Nonlinear acoustics measurements of intact and damaged samples: fast and slow dynamics

When excited by elastic waves, nonlinear mesoscopic elastic materials (for example, consolidated granular materials) show, at the same time, fast and slow dynamics effects. Here we introduce suitable parameters for quantifying them and for studying their correlations. We found that significant differences between intact and damaged samples can be observed by studying slow dynamics effects. The longitudinal profiles of the surface deformations induced by a sinusoidal excitation of a cracked sample were also investigated during different measurement configurations, showing that a considerable distortion of the original profile is induced by conditioning. These results can be useful for studying the behavior of cracks and defects in the nonclassical nonlinear regime, in view of their modeling at the microstructural level and for applications in innovative nondestructive test and evaluation techniques.