Leaky surface acoustic waves

By measuring V z), which includes examining the reflectance function of solid material, measuring the phase velocity and attenuation of leaky surface acoustic waves at the liquid-specimen boundary, the SAM can be used indetermining the elastic constants of the material. 

As shown in Fig. 4.19, in anisotropic medium, a surface acoustic wave represents a combined longitudinal (4.19a) and shear (4.19b) motion of the lattice in the y-(0)-z plane this is the saggital plane. In anisotropic media, in certain multilayer structures and at some interfaces, the surface wave velocity exceeds the velocity of the shear wave and the energy continuously leaks from the surface to the bulk of the material. In such cases, we talk about pseudo- or leaky waves. Various energy-loss... 

Using a ray-tracing technique, one may understand this mechanism understood as follows. The period of this variation results from interference between the two components. Figure 6 shows one component which is spectrally reflected at normal incidence, while the second one undergoes a lateral shift on incidence and reradiates at the critical phase-matching angle for the surface acoustic wave (also referred to as leaky Rayleigh waves ). 

Obata, M., Shimada, H., and Mihara, T. (1990). Stress dependence of leaky surface wave on PMMA by line-focus-beam acoustic microscope. Exp. Mechanics 30, 34-9. [148]... 

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