Reconstruction of residual stress and work hardening and their effects on the mechanical behaviour of a shot peened structure

Generation of residual stress through inhomogeneous plastic deformation is inevitably coupled with work hardening/softening activities of materials. Being able to precisely model the residual stress and the work hardening is of great importance for structure optimization and design. Eigenstrain is an effective method to reconstruct residual stress field in a structure with the consistency of stress equilibrium and strain compatibility. However, the hardening behaviour of materials is generally not considered in the eigenstrain method. This paper presents a reconstruction approach of residual stress and work hardening generated by shot peening in a cylindrical structure. This approach takes into account both the stress equilibrium and the elastic-plastic equilibrium conditions. In order to experimentally validate this reconstruction approach, a cylindrical sample in 316 L stainless steel is shot peened. The in-depth residual stress and work hardening variations are measured and evaluated using X-ray diffraction. Self-equilibrium analyses based on Finite Element (FE) modelling indicate that the approach developed in this work is efficient to reconstruct equilibrated residual stress and work hardening fields. Moreover, the effects of the initial residual stress and the work hardening on the mechanical behaviour of the structure are investigated through simulation of tensile tests using the FE model. It is demonstrated that an accurate consideration of work hardening during reconstruction, which is strongly deformation history-dependent, is essential to precisely describe the mechanical behaviour of a shot peened material.