Aj. Beaudoin et al., Consideration of grain-size effect and kinetics in the plastic deformationof metal polycrystals, ACT MATER, 48(13), 2000, pp. 3409-3423
This work extends the constitutive model For the prediction of grain-size d
ependent hardening in f.c.c, polycrystalline metals proposed by Acharya and
Beaudoin [1] (Grain-size effect in fee viscoplastic polycrystals at modera
te strains, 1999, in press) to include effects of temperature and strain ra
te dependence. A comparison is made between model predictions and compressi
on data, taken at varying temperature and strain rate, for pure Ag having t
wo different grain sizes. It is shown that an initial increase in yield str
ess and concomitant decrease in hardening rate for a fine-grained material,
relative to a coarse-grained counterpart, can be captured through initiali
zation of a state variable serving to describe stress response at prescribe
d reference conditions of temperature and strain rate. A grain-size depende
nce of hardening rate during parabolic (stage III) hardening is characteriz
ed by the evolution of net dislocation density in a finite element model of
a polycrystal aggregate. Finally, observations from simulations of de form
ation of the polycrystal aggregate are introduced into an existing macrosco
pic constitutive model for metal plasticity based on the mechanical thresho
ld. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All
rights reserved.