Phase Transformation Effects on the Bending Stress Distributions in Carburized Steel Components

Abstract

An analytical model has been developed for the elastic and elastoplastic bending of rectangular bars in which the neutral bending plane need not remain in the geometric center of the bar. With this model, distribution of both longitudinal and transverse stress can be computed on the basis of applied bending moment and measured, surface strains. The strain-induced transformation of austenite retained in the case of carburized steel bars of several compositions was found to occur at linear rates whose values depend upon the sign of the stress and the composition of the steel. It was further found to produce pronounced shifts in the neutral bending plane and to have major effects on the magnitude of the transverse bending stresses. The bending fracture characteristics of the carburized steel bars were found to be affected by the inherent toughness of the case, and all factors which influence it, as well as the inherent toughness of the core. In general, the presence of nickel in the steel enhanced the fracture resistance of the steels because of its contribution to the toughness of both case and core.