Experimental Validation of Non-Collinear Wave Mixing Model in a PVC Specimen

A scattering wave generated from the interaction of two incident acoustic waves contains information on the third order elastic constants of a solid material. The scattering amplitude is known to be dependent on the interaction angle between the two incident waves. However, the realization of experimental tests is hampered due to the geometry and accessibility to the surfaces. In this research, the amplitude of the scattering wave is investigated as a function of the excitation frequency of the incident waves, while the interaction angle is kept constant. The amplitude coefficient and scattering amplitude were solved analytically for two interaction processes. The analytical solutions were validated with experiments. The model qualitatively agrees with the experiments. The two main results are stressed: the angle of the scattering wave is controlled by the frequency ratio of the two interaction waves, rather than by the angle between these waves. The second advantage is the possibility to use a wider range of excitation frequencies of the incident waves. This is a great advantage in applications where, for example, there is only access to one surface of a flat specimen.