Experimental and numerical study on stress peen forming of aluminum alloy metal sheets

As an effective forming method in aeronautical industries, peen forming is derived from shot peening process. Major application of this process is for production large thin components with gentle curvature such as aircraft panels and wing skins. This process can be divided into two categories; peen forming without elastic pre-strain (conventional peen forming) and with elastic pre-strain (stress peen forming). In this research, numerical and experimental study of shot peening, peen forming and stress peen forming of aluminum alloy sheets were conducted. In order to perform experimental tests, steel shots with 0.4 mm and 0.6 mm diameter and aluminum alloys Al 6061-T6 strips were used. For applying elastic pre-strain, fixtures with four pre-bending radii ∞, 500 mm, 375 mm and 250 mm were designed and manufactured. In numerical section, using same parameters as applied in experiments, first by using a 3D model with random distribution of shots, shot peening process was simulated and created stresses in sheet (induced and residual stresses), were obtained. Next by using this model and in a three step procedure, peen forming and stress peen forming processes were simulated. The results showed that applying pre-strain is very effective in distribution of stress profile inside the sheet metal and thus in the final deformation of it. Accordingly, in compared with conventional peen forming, stress peen forming produces larger curvatures in the sheet metal. Furthermore, with increasing pre-bending moment (decreasing pre-bending radius), the resultant curvature in the sheet in the direction of the applied pre-bending, increases.