Development of finite element analysis based tools and methods for the design of advanced superplastic forming dies and processes

Superplastic forming (SPF) is a low investment process that takes advantage of certain material's ability to undergo large strains to failure when deformed under the right conditions, which usually involve elevated temperature and low strain rates. Product development and manufacturing benefits associated with SPF include low capital investment, part consolidation and increased design freedom with materials that have limited room temperature ductility. Although these attributes have led to significant interest in the SPF of aluminum automotive panels, with long forming times often exceeding 20 minutes and the high cost of aluminum sheet specially processed for SPF, conventional super-plastic forming has found limited applicability in automotive manufacturing. Advanced SPF die technology can reduce forming time and enable the forming of low cost aluminum sheet; however, accurate forming simulation is needed for the successful design of tooling for complex SPF processes.; A simulation capability has been established and experimentally verified for modeling superplastic forming with finite element analysis and is the result of fundamental research into experimental forming, simulation and constitutive modeling. Contributions include simulation parameters, die design and finite element model guidelines as well as novel approaches to material model refinement and pressure cycle optimization. Based on this work, FEA based tools were developed for a die design strategy that separates design into two steps of die design and process optimization. The simulation tools and design strategy were applied to design a complex multi-stage superplastic forming die with a forming cycle that is less than 150 seconds and enables the forming of a lower cost non-SPF aluminum sheet alloy. The design and experimental validation of multi-stage die technology represents a novel contribution to superplastic forming research.; Conclusions on superplastic forming die design and simulation are provided as well as recommendations for future work.