Study of Asymmetric Extrusion and Drawing of Tube Analysis of Inclined Wall-Thickness Distribution of Tube

Using upper bound theory, an analytical method has been newly developed in order to simulate and to anticipate the change of cross-sectional inclined distributions of wall-thickness of tubes occurred in symmetric and/or asymmetric extrusion and/or drawing processes. In this analysis, generalized formulas of kinematically admissible velocity field of the tube moving through a symmetric or asymmetric die are proposed and mathematical procedure to simulate deformation behaviours of the tube is developed. By this method, power requirements, extrusion pressure and/or drawing stress and the change of inclined wall-thickness distribution of the tube have been successfully calculated. From these results, it has become possible to anticipate wall-thickness distribution of the product tube. Moreover, it has become possible to find out the optimal working conditions of extrusion and/or drawing process which are able to correct inclination of wall-thickness distribution of the original tube and to attain exactly uniform wall-thickness of the product tube.