Some initial experiments with an electrically conducting powder under static and vibrating conditions

An electrically conducting powder was produced by mixing bronze spheres wit h a small amount of carbon black powder. The potential difference across be ds of this powder was measured under static conditions and vibration. The s ystem was very sensitive and monitored changes during vibration cycles at r apid rates. Horizontal and vertical conductances were measured. above a min imum vertical stress, the ratio of the two was constant. The conductance wa s related to vertical stress by a linear relationship with hysteresis, for both static conditions and vibration at small accelerations. A simple model has been proposed to describe this system. At high accelerations (< 10 m/s (2)) changes were much larger. There were permanent changes in conductance and the system was non-linear. The data demonstrate that the internal struc ture of a particle bed displays great sensitivity, hysteresis and a depende nce upon stress history.