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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]

Hydrogen energy is a candidate of the "ultimate energy". However, the quantified evaluation of hydrogen embrittlement phenomenon remains to be a challenging topic. This paper provides a continuum damage model to quantify hydrogen embrittlement. Firstly, theoretical model of the proposed method was introduced. The proposed model applied multi-axial fracture strain based ductile damage evolution law coupled with HELP mechanism to evaluate hydrogen accelerated micro-void coalescence (MVC) fracture. Void growth and coalescence were described by hydrogen enhanced plastic strain and hydrogen reduced fracture strain. Then, the proposed method was implemented on commercial finite element software package. Compact tensile (CT) test and slow strain rate tensile (SSRT) test of two commercial steels were investigated numerically and compared with available experimental results to verify the rationality of the proposed model. The results indicated the proposed method reproduced CT and SSRT tests result with different hydrogen concentrations precisely. Hydrogen's effect on MVC process was discussed. It is suggested HELP based MVC could be a viable model to quantify hydrogen embrittlement. The proposed method was also highlighted with the advantage of describing hydrogen's effect with only one parameter. • Continuum damage model for hydrogen embrittlement based on micro-void coalescence. • Description of hydrogen-assisted void growth and coalescence with HELP mechanism. • Practical model cover ductile and brittle fracture with few model parameters. [ABSTRACT FROM AUTHOR]