On the optimum die angle in rod drawing process considering strain-hardening effect of material

In this paper, rod drawing process of strain-hardening materials is investigated by analytical, numerical and experimental methods. The classic upper bound solution, based on the assumption of perfect plasticity, has been extended to consider the work-hardening of the material during the drawing process. For a given process conditions and mechanical properties of the rod material, the power terms and the required drawing force are determined and optimized with respect to the die angle. The results afforded by this solution agree with data from finite element simulation, using the finite element code DEFORM 2D, and some experiments performed by the authors. It is shown that the drawing force and the optimum die angle are affected primarily by the work-hardening exponent. The amount of drawing force increases as work-hardening of material considers in the analytical solution and by increasing the work-hardening exponent, the drawing force and the optimum die angle are decreased. It is also shown that by increasing the work-hardening exponent of the rod material, the maximum possible reduction in area is increased.