High-strength low alloy (HSLA) steel structures are often exposed to hydrogen due to cathodic
protection towards corrosion (e.g. in offshore conditions). The structural integrity of these
structures is degraded as hydrogen reduces material ductility and toughness. The effects of
hydrogen on HSLA steels are not yet fully understood from a materials perspective. This proposal
looks at the hydrogen based degradation of HSLA steels in a combined and synergetic experimental
and numeric study, and aims to acquire fundamental understanding in the form of a mechanics
based damage law for hydrogen induced failure. This damage law will be calibrated on the basis of
microstructural and micromechanical measurements, and validated by means of fracture toughness
tests of in-situ hydrogen charged specimens. Particular attention is given to the coupled dynamics of
hydrogen diffusion and stress (re)distribution as a crack initiates and grows, and the effect of
specimen size in these dynamics.