## 5pSA9. Modal impedances for nonaxisymmetric vibrations of a thin spherical shell.

### Session: Friday Afternoon, May 17

### Time: 4:05

**Author: Richard B. Evans**

**Location: Science Applications Intl. Corp., 21 Montauk Ave., Ste. 201, New London, CT 06320**

**Abstract:**

Modal impedances are found by solving the equations of motion of a thin
spherical shell in terms of nonaxisymmetric modes of vibration. These mechanical
impedances relate the modal expansion coefficients of the applied force per unit
area and the velocity of the shell. The application and interpretation of these
modal impedances require an awareness of the lack of orthogonality of certain
modes. In proper combinations, the modal impedances in the nonaxisymmetric case
are found to be identical to known modal impedances in the axisymmetric case.
The analysis is restricted to extensional effects of a thin shell with radial
forcing. An application of the modal impedances is given in the prediction of
the radiation pattern of a three-dimensional array of closely spaced interacting
spherical shells.

from ASA 131st Meeting, Indianapolis, May 1996