The Role of Friction and Shear stress in the Jamming Transition

1

The Role of Friction and Shear stress in the
Jamming Transition
Antonio Coniglio
Discussion Peter Schall University of Amsterdam
2
No friction, applied shear stress
Viscosity
h
G
Newtonian behavior ?
.
s h g

• System still homogeneous ?
• Shear banding ?

Protocol
3
No friction, applied shear stress
Experiments

• Grains density-matched (no sedimentation)

fgt0.62
stress
flt0.62
strain
A. Fall and D. Bonn (unpublished)
4
No friction, applied shear stress
Experiments

• 2D foam

5
No friction, applied shear stress
Hysteresis
16 x 16 x 8 2048 particles
How reliable is fc ?
OHern et al. 2003
6
No friction, applied shear stress
Hysteresis
16 x 16 x 8 2048 particles
Is fc a good measure ?
Confining pressure p
Particle overlap d
d
7
No friction, applied shear stress

• Model motion in energy landscape W(x)

Crystal potential
Jamming general for solids, crystalline and
amorphous systems
8
Nature 2001
Science 2003
9
Frictional particles
Simulations at V const
but particles want to dilate ...
Behavior at p const ?
10
Frictional particles
Support simple scenario of dilation ?
11
Frictional particles
Experimental examples ?
Relation with Shear thickening ?
(Suspensions under rapid shear, e.g. cornstarch,
bullet-proof wests)
Constant volume or pressure ?
Constant pressure Laplace pressure that holds
particles in suspension