  In this paper, we have investigated, using finite element calculations, the
effect of initial texture on the formation of multiple necking patterns in
ductile metallic rings subjected to rapid radial expansion. The mechanical
behavior of the material has been modeled with the elasto-viscoplastic single
crystal constitutive model developed by \citet{marin2006}. The polycrystalline
microstructure of the ring has been generated using random Voronoi seeds. Both
$5000$ grain and $15000$ grain aggregates have been investigated, and for each
polycrystalline aggregate three different spatial distributions of grains have
been considered. The calculations have been performed within a wide range of
strain rates varying from $1.66 \cdot 10^4 ~ \text{s}^{-1}$ to $3.33 \cdot 10^5
~ \text{s}^{-1}$, and the rings have been modeled with four different initial
textures: isotropic texture, $\left\langle 001\right\rangle\parallel\Theta$
Goss texture, $\left\langle 001\right\rangle\parallel$ R Goss texture and
$\left\langle 111\right\rangle\parallel$ Z fiber texture. The finite element
results show that: (i) the spatial distribution of grains affects the location
of the necks, (ii) the decrease of the grain size delays the formation of the
necking pattern and increases the number of necks, (iii) the initial texture
affects the number of necks, the location of the necks, and the necking time,
(iv) the development of the necks is accompanied by a local increase of the
slip activity. This work provides new insights into the effect of
crystallographic microstructure on dynamic plastic localization and guidelines
to tailor the initial texture in order to delay dynamic necking formation and,
thus, to improve the energy absorption capacity of ductile metallic materials
at high strain rates.
