Abstract
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, σmax, 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, σmax, 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.
Published Version
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