5. Conclusions
This paper enlarges a recently proposed vision for the fracture
loci in sheet metal forming that makes use of fundamental concepts
of plastic flow, ductile damage and void coalescence and growth to
include fracture toughness in two different crack opening modes.
An analytical framework is proposed to estimate the location
of the fracture loci in the principal strain space directly from the
experimental measurements of fracture toughness and thickness
at fracture in double notched test specimens loaded in tension and
plane torsion.
The comparison between the fracture loci of AA1050-H111
aluminium sheets with 1 mm thickness obtained by means of
the new proposed analytical framework and that retrieved from
experiments with different sheet formability tests shows a good
agreement in case of failure by tension and a fair agreement in case
of failure by in-plane shear. The investigation also allows inferring
the existence of a transition fracture loci associated to crack
opening by mixed modes.