Analytical and experimental study of the die drawing of circular rods through conical dies

An analysis is presented of the process of die drawing isotropic polymers, in the form of circular rods, to produce highly oriented materials with enhanced mechanical properties. The stresses in a small element of material undergoing the drawing process have been analyzed using a force‐equilibrium approach and the initial yield and flow stresses in the material have been predicted from the von‐Mises yield criterion. The stress‐strain‐strain rate characteristics of the polymer used in the analysis were deduced from uniaxial tensile test data obtained at the same temperature at which the die drawing occurred. Experimental results are presented of the stress in polypropylene GSE‐108 rods when die drawn at 90°C in a purpose‐built die drawing facility. Novel techniques were used to determine the stress and strain distributions along the die. A comparison of the experimental results and the analytical predictions shows good agreement.