Simulation of hydride-induced steady-state crack growth in metals ? Part I: growth near hydrogen chemical equilibrium

Abstract

Hydride-induced sub-critical crack growth in metals is simulated, by taking into account the coupling of hydrogen diffusion, hydride precipitation and material deformation. The terminal solid solubility of hydrogen in a stressed metal is derived analytically for hydrides of any shape with different elastic properties than those of the solid solution. The general relation considers full anisotropy of both hydride and metallic phases. It is shown that a hydrostatic stress plateau develops in the area of hydride precipitation near the crack tip, when crack propagates under conditions approaching hydrogen chemical equilibrium, near the threshold stress intensity factor. The plateau hydrostatic stress depends strongly on remote hydrogen concentration and temperature. However, it is nearly independent of the yield stress and the hardening of the metal. The same hydrostatic stress develops also behind the crack tip in the presence of hydrides. The characteristics of the near-tip field are used for estimating a critical remote hydrogen concentration, below which no hydride precipitation occurs, and the threshold stress intensity factor. The theoretical estimates compare favorably with experimental measurements.

NGNP Reactor Coolant Chemistry Control Study

“…When the terminal solid solubility of hydrogen in a metal is reached, hydrides often precipitate in regions of stress concentrations. 16 Terminal solid solubility for hydrogen is greater at higher temperatures, which suggests that temperature fluctuations in areas of high hydrogen content may increase the formation of hydrides. Hydrides are generally very brittle, and induced stresses readily cause crack generation and propagation.…”

On the Coupling of Mass Diffusion and Non-Mechanical Energy Flow in Metals under Finite Deformation~!2008-03-24~!2008-06-02~!2008-06-12~!

“…Relations (6) and (7) are original. These relations are expected to contribute to the improvement of existing models (e.g.…”

“…They are based on infinitesimal displacement gradient theory. In the case of steady-state crack growth, the deformation of the material is adequately described by infinitesimal displacement gradient theory [6] (see also [7] and referenced publications). However, in the case of stationary cracks or during initial crack growth, infinitesimal displacement gradient theory is sufficient only outside the region of crack tip blunting.…”

On the Diffusion in Solids under Finite Deformation

“…iron, nickel, titanium, zirconium) and has important industrial implications. In the case of steady-state hydrogen induced crack growth, the deformation of the metal is adequately described by infinitesimal displacement gradient theory [1]. In this case, the well-known equation of hydrogen mass conservation, which does not distinguishes between the non-deformed and the deformed body, is used.…”