Failure analysis based on J-integral values: A case study of hydrogen blistering defect

Hydrogen blistering defect, which is one of the common material degradation types caused by hydrogen with high-pressure, is paid more and more attention in the vessel safety research field. This article proposed a procedure of failure analysis to one of the liquefied natural gas tank with defects of hydrogen blistering. J-integral value, which was calculated by using finite element method, was used as a failure criterion for ensuring no crack growth in service. At first, based on the inspected database, a three-dimensional finite element analysis was performed by using Abaqus code to analyse the stress distribution and calculate J-integral values of a crack tip through direct definition and stress intensity factor. Then, the calculated J-integral values were compared with a critical value of the material to evaluate the propagative tendency of the crack under static loading. The results indicated that the existing crack in hydrogen blistering defect was likely to propagate in design and the actual operating pressure, thus the liquefied natural gas tank should be out of service timely. However, it may be used continuously with proper monitoring tools when the operating pressure is less than 0.5 MPa. The example shows that failure analysis based on J-integral values will be useful for engineering application with the advantage of timesaver, low cost and high reliability.