Photoelastic force measurements in granular materials

TL;DR

This paper reviews photoelastic techniques for measuring forces in granular materials, explaining the optical principles, software tools, and experimental setups for quantitative force analysis in 2D granular systems.

Contribution

It provides a comprehensive summary of past work, detailed methodology, and resources for implementing photoelastic force measurements in granular materials.

Findings

Quantitative determination of contact forces in 2D granular systems.

Optical setup and software resources for force measurement.

Guidelines for building experimental apparatus.

Abstract

Photoelastic techniques are used to make both qualitative and quantitative measurements of the forces within idealized granular materials. The method is based on placing a birefringent granular material between a pair of polarizing filters, so that each region of the material rotates the polarization of light according to the amount of local of stress. In this review paper, we summarize past work using the technique, describe the optics underlying the technique, and illustrate how it can be used to quantitatively determine the vector contact forces between particles in a 2D granular system. We provide a description of software resources available to perform this task, as well as key techniques and resources for building an experimental apparatus.