Self-assembly of granular particles

Abstract

Granular particles are ubiquitous in nature and daily life, and have wide applications in various disciplines such as infrastructure engineering, architecture, agriculture, etc. Yet, their fundamentals have not been fully understood by scientists. This is mainly because the structure of granular particles, which determines their properties, is complicated and can experience critical changes from disorder to ordered state. In recent years, understanding the fundamentals of such critical structural transitions of granular materials has become a hot multidisciplinary research topic attracting both scientists and engineers. Generally the transition from disordered to ordered structure can be regarded as a self-assembly process, which happens at different scales. In the nucleation of crystals, atoms or molecules can self-assemble due to thermal energy. For such thermodynamics systems, the theory of self-assembly is well established and is dependent on the Gibbs free energy. However, granular particles are much bigger and can dissipate energy quickly with the collision between particles, so they are normally at athermal or low-thermal states. The granular packings are prone to be disordered in structure, whereas they can also self-assemble with the input of external energy via vibration or shear, which can densify the granular packings and hence improve their properties for different applications. This thesis is devoted to advancing the knowledge of the self-assembly of granular spheres, particularly in better understanding the effects of the energy input and the boundary shape. The thesis has revealed a rich and deep picture for the effect of various factors on the self-assembly of granular particles, including the vibration mode, the container shape, material properties, different wall motions and gravity. The obtained results can improve the current understanding of the structural evolution and phase transition of the granular packings with or without vibration. The findings of this study enhance the knowledge on the self-assembly of granular systems and help take a step forward toward stablishing the mechanism behind the phenomenon. Thorough comprehension of the structure of the granular particles are essential for controlling the behaviour and properties of the granular materials, which can be of paramount importance for both the science and technology and have sensible influence on the mankind's life.

Date of Award	2020
Original language	English