The Photoelastic Grain Solver (PeGS) is a MATLAB-based tool designed to extract per-particle force measurements from video recordings of photoelastic granular materials. These materials are made from birefringent particles placed between polarizing filters, which causes regions under stress to produce a visible light pattern, called a fringe pattern, when viewed through the filters. (Pictured above) The intensity and shape of these fringes relate directly to the internal stresses within each particle.

PeGS works by comparing the observed fringe patterns in the video to simulated patterns generated based on predicted force configurations. Through optimization, it iteratively adjusts these force guesses until the simulated and observed patterns match closely, allowing it to recover the actual contact forces between particles. Open-source versions of earlier PeGS builds are available on GitHub. Under the guidance of Professor Kenneth Kamrin, my research partner Will Siemens and I have been refactoring and improving the tool to deliver more accurate results with significantly better computational performance.