The Crack Initiation Behaviors of Fatigue-damaged High Strength Steels under Hydrogen Charging

Abstract

This study is concerned with an attempt to establish the effects of fatigue damages on the initiation of cracks in high strength steels charged with hydrogen. The experiments were carried out on the notched specimens which were pre-fatigued to various numbers of cycle of loading with constant amplitudes, in order to examine the time to crack initiation at the tip of notch by means of static load tests under cathodic hydrogen-charging.
The prior fatigue damage accumulation reduced significantly the time to hydrogen crack initiation at the notch tip of specimens. The possible mechanism for prior fatigue damage effects on hydrogen crack initiation in high strength steels was discussed in terms of the interactions between the hydrogens and microstructural defects within the cyclically plastic damage zone, such as hydrogen trapping due to dislocations and hydrogen segregations to microcracks.