Reliability of hydrogen storage tanks is significantly influenced by the mechanical performance of the container materials in the hydrogen environment. Fracture behavior and fracture toughness are of specific interest since they are relevant to many catastrophic failures. However, many conventional fracture testing techniques are difficult to be realized under the presence of hydrogen. Thus it is desired to develop novel in situ techniques to study the fracture behavior of structural materials in hydrogen environments.
In this study, special testing apparatus were designed to facilitate in situ fracture testing in H2. In addition to a multi-notch tensile fixture, a torsional fixture was developed to utilize an emerging fracture testing technique, Spiral Notch Torsion Test (SNTT). The design concepts will be discussed.
Preliminary in situ testing results indicated that the presence of H2 significantly reduces the fracture toughness of 4340 pipeline steels by up to 50 percent. On the other hand, SNTT tests conducted in air demonstrated a significant fracture toughness reduction in samples subject to Gleeble heat treatment, which illustrated the effect of welding on the fracture toughness of this material.