Hydrogen Degradation Effects on Crack Propagation in High-Strength Steels: A Fully Coupled Approach

Abstract

This study presents a fully coupled cohesive zone model (CZM)-based computational framework to simulate crack propagation in high strength steels. The model comprises initially zero thickness, cohesive-interface elements with the constitutive response described by a hydrogen-degraded Park-Paulino-Roesler (PPR) model. The linear dependence on hydrogen concentration according to a phenomenological decohesion model is chosen for the critical cohesive traction. Moreover, the value of the cohesive energy of the traction separation law (TSL) is adopted from the experimental data of hydrogen-charged specimen. The computational framework accounting for both hydrogen enhanced localized plasticity (HELP) and hydrogen enhanced decohesion (HEDE) mechanisms is employed to simulate crack growth in a C(T) specimen made of AISI 4130 high-strength steel. The parameters included in the PPR model are satisfactorily calibrated with experimental data for the uncharged and hydrogen-charged specimens. It has been concluded that the lattice hydrogen has the dominating factor in the hydrogen degradation compared with trapped hydrogen.KeywordsHydrogen embrittlementDuctile crack growthCohesive-interface elementsPark-Paulino-Roesler (PPR) modelHydrogen enhanced localized plasticity