Ageing of a granular pile induced by thermal cycling

TL;DR

This study demonstrates that small temperature variations cause aging in a granular pile, affecting its thermal properties over repeated thermal cycles, with implications for understanding granular material behavior.

Contribution

It introduces a new method to impose thermal cycles on a granular pile and studies the evolution of its thermal properties with cycling.

Findings

Thermal cycling induces aging in granular piles.

Thermal linear-expansion coefficient increases with cycles.

Thermal conductivity changes as the pile ages.

Abstract

Here 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. \textbf{101}, 148303 (2008)] and introduces a different and promising method to impose temperature cycles to a granular pile.