Abstract
In this paper, emphasis on physical meanings of hysteresis loops denoting a relationship between loads and strains near the fatigue crack tip, variations of the tensile plastic load zone in loading and the compressive plastic load zone in unloading are studied respectively under various test conditions, and the effects on acceleration, delayed retardation and non-propagation during fatigue crack propagation are also studied. It can be speculated that the compressive plastic zone at the crack tip has some effects on fatigue crack propagation. Furthermore, it is known that the crack closure phenomenon ends after the compressive plastic zone appears but before the minimum load. Therefore, a parameter PCF called the crack closure finish load is presented for evaluating behavior of fatigue crack propagation.
