Analysis of residual stress distribution in shot peened Al 6082 T5 alloy subjected to fatigue loading

In this paper the relationship between the residual stress field and the fatigue behaviour of the Al 6082 T5 alloy subjected to two shot peening treatments characterised by different intensities is studied. The experimental work is aimed, in particular, at investigating the redistribution of the residual stress field during cyclic loading and is based on the measurements either of: initial stress profile (a), evolution of the surface stress in dependence of the loading condition (b) and stress profile after an appropriate number of loading cycles (c). Measurements were carried out by XRD (X-ray diffraction) and BHD (Blind hole drilling) techniques, obtaining always similar stress values, which point out the relaxation of the surface stress up to a stabilised value depending on the loading level. On the contrary the subsurface compressive stress peak does not present evident modification and in general the whole residual stress profile is nearly unchanged up to the initiation of fracture crack. Results of residual stress measurements are discussed on the basis of the fatigue behaviour obtained for the different material conditions.