M. A. Nazzal, German Jordanian University, Amman, Jordan; F. Abu-Farha, Penn State University/Erie, Erie, PA
It is well established that many superplastic alloys exhibit cavitation during deformation. Cavitation not only limits the superplastic ductility of the material, but also adversely affects the service properties and fatigue performance of the formed parts. In this paper, finite element simulations and experiments are carried out to study the effects of contact conditions and hydrostatic pressure on the evolution of cavities during superplastic forming of both the 5083 aluminium and AZ31 magnesium alloys. The finite element analysis is based on a three dimensional model, that uses experimentally calibrated microstructure-based equations, and takes both damage evolution and grain growth into account. Elements that can handle contact, large deformation and the generated triaxial stress state are used. An elevated temperature pneumatic forming setup, with both forward and back pressure forming capabilities, is also built to accommodate different amounts of hydrostatic pressure. The area fraction of voids is measured at different places across the formed sheet and correlated to the associated friction coefficient and hydrostatic pressure.
Summary: It is well established that many superplastic alloys exhibit cavitation during deformation. Cavitation not only limits the superplastic ductility of the material, but also adversely affects the service properties and fatigue performance of the formed parts. In this paper, finite element simulations and experiments are carried out to study the effects of contact conditions and hydrostatic pressure on the evolution of cavities during superplastic forming of both the 5083 aluminium and AZ31 magnesium alloys. The finite element analysis is based on a three dimensional model, that uses experimentally calibrated microstructure-based equations, and takes both damage evolution and grain growth into account. Elements that can handle contact, large deformation and the generated triaxial stress state are used. An elevated temperature pneumatic forming setup, with both forward and back pressure forming capabilities, is also built to accommodate different amounts of hydrostatic pressure. The area fraction of voids is measured at different places across the formed sheet and correlated to the associated friction coefficient and hydrostatic pressure.
