Strip-Drawing Experiments With a Sigmoidal Die Profile

Abstract

Strip-drawing experiments were conducted to evaluate a sigmoidal die profile which, according to slip-line theory, can achieve perfect work efficiency and uniform deformation. The performance of this die profile was compared with that of a straight, a convex circular, and a concave circular die profile, each designed for a similar reduction and axial length. The sigmoidal profile proved best in all criteria examined: Efficiency, uniformity of deformation, and product strength, ductility and fatigue life. The concave circular profile, which is similar to a rolling profile, proved worst in all of these same criteria. The improvement of the sigmoidal profile over the straight profile in fatigue life and ductility was of the order of 20 and 30 percent, respectively, but in efficiency, uniformity of deformation and tensile strength was less than 4 percent. When fabrication of the sigmoidal die is unwarranted by these improvements, the analysis for the sigmoidal profile may yet be useful for approximating the best die angle for a straight profile.