Combining the finite element method and response surface methodology for optimization of shot peening parameters

In this study, a finite element shot peening model was employed in order to obtain the values of maximum compressive residual stress (sigma(RS)(max)), the depth of compressive residual stress field (delta(0)) and the stress concentration factor (K) in specimens treated by shot peeing process. Based on the finite element simulation results, Response Surface Methodology was conducted to optimize the response variables of sigma(RS)(max), delta(0) and K. The effects of three shot peening parameters (shot velocity, shot diameter and coverage ratio) on the values of sigma(RS)(max), delta(0) and K were investigated. The influence of the values of sigma(RS)(max), delta(0) and K on the fatigue property was discussed via giving different weights to these response variables in the optimization approach. The results showed that the proposed shot peening finite element model could give a reasonable prediction of compressive residual stress field and dimple size. Meanwhile, response surface methodology could be used to optimize these response variables (sigma(RS)(max), delta(0) and K) well. The priority should be given to the values of sigma(RS)(max), delta(0), and K in sequence when shot peening parameter optimization was conducted within a reasonable shot peening parameters range without microcrack appearing on treated surface. The optimal shot peening parameters were the shot velocity of 88 m/s, the shot diameter of 0.8 mm, and the coverage ratio of 170% for 42CrMo specimens. The fatigue life of 42CrMo specimens treated by shot peening with optimal parameters was improved by 104% in experiments.