Thermal conductivity associated with a bead-bead contact decorated by a liquid bridge - An experimental study based on the response of a chain subjected to thermal cycles

International audienceWe report an experimental study of the heat transport along a chain of macroscopic beads: at one end, one bead is periodically heated and we record the resulting temperature variations of another bead as a function of position and time. The experimental results show that the chain behaves like a high-order low-pass filter. The measurement of the associated cut-off frequency makes it possible to determine accurately the resistance of the bead-bead contact: we make use of the experimental setup for studying the effects of liquid bridges decorating the bead-bead contacts. which provides important clues for understanding the thermal properties of partially wet granular matter

Creep motion of a granular pile induced by thermal cycling

We report a time-resolved study of the dynamics associated with the slow compaction of a granular column submitted to thermal cycles. The column height displays a complex behavior: for a large amplitude of the temperature cycles, the granular column settles continuously, experiencing a small settling at each cycle; By contrast, for small-enough amplitude, the column exhibits a discontinuous and intermittent activity: successive collapses are separated by quiescent periods whose duration is exponentially distributed. We then discuss potential mechanisms which would account for both the compaction and the transition at finite amplitude.Comment: 4 pages, 5 figures, accepted for publication in Physical Review Letters (05sep08

Ageing of a granular pile induced by thermal cycling

4 pages, 5 figures, Proceeding of the Powders and Grains conference 2009, Golden (Colorado)International audienceHere we show that variations of temperature, even of a few degrees in amplitude, induce the ageing of a granular pile. In particular, we report measurements of physical properties of a granular heap submitted to thermal cycles. Namely, we focus on the evolution of the thermal linear-expansion coefficient and of the thermal conductivity of the pile with the number of cycles. The present contribution nicely supplements a recent article we published elsewhere [Phys. Rev. Lett. 101, 148303 (2008)] and introduces a different and promising method to impose temperature cycles to a granular pile

Aging in humid granular media

Aging behavior is an important effect in the friction properties of solid surfaces. In this paper we investigate the temporal evolution of the static properties of a granular medium by studying the aging over time of the maximum stability angle of submillimetric glass beads. We report the effect of several parameters on these aging properties, such as the wear on the beads, the stress during the resting period, and the humidity content of the atmosphere. Aging effects in an ethanol atmosphere are also studied. These experimental results are discussed at the end of the paper.Comment: 7 pages, 9 figure