Effect of friction factor on barrelling in elliptical shaped billets during cold upset forging

This work deals with the effect of friction factor of different lubricants on barrelling in elliptical shaped billets during cold upset forging. Experiments were carried out to generate data on cold upset forging of commercially pure aluminium solid of elliptical billets with different lubricants applied on both sides in order to evaluate the effects of friction factor on the forming behavior of barrelling phenomenon under plane stress state condition. The radius of curvature of both major and minor bulge measured conformed to the calculated one using experimental data and the calculations were made with the assumption that the curvature of the bulge followed the form of a circular arc. Three different b/a ratios (ratio of minor to major diameter) namely, 0.6, 0.7 and 0.8 and aspect ratio (ratio of height to diameter) of 0.75 were prepared and cold upset forged. The relationship was also established between the various bulge parameters like the hoop strain, the axial strain, the new geometric shape factor, the stress ratio parameters, the major and minor radius of curvature of the bulge and the friction factor ‘m’ of different lubricants.