Experimental and numerical investigation of restoration behavior of sheet metals subjected to bulging deformation

In this study, the restoration behavior of sheet metals subjected to bulging deformation was investigated experimentally and numerically. Soft aluminum (Al–O), mild steel (SPCC) and stainless steel (SUS) sheets of different thickness were used as test specimens. The bulge height and bulge diameter were also varied. The effects of these parameters on the restoration behavior and on the formation of wrinkles after restoration were examined. Results showed that when a bulged specimen was compressed to a flat sheet, circular wrinkle patterns appeared on the sheet surface due to buckling at the bulged portion during compression. The thickness of the sheet has a direct influence on its restoration behavior, which is divided into three patterns. Moreover, the bulge height and bulge diameter influenced the number and size of wrinkles formed after restoration. Results derived from the FEM analysis show reasonable agreement with the experiments.