The experiments suggest that a progression of
intermediate ironing reductions is better than a
single large reduction in order to form the can
wall, in compliance with common practice. Anyhow,
in the event of residual formability needed
after the ironing stages, the benefits of a maximised
density are fairly low. This is illustrated by
the strong effect of redraw die radius on density as
well as wall elongation. The smaller die radius
definitely brought a higher damage level and a
lower elongation than the larger one. As pointed
out by Baudelet and Grange [3], sheet bending
over a small radius nucleates a large number of
damage sites, ready to grow under further forming.
And compressive hydrostatic stresses only
reduce the void volume without wiping it out
completely.