Creep of Mild Steel under Periodic Stresses of Rectangular Wave : (II) Creep Deformation under Unsymmetrical Periodic Stress Waves

Abstract

Creep of mild steel was studied at a temperature of 450°C under unsymmetrical periodic stresses such that in a stress cycle the time under stresses higher than the mean stress was shorter than the time under stresses lower than the mean stress. It was found that in this case the mechanical equation of state in solid predicted a smaller deformation as compared with the one obtained by experiment, while it had been applicable without any appreciable error in the case of a symmetrical stress wave. It was also ascertained that the smaller the ratio of the loading time of the higher stress to that of the lower stress and the shorter the period of a stress cycle, the more the tendency was accentuated, although the lower stress affected little the total deformation under a given stress wave provided that the higher stress was constant.