  Competing time scales generate novelty. Here, we show that a coupling between
the time scales imposed by instrument inertia and the formation of
inter-particle frictional contacts in shear-thickening suspensions leads to
highly asymmetric shear-rate oscillations. Experiments tuning the presence of
oscillations by varying the two time-scales validate our model. The observed
oscillations give access to a shear-jamming portion of the flow curve that is
forbidden in conventional rheometry. Moreover, the oscillation frequency allows
us to quantify an intrinsic relaxation time for particle contacts. The coupling
of fast contact network dynamics to a slower system variable should be generic
to many other areas of dense suspension flow, with instrument inertia providing
a paradigmatic example.
