Method of measuring the thickness of layers by surface waves

摘要

The method involves generating a beam of Rayleigh waves on a surface of a part e.g. ball bearing race (10), at a frequency, and measuring a wave propagation velocity. The steps are repeated several times with Rayleigh waves at different frequencies, and the velocities and corresponding wavelengths are then recorded. The velocities are classified by increasing wavelengths. Thickness of a surface layer is defined by the wavelength above which a plateau in the variation of the wave propagation velocity is observed, where the frequencies of the generated waves lie between 1 and 15 MHz.