| Most of buried objects are elastic shells. Echo from elastic shells is composed of mirrorreflection wave, edge scattering wave and elastic scattering wave. Mirror reflection wave andedge scattering wave reflect the geometry informations. Elastic scattering wave reflect thematerial properties informations and how the wave propagates. So echo characteristic fromelasitc shells are very important for detection of buried objects.It is very hard to find the analytical solution of acoustic scattering by elastic shells withirregular geometry. Numerical methods are needed. Finite Element Method (FEM in short)and Boundary element Method (BEM in short) are used in this paper to solve the problem.Firstly, the basic theory of FEM and BEM is introduced and the singularity problem inBEM is solved. Formulas of surface sound pressure and particle vibration velocity are given.Secondly, Calculation programs are written to calculate the scattering field of sphericalelastic shells. The numerical results are compared with the analytical results and thecalculation programs were proved correctly. Then the scattering field by elastic shells withirregular geometry was calculated. The main researchs were on angle characteristic andfrequency characteristic.Lastly, an acoustic experiment was carried out. The experiment results were comparedwith the numerical results. The characteristic of the scattering field are analysed in detail. Thecalculation programs are proved again by experimental method. |
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