Fracture strain model for hydrogen embrittlement based on hydrogen enhanced localized plasticity mechanism

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. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.