Yoon-Suk Chang

The expansion of liquid hydrogen (LH₂) technologies has increased the demand for structural materials that maintain fracture resistance under combined cryogenic and hydrogen conditions. Although austenitic stainless steels (ASSs) are widely regarded as viable candidates for LH₂ tanks, multiple degradation mechanisms associated with hydrogen transport and phase transformation can induce competition between ductile failure and quasi-cleavage fracture. This study evaluates the fracture resistance of ASS 316L by formulating an integrated constitutive model developed in conjunction with mechanical tests under representative temperature and hydrogen conditions. A plasticity model was constructed by incorporating hydrogen transport and martensite evolution under different stress states. Finite element analyses of V-notched specimens were performed to calibrate the parameters of a mixed-mode damage model based on a ductile damage formulation with a critical stress criterion implemented via user-defined subroutines. Subsequently, crack growth analyses as well as tests of compact tension specimens were conducted, enabling the systematic assessment of the sensitivity of fracture resistance of ASS 316L under cryogenic and hydrogen conditions, and demonstrating the applicability and extensibility of the proposed constitutive model.