Influence of Loading Rate on the Hydrogen-Assisted Micro-Damage in Bluntly Notched Samples of Pearlitic Steel

The influence of loading rate (crosshead speed) on the fracture process of bluntly notched samples of pearlitic steel under hydrogen environment is analyzed in this paper. Results indicate that the location of the zone where fracture initiates (fracture process zone) in pearlitic steel samples with a blunt notch directly depends on the loading rate or crosshead speed. For slow testing rates, such a zone is placed in the specimen center due to hydrogen diffusion towards the prospective fracture places located in the central area of the section. On the other hand, in the case of high testing rates, the process of hydrogen-assisted fracture initiates near the sample periphery, i.e., in the vicinity of the notch tip, because in such quick tests hydrogen does not have enough time to diffuse towards inner points of the specimen.