EFFECT OF SPECIMEN THICKNESS AND STRESS RATIO ON FATIGUE CRACK G ROWTH AFTER A SINGLE OVERLOAD CYCLE ON STRUCTURAL STEEL

摘要

Effects of specimen thickness and stress ratio on fatigue crack growth transients after a single overloadrnapplied among constant amplitude cycles of a smaller amplitude have been studied experimentally for a lowrncarbon structural steel. The corresponding crack growth data from the fatigue tests have been presented andrnevaluated. The overload cycles introduced crack growth retardation in all cases and the transient crackrngrowth response depended on a specific combination of specimen thickness and stress ratio. The retardationrneffect at a given stress ratio decreased as specimen thickness was increased. For a given specimen thickness,rnthe benefit from the overload application was larger at a higher stress ratio than at a lower stress ratio. Therntest variables predominantly affected crack growth retardation during the period when the crack growth raternwas recovering from the minimum value, whilst their effects prior to this minimum (i.e. in the delayedrnretardation period) were negligible. The observed experimental trends were compared to those reported inrnthe literature for other structural steels.