Photoelastic Grain Solver v2.0: An updated tool for analysis of force measurements in granular materials

¹ Department of Physics, North Carolina State University, NC, USA
² Mount Holyoke College, MA, USA
³ University of Cambridge, UK
⁴ Indian Institute of Science
⁵ University of Edinburgh, UK
⁶ Haverford College, PA, USA

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Published online: 1 December 2025

Abstract

Photoelastic force imaging is an experimental technique whereby a birefringent granular material is imaged with a polariscope to characterize the internal stress state of a granular material. Photoelasticimetry is the only proven experimental technique that allows researchers to measure the shear and normal forces at every particle contact in a granular packing. In 2017, Kollmer et al. [Rev. Sci. Instrum. 88, 051808 (2017)] developed an open-source software to perform this analysis. Here, we present the next substantial update to this software package. The new version improves resolution and efficiency and substantially changes the software architecture. The structural changes better facilitate add-ons, modules, and future improvements to the performance, accessibility, and versatility of the tool. Besides updates to the core software, we introduce new infrastructure to support the ongoing development of software, documentation, and training materials. The full development team, software, and supporting resources are available at https://github.com/photoelasticity.