Investigation of Shot Peening on Residual Stress Distribution in Common Aerospace Materials

Intensity is an indirect quantification of the kinetic energy in the air-media stream through the usage of Almen strips in shot peening. However, intensity does not give an insight to the energy transferred into the material nor the compressive residual stress (CRS) on different materials. Previous studies have been done on individual materials but few serve to investigate and compare across materials. In this study, the effect of Shot Peening on common aerospace materials Al7075-T6, IN718, SUS304 and Ti-6Al-4 V were investigated to assess residual stress distribution and other material properties such as hardness across different material properties for the same peening intensity. Through this work, the authors aim to elucidate the mechanism of differences in residual stress distribution by establishing a relationship with the different material properties studied. Specimens were shot peened using ASR70 media, while residual stress and hardness measurements were conducted at various depths thereafter. It was found that the variation in pre-peened material hardness from all materials does not correlate to obtaining higher work hardening and deeper residual stresses under the same shot peening intensity and coverage. Among the materials studied, Al7075-T6, the softest, exhibited the highest post-peening surface roughness, but showed limited work hardening and induced residual stresses. In contrast, Ti-6Al-4 V, the hardest material, demonstrated the lowest post-peening surface roughness, with relatively minor work hardening and residual stresses compared to Inconel 718 and SS304. These differences can be attributed to the distinctive material properties and microstructure, leading to varying deformation behavior when subjected to cold work processes like shot peening.