Simulation of hydride-induced steady-state crack growth in metals ? Part II: general near tip field

Abstract

Hydride-induced steady-state crack propagation in metals is investigated under conditions of constant temperature, plane strain, small-scale yielding and small-scale hydride precipitation, by taking into account the coupling of the operating physical processes. It is shown that the near-tip field depends on a normalized stress intensity factor, which incorporates both effects of the applied stress intensity factor and the crack velocity. According to Part I of the present study, when the normalized stress intensity factor tends to zero, the crack-tip field near the threshold stress intensity factor is produced, which is characterized by a constant hydrostatic stress in the hydride precipitation zone. As the value of the normalized stress intensity factor increases, the evolution of the near-tip field for crack propagation from stage-I to stage-II regime is produced: the actual size of the hydride precipitation zone decreases, the hydrostatic stress increases, deviating from the level of the plateau, and the near-tip field tends to that of a hydrogen-free metal. The near-tip field depends strongly on hydrogen concentration, far from the crack tip. The stage-II crack growth velocity is predicted and the experimentally observed effect of metal yield stress and temperature on crack velocity is confirmed.