Abstract
In order to clarify the influence of moisture in air on fatigue crack propagation characteristics of high strength steels, fatigue tests were conducted in laboratory air and dry air using CT specimens.
The following results were obtained:
(1) In case of low stress ratio (R=0.1), the retardation-effect by moisture in air was recognized in low ΔK region (stage 2a) of the specimen whose tensile strength was below about 2000MPa. This behavior was explained due to the oxide-induced crack closure promoted by moisture in air.
(2) In case of high stress ratio (R=0.8), the acceleration-effect by moisture in air was recognized in the medium ΔK region (stage 2b) of the specimen whose tensile strength was higher than 1000MPa. This acceleration-effect might be caused by the hydrogen embrittlement which occurred near the specimen surface, and became more remarkable when the test frequency was low.
