A critical test on theories of work-hardening for the case of drawn iron wire

Abstract

A recent extensive set of experimental data and electron micrographs derived from drawn iron wire by G. Langford and M Cohen have been employed for a critical test of the most important theories of work-hardening. As a first step, electron micrographs taken by the named authors were compared with the dislocation models used in the different theories. When these micrographs were found qualitatively to conform to the model of the “unified theory of work-hardening” and to none other, they were employed to determine the numerical values of a few simply defined parameters, describing the geometry of the dislocation structure, which appear in that theory. The thus measured values of the geometrical parameters were inserted into the equations derived from the theory for a quantitative test of it. Specifically compared were the theoretical and experimental values of the average free dislocation length, and of the linear work-hardening coefficient, the shape of the composite stress strain curve, and the rate of energy storage. In all cases agreement within the accuracy of the measurements was found over the whole range of deformation used by Langford and Cohen, extending between 22 and 740 pct true tensile strain.