Application of a Model of Hydrogen-Assisted Fatigue Crack Growth in 4130 Steel

In this work, we applied a finite element model to predict the cyclic lifetime of 4130 steel cylinders under the influence of hydrogen. This example is used to demonstrate the efficacy of a fatigue crack growth (FCG) model we have developed. The model was designed to be robust and incorporate features of stress-assisted hydrogen diffusion, large-scale plasticity, hydrogen gas pressure, loading frequency, and effects of microstructure. The model was calibrated to the 4130 steel material by use of tensile tests and experimental FCG results of a compact tension specimen. We then used the model to predict the hydrogen-assisted FCG rate and cycle life of a pressurized cylinder with a deliberate initial thumbnail crack. The results showed good correlation to the cyclic lifetime results of 4130 pressurized cylinders found in the literature.