Compression Causes Expansion and Compaction of the Jammed Polydisperse Particles

TL;DR

This paper investigates how mechanical annealing affects the packing and segregation of polydisperse granular materials, revealing that extensive annealing causes expansion due to size segregation driven by effective attraction.

Contribution

It uncovers the history-dependent expansion and compaction behaviors in polydisperse particles and introduces a potential-energy-driven segregation mechanism.

Findings

Expansion occurs after extensive annealing in polydisperse systems.

Size segregation results from particle-size-dependent effective attraction.

Packing fraction and structure depend strongly on the system's history.

Abstract

This study focused on the expansion in polydisperse granular materials owing to mechanical annealing, which involved compression and decompression. Following minor annealing, the polydisperse systems exhibited compaction as well as the systems having uniform-sized particles. However, following extensive annealing, only the polydisperse systems were observed to expand. Pressure history and structure analysis indicated that this expansion results from the size segregation of the particles. We attribute this segregation to particle-size-dependent effective attraction. The results of this study highlight the strong history dependence of the packing fraction and structure in polydisperse particles and reveal a potential-energy-driven segregation mechanism.