SOUND SCATTERING FROM CYLINDRICAL-SHELLS WITH INTERNAL ELASTIC PLATES

This paper examines sound scattering from cylindrical shells with internal structural loading. Here, the internal system is modeled by elastic plates, which support both longitudinal and flexural waves. It is shown that an internal plate may affect the scattering process in two ways: it may interact with shell waves at the attachment points and it may resonantly respond to the incidence excitation. For the former, the acoustic effects are the same as those caused by any other forms of internal loading, such as mass-spring systems, or by inhomogeneities of the shell itself, such as material imperfection. For the latter, it is shown that internal plate resonances may result in large amplitude coupling forces at the attachment points connecting the plate with the shell, which in turn affect the scattered field. It is shown that this resonance effect is clearly seen in the acoustic field only for light structural loading. Both pinned and clamped plates are examined, which only reveals small differences in the low- to mid-frequency domain. The effects of attachment locations are also examined. Three different regions on the shell surface are identified, in each of which the loading interacts with different kinds of shell waves, resulting in different scattering characteristics.