On the Ratio of Transverse to Axial Strain and other Tensile Properties of a Cold-Rolled Steel Alloy

Abstract

Tensile tests have been performed on a 0.4 per cent carbon steel alloy in order to determine the behaviour of the lateral/longitudinal strain ratio. The material was cold rolled to produce a number of sheets covering the range 0–80 per cent reduction and test-pieces were prepared from strips cut from these sheets at each 15° between 0° and 90° to the rolling direction. The results are presented in graphical form and show the relationship between true tensile stress versus rolling reduction and the corresponding point-by-point equivalent contraction ratio versus rolling reduction. The experimental contraction ratio curve was computed from the strains in two transverse directions and represents the uniform contractions which would be experienced by an isotropic bar. This curve is compared with a theoretical curve which is based on the assumption that a metal flows without change in its permanent volume. The influence of cold rolling on some of the mechanical properties of these metals is also shown. It is concluded that provided accurate values of the elastic constants are known, the equivalent isotropic contraction ratio for a given tensile strain may readily be computed. The results show that very small permanent volume changes occur but that it is impossible to obtain absolute values by this method. It is also concluded that large errors can arise in stress analysis problems if the variation in the elastic ‘constants' with cold work is ignored.