The influence of the roughness of the interface between two media on its non-linear elastic properties

The goal of this study was to understand how the roughness of the boundary of two solids surfaces effects their nonlinear elastic properties and the possible usage of these results for the solid state surface diagnostic. The investigation of two media boundary properties was conducted by surface acoustic waves (SAW), which were excited and received in optically polished glass padding with angled beam transducers. The samples with different roughness level were pressed to the glass padding surface. The influence of external pressure applied to the boundary between the sample and padding to the nonlinear acoustic parameter (NAP) value was investigated. The dependence of NAP from applied pressure was non-monotonic: it raised up with the pressure increase, passed through the maximum and lower down with the further pressure increase. At the same time, the maximum value of nonlinear parameter and the range of pressure changes was demonstrated by the sample with the smallest grain size. The effects of Fast Dynamics in samples were also investigated. The experimental results analysis demonstrated that the suggested experimental method for studying nonlinear elastic properties of flat rough boundary with SAW could be potentially used in nondestructive diagnostics of rough surfaces of flat solid bodies.