Stress Network Analysis of 2D Non-Cohesive Polydisperse Granular Materials using Infrared Thermography

The objective of the study is to analyze the hydrostatic stress network in two-dimensional cohesionless polydisperse granular materials under confined compression. Infrared (IR) thermography and thermoelastic stress analysis were used for this purpose. As model materials, the granular media under study were composed of cylinders made in POM polymer. Three cylinder diameters were used to prepare different samples differing in terms of the ratio between the numbers of cylinders of each diameter. These samples comprised between 200 and 324 cylinders. The temperature variations due to thermoelastic coupling under loading were measured on a cross-section of the cylinder network using an IR camera. The processing enabled us to identify the hydrostatic stress network in the samples. Molecular dynamics (MD) simulations were then performed to obtain a numerical network of hydrostatic stresses for each sample. The fields obtained from IR experiments and MD simulations are rarely in agreement, except in some zones of the sample. This was expected as it is not possible to have exactly the same geometrical configurations with both approaches. However, a good agreement is obtained in terms of statistical distributions.