Detecting a structure in two dimensions combining the Voronoï tessellation and a shape factor

Abstract

We present a methodology to quantify the structural changes in the internal structure of granular packing. To this end, we use the Voronoï tessellation and a specific shape factor which is a clear indicator of the presence of different domains in the granular packing. Distributions of the shape factor in a 2D granular system of metallic disks are experimentally investigated. The analysis of disk packings at a 'microscopic' level requires a precise measurement of grain positions. For this reason, we develop an accurate image processing technique based on the Standard Hough Transform. It is found that the properties of the probability distribution of the shape factor of the Voronoï cells are in accordance with the fact that the packings of monodisperse hard disks spontaneously assemble into the regions of local crystalline order.

Keywords

• granular materials
• granular compaction
• packings
• shape factor
• experimental results
• military application