Influence of Irreversible Hydrogen and Stress Cycle Frequency on the Fatigue Crack Growth Property in High-strength Steel and Hydrogen Visualization

The influence of irreversible hydrogen on the fatigue crack growth in cold-drawn high-strength steel was investigated to clarify the mechanism of fatigue strength degradation by irreversible hydrogen. The fatigue crack growth rate was accelerated by irreversible hydrogen in low ΔKeff region, and the acceleration increased with a decrease in ΔKeff. Moreover, the fatigue crack growth rate under irreversible hydrogen charged condition increased as the stress cycle frequency decreased. The behavior of irreversible hydrogen under cyclic loading was visualized using a hydrogen microprint technique. It was proved that irreversible hydrogen desorbed out from its trap site under cyclic loading.