Processes affected by the formability of a material include: rolling, extrusion, forging, rollforming, stamping, and hydroforming.
For example, a length of 80 mm (3.1 in) is used for the standardized uniaxial test of flat specimens, pursuant to EN 10002.
Forming-limit curves depict the extreme, but still possible, deformation which a sheet material may undergo during any stage of the stamping process.
Typical plane strain values range from 10% for high-strength grades and 50% or above for mild-strength materials and those with very good formability.
It is recognized by many authors that the nature of fracture and therefore the Forming limit diagrams are intrinsically non-deterministic since large variations might be observed even within a single experimental campaign.
Extensive research has focused in recent years on understanding and modeling ductile fracture.
The approach has been to identify ductile forming limits using various small-scale tests that show different strain ratios or stress triaxialities.
One major objective of the International Deep Drawing Research Group (IDDRG, from 1957) is the investigation, exchange and dissemination of knowledge and experience about the formability of sheet materials.