Numerical and asymptotic approach for evaluating complex wavenumbers of guided modes in viscoelastic plates.

The approximate description of the dispersion curves is obtained using asymptotics of complex wavenumbers for different boundary conditions on the plate surfaces. Their comparison with the exact results shows satisfactory agreement. This approach provides an algorithm to evaluate the infinite spectrum of non-propagating modes more easily and numerically stable even for wavenumbers of big values. Results are verified by the alternative semianalytical finite element method, which also supplies the mode shapes for better identification and classification.