Simulation of hydrogen assisted stress corrosion cracking using the cohesive model

This paper investigates the effect of hydrogen diffusion on stable crack propagation by using numerical finite element simulations based on the cohesive model. The model with its two common parameters, cohesive strength, T0, and critical separation, δ0, and its two additional parameters for stress corrosion cracking, the effective diffusivity, Deff, and a material parameter, α, which represents the reduction of the cohesive strength, is described. This model is then employed to predict the stable crack propagation in C(T) specimens made from a high strength structural steel which were tested under hydrogen charging conditions in rising displacement tests using various deformation rates. It is shown that, in general, the prediction of stable crack propagation is promising, but may be further improved by the use of a more sophisticated diffusion equation. Finally, the influence of variations of the effective diffusivity and the cohesive strength reduction on the thus simulated crack growth resistance curves is studied.