Analysis of superplastic forming processes using a finite-element method

An incremental rigid-viscoplastic finite-element method (FEM) has been developed in order to simulate superplastic forming (SPF) processes. The optimum pressure-time relationship for a target strain rate is calculated simply by a liner interpolation of the pressure values at the previous iteration step. The material is assumed to be isotropic and a modified Coulomb friction law is adopted. SPF processes of aluminum alloy with various geometries have been analyzed using axisymmetric and plane-strain line elements. based on the membrane approximation. Through the analysis, optimum pressure-time curves and deformation behavior are predicted. Experiments have been performed successfully using the calculated optimum pressure-time curves as a control value. Comparison between the prediction of the FEM and the results of experiment shows good agreement, the present study demonstrating the usefulness of the method in process simulation of superplastic forming. Also, the combined stretch-blow forming process is modeled to improve thickness distribution.