Chilou Zhou

Design fatigue life evaluation of high-pressure hydrogen storage vessels based on fracture mechanics:

Design fatigue life of high-pressure hydrogen storage vessels constructed of low alloy steels, austenitic stainless steels, and iron-based superalloy was analyzed based on facture mechanics in 45 MPa, 85 MPa, and 105 MPa hydrogen and air. Cylindrical model was used and the wall thickness of the model was calculated following five regulations including the High Pressure Gas Safety Institute of Japan (KHK) designated equipment inspection regulation, KHKS 0220, Chinese special equipment regulation (TSG) R0002, Chinese machinery industrial standard (JB) 4732, and ASME Sec. VIII, Div. 3. Design fatigue life for four typical model materials was also analyzed to discuss the effect of ultimate tensile strength, pressure, regulations and hydrogen sensitivity on the design fatigue life in hydrogen. It was discussed that hydrogen influence decreases with decreasing pressure or ultimate tensile strength. The design fatigue life data of the model materials under the conditions of pressure, ultimate tensile strength, KIH, fatigue crack growth rates, and regulations in both hydrogen and air were proposed quantitatively for materials selection for high-pressure hydrogen storage vessels.

Crack Growth Analysis of High-Pressure Equipment for Hydrogen Storage

Crack growth analysis (CGA) was applied to estimate the cycle life of the high-pressure hydrogen equipment constructed by the practical materials of 4340 (two heats), 4137, 4130X, A286, type 316 (solution-annealed (SA) and cold-worked (CW)), and type 304 (SA and CW) in 45, 85 and 105 MPa hydrogen and air. The wall thickness was calculated following five regulations of the High Pressure Gas Safety Institute of Japan (KHK) designated equipment rule, KHKS 0220, TSG R0002, JB4732, and ASME Sec. VIII, Div. 3. We also applied CGA for four typical model materials to discuss the effect of ultimate tensile strength (UTS), pressure and hydrogen sensitivity on the cycle life of the high-pressure hydrogen equipment. Leak before burst (LBB) was confirmed in all practical materials in hydrogen and air. The minimum KIC required for LBB of the model material with UTS of even 1500 MPa was 170 MPa·m0.5 in 105 MPa. Cycle life qualified 103 cycles for all practical materials in air. In 105 MPa hydrogen, the cycle life by KIH was much shorter than that in air for two heats of 4340 and 4137 sensitive to hydrogen gas embrittlement (HGE). The cycle life of type 304 (SA) sensitive to HGE was almost above 104 cycles in hydrogen, while the cycle life of type 316 (SA and CW) was not affected by hydrogen and that of A286 in hydrogen was near to that in air. It was discussed that the cycle life increased with decreasing pressure or UTS in hydrogen. This behavior was due to that KIH increased or fatigue crack growth (FCG) decreased with decreasing pressure or UTS. The cycle life data of the model materials under the conditions of the pressure, UTS, KIH, FCG and regulations in both hydrogen and air were proposed quantitatively for materials selection for high-pressure hydrogen storage.Copyright

Materials Safety for Hydrogen Gas Embrittlement of Metals in High-Pressure Hydrogen Storage for Fuel Cell Vehicles

Materials safety and selection for the application of metals in high-pressure hydrogen storage of fuel cell vehicles were introduced based on the hydrogen gas embrittlement (HGE) examinations using the materials testing equipment. Testing steps are as follows; the 1st step is the tensile test in high-pressure hydrogen by slow strain rate technique to evaluate the effect of hydrogen and divide the materials into five categories based on stress-strain curves. The materials of type III, IV and V are picked up and their yield points and ultimate tensile strengths are collected. The 2nd step is the fracture mechanics test to obtain KICs and KIHs of type III, IV and V materials. The materials of type IV and V are considered to be applicable as usual. The 3rd step is the crack growth test to obtain the fatigue crack growth data. A special consideration of HGE is taken for the design of the equipment with limited operation period or cycles for the materials of type III. The issue of the Kth’s reproducibility remains unresolved, which calls another testing method and design concept. Candidate materials are then nominated following the procedure of materials selection.Copyright