Forming limit curves
Metal sheet drawing - Importance of deformation modes

To make the preceding notions more quantitative, we measure local deformations and plot them on a graph, generally observing the following conventions:

• main deformation (index 1): the largest in algebraic value, it determines the main direction of deformation;

• secondary deformation (index 2): the smallest in algebraic value. In practice, the secondary direction is considered to be perpendicular to the previous one.