Dispersion of circumferential waves on evacuated, water-loaded spherical steel shells

The phase-velocity dispersion curve of the Ao Lamb wave on a free plate ten ds to zero at the vanishing frequency while on an evacuated, free spherical shell, it turns upward. On a fluid-loaded shell, and for the analogous cir cumferential Ao wave, it again tends to zero, however, while a new A-wave ( Scholte-Stoneley wave) which gets added due to fluid loading, is the one wh ose dispersion curve turns upward. This phenomenon is studied here for a th in stainless-steel shell on the basis of dispersion curves calculated from 3D elasticity theory, or obtained from the calculated shell resonances, and is explained by the physical nature (shell-borne or fluid-borne) of approp riate circumferential wave portions. We also establish connections with the previously found partial dispersion curves. (C) 2000 Elsevier Science B.V. All rights reserved.