An experimental fracture mechanics study of the combined effect of hydrogen embrittlement and loss of constraint

Hydrogen Embrittlement as a Conspicuous Material Challenge─Comprehensive Review and Future Directions

“…While the HESIV mechanism enjoyed great popularity over the past two decades, little follow-up study was conducted on H-informed Gurson modeling until 2019 711 and the concept has increased in popularity since then. [710][711][712]723 As mentioned in the previous section, an H-informed Gurson model is more about predictive modeling of HE than about mechanistic investigation, so the technical details of this approach will be presented in Section 3.4. We put here a brief discussion about aspects related to the basics of the mechanism.…”

“…Moreover, voidbased predictive models, including unit cell and Gurson-type models, link plasticity, material separation, and vacancies and stand out as a platform to incorporate several major HE mechanisms, i.e., HELP, HEDE, and HESIV mechanisms. 20,710,712,723 It is noted that these models represent a promising but not exhaustive list.…”

“…Recently, Halilovićet al 759 explored the impact of pre-crack length ratio, which is a measure of geometric constraint, on the H-reduced fracture toughness in single edge notch bend tests of high strength steel. H was introduced using in situ electrochemical charging method, and a larger length ratio represented a higher level of constraint.…”

“…Meanwhile, inconsistency existed in that a lower sensitivity to HE in a thicker specimen, which should also possess a higher level of constraint, was reported by Halilovicé t al. 759 Further investigation is needed to probe the discrepancy. In all the above-reviewed studies, the influence of geometric constraint on HE was attributed to the interplay between H, plasticity, and constraint.…”

“…Birenis et al conducted in situ compact tension test on iron in gaseous H. Samples tested in air possessed large crack-opening and blunted crack-tips, while specimens tested in H 2 had much smaller crack-openings and substantially sharper tips, as shown in Figure a; specimens tested in H 2 were found to have a significantly lower fracture toughness as shown in Figure b. Halilović et al conducted three-point bending test under in situ H charging condition and found that H reduced the fracture toughness of a high strength steel. In their experiments, the fracture surface still displayed considerable amount of dimpled feature when the concentration of H was low; the fractography became IG at a high concentration.…”