Empirical Equations for Describing the Strain-Hardening Characteristics of Metals Subjected to Moderate Strains

Abstract

The strain-hardening characteristics of a metal have often been described by a power function which employs a work-hardening exponent, “n.” Usually the material is assumed to be rigid to the yield point and therefore the possibility of any elastic recovery is denied. The authors show that, particularly for the initial portion of a stress-strain curve, n is not a constant and therefore the curve cannot be described by one power law alone. A method is proposed for fitting equations to experimental stress-strain curves up to strain values of 0.05. The equations take into account possible elastic recovery. The equations should facilitate more accurate assessment of underload stress and strain distributions in various design problems.