A fracture mechanics approach to hydrogen-assisted micro-damage in eutectoid steel is
presented. Fractographic analysis revealed micromechanical effects of hydrogen in the form of tearing
topography surface (TTS). The progress of this micro-damage is modeled as a macroscopic crack that
extends the original fatigue pre-crack and involves linear elastic fracture mechanics principles. In this
case, the change from hydrogen-assisted micro-damage (TTS) to cleavage-like topography takes place
when a critical stress intensity factor (KH) is reached, and this value depends on the amount of hydrogen
which penetrated the vicinity of the actual crack tip (the fatigue pre-crack plus the TTS area). The
present study analyzes the effect of the TTS zone aspect ratio on KH.
Keywords: Fatigue pre-loading, TTS, SIF.