Abstract
The design of safe and low-cost, high-pressure hydrogen storage systems are a critical need for harnessing clean power but must consider the propensity of hydrogen to accelerate fatigue crack growth rates in the construction materials. Design of safe pressure vessels needs robust models for predicting crack growth rates and how they are affected by variables such as loading frequency, load ratios, hydrogen pressure, gaseous impurities, temperature, and material variability. In this study, fatigue crack growth rates were measured in the liner material in 10 MPa gaseous hydrogen at various load ratios, R, in the range -1 ≤ R ≤ 0.2. The effects of varying loading frequency were investigated, and the results were pooled with those from literature for similar alloys tested in 103 MPa gaseous hydrogen pressure. The differences in crack growth rates between H2 pressures of 10 to 103 MPa as well as the effects of frequency on the environment assisted crack growth rates were assessed. Loading frequency effects tend to saturate at frequencies of 1 Hz and less. H2 pressure effects appear to saturate at pressures of 45MPa, while load ratio effects are not significant for –1 ≤R≤ 0.2 but become important for R ≥ 0.2.
Highlights
Safe and low-cost, high-pressure hydrogen storage systems are a critical need for refueling stations for fuelcell powered vehicles, for back-up power in residential and office buildings, and for fork-lifts in warehouses
The results show that the crack growth rates are higher in air than in He and substantially higher in H2 at 10 MPa
Fatigue crack growth rate data obtained on SEC(T) specimens from this study and Sandia’s data obtained on C(T) specimens appear to be identical at load ratios of 0.1 and a H2 pressure of 10 MPa
Summary
Safe and low-cost, high-pressure hydrogen storage systems are a critical need for refueling stations for fuelcell powered vehicles, for back-up power in residential and office buildings, and for fork-lifts in warehouses. Type I, steel pressure vessels that have been in use in the industry for decades to store hydrogen on ground are constructed from seamless high strength low alloy steels, but are restricted to maximum pressures of 450 bar This is due to hardenability considerations that limit the maximum permissible wall thickness of the vessel. There has been progress in our understanding of mechanisms of hydrogen embrittlement in the crack tip process zone [5] but not sufficient to allow development of robust models for predicting crack growth rates and how they are affected by variables such as loading frequency, load ratios, hydrogen pressure, gaseous impurities, temperature, and material variability This need has been partially met by empirical studies conducted by Sandia National Laboratory and by Japanese and European research programs[6,7,8]. The acceleration of fatigue crack growth rates have been quantified for tension only loading conditions, but autofrettaged pressure vessels experience compression to tension load cycles during service [9]
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