Numerical study of superplastic deformation with superimposed pressure for cavity sensitive materials

Abstract

The non-uniform deformation (necking and thinning) development and fracture of superplastic materials under both uniaxial tension and circular sheet bulging are numerically analysed by considering the effects of strain rate sensitivity and cavity growth with superimposed pressure. It is found that the fracture mode, which is controlled by both strain rate sensitivity and cavity growth rate, can be changed by superimposed pressure from fracture without external necking for cavity sensitive alloys at zero pressure to fracture with necking development or extensive thinning at pressure large enough to completely suppress cavity growth. Fracture mechanism diagrams are presented which enable prediction of the fracture mode to be made as a function of material parameters and pressure conditions for uniaxial tension and bulging.

MST/724