Development of Photoelastic Gelatin Spheres for Force Measurement and Visualization in Granular Media

Abstract

A new method for measuring forces in granular media experiments using photoelastic gelatin spheres was developed. The photoelastic performance of gelatin spheres based on composition was evaluated and calibration curves were developed. The photoelastic response of the spheres was determined to be linear with load. Sensitivity was observed to change with gelatin concentration as well as the concentration of other additives, however there was not a simple correlation. It was found that photoelastic gelatin sphere could detect forces as small as 20 μN. Gelatin hydration was controlled by manipulating the osmotic pressure across the sphere boundary. It is likely that smaller forces could be observed with more sensitive equipment.