| Safe storage and transport of high-pressure hydrogen gas are the basis for large-scale development of hydrogen energy and hydrogen fuel cell vehicles(HFCV).4130X is a typical Cr-Mo steel that is commonly used for seamless steel gas cylinders,which unluckily shows a little hydrogen embrittlement(HE)when served in hydrogen gas service.And higher pressure hydrogen will lead to more severe HE problem to 4130X.Coupled with frequent high-pressure hydrogen filling and relief process,crack susceptibility becomes a great obstacle for higher hydrogen gas storage and transport.For the safe design and usage of the high-pressure hydrogen storage cylinder,and compensating for the missing mechanical properties of 4130X HE in high pressure(92 MPa)hydrogen gas,the following works are done within this paper:(1)A comprehensive introduction is made about the high-pressure HE in-situ testing methods,and a systematical analysis is made to illustrate the similitude requirements for the in-situ testing,which can be classified into:environmental similitude;hydrogen concentration field similitude,mechanics similitude.Besides,a mathematic model is established to translate the crosshead displacement into the specimen elongation,since it has always been a big inconvenience to directly measure the elongation in the high pressure test chamber.Based on ABAQUS software,a numerical analysis was carried out to analyze the effectiveness of the mathematic model.(2)The durability of 4130X with high pressure(92 MPa)hydrogen gas is studied with the high-pressure hydrogen environment material durability testing apparatus,and the tensile properties and fatigue crack growth rates in more than 45 MPa high pressure hydrogen atmosphere were measured for the first time in the world.In addition to the effects of different pressures,spinning process was also tested to assess its influence on the HE.The results show that the tensile yield strength and ultimate tensile strength of 4130X in high-pressure hydrogen environment are not affected by hydrogen,but the percentage reduction of area after fracture is reduced in the presence of hydrogen which indicates more severe HE.The fatigue crack growth rates in a hydrogen atmosphere increases significantly to about 30 to 50 times of that without hydrogen.The higher the pressure,the quicker fatigue crack growth rate is.(3)Methods and calculation algorithm based on fracture mechanics to assess the crack tolerance of a high pressure cylinder that experiences an elliptical surface crack are established.Based on the algorithm,the crack tolerance of certain remaining fatigue life of different hydrogen storage cylinders is calculated.The influence of the ratio of crack depth to length,pressures,heat treatment process on the crack tolerance is also studied.A fatigue assessment based on the crack tolerance is established and stress control requirements are discussed for the design of high-pressure hydrogen storage cylinder.Results of this study may provide basic data for the design of high-pressure hydrogen storage and transport apparatus,and provide guidance and theoretical support for the management,and maintenance of these hydrogen storage cylinders. |
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