Shearing of frictional sphere packings

摘要: We measure shear response in packings of glass beads by pulling a thin, rough, metal plate vertically through a bed of volume fraction ϕ, which is set, before the plate is pulled, in the range from 0.575 to 0.628. The yield stress is velocity independent over 4 decades and increases exponentially with ϕ, with a transition at ϕ≈ 0.595. An analysis of the measured force fluctuations indicates that the shear modulus is significantly smaller than the bulk modulus.