabsorbing structure.In the part of simulation analysis,the author establishes a simulation model of underwater sound-absorbing structure and transform it from a threedimensional model into a two-dimensional model,verifying it through acoustic performance testing.This part also introduces some factors which affect performance of underwater sound-absorbing structure,including different parts of pressure acoustics and solid mechanics,structural parameters and material parameters,and getting the conclusion that single structure could not achieve broadband sound absorption effectively.So,it is necessary to adopt a parallel arrangement to obtain a relatively broadband sound absorption effect;the last part provides analysis about the mechanism of sound-absorption and the reasons for each absorption peak/valley,based on the displacement map and power density map of the structure.The design optimization part,based on the underwater sound absorption structure with interpolation cavity,discusses the possibilities of improving the structure’s pressure resistance performance,low-frequent sound absorption and process ability and provides three improved underwater sound-absorption structures(Improved,compression-resistant,gradient circular cavitary).According to above,author designs an underwater sound absorption structure with a maximum sound absorption coefficient of 0.99(in the frequency band at700Hz),more importantly its sound absorption coefficient greater than 0.7 in the frequency band of 550～1000Hz.At the same time,author improved the soundabsorption structure at low frequency and designs an underwater sound-absorbing structure with better pressure resistance at medium and high frequency.After comparing the sound absorption performance of the improved structure and pressure-resistant cavity structure,the latter is finally selected and optimized into a structure with the sound absorption of more than 0.7(in the frequency band of1800Hz～10000Hz);finally,after parallel improvement,an underwater sound absorption structure with a sound absorption coefficient exceeding 0.7(in the frequency band of 900 Hz to 10000Hz)is obtained which at the expense of certain sound absorption performance. |
