Thermal expansion and thermal fluctuation effects in a binary granular mixture

- Thermal expansion dynamics in the granular system is analyzed in detail.
- Thermal perturbations degenerate the force networks in granular mixture.
- Friction exhibits the inhibiting role on the effect of thermal perturbations.

Considering that in many practical problems thermal expansion and thermal perturbations are the factors that granular materials are often faced with, in this study the 3D numerical experiments based on the discrete element method (DEM) were first carried out to investigate their effects in a binary granular mixture at high temperature levels. The granular system consists of mixed ceramic and steel grains. The thermal expansion dynamics induced is analyzed in detail. Besides, the stress in pebbles (or force chains) inside the system was founded to be much relieved by temperature changes and force networks were subsequently degenerated in magnitude and space, especially under larger temperature change amplitudes. At the same time, the segregation between the statistical probability distributions of internal forces of the two grain components was also observed, reflecting that thermal perturbations have induced the density segregation between the two kinds of solid materials and damaged their mixing homogeneity in space. Moreover, the effect of friction was also studied. It was observed that friction can play the inhibiting role on the effects of both thermal expansion and thermal perturbations, but it would become insignificant once the friction coefficient exceeds one specific threshold value. These messages may provide important implications for the handling of granular materials.