A cohesive zone model to simulate fatigue crack propagation under high pressure gaseous hydrogen

In this study we focus on the effect of hydrogen gas on the cracking resistance of metals. The main objective is to predict the fatigue crack propagation rates in the presence of hydrogen. For this purpose, a Cohesive Zone Model (CZM) dedicated to cracking under monotonic as well as cyclic loadings has been implemented in the ABAQUS finite element code. A specific traction-separation law, adapted to describe the gradual degradation of the cohesive stresses under cyclic loading, and sensitive to the presence of hydrogen is formulated. The coupling between mechanical behaviour and diffusion of hydrogen can be modelled using a coupled temperature - displacement calculation available in ABAQUS. The simulations are compared with fatigue crack propagation tests performed on a 15-5PH martensitic stainless steel. They show that while the proposed model is able to predict a lower resistance to cracking in presence of hydrogen, at this stage it cannot fully account for the detrimental effect induced by high pressure of gaseous hydrogen.