Effects of hydrogen-altered yielding and work hardening on plastic-zone evolution: A finite-element analysis

Spatially and Kinetically Resolved Mapping of Hydrogen in a Twinning-Induced Plasticity Steel by Use of Scanning Kelvin Probe Force Microscopy

“…This is attributed to two factors: the relatively high strain rate and the shallow hydrogen-affected zone. The former factor is associated with hydrogen localization at a crack tip 60,61 and hydrogen/dislocation competitive motion associated with hydrogen-enhanced localized plasticity. [62][63][64] Therefore, a hydrogen-effect may appear at a lower strain rate than that used for the present tests.…”

Influence of Stress Re-distribution on Hydrogen-induced Fatigue Crack Propagation

“…Then, the strain localization at the crack tip causes void formation and subsequent coalescence, resulting in stable crack propagation during the loading process. 22) As mentioned above, the localized plasticity at the crack tip accelerates the fatigue crack growth, but the stress redistribution associated with the plastic constraint decelerates the fatigue crack propagation. 23,24) The stress redistribution is a result of the accommodation of the strain incompatibility around the interface of the two phases with different material constants.…”

“…Factors that are essential in the hydrogen promotion of fatigue crack propagation are the local hydrogen concentration and local plastic strain at the crack tip. 19,22) Based on the simulation results and result 4) of the surface observations, the increase of the thickness and the decreased soft phase interval promotes stress redistribution, resulting in the relaxation of the local hydrogen concentration and the suppression of hydrogen supported fatigue crack propagation.…”

“…Hydrogen diffusion is influenced by the lattice diffusion coefficient, diffusible hydrogen concentration, time, temperature, hydrostatic stress gradient, number of trap sites related to plastic strain amount, etc. 22,29,31) In the case of plane strain conditions, as the numerical analysis results show, the hydrostatic stress is high, and the hydrostatic stress gradient is large, inducing hydrogen localization at the crack tip. Thus, in the plane strain state, a significant difference in hardness between the two phases is required mechanically for suppression of hydrogen-assisted fatigue crack propagation.…”

“…Local hydrogen concentration at the crack tip is vital for hydrogen-promoted fatigue crack propagation. 19,22) From the viewpoint of the hydrogen concentration, the suppression of the fatigue crack propagation by stress redistribution was expected to be lower in the plane strain condition mechanically.…”