Tailoring the frictional properties of granular media

TL;DR

This paper presents a systematic method to modify and measure the surface roughness of glass spheres to tune their inter-particle friction, impacting bulk granular behavior.

Contribution

It introduces a chemical etching technique to control surface roughness and correlates it with bulk frictional properties in granular media.

Findings

Friction coefficient depends on vertical roughness length scale.

Chemical etching effectively modifies surface roughness.

Bulk frictional behavior correlates with surface topography.

Abstract

A method of modifying the roughness of soda-lime glass spheres is presented, with the purpose of tuning inter-particle friction. The effect of chemical etching on the surface topography and the bulk frictional properties of grains is systematically investigated. The surface roughness of the grains is measured using white light interferometry and characterised by the lateral and vertical roughness length scales. The underwater angle of repose is measured to characterise the bulk frictional behaviour. We observe that the co-efficient of friction depends on the vertical roughness length scale. We also demonstrate a bulk surface roughness measurement using a carbonated soft drink.