Barrelling in square billets of aluminium during cold upset forging under dissmilar friction

In upset cold forging the existence of frictional constraints between the dies and the work piece directly affect the plastic deformation of the latter. The friction at the contact faces retards the plastic flow of metals and the surfaces and in its vicinity. A conical wedge of a relatively undeformed metal is formed suffers high strain hardening and bulges out in the form of barrel. This work has been taken up to generate data on the cold upset forging of square billets of annealed aluminium under dissimilar frictional conditions. Experiments we're conducted by applying lubricant at one end of the square specimen and the other end with dry friction (with no lubrication). By the application of differential lubrication, a barrel and a truncated part near the unlubricated surfaces have been developed. The measured radius of curvature of the barrel was found to confirm with the calculated value. The calculations were made on the assumption that the curvature of the barrel followed the geometry of circular arc. Relationship is established between the measured radius of curvature of the barrel and the stress ratio parameter.