Young's Modulus and Poisson's Ratio on Low-Cycle Fatigue

Abstract

Axial-and diametral-strain-controlled low-cycle fatigue tests were performed on carbon and low-alloy steels with both an axial and a diametral extensometer mounted on the same cylindrical specimen. The results obtained are summarized as follows. (1) Young's modulus, E, under cyclic plastic deformation was given by E=σa/el =σa/(el -el ), where σa is stress amplitude, and el , el and el are total, elastic and plastic strain amplitudes in the axial direction, respectively. E was nearly equal to 206 GPa when el =0, while it decreased with increasing el . (2) Poisson's ratio for elastic and plastic strain, υe=-(ed /el ) and υp=-(ed /el ), were nearly equal to 0.3 and 0.5, respectinely, where ed and ed are diametral elastic and plastic strain amplitudes. (3) Strain-fatigue life properties for axial and diametral strain-controlled tests were coincident each other when the axial strain was calculated from the measured diametral strain through an equation of tranformation on the assumption that E=206GPa, υe=0.3 and υp=0.5.