Signature of Structural Memory in Shear jammed Dense Suspension

Sachidananda Barik

A wide verity of dense particulate suspensions can show a shear induced transformation from a liquid like state to a solid like jammed state called shear jammed (SJ) state. Such shear jammed system also show very fast relaxation dynamics where the stress in the system relaxes quickly so that the solid like jammed state comes back to the liquid like state when no shear is applied. Here we study the effect of such drastic stress relaxation over the structural relaxation. We observe that under unidirectional step strain perturbation there is an enhancement in the mechanical response whereas under the step strain perturbation in the alternative direction the mechanical response is weak. This is suggestive of the structural memory in the system even after the dramatic decrease of the stress in the system and complete change of mechanical properties. We further find that this structural memory is significant only for the volume fractions above the minimum volume fraction required for the shear jamming. Using in-situ boundary imaging, shear reversal technique and numerical simulation we explore the possible microscopic mechanism and propose a model which can explain such structural memory in SJ dense suspensions.