Deformation behavior and failure conditions in pneumatic bulge forming using circular and elliptical dies

The deformation and failure behavior of AA1050 aluminum sheet during warm pneumatic bulge forming (PBF) were investigated experimentally and numerically using circular and elliptical dies. The simulations were performed in Abaqus/Explicit using the Johnson-Cook (JC) model at 300 °C under constant pressure levels. The results showed that the die aspect ratio has a strong effect on deformation and failure. The circular die led to more uniform biaxial deformation and high dome height, while elliptical dies caused non-uniform deformation and strain localization along the major axis. The failure occurred in the region of maximum thinning, where a crack extended along the major axis. The crack was small and located at the dome apex in the circular die, while in the elliptical dies, it became longer and more extended. The formability improved with increasing the sheet thickness (STH) from 0.7 mm to 1 mm, allowing higher strain and dome height before failure.