Hydrogen/plasticity interactions at an axial crack in pipeline steel

The technology of large scale hydrogen transmission from central production facilities to refueling stations and stationary power sites is at present undeveloped. Among the problems which confront the implementation of this technology is the deleterious effect of hydrogen on structural material properties, in particular at gas pressure of 15 MPa which is the desirable transmission pressure suggested by economic studies for efficient transport. To investigate the hydrogen embrittlement of pipelines, a hydrogen transport methodology for the calculation of hydrogen accumulation ahead of a crack tip in a pipeline steel is outlined. This work addresses the interaction of hydrogen with an axial crack on the inside surface of the pipe. The approach accounts for stress-driven transient diffusion of hydrogen and trapping at microstructural defects whose density evolves dynamically with deformation. The results address the effect of hydrostatic constraint, stress, and plastic strain on the time it takes for the steady state hydrogen profiles to be established.