General Stress Conditions Dominating in the Hydride Precipitation Zone of Metals Under Steady State

The general stress conditions, which dominate in the zone of hydride precipitation under steady state for hydrogen diffusion, are derived, by rigorously taking into account the coupling of the operating physical processes. The conditions are valid, irrespective of metal elastic anisotropy, plastic deformation or geometry. According to these conditions, stress trace is a function only of temperature, leading to loss of dominance of the well-known asymptotic crack-tip stress fields of hydrogen-free metals, including those of constraint-based fracture mechanics. The present analysis is applied to a hydrided cylindrical wall and a hydrided plate under steady state heat conduction. It is shown that a nearly linear variation of hydrostatic stress dominates within the area of hydride precipitation, even in the presence of a surface crack, being in excellent agreement with existing detailed finite element calculations.