title: Complex oscillatory yielding of model hard-sphere glasses.
abstract: The yielding behavior of hard sphere glasses under large-amplitude oscillatory shear has been studied by probing the interplay of Brownian motion and shear-induced diffusion at varying oscillation frequencies. Stress, structure and dynamics are followed by experimental rheology and Browian dynamics simulations. Brownian-motion-assisted cage escape dominates at low frequencies while escape through shear-induced collisions at high ones, both related with a yielding peak in G''. At intermediate frequencies a novel, for hard sphere glasses, double peak in G'' is revealed reflecting both mechanisms. At high frequencies and strain amplitudes a persistent structural anisotropy causes a stress drop within the cycle after strain reversal, while higher stress harmonics are minimized at certain strain amplitudes indicating an apparent harmonic response.
authors.affiliation: FORTH/IESL and Department of Materials Science and Technology, University of Crete, 71110 Heraklion, Greece.
authors.forename: N
authors.initials: N
authors.lastname: Koumakis
authors.forename: J F
authors.initials: JF
authors.lastname: Brady
authors.forename: G
authors.initials: G
authors.lastname: Petekidis