Numerical pressure prediction algorithm of superplastic forming processes using 2D and 3D models

The paper describes a finite element model allowing for the prediction in a rapid way the optimum pressure cycle law, the deformed shapes, the distributions of the strain rate and the evolution of the thickness during superplastic forming processes. During the calculation, a pressure-cycle control algorithm is used in the analysis which keeps track of the maximum strain rate sensitivity index m, and adapts the pressure law applied in order to approach as nearly as possible the optimal pressure time history law. The purpose is not to follow the target exactly but obtain a practical pressure time history in a low computation cost time. To compare the performance of 2D and 3D approaches, two analyses have been performed using 2D and 3D finite element modeling. The numerical results are compared with the experimental ones to verify the validity of the pressure algorithm control.