ИСТИНА

We investigated experimentally reflection of monochromatic elastic waves of finite amplitude on the boundary of two flat metal surfaces. We placed different interface layers between the surfaces: a) flat rough metal surfaces, b) rough surfaces with the metal foil with a thickness of 10 microns between them, c) one-dimensional layer of steel balls with a diameter of 4 mm between rough metal surfaces, and d) layer of steel balls with foil between the balls and one of the surfaces. For the case of two rough metal surfaces amplitude of the reflected 2nd harmonic increased, amplitude of the 1st reflected harmonic decreased. When there is a one-dimensional layer of steel balls between the surfaces, the amplitude of the reflected 1st elastic harmonics decreases smoothly with rising the pressure, but amplitude of the reflected 2nd harmonics has a maximum. The experimental results are analyzed using the theory of Hertz contact nonlinearity.