Decoding Attractive Interactions in Granular Materials through Vibration-Induced Densification

Within the intricate world of granular materials, the behavior of grain assemblies presents complexities characterized by nonlinear and inelastic phenomena, which seamlessly link the microscopic grain scale to the macroscopic bulk scale. A key challenge in understanding the mechanics of granular materials lies in establishing connections between these microscopic grain properties and their macroscopic flow behavior. This study delves into vibration-induced densification, a phenomenon relevant across various technological domains in powder processing and manufacturing. Specifically, we explore the vibrational conditions that induce compaction and decompaction under vertical vibration, employing a particle damper across industrial powders, including glass beads, joint filler, wheat flour, and pharmaceutical excipients. The experiments involve controlling the vibration wave by adjusting parameters such as frequency and amplitude while measuring and recording the acceleration and force signals. Our findings reveal a significant correlation between the force required to decompact the powder bed and the attractive forces between grains. This correlation facilitates the determination of a dimensionless granular number Ad, offering insights into the contact force network at a macroscopic level and its relation to flow indices. By proposing this experimental approach, we provide a straightforward method to unveil the intricate relationship between local particle interactions and the overarching mechanical behavior of granular materials, contributing to advancements in understanding and predicting powder flow behavior.