Variation of Yield Stress With Strain and Strain Rate in Mild Steel

Abstract

Knowledge of the yield stresses characterizing steel strip is essential to a correct discussion of the cold rolling process. Various authors have noted that yield stress rises, in general, with increasing strain rate. However, these results have been noted in compression and tension tests, and not in situations directly similar to cold rolling, though this of course does not necessarily obviate the conclusions reached. Previously, work has been done to deform steel strip in Steckel rolling, using strip of an initial thickness of 0.025 in. If we consider the work to be a function of the deformation only, we may find the yield stresses involved by differentiating with respect to strain, obtaining it as a function of strain and strain rate. The derived curves agree well with results obtained from Manjoine and others on the variation of yield stress. It can also be shown that the differential change in yield stress drops off almost exponentially with strain, showing that the effect is almost nonexistent for medium and high strains.