Fatigue crack growth acceleration caused by irreversible hydrogen desorption in high-strength steel and its mechanical condition

► Irreversible hydrogen accelerates the fatigue crack growth rate. ► The acceleration increases with a decrease in stress cycle frequency. ► The acceleration does not depend on the stress ratio. ► Irreversible hydrogen desorbs out from its trap site under cyclic loading. ► The desorption is determined by effective equivalent stress range. In this paper, the influence of irreversible hydrogen on the fatigue crack growth in high-strength steel is discussed. The fatigue crack growth rate was accelerated by irreversible hydrogen, and the acceleration increased with a decrease in stress cycle frequency. However, the stress ratio did not influence the fatigue crack growth rate evaluated in terms of ΔKeff. The behavior of irreversible hydrogen under cyclic loading was visualized by a hydrogen microprint technique. This proved that irreversible hydrogen desorbed out from the trap site under cyclic loading. The mechanical condition for irreversible hydrogen desorption was investigated by stress analysis and EPMA analysis.