Superplastic bulge forming of domes

Abstract

An experimental method has been developed to study the effects of different forming procedures, including constant pressure, constant apex velocity, constant apex strain rate (and, indeed, any arbitrary forming operation), on the strain rate sensitivity index m–log (strain rate ɛ) curve for the bulge forming of domes. The materials examined were Zn–22Al and Zn–4Al–1Cu alloys (both wt-%) supplied in the form of crossrolled superplastic sheet. The results show that the optimum forming operation, which is defined as the procedure that maintains strain rate sensitivity at the highest level for a wide range of strain rate, involves deformation at a constant apex strain rate.

MST/1580