Investigation of the Mechanics of Wire Drawing

Abstract

Round wire was drawn slowly and without backpull through dies with bores in the shape of truncated cones, in a study of the relations between external forces and process parameters. Not only the drawing force but also the mean die pressure and the mean coefficient of friction were measured, so that existing theories of wire drawing could be put to a more exacting test than had hitherto been possible. The investigation has revealed weaknesses in all wire-drawing theories; the use of Hill and Tupper's (1948)† sheet-drawing theory for the prediction of forces in wire drawing is not justified. Semi-empirical formulae for the forces have been devised. A simple relation between tool-stock configuration and non-homogeneity of deformation was discovered, which is also applicable to the mechanics of swaging. The assumption that the deformation is independent of the properties of the wire is not valid for annealed wires drawn with very light reductions, but is acceptable otherwise. The occurrence of thickening of the wire before entering the die and its continued thinning beyond the die deserves attention in bar drawing. There was no correlation between die pressure and coefficient of friction.