We report experimental results on the evolution of the particle microstruct
ure for noncolloidal particles that are suspended in a viscoelastic medium.
For dilute suspensions consisting of particles having a monodisperse parti
cle size distribution subjected to steady and oscillatory shear flows, as w
ell as suspensions having a bidisperse size distribution subjected to stead
y shear, we verify previous results reported in the research literature. We
also present new results of the particle microstructure for a dilute bidis
perse system that was subjected to oscillatory shear. For moderately concen
trated suspensions we report the formation of particle strings that corresp
ond to a quantitative reduction in the simultaneously measured shear stress
. (C) 2001 The Society of Rheology.