The Petch–Hall Factor during Discontinuous Yielding

Abstract

It is shown that the dynamical properties of dislocations alone cannot usually explain the magnitude of the yield drop and the gtain-size-dependence of the Lüders strain found experimentally for mild steels. On the basis of a great deal of experimental evidence a Petch–Hall term which decreases with increasing dislocation density is proposed. Explicit expressions of the lower yield stress and the Lüders strain, containing the relevant dislocation-dynamical, structural, and experin1ental parameters, are presented.