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This work presents a novel strategy to model the coexistence of HELP & HEDE mechanisms. The proposed method accounts for ductile and brittle damage with a competitive fracture criterion to describe the competition effect between HELP & HEDE mechanisms. The cooperation aspect is addressed by a dislocation-enhanced hydrogen accumulation model, which agrees with the HELP-mediated HEDE mechanism. The tensile, fracture toughness, and threshold stress intensity factor tests are simulated in different hydrogen environments. The results demonstrate that the proposed method reproduces the hydrogen-dependent ductile to brittle transition phenomenon. Under different hydrogen conditions, the dominating damage mechanism and degradation trends agree with experimental observations. Furthermore, for the investigated 4130 steel, the predicted value of fracture toughness and threshold stress intensity factor match the experiment results. The difference in damage kinetics inherent in the two test methods is captured, which supports the rationality of the proposed strategy for HELP and HEDE interaction. [Display omitted] • Competitive & Cooperative ductile-brittle damage model on HELP & HEDE interplay. • Predicted Hydrogen embrittlement features match experimental observations. • K JC and K THa prediction outputs match experiment values. • Difference in hydrogen damage kinetics in different test methods captured. [ABSTRACT FROM AUTHOR]

In this work, a practical numerical model with few parameters was proposed for the prediction of environmental hydrogen embrittlement. The proposed method adopts hydrogen enhanced plasticity-based mechanism in a fracture strain model to describe hydrogen embrittlement. Fracture toughness degradation of three commercial steels SA372J70, AISI4130 and X80 in high pressure hydrogen environment were investigated. Firstly, governing equations for hydrogen distribution and material damage evolution was established. Hydrogen enhanced localized flow softening effect was coupled within fracture strain dependency on stress triaxiality. Then, the numerical implementation and identification process of model parameters was described. Model parameters of the investigated steels were determined based on experiment results from literatures. Finally, with the calibrated model, fracture toughness reduction of the steels was predicted in a wide range of hydrogen pressure. The prediction results were compared with experimental results. Reasonable accuracy was reached. The proposed method is an attempt to reach balance between physical accurate prediction and engineering practicality. It is promising to provide a simplified numerical tool for the design and fit for service evaluation of hydrogen storage vessels. • Hydrogen embrittlement prediction model with few parameters was proposed. • Identification of model parameters with a few support of experiments. • Simplified Fracture toughness prediction model with acceptable accuracy. [ABSTRACT FROM AUTHOR]