Fatigue Crack Propagation Prediction for Pipeline Steel Under Gaseous Hydrogen Environment

Abstract

Abstract Hydrogen embrittlement (HE) refers to the irreversible damage caused by hydrogen diffused in the metal lattice with the metal material itself or other chemical elements in the matrix, which may lead to fatigue failure. Therefore, for safety reasons, it is of great significance to investigate the impact of HE on the fatigue strength of pipeline steel under gaseous hydrogen environment. Cyclic cohesive zone model (CCZM) is one of the potential methods for simulating the hydrogen assisted crack (HAC). A fatigue crack propagation simulation for API X52 pipeline steel based on a modified CCZM under gaseous hydrogen environment is performed in this paper. The modified CCZM is proposed where not only the degradation of cohesive strength but also the degradation of accumulated cohesive length is considered in order to clarify the impact of HE on the fatigue crack propagation. The degradation of cohesive strength and that of accumulated cohesive length is expressed with piece-wise linear relationships. The results of simulation are then compared with test results to demonstrate the capability of the proposed CCZM. The proposed model tends to provide a useful reference for further research on the simulation for HAC by CCZM.