Surface Roughness of Laser-Shock-Peened Aluminum Alloys and Its Effect on the Dispersion of Surface Acoustic Waves

Abstract

The experimental dispersion curves of laser-shock-peened aluminum samples were obtained from the phase spectra of the laser induced surface acoustic waves (SAWs) and the results indicated that the more the peening times, the greater the dispersion. The change in phase velocity resulting from the surface roughness was obtained by comparing the dispersions of the samples before and after being polishing. It was found that the surface roughness decreased the phase velocity, and the change in velocity depended on the frequency of the SAW as expected from the theoretical analysis of the case when the lateral correlation length is much smaller than the wavelength of the SAWs. Furthermore, the experimental dispersion results of the SAWs for three samples with different peening times showed that the more the peening times, the smaller the roughness, which was verified by the values measured with a roughmeter.