Hydrogen assisted fatigue life of Cr-Mo steel pressure vessel with coplanar cracks based on fatigue crack growth analysis

Fatigue life of 4130X steel hydrogen storage vessel with coplanar cracks for hydrogen refueling station was analyzed in this paper. Subcritical cracking threshold (K-IH) in 45 MPa hydrogen and fracture toughness (K-IC) of 4130X were measured by sampling on a manu- factured vessel. Based on the test results, fatigue growth behavior of coplanar cracks was analyzed using the numerical simulation method, and the fatigue lives of the vessel with coplanar cracks were calculated. Furthermore, the re-characterisation methods which were used to simplify the coplanar cracks in different standards were compared. Results indicate that the fracture toughness of 4130X can be reduced by 73.7% in 45 MPa hydrogen compared with that in air. Because of the deterioration of material mechanical properties, the fatigue life of the vessel with coplanar cracks under hydrogen pressure cyclic loading can be reduced by more than 90% compared with that under hydraulic pressure cyclic loading, which is similar to the case of one single crack. The smaller the critical distance of the coalescence criterion, the greater the fatigue life determined by the re-characterisation methods. The fatigue life calculated according to the coalescence criterion in BS 7910 or ASME BPVC. XI is closer to that determined by the numerical simulation method. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.