Influence of Surface Roughness on Surface Acoustic Waves

Machining often changes the surface roughness of metal parts. However, when we use surface acoustic waves (SAW) to test and evaluate the properties of metal parts, the surface roughness will affect the propagation of SAW. To study the influence of surface roughness on the propagation of SAW, finite element models of 304 stainless steels were built with a Gaussian random surface. The pulsed laser was substituted by a heat flux loading to excite the SAW. Then the relationship between the velocity of SAW and the surface roughness was obtained by a quadratic function fitting. The results showed that the phase velocity of SAW decreases with the increase of surface roughness. Moreover, the change of phase velocity at high frequency is greater than that of low frequency when the SAW propagates on the surface with different surface roughness. The simulation results were verified by the theoretical calculating, and the difference of disperse curves is small when the value of surface roughness is between Rq2.101 and Rq6.086.