This work ddresses the applicability of a local criterion incorporating the coupling of critical stress and a critical hydrogen concentration to predict hydrogen embrittlement effects on the fracture strength of high strength steels using notched round specimens with different notch root radii. The numerical simulations incorporating a relatively simple hydrogen transport model provide strong support to the adoption of a failure criterion in terms of achieving a critical level of tensile stress coupled to the local hydrogen concentration, which, in turn, enable the construction of a failure locus for the material. For the cases analyzed here, construction of such a failure locus based on a critical combination of maximum principal stress and hydrogen concentration enabled predictions of fracture strength for hydrogen-charged tensile specimens which are in very good agreement with experimental data. Overall, the results presented here lend additional support for further developments of a local stress-based criterion to predict hydrogen embrittlement effects on the fracture strength of high strength steels.

This work conducts an exploratory evaluation of the brittle fracture behavior for a high-strength martensitic steel using conventional three-point bend SE(B) and pre-cracked Charpy V-notch (PCVN) specimens. A primary purpose of this study is to verify the effectiveness of the Master Curve methodology in providing a reliable estimate of the reference temperature ( T 0 ) derived from fracture toughness data sets measured in the ductile-to-brittle transition region (DBT) of a ultra high strength, low alloy martensitic steel. Fracture toughness testing conducted on three-point bend SE(B) specimens and pre-cracked Charpy (PCVN) configurations at different test temperatures in the DBT region provides the cleavage fracture resistance data in terms of the J -integral at cleavage instability, J c , and its corresponding K J c -values for the tested material. While this class of ultra high strength steel having a martensitic microstructure is currently beyond the reach of ASTM E1921, the analyses described here show that the predicted normalized curves of median fracture toughness vs. temperature are in good agreement with the experimental measurements.