Identification of Interparticle Contacts in Granular Media Using Mechanoluminescent Material

Abstract

© Society for Experimental Mechanics, Inc. 2020. Mechanoluminescent powders are new materials that can be considered as intelligent, active or responsive because they have the property of emitting light when they are mechanically deformed. They open perspectives for the measurement of stresses in mechanical parts. The present study focused on the stress concentrations in granular materials. Granular systems are defined as a collection of particles whose macroscopic behavior depends on the contact forces at the local scale. Some techniques are available for measurements in the bulk, such as X-ray tomography combined with volumetric digital image correlation. An extensive literature also deals with two-dimensional approaches: optical photography combined with digital image correlation, photoelasticimetry, infrared thermography. Mechanoluminescent materials offer new possibilities for revealing contact force networks in granular materials. Epoxy resin and mechanoluminescent powder were mixed to prepare dumbbell-like specimens and cylinders. Dumbbell-like specimens were used for preliminary uniaxial tensile tests. Cylinders were used to prepare granular systems for confined compression tests. Homogeneous light emission was obtained in the former case, while light concentrations were evidenced in the latter case.