This part of ISO 12004 provides guidelines for developing forming-limit diagrams and forming-limit curves for metal sheets and strips of thicknesses from 0,3 mm to 4 mm.
A forming-limit diagram (FLD) is a diagram containing measured major/minor strain points on a formed part.
An FLD can distinguish between safe and necked, or failed, points. The transition from safe to failed points is defined by the forming-limit curve (FLC).
To determine the forming limit of materials, two different methods are possible.
1) Strain analysis of failed press shop components to determine component and process dependent FLCs:
In the press shop, strain paths to reach these points are generally not known. Such an FLC depends on the material, the component and the chosen forming conditions. This method is described in this part of ISO 12004.
2) Determination of FLCs under well-defined laboratory conditions:
For evaluating formability, one unique FLC for the defined material is necessary. The determination of FLC has to be specific and it is necessary to use different linear strain paths. This method should be used for material characterization as described in ISO 12004-2.
