Shot peening treatment characterization by surface acoustic waves

Shot peening is a classical mechanical surface treatment used to improve the properties of components, principally the fatigue and stress corrosion resistance. The possibility of characterization of shot peening treatment efficacy was assessed by leaky Rayleigh SAW generated and detected by a large aperture, broadband and lens-less focused transducer. The broadband pulses propagated in the material surface were processed in order to obtain the dispersion curves, and were compared for different samples that were submitted to different treatment conditions. The results showed that the dispersion curve is sensitive to these treatment parameters. The possibility of depth profiling of the elastic properties changes due the shot peening are discussed on base of the fact that the penetration of SAW depends on the frequency and so the dispersion curve should have information of the elastic properties in different depths. The source of these elastic changes is also analyzed in terms of plastic deformation, residual stresses, roughness and microstructural changes. A comparison of the dispersion curves with a laser based SAW system was also performed showing equivalence of the methods.