A pressure effect on the nonlinear reflection of elastic waves from the boundary of two solid media

Abstract

Experimental studies of how static pressure affects the features of reflection of a monochromatic longitudinal elastic wave from the boundary of two rough metal surfaces with different interface layers were performed. The following layers were investigated: (a) two flat metal surfaces; (b) two metal surfaces with a layer of 10-μm-thick foil between them; (c) a one-dimensional layer of steel spheres between two metal surfaces; and (d) a one-dimensional layer of steel spheres with 10-μm-thick foil between the spheres and one of the surfaces. Apart from a wave at the fundamental frequency, a second-harmonic wave was observed in the reflected-wave spectrum. The reflected-wave amplitudes depended on the value of the static pressure applied to the layer. It is pointed out that the structural elastic nonlinearity at the solid-layer interface significantly exceeds the elastic nonlinearity related to the anharmonicity of molecular forces in the investigated materials.