High-energy synchrotron X-ray analysis of residual plastic strains induced in shot-peened steel plates

Shot peening has long been recognized as a method for treating metal surfaces in order to improve their resistance to crack initiation and propagation. In view of shot-peening control, it would be useful if methods for direct measurement or estimation of residual stresses and depths of deformed layers were available. The focus of the present paper is on the presentation of high-energy synchrotron X-ray diffraction that allows better understanding of shot-peening residual strain profiles. Furthermore, it attempts to show that considerable elucidation of shot-peening effects can be attained if plastic strain profiles (eigenstrains) are considered, rather than residual stresses. Indeed, bending analysis shows that residual stresses depend on the sample geometry, and on the thickness in particular. In contrast, the experimental analysis presented in this paper suggests that the plastic strain profile induced in a particular material, on the other hand, is a function of the peening intensity alone and does not depend on the specimen thickness.