J. Gregory McDaniel
Bolt Beranek and Newman Inc., 70 Fawcett St., Cambridge, MA 02138
This presentation describes methods of using an approximate elasticity formulation to compute natural wave numbers of waves in coated cylindrical shells. The efficient computation of these wave numbers is critical to coating design. A previously developed displacement-based variational formulation for coated shells [J. G. McDaniel and J. H. Ginsberg, J. Appl. Mech. 60, 463--469 (1993)] retains the accuracy of analytical formulations, but avoids the computational burdens associated with special functions of complex argument. This formulation, which was previously applied to two-dimensional problems, is extended to address wave propagation in the axial coordinate for each circumferential harmonic. Because the formulation is energy based, one has ready access to the strain energy distributions of each wave. For a specified real axial wave number, one obtains an easily solvable generalized eigenvalue problem for complex natural frequency. For a specified real frequency, the search for complex axial wave number is iterative. A fast algorithm for finding the complex axial wave numbers, which facilitates the design process, will also be discussed.