Signature of jamming under steady shear in dense particulate suspensions

Abstract

Under an increasing applied shear stress ([ image ]), the viscosity of many dense particulate suspensions increases drastically beyond a stress onset ([ image ]), a phenomenon known as discontinuous shear-thickening. Recent studies point out that some suspensions can transform into a stress induced solid-like shear jammed (SJ) state at high particle volume fraction ([ image ]). SJ state develops a finite yield stress and hence is distinct from a shear-thickened state. Here, we study the steady state shear-thickening behaviour of dense suspensions formed by dispersing colloidal polystyrene particles (PS) in polyethylene glycol (PEG). We find that for small [ image ] values the viscosity of the suspensions as a function of [ image ] can be well described by Krieger─Dougherty (KD) relation. However, for higher values of [ image ] ([ image ][ image ]), KD relation systematically overestimates the measured viscosity, particularly for higher [ image ] values. This systematic deviation can be rationalized by the weakening of the sample due to flow induced failures of the solid-like SJ state. Using Wyart─Cates model, we propose a method to predict the SJ onset from the steady state rheology measurements. Our results are further supported by in situ optical imaging of the sample boundary under shear.