Numerical study of grain refinement induced by severe shot peening

Abstract Three-dimensional finite element models of single shot impact and multiple shot impacts are developed to study grain refinement induced by severe shot peening. A multiscale constitutive model coupling the microscopic dislocation density and the macroscopic plasticity theory is proposed and implemented into the finite element models to characterize the formation and evolution of dislocation cell structure. The random distribution of the indentations under probability control is achieved by parametric modeling to simulate multiple shot impacts with respect to 100% peening coverage. Severe shot peening of AISI 4340 steel under various coverages is simulated and the cell sizes predicted by the finite element models are in good agreement with the experimental data. Parametric analysis of severe shot peening is carried out by using different size shots with the same kinetic energy. The numerical results indicate that: (1) the larger shot causes a larger depth of grain refinement, (2) the smaller shot is beneficial for grain refinement of the peened surface and subsurface, and (3) the shot oblique impact results in a finer dislocation cell structure. Moreover, the interactive effect of multiple shot impacts can effectively improve grain refinement of near surface materials.