Shear and Surface Acoustic Waves (Ultrasound Experimental Set 4)

In the classic applications of ultrasound, such as e.g. the time of flight measurements in liquids (level measurement, flow measurement), only the longitudinal propagation of the ultrasonic waves plays a role. Ultrasonic waves can, however, also propagate in the form of shear and surface acoustic waves (SAWs), especially in solid bodies. These wave modes, their propagation characteristics and their dependence on elastic material properties make possible a large number of new methods in material testing (aircraft construction), signal processing (SAW filter) and modern medicine (elastography).With this set it is possible to carry out experiments to demonstrate the mode transformation of ultrasonic waves at boundaries between liquids and solids or at boundaries of different solids. They can also be used to determine the sound velocity of shear and surface acoustic waves (Rayleigh and Lamb waves) in different material samples. These measurements make it possible to determine the elastic coefficients of the materials such as the elasticity modulus and shear modulus.This set can also be used to demonstrate the dispersion of ultrasonic waves (frequency dependence of sound velocity) by means of the propagation of Lamb waves on thin glass sheets.A crack depth test can be carried out on an aluminium sample by means of Rayleigh waves as an application of surface waves in non-destructive testing (NDT).