Incorporating the principles of shot peening for a better understanding of surface mechanical attrition treatment (SMAT) by simulations and experiments

Surface mechanical attrition treatment (SMAT), an effective tool to refine the surface microstructure of materials, is based on the same concept of conventional shot peening; however, it is very difficult to relate its experimental data with those obtained from other SMAT studies or other impact based grain refinement methods. Herein, a detailed finite element model for SMAT is developed based on the well-defined coverage and Almen intensity parameters, which are the gold standard parameters world-widely used to characterize shot peening. The surface coverage was experimentally measured on pure Al and was implemented to build a realistic coverage assessment model. X-ray diffraction technique was used to measure the induced residual stresses and evaluate plastically deformed layer detected by peak broadening. The proposed model is shown to be able to accurately describe the trend of surface coverage by using a reasonable number of impacts. The comparison of residual stresses from the numerical model showed a good agreement with the experimental measurements. The thickness of deformed layer calculated by finite element method and measured by XRD peak broadening are in good conformity. This study establishes the basis for the direct comparison of any two SMAT or SMAT and other similar impact-based processes.