Effects of superimposed hydrostatic pressure on fracture in sheet metals under tension

The effect of superimposed hydrostatic pressure on fracture in sheet metals under plane strain tension is studied numerically using the finite element method based on the Gurson damage model. It is demonstrated that the superimposed hydrostatic pressure p has no noticeable effect on necking but significantly increases the fracture strain due to the fact that a superimposed pressure delays or completely eliminates the nucleation, growth and coalescence of microvoids or microcracks. The experimentally observed transition of the fracture surface, from P-type mode under atmospheric pressure to C-type mode under high pressure, is numerically reproduced.