Simulation of hydrogen assisted stress corrosion cracking using the cohesive model

Abstract

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, T 0 , and critical separation, δ 0 , and its two additional parameters for stress corrosion cracking, the effective diffusivity, D eff , 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.

Modelling of stress-corrosion cracking by using peridynamics

“…The chemical and physical interactions between material and corrosive solution are complex and particularly challenging to model. According to (Rimoli and Ortiz, 2010), it is widely reckoned that these interactions are not entirely understood at present, and, as argued in (Scheider et al, 2008), it is not currently possible to obtain a direct measure of hydrogen concentration in the region adjacent to the crack tip. As described in (Serebrinsky et al, 2004) and in (Sofronis and McMeeking, 1989), an alternative approach, adopted in different studies, such as (Scheider et al, 2008), (Raykar et al, 2011), (Alvaro et al, 2014a) and (Olden et al, 2014), consists in assuming that hydrogen adsorption can be represented via appropriate boundary conditions.…”

“…4). Similar to the approach adopted in (Rimoli and Ortiz, 2010), (Serebrinsky et al 2004), (Sofronis and McMeeking, 1989), (Scheider et al 2008), (Alvaro et al 2014a), (Olden et al 2014) and (Raykar et al 2011), hydrogen adsorption is treated by the application of appropriate boundary conditions. Fracture initiation due to the SCC hydrogen AIDEC mechanism is described by using the Fisher grain boundary diffusion model (Fisher, 1951).…”

“…Moreover, the number of SCC numerical models is increasing in the scientific literature, and many of them are based on the coupling of fracture mechanics and classical continuum mechanics (CCM) theory within the finite element method (FEM) via implementation of the cohesive zone model (CZM) by using cell mesh cohesive elements. Some studies of this kind are described in (Raykar et al, 2011), (Scheider et al, 2008), (Falkenberg et al, 2009), (Rimoli and Ortiz, 2010) and (Ahn et al, 2007), where hydrogen assisted SCC in high-strength steels is modelled. A similar approach is used in (Traidia et al, 2012), (Alvaro et al, 2014a) and (Alvaro et al, 2014b) for the modelling of hydrogen embrittlement in steel pipelines.…”

Environmentally Assisted Cracking of Magnesium Alloys

“…In various studies by the authors group experimental data which had been obtained from fracture mechanics tests on smooth and pre-cracked specimens were analysed using a number of modelling approaches for crack initiation and growth caused by hydrogen embrittlement [6][7][8][9][10]. The models proved that they had the potential to simulate the effects of hydrogen embrittlement in the material under investigation.…”

Strain Gradient Plasticity-Based Modeling of Damage and Fracture

“…Models adopting the hypothesis that interstitial hydrogen lowers the cohesive strength are able to capture the experimental trends depicted by high-strength steels in aqueous solutions and hydrogen-containing gaseous environments (see [36]). Several attractive hydrogen-sensitive cohesive zone formulations have been proposed within this HEDE framework (e.g., [123][124][125][126]); and accurate estimations of the threshold stress intensity K T H and the stage II subcritical crack growth rate have been obtained by means of the Gerberich et al [127] dislocation-based model [92,102,128]. However, uncertain adjustable parameters are a shortcoming of the models and it is necessary to better define conditions within 0.1-5 µm of the crack tip, where dislocations, microstructure and chemistry dominate material behavior [129].…”