The aim of this study is to elucidate the effects of compressive mean stress on the fatigue crack threshold in SAE52100 bearing steel with Vickers hardness of 703. Tension-compression fatigue tests were carried out on specimens which have semi-circular notches, each measuring 2a of 300 μm in length. The threshold maximum stress, σ max, th , was seen to decrease at the corresponding reductions in stress ratio, R, of-5,-3 and-1, at which points the fatigue limit was determined by the crack initiation limit. On the other hand, σ max, th at R =-10 was unexpectedly higher than that measured at R =-5. The unbroken specimen at R =-10 possessed non-propagating cracks, in which the maximum length was 2a of 535 μm, at both ends of the notch. In order to clarify the reason for such a peculiar phenomenon, the crack closure behavior of the non-propagating crack was measured, using the unbroken specimen at R =-10. The results indicated the existence of crack closure which can arrest crack growth.
All Science Journal Classification (ASJC) codes
- Mechanical Engineering
- Mechanics of Materials
- Civil and Structural Engineering
- Materials Science(all)