An Analysis for Three-Dimensional Upset Forging of Elliptical Disks

The axial compression of solid cylinders has been investigated by many authors due to its application in the area of metal forming. In the axial compression the frictional condition between the dies and workpiece directly affect the plastic deformation. During the deformation, friction causes heterogeneous deformation which results in barrelling of cylinders. The prediction o f defects occurrence in any forming process requires an understanding o f the mechanism of the deformation and a knowledge of the stress, strain, strain rate and temperature that takes place during deformation. In the present study, barrelling of elliptical shaped cylinders have been investigated. The radius of barrel for different deformation loads has also been studied. Experiments were carried out to generate data on the upset forming of elliptical and circular cylinders at room temperature of hot-rolled commercially pure aluminium with different lubrication conditions. Calculations were made on the assumptions that the curvature of the barrel surface followed the geometry of both elliptical and circular arcs. It was observed that the true axial strain of the barrel shows a straight-line relationship with true diameter strain irrespective of the geometry of the cylinders. It was also observed that the measured radius of curvature of the barrel also exhibited a straight-line relationship with a new geometrical shape factor, irrespective of the aspect ratio and b/a ratio. Further, empirical relationships were found to exist between the measured radius of curvature of the barrel and other variables such as hydrostatic stress and the stress-ratio parameter.