SELF-CONSISTENT CALCULATION OF STEADY-STATE CREEP AND GROWTH IN TEXTURED ZIRCONIUM

Irradiation creep and growth in zirconium alloys result in anisotropic dimensional changes relative to the crystallographic axis in each ind ividual grain. Several methods have been attempted to model such dimen sional changes, taking into account the development of intergranular s tresses. In this paper, we compare the predictions of several such mod els, namely the upper-bound, the lower-bound, the isotropic K self-co nsistent (analytical) and the fully self-consistent (numerical) models . For given single-crystal creep compliances and growth factors, the p olycrystal compliances predicted by the upper- and lower-bound models are unreliable. The predictions of the two self-consistent approaches are usually similar. The analytical isotropic K approach is simple to implement and can be used to estimate the creep and growth rates of t he polycrystal in many cases. The numerical fully self-consistent appr oach should be used when an accurate prediction of polycrystal creep i s required, particularly for the important case of a closed-end intern ally pressurized tube. In most cases, the variations in grain shape in troduce only minor corrections to the behaviour of polycrystalline mat erials.