Analysis of superplastic blowforming of 7475 aluminum alloy sheets into a truncated cone

Abstract

A numerical analysis method of superplastic blowforming for axial symmetry cups has been developed. A relationship of stress-strain used in the analysis is taken into account the work hardening of material. Also this method is able to account an influence of friction forces with die caused by forming pressure. Ratio of stress for each direction of circumference and meridian on small elements in a blank sheet is determined by morphological functions which are supposed with the contacting condition of die and material. The ratio of stress are kept in conformity with the basic condition, plane stress in apex and plane strain in periphery. And its distribution along axial cross section is accommodated to them through the deformation process, from plane disk to hemispherical dome or truncated cone. To verify the validity of this analytical method, a superplastic forming experiment was carried out by using 7475 aluminum alloy sheets. The optimum pressurization schedule was determined for a truncated cone with the simulation of the deformation process. The deformation process and the thickness distribution on the formed sheet agreed well with calculated ones.