Prediction of shot peen forming effects with single and repeated impacts

Peen forming processing is widely used for shaping a large thin-walled component by introducing compressive stresses in surface layer. To predict the peening stress, expensive and time-consuming analyses were needed in experiments and numerical simulations. This paper is aimed to calculate the random peening effects based on the results of single and repeated impacts. Three kinds of finite element simulation models are adopted, including repeated impacts and two shots apart impacts as well as random peening models. With the repeatedly impacting simulations, the stress fields under different repeated numbers are obtained. With the two shots apart impacting simulations, the interactions of adjacent impacts are revealed and a size of isoeffect region of one impact obtained. Comparing the results of the repeated impacts and of random peening simulations, an expression is proposed to calculate random peening stresses with peening coverage less than 90% from the stresses of single and twice repeated impacts. Comparisons of the calculated and simulated stresses of random peening shows the same tendency and depth of compressive stress as well as the close magnitude of maximum compressive stress. The equivalent stretching force and bending moment of the calculated stress are in good agreement with the values of random peening simulation. The simulated results are verified with experimentally measured dimple sizes and resultant curvatures of peened plates.