A FINITE-ELEMENT PROCEDURE FOR THE SIMULATION OF SUPERPLASTIC SHEET-METAL FORMING PROCESSES

An incremental finite element procedure is described for the simulation of superplastic sheet forming processes. In general, the problem is treated as a nonlinear viscous flow of the superplastic material. A special frictional rigid boundary algorithm is suggested for the simulation of the kinematic constraint conditions involved in the actual forming process. The high degree of rate sensitivity displayed by the material combined with the concerns for the accumulated microstructural damage and the differential thinning of the blank usually require that the formation proceeds at a certain rate. An adaptive algorithm is also presented whereby the loading rate is adjusted automatically to achieve the optimum forming characteristics. The procedure is applied to the superplastic free bulging of circular blanks and the forming of a metal sheet into a rectangular die. Numerical predictions are compared with the experimental results. © 1990.