3. Elastoplastic properties of diaphragm steel taken into account

3.1 Isotropic metal approximation

The steels used for the diaphragms are type 50CV4 or XC70 spring steels.

As a first approximation, we consider the sheet to be isotropic, which in particular means neglecting the differences in mechanical properties between the rolling direction and the transverse direction in the plane of the sheet.

This is, of course, an approximation: for example, differences of several percent in yield strength are generally observed between these two directions.

In practice, the anisotropy of sheet metal contributes (in addition to the non-symmetries of production tooling) :

• ovalization" of flanks during hot stamping (orthotropic variations in...