Note on the Crack Closure Phenomenon in Low - Cycle Fatigue

Life time during low-cycle fatigue (LCF) is mainly consumed by crack growth. To correlate LCF with crack growth rate a cyclic integral Δ J has been proposed and widely used in the past. However, to compute Δ J values it is necessary to know about crack opening behaviour during LCF. This paper reports on strain controlled LCF tests to determine the crack opening behaviour and to evaluate Δ J based on experimental crack opening stress. It is found that the short cracks show constant crack opening behaviour. For long cracks a crack opening behaviour will be affected by crack length thus influencing the Δ J estimation.