M. A. Nazzal, German Jordanian University, Amman, Jordan; F. Abu-Farha, Penn State University/Erie, Erie, PA
One of the major drawbacks of superplastic forming is the non-uniform thickness distribution of the formed part, and the potentially severe thinning associated with large plastic strains. One approach to tackle the problem is by reverse free bulging of the sheet, before the actual forward forming into the desired die cavity. In this work, finite element simulations and experiments are carried out to study the merits of performing a reverse bulging step prior to the superplastic forming process. In the reverse bulging step, the sheet is blown away form the female die to selected heights, hence causing various levels of deformation in the polar region of the formed sheet. Then the forming pressure is reversed so that most of the deformation takes place in the region next to the clamping flange instead of the polar region. Thickness distributions were measured and then compared to those corresponding to conventional forward forming, and hence the effects of the initial reverse bulging heights were quantified. The study is carried out using both 5083 aluminium and AZ31 magnesium sheets.
Summary: One of the major drawbacks of superplastic forming is the non-uniform thickness distribution of the formed part, and the potentially severe thinning associated with large plastic strains. One approach to tackle the problem is by reverse free bulging of the sheet, before the actual forward forming into the desired die cavity. In this work, finite element simulations and experiments are carried out to study the merits of performing a reverse bulging step prior to the superplastic forming process. In the reverse bulging step, the sheet is blown away form the female die to selected heights, hence causing various levels of deformation in the polar region of the formed sheet. Then the forming pressure is reversed so that most of the deformation takes place in the region next to the clamping flange instead of the polar region. Thickness distributions were measured and then compared to those corresponding to conventional forward forming, and hence the effects of the initial reverse bulging heights were quantified. The study is carried out using both 5083 aluminium and AZ31 magnesium sheets.
