A study on barrelling in magnesium alloy solid cylinders during cold upsetforming

Experiments were carried out to generate data on the upset forming of circu lar solid cylinders of hot-rolled magnesium alloy ZM-21. During the experim ental investigation, the magnesium alloy cylinders were observed to show a change Born a circular contact area on the top and bottom surfaces to an el liptical surface area. Calculations were made on the assumptions that the c urvature of the barrel surface followed the geometry of both circular and e lliptical arcs. It was observed that the measured radius of curvature of th e barrel exhibited a straight-line relationship with a new geometrical shap e factor, irrespective of the orientations, i.e., irrespective of whether t he specimens were machined in the rolling, transverse or thickness directio n of the hot-rolled plate. Further, empirical relationships were found to e xist between the measured radius of curvature of the barrel and other varia bles such as the hydrostatic stress and the stress-ratio parameter. (C) 200 0 Elsevier Science S.A. All rights reserved.