Modelling the test methods used to determine material compatibility for hydrogen pressure vessel service

This work aims to create finite element models to simulate the three ISO 11114-4 test methods applicable to hydrogen gas cylinders, coupled with calibrated constitutive models, to predict the deformation response of each. Experimental measurements are used to calibrate a monotonic constitutive model and a constitutive model of cyclic deformation. Six finite element solid models are discussed: monotonic tensile test of dog bone-shaped specimens, strain-controlled fatigue test of dog bone-shaped specimens, ISO test Method A, ISO test Method B, and ISO Method C (from ISO 11114-4), and a gas cylinder. Each finite element solid model is paired with the appropriate constitutive model based upon loading conditions. The modeling results are then combined with a new damage parameter in an attempt to compare each of the test methods to the others, as well as to in-service conditions. It is shown that the proposed damage parameter may be used to correlate all test methods considered (except for ISO Method A, a burst-disc test) as well as in-service conditions. The calibrated damage parameter may be coupled with any geometry, loading condition, and boundary condition modeled within a finite element package to predict the onset of critical damage in the material for which the coupled constitutive model is calibrated to. Parametric modelling study results provide estimated cycles to the onset of crack extension for DOT 3AA cylinders having varying sizes of internal thumbnail-shaped cracks. This work provides the baseline for measurements and models in air, with similar work in hydrogen to follow.