ABSTRACT

The previous chapter dealt with Rayleigh waves guided along the surface of a semi-infinite solid. This chapter deals with a similar problem, again for the case of sagittal waves, that of Lamb waves [48] propagated along a thin plate. Mathematically, the problem for Lamb waves is rather more complicated than for Rayleigh waves. We will not stress the mathematical development here but rather look at the nature of the simplest solutions, the

S

symmetric modes and the

A

antisymmetric modes, as well as the physical nature of the higher-order modes. The origin of the modes will be looked at from another angle, that of guided modes, in the following chapter. Very detailed and rigorous mathematical treatments of Lamb waves have been given elsewhere [26, 35, 49].