Jean-Francois Metayer, Donald J. Suntrup III, Charles Radin, Harry L. Swinney, Matthias Schroeter Shearing of frictional sphere packings (999K, pdf) ABSTRACT. We measure shear response in packings of glass beads by pulling a thin, rough, metal plate vertically through a bed of volume fraction $\phi$, which is set, before the plate is pulled, in the range 0.575 to 0.628. The yield stress is velocity independent over 4 decades and increases exponentially with $\phi$, with a transition at $\phi pprox 0.595$. An analysis of the measured force fluctuations indicates that the shear modulus is significantly smaller than the bulk modulus.