CONCEPTS FOR THE DESCRIPTION OF PLASTIC ANISOTROPY IN COLD BULK METAL-FORMING

Similarly to normal and planar anisotropy of sheet metal the axial and radial anisotropy of round bars having axisymmetric properties are defined. The axial anisotropy is a measure of the deviation of plastic behaviour in axial direction from that vertical to the axis. It can be evaluated by upsetting tests on Rastegaev specimens machined out of a bar vertically to the axis whereby the specimens obtain elliptic cross-sections. This is demonstrated by test results for hexagonal metals. The radial anisotropy is a measure of the deviation of plastic behaviour in radial direction from that in tangential direction at some distance from the axis. Possible experiments for determining the radial anisotropy ana effects of radial anisotropy to be expected in metal forming processes are discussed.