On the Variation of Stress-Strain Characteristics in the Plastic Fatigue under Rotating Bending

Abstract

A 0.22% carbon steel and a"roll material"have been fatigue-stressed in the high stress levels under rotating bending with very low frequency in order to investigate the stress-strain behaviour in the plastic fatigue process. The constant strain tests as well as the constant stress tests have been conducted to compare both results. As a result, the curves of variation of strain or stress with number of stress repetitions have been obtained and the tendency of variation of the stress-strain hysteresis loop as well as the dynamic modulus is also reported. The special interrupted fatigue tests under constant stress amplitude have been performed to obtain some information about the effect of unloading, aging and reloading on the fatigue lives and the stress-strain behaviours. The multiple repeated stress tests of two-step level have been carried out, too, and the relation between the Palmgren's criterion Σ(n/N)=1 and the stress-strain behaviour under such conditions are discussed.