“…Non-linear ultrasonic techniques (NLU) show promise for the research of non-linear dynamic properties of structures and materials because of their enhanced detection of features related to pore structure within materials. The existence of defects on a wide scale range (from nanoscale to macroscale) enhances non-linear acoustic phenomena (Eiras, 2016;Climent et al, 2022). Overall, materials whose mechanical behavior has a high dependence on the quality of the bond between their constituents fall into the non-linear mesoscopic elasticity (NMEM) class (Guyer and Johnson, 2009).…”