Automated Point-Tracking Measurements Using a Smartphone to Measure Strain and Displacement

Image-based techniques, such as DIC and grid method, have been developed to measure strain and displacement. The equipment used can be prohibitively expensive, and most of these techniques require marking the sample to track their motion/deformation. However, speckling samples is not always possible to get full-field measurements. Fiducial markers are primarily used in this case. This study explores a color tracking technique to track colored fiducial points on materials that cannot be speckled via standard techniques – such as fiber tows – and explores how to perform these measurements at a lower cost by using a conventional smartphone. A moving pendulum setup is used as an example for image tracking with a green ball tied to a tow of nylon fibers. The imaging process uses the color differences to automatically detect the point. This noncontact method showed positive results in tracking displacement with minimal noise and is being further explored for strain measurements and as an educational tool.