Barrelling of aluminium solid cylinders during cold upset forging with constraint at one end

Abstract

Experiments were carried out to generate data on the cold upset forging of solid cylinders of annealed aluminium using different lubricants, with a die at one end providing a constraint. The die had created back extrusion of metal through its hole and developed two barrels in the unrestrained portion of the cylindrical specimens. The curvatures of the barrels, top and bottom, developed in the unrestrained portion were found to conform one to one to calculated values using experimental data. The calculations were made on the assumption that the curvatures of the barrels followed circular arc geometry. It was further found that the measured radius of curvature of both barrels exhibited a straightline relationship with the new geometrical shape factor, irrespective of the aspect ratios of the cylinders. Further empirical relations were found to exist between the measured radius of curvature of both barrels and other variables, namely hydrostatic stress and stress ratio parameter.