The effect of material hardness and mean stress on the fatigue limit of steels containing small defects

摘要

Fatigue tests on material containing small defects were performed under a wide range of mean stress for three grades of steels with different hardness. The ΔK_(th) of small defects had a peculiar dependency on material hardness and mean stress, which was quite different from those of long cracks or plain specimens. The crack closure of short cracks was measured. It was shown that the formation of the crack closure was affected by the material hardness and mean stress. This behaviour of crack closure resulted in characteristic fatigue limit properties of materials containing small defects.