ON THE OPTIMIZATION OF SUPERPLASTIC BLOW-FORMING PROCESSES

The superplastic blow-forming process of thin sheets is analyzed, and an optimal stable deformation path that reduces production time is obt ained. The analysis is based on an analytical model for the superplast ic forming (SPF) of a long rectangular box made of Ti-6Al-4V alloy at 900 degrees C, use of a microstructure-based constitutive equation for the strain rate and grain growth, a stability criterion, and a variab le strain rate control. It is shown that by imposing a variable strain rate control scheme derived from the stability analysis, an optimal f orming time can be developed while maintaining a stable deformation pa th. Some other control schemes also show effectiveness in either reduc ing the localized thinning in the formed sheet or reducing the require d forming time, Effects of friction and initial grain sizes on the for ming pressure profile and the thickness distribution of the formed she et are also investigated.