Some aspects of barrelling in elliptical shaped billets of aluminium during cold upset forging with lubricant

Experiments were carried out to generate data on cold upset forging of commercially pure aluminium solid of irregular shaped billets; say 'Elliptical billets' with white grease as a lubricant applied on both sides in order to evaluate the bulging characteristics. The radius of curvature of both major and minor bulge measured was conforming to the calculated one using experimental data. The calculations were made with the assumption that the curvature of the bulge followed the form of a circular arc. It was further found that the measured major and minor radius of curvature of the barrel exhibited a straight line relationship against the new geometrical shape factor irrespective of the aspect ratios of the elliptical billets. The hydrostatic stress, hoop stress, effective stress, effective strain were evaluated under various stress state conditions namely the uniaxial, the plane and the triaxial. Three different aspect ratios (ratio of height to diameter), namely 0.5. 0.75, 1.0, were prepared and cold upset forged. The relationship was also established between the various bulge parameters like the hoop stress, the hoop strain, the hydrostatic stress, the new geometric shape factor, the stress ratio parameters and the radius of curvature of the bulge. The theoretical predictions of deformed configurations are in good agreement with the experimental results. (C) 2006 Elsevier Ltd. All rights reserved.