Fatigue life analysis of high-pressure seamless steel cylinder for hydrogen using autofrettage design

Abstract

The seamless steel gas cylinders remain widely used for hydrogen refueling stations due to its intrinsic safety, especially for the situations with high pressure over than 60 MPa. When the internal pressure thick wall cylinder is subjected to high pressure even ultra-high pressure, autofrettage process is usually adopted to improve its bearing capacity and fatigue life. In this paper, fatigue life analysis was performed on the seamless steel cylinder for hydrogen using the autofrettage design approach. The stress distribution along the wall thickness direction before and after the autofrettage process were analyzed. Based on the ideal elastic-plastic material, the residual stress caused by the autofrettage pressure were obtained. On this basis, the expressions of residual stress and total stress along the cylinder wall in elastic-plastic deformation region were obtained, which will affect the fatigue crack growth rate (FCGR). Therefore, the fatigue crack growth tests of 34CrMo4 steel under different stress ratios (R) were carried out, especially for R < 0 to simulate the residual stress. Using the FCGR corrected with stress ratio, the fatigue life of the autofrettage high-pressure seamless steel cylinder was estimated and compared with the conditional cylinder. The results showed that fatigue life can be improved using the autofrettage design approach.