Effect of various stress ratio parameters on cold upset forging of irregular shaped billets using white grease as lubricant

Abstract

The aim of this study is to investigate the effect of various stress ratio parameters on cold upset forging of commercially pure aluminium solid billets of irregular shaped billets using white grease as lubricant applied on both sides. Samples with two different aspect ratios (ratio of height to diameter) namely, 0.5, 0.75 and 1.0, with different <i style="">b</i>/<i style="">a</i> ratios (ratio of minor to major diameter) namely 0.6 and 0.7 were prepared and cold forged. Cold deformation experiments were carried out in an incremental step and at the end of each step, dimensions such as height, contact and bulged diameters being measured. The calculations were made with the assumption that the radius of curvature of the barrel followed the form of a circular arc. Analysis of the experimental data showed that there exists a relationship between the measured barrel radius and various stress ratio parameters namely, (σ_{<img src='/image/spc_char/theta.gif' border=0>}/σ_z), (σ_m/σ_z), (σ_eff/σ_z), and (σ_m/σ_eff) developed under plane stress condition. An attempt has also been made to relate the percentage height reduction with respect to the stress ratio parameters namely, (σ_{<img src='/image/spc_char/theta.gif' border=0>}/σ_z), (σ_m/σ_z), (σ_eff/σ_z), and (σ_m/σ_eff) developed under plane stress condition and found to have an increasing trend with enhanced level of deformation.