Influence of surface topology on the electrical response of many bead assemblies

We propose an interpretation of the voltage creep observed in metallic grain assemblies based on the sensitivity of the electrical properties to the surface topology of the beads. From the real area of contact between adjacent beads, directly measured through the bulk resistance of a single bead, we derive a simple relation between the voltage creep rate and the creep rate of the interface friction coefficient, regarded as an aging process expressing asperity creep. The likely influence of the Branly effect on the aging process is briefly discussed.