If a minimum radius to which a sheet metal workpiece can be bent exists, a very severe limitation is set on the shape of the part that can be produced.
The exercise is intended to show how material deformation behavior determines the deformation that can be imposed on the workpiece. Such limitations imposed by material behavior set limits on the deforamtion that can be imposed in metal forming processes.
Figure 19-25 shows the dependence of minimum bend radius on a measure of material ductility, the percent reduction in area at fracture in a tensile test. A process model is developed
A graphical representation of this bending process model is used in the exercise. It is intended to show
- a measure of ductility derived from tensile test data, Af / Ao,
- the use of another widely used measure, the percent reduction of area, (Af - Ao) / Ao) 100%
- the variation of the minimum bend radius possible as a function of ductility.