Upper bound analysis of die land length in cold extrusion

Upper bound analysis of the effect of die land length on the cold extrusion of selected geometries is reported. The upper bound determination of extrusion pressure was extended to include the power due to ironing effect for shaped sections (rectangular, square and circular) resulting from boundary friction forces on the surface of the die land. The present investigation reveals that the contribution of die land length to the extrusion pressure increases with increasing complexity of die opening geometry with the rectangular section giving the highest extrusion pressure and the square section giving the least, for certain die reduction in area at a particular die land length. For a percentage reduction in area, the normalized extrusion pressure contribution, ΔPo/Y, increases with increasing die land length. Also, for a particular die land length, the normalized extrusion pressure increases with increasing percentage reduction in area.