Internal Symmetrical Lamb Waves for High Phase Velocities

Symmetrical Lamb waves with a phase velocity exceeding the velocity of expansion waves in an infinite medium are considered. It has been proven that internal waves are possible in this range of phase velocities, i.e. solutions to the wave equation that have zero values of the strain and stress components on the surface and, at the same time, their non-zero values inside the plate. The parameters of internal waves (phase velocity, frequency, wavelength) were calculated, and it was also proven that the frequencies of internal waves of the same phase velocity form an arithmetic progression. Several internal waves are considered, sections of the corresponding deformed plates, and distributions of maximum values of tension and shear are presented.