Modelling Hydrogen Induced Crack Growth: Validation by Comparison with Experiment

Abstract A finite difference hydrogen induced crack (HIC) growth model has been developed, enabling for the first time an accurate simulation of the growth of HIC cracks in the wall of pipelines and/or pressure vessels. In the model, parameters such as defect size, location, fracture toughness and hydrogen concentration, can be varied. The predictions of the HIC model are compared with experimental HIC crack growth curves, which were generated in a unique hydrogen permeation-ultrasonic scanning experiment. Both the observed time until initiation for HIC cracks and the crack growth rate show excellent agreement with the model calculations. The experiment in combination with the HIC model shows that defects initiate and propagate through segregation zones with a low fracture toughness. As soon as the defects reach the end of the segregation zone the HIC growth stops. The fracture toughness of the segregation zone as well as the bulk fracture toughness were determined by fitting the HIC model to the experimental data.