Development of an advanced superplastic forming process utilizing a mechanical pre-forming operation

Abstract

Despite considerable advantages with regard to formability and tooling costs, superplastic forming (SPF) has been mostly limited to low-volume production due to relatively long cycle times that can exceed 30 min and high material costs. This paper focuses on the development of a novel SPF process that utilizes mechanical pre-forming to enhance formability, reduce costs and improve production efficiency. Finite element analysis (FEA) was adopted to establish feasibility of the process and to design the new die system. The predictive accuracy of the FEA code was established in terms of thickness distribution and material draw-in by correlating simulation results with experiments conducted with a deep-draw die. The influence of different forming process parameters was investigated by comparing the simulation results of final thickness distribution. Experimental forming trials verified that as compared to conventional SPF for high aspect ratio, deep-draw panels, this novel die technology can deliver a superior thickness profile, where maximum thinning was decreased from over 50% to less than 20% and forming time was significantly decreased from 20 to 3 min. Furthermore, it was shown this technology allows for the use of lower-cost commodity alloys, such as AA5182 and AZ31, instead of specially processed high-cost fine-grain materials.