Process Simulation for Optimizing Superplastic Forming of Sheet Metal

Superplastic forming (SPF) is conducted in a heated, pressurized die where direct monitoring of critical SPF parameters is extremely difficult. Numerical models provide a critical means of tracking the forming process, allowing the applied gas pressure to be adjusted to maintain optimum SPF behavior throughout the forming process. This paper describes how the MARC finite element code was used to predict accurate pressure/time cycles for the forming of aluminum test trays. Partially formed trays were made in our SPF press to compare thickness profiles and extent of forming with the model results. This work shows the importance of accurate constitutive models in reproducing the actual forming behavior of rate sensitive, SPF materials. The paper also discusses material testing methods and the implementation of solution control methods within the MARC code.