Vibration-induced jamming transition in granular media - art. no. 011306

The quasistatic frequency response of a granular medium is measured by a fo rced torsion oscillator method, with forcing frequency f(p) in the range 10 (-4) Hz to 5 Hz, while weak vibrations at high-frequency f(s), in the range 50 Hz to 200 Hz, are generated by an external shaker. The intensity of vib ration Gamma is below the fluidization limit. A loss factor peak is observe d in the oscillator response as a function of Gamma or f(p). In a plot of 1 n f(p) against l/Gamma, the position of the peak follows an Arrhenius-like behavior over four orders of magnitude in f(p). The data can be described a s a stochastic hopping process involving a probability factor exp(-Gamma (j )/Gamma) with Gamma (j) a f(s)-dependent characteristic vibration intensity . An f(s)-independent description is given by exp(- tau (j)/tau), With tau (j) an intrinsic characteristic time, and tau = Gamma (n)/2 pif(s), n = 0.5 -0.6, an empirical control parameter with unit of time. tau is seen as the effective average time during which the perturbed grains can undergo struct ural rearrangement. The loss factor peak appears as a crossover in the dyna mic behavior of the vibrated granular system, which, at the time scale 1/f( p), is solidlike at low Gamma, and the oscillator is jammed into the granul ar material, and is fluidlike at high Gamma, where the oscillator can slide viscously.