Use of response surface methodology for shot peening process optimization of an aircraft structural part

The shot peening process causes the surface of metallic parts to become hardened by bombarding it with a stream of small particles called shots, generating compressive residual stress at the material surface and resulting in surface hardening. In the aerospace industry, proper selection and control of peening factors (parameters) is needed to ensure that the Almen intensity is within specifications and full surface coverage. In this study, the effects of four parameters (nozzle distance, pressure, impact angle, and exposure time) on Almen intensity and coverage are investigated. In order to systematically estimate the models of Almen intensity and coverage in terms of the four parameters, a Box-Behnken design with blocking is employed. Based on the estimated quadratic models, optimum peening conditions are determined using the desirability function approach. Additionally, in order to verify the validity of the optimal conditions obtained from experimental results, metallurgical analyses of the shot-peened aerospace structural part were conducted to examine the hardness, surface morphology, and residual stress.