Large amplitude oscillatory shear of hard-sphere colloidal dispersions: Brownian dynamics simulation and Fourier-transform rheology

Brownian dynamics simulations of large amplitude oscillatory shear (LAOS) in freely draining, hard-sphere colloidal dispersions are performed. The time varying stress and microstructure under LAOS are measured, and the relationship between microstructural deformation and rheological response is explored. The shear stress, first and second normal stress differences are analyzed by Fourier-transform rheology for dispersions with two volume fractions ϕ=0.10,  0.40. Highly nonlinear microstructural perturbations are identified and correlated with the magnitude of the stress response. The first departures from linearity in the shear and normal stresses are compared to recent theoretical predictions of the same, and agreement with scaling predictions in the limit of high frequency oscillation is found. Higher order nonlinearities in the stress response are found in the regime of rapid oscillation with order unity strain amplitude. These derive from symmetry breaking through shear induced ordering of the dispers...