Numerical characterization of shot peening induced work hardening gradient and verification based on FEM analysis

Abstract

Work hardening can be inevitably generated along with residual stress due to shot peening. Precise characterization of the work hardening is of great importance for the prediction of in-service performance of a structure. A new method of numerical characterization of shot peening induced work hardening (Peening-WH) gradient is presented in this work. For this purpose, a stress circle model is proposed to highlight the relation between residual stress and Peening-WH. The latter is composed of residual isotropic hardening (RIH) and residual kinematic hardening (RKH). Two RKH parameters δ∗ and θ∗ are proposed to characterize the tensor feature of the Peening-WH. FEM simulations of shot peening process are performed to analyse the plastic flow during peening and the mechanism of work hardening generation. Materials with pure isotropic hardening, pure kinematic hardening, and combined isotropic/kinematic hardening behaviours are used and rate-independence and rate-dependence are respectively taken into account for the simulations. Results show that the parameter δ∗ follows, to some extent, certain regular distributions in the plastically affected region, while the average θ∗ is equal to π in this region. Impact number, hardening behaviour, and rate sensibility have little effect on the two parameters, even in the case where induced residual accumulated plastic strain and residual stress present a large difference. It is concluded that the proposed RKH parameters δ∗ and θ∗ are a group of intrinsic parameters of the shot peening process, and are able to describe the tensor nature of Peening-WH. They can thus be used to reversely deduce RKH through residual stress of a shot peened component. The method developed in this work can be extended and used in the investigation of work hardening generated by other complex plastic deformation processes.