X-ray computerized tomography observation of Lycopodium paste incorporating memory of shaking

TL;DR

This study uses microfocus X-ray CT to observe how shaking influences the three-dimensional arrangement of Lycopodium particles, revealing anisotropic structures and crack growth patterns that retain the memory of shaking direction.

Contribution

It provides the first detailed 3D visualization of shaking-induced particle arrangements in Lycopodium paste, linking microscopic structure to crack propagation behavior.

Findings

Shaking causes anisotropic particle arrangements.

Density fluctuations form mainly in the lower layer.

Cracks grow along interstices perpendicular to shaking direction.

Abstract

In a uniform layer consisting of a mixture of granular material and liquid, it is known that desiccation cracks exhibit various anisotropic patterns that depend on the nature of the shaking that the layer experienced before drying. The existence of this effect implies that information regarding the direction of shaking is retained as a kind of memory in the arrangements of granular particles. In this work we make measurements in paste composed of Lycopodium powder using microfocus x-ray computerized tomography ($\mu$CT) in order to investigate the three-dimensional arrangements of particles. We find shaking-induced anisotropic arrangements of neighboring particles and density fluctuations forming interstices mainly in the lower part of the layer. We compare the observed properties of these arrangements with numerical results obtained in the study of a model of non-Brownian particles under shear deformation. In the experimental system, we also observe crack tips in the $\mu$CT images and confirm that these cracks grow along interstices in the direction perpendicular to the initial shaking.