Critical issues in the industrial application of SPF-process modeling and design practices

With the continued use of superplastic forming (SPF) process in the manufacture of various aerospace and automotive components, there is an imminent need to accurately predict the process parameters for complex 3-D configurations. New SPF products are finding their way into architectural, rail, heavy industry, biomedical, sports and textile sectors apart from the traditional aero- and auto-industries. High fidelity process models in combination with other concurrent design tools (CAD, stress analysis, cost analysis) should be able to provide the platform necessary for the wider use of superplastic (SP) products across a range of industries. The objective of this paper is to first introduce the various industrial applications of SPF products and the design bottlenecks hindering their wider use. Practical considerations in the development of appropriate material constitutive models for superplastic materials and their relevance to numerical simulations are then discussed. Three different models including a micromechanics based model are used to describe the constitutive behavior of a selected SP material (Aluminum 5083). The performance of the models are then compared with respect to experimental results. The effect of the actual material parameters on the simulated results, and hence the design are outlined. Some of the commercial and other finite element codes used in SPF process modeling are enumerated, and the features of each of the codes with respect to the type of elements, contact/friction algorithms, and pressure-prediction schemes are compared. In closing, other practical considerations in the manufacture of SPF products, e.g., die materials, optimal SPF/DB design, alpha-casing, product thickness control are also discussed.