of the force is independent of the shear rate. But the chain
rotates at a rate ∼γ and eventually become unstable and selfdestructs.
Thus, the lifetime of the chain is proportional to 1/γ.
Consequently, the product of (formation−rate)×(lifetime) for a
chain is γ-independent and because the force generated is also
γ-independent, The stresses generated are quasistatic. This is
the Elastic–Quasistatic regime. It is the same as the old
Quasistatic regime; the word Elastic is added to indicate that it
is a subregime of the global Elastic regime.
But at high shear rates, the elastic forces in the chain must
absorb the inertia of the particles that are gathered in the chain,
requiring an extra force required to accelerate the particles in the
chain so that it rotates at a rate proportional to the shear rate.
Thus, even though the particles are locked in force chains, the
forces generated must reflect the particle inertia. The force F
generated in the chain must have the form F=a+bγ where a is
the baseline elastic force and bγ is the inertial augmentation.
Still the (formation−rate)×(lifetime) of the chain is γ-
independent so that the resultant stresses τ∼F∼a+bγ increase
linearly with the shear rate. (This is shown in Campbell [67].)
Naturally, there will be some inertial effect throughout the
Elastic regime, but for a wide range of flows, bγ≪a and the
flows appear quasistatic. However, when bγ becomes of the
same the same order as a, i.e. the inertial forces become of the
same order as the elastic forces, the flow transitions into the
Elastic–Inertial regime in which the forces are linearly
proportional to the shear rate γ.
The ratio of elastic to inertial effects is govern by a
dimensionless parameter: