Induced stress relationships for wing skin forming by shot peening

Shot peening has been used to provide fatigue resistance and form to airplane wing skins for many years. In the past, the peening intensities used to form these wing skins were obtained through the use of geometric relationships along with trial and error testing. A computer model was developed to model shot peening, which could eliminate the trial and error phases of the existing process. The computer model is used to determine the peening intensities across the wing skin and the initial size of the skin (flat pattern). To support such a computer model, we have developed in this paper relationships among the thickness of the material, the stress induced into the aluminum, and the intensity of the shot peening (shot wheel revolutions per minute, rpm). Asimple induced stress theory is proposed. Results for a cylindrical wing skin utilizing the new relationships are included.