A study on energy conversion behavior of single-shot elastic-plastic impact during shot peen forming

Shot peen forming is a process for the forming of aircraft integral wing skin panels by the cumulative impact effects of an enormous number of shots. The action of a single shot determines the fundamental characteristics of the entire shot peening process relative to the comprehensive forming effect of a large number of shots. A study of the elastic-plastic impact behavior of a single shot is essential for an in-depth understanding of the shot peening process. In this paper, the conversion process of the kinetic energy of the shot to the elastic-plastic deformation energy within the material through the elastic-plastic impact is systematically investigated during shot peen forming. An energy conversion model and a finite element model of the elastic-plastic shot impact are first developed, and various energies, e.g., the kinetic energy of the shot, the elastic-plastic deformation energy of the impacted material, and the energy dissipation caused by material damping and friction, are then evaluated by simulation. A single shot impact experiment is designed to verify the validity of the simulation results by comparing the indentation diameters. The results show that in the shot peening process, the energy input into the target material by the shot impact is mainly in the form of elastic-plastic deformation energy, of which plastic deformation energy accounts for the significant part (>= 72%) and the rest (<= 28%) is elastic deformation energy. Up to 70% of the elastic deformation energy is released during the elastic recovery of the material. The remaining 30% of the elastic deformation energy is stored to provide the driving power for the macroscopic deformation of the shot-peened components. It is also worth noting that the proportion of these energies varies further with the shot impact velocity.